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NUCLEAR POWER CORPORATION (A Government of India Enterprise) Madras Atomic Power Station Nuclear Training Centre HAND BOOK OF MECHANICAL MAINTENANCE Prepared by : E. Jayaprakash S. Jawahar Checked by : P. Mani, SO/F (Maint. Trg.) Reviewed by : S. Singaroy, M.S. K.G. Panicker, TS Approved by : S. Krishnamurthy, CS

Mechanical Handbook

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Page 1: Mechanical Handbook

NUCLEAR POWER CORPORATION (A Government of India Enterprise)

Madras Atomic Power Station Nuclear Training Centre

HAND BOOK

OF MECHANICAL MAINTENANCE

Prepared by : E. Jayaprakash S. Jawahar Checked by : P. Mani, SO/F (Maint. Trg.)

Reviewed by : S. Singaroy, M.S. K.G. Panicker, TS Approved by : S. Krishnamurthy, CS

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Rev: 0 January`2004

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PREFACE

The Handbook of Mechanical maintenance consists of two parts. The

first part deals with mechanical equipments and the second part deals

with mechanical general. This book provides with Definitions,

explanations, thumb rule, important information and examples on the

entire gamut of Activities encompassing mechanical maintenance.

To write a book of this type, a large number of standard books have

been consulted. Though every care has been taken in checking the

manuscripts and proof reading, yet to claiming perfection is very difficult

.We shall be very thankful to the readers and users of this book for

pointing out any mistakes/corrections that might have crept in.

Suggestions for improvement are most welcome and would incorporate

in the next revision.

We are grateful to all those who gave their valuable suggestion for

making this work, we are also grateful to all those persons to whom it is

not possible to acknowledge here individually due to paucity of space,

from whom help is taken in making this book.

January 2004. S.JAWAHAR

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CONTENTS

PART-A – MECHANICAL EQUIPMENTS

Sl.No. Title PAGE NO. 1. Pumps 6 2. Seals & Packing 11 3. Power transmission components 17 4. Bearing and Lubrication 23 5. Piping 29 6. Valves and Actuators 33

7. Heat Exchangers 37 8. Compressor 42 9. Diesel Engine 47 10. Fans & Blowers 54

11. Refrigeration 58 12. Turbine 62

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PART-B - MECHANICAL GENERAL

Sl.No. Title Page No. 1. Vibration & Balancing 67 2. Shock Pulse Measurements 70 3. Material Handling 71 4. Hydraulics 76 5. Engineering Metals 83 6. Surface Finish and Flatness 88 7. Hardness Testing 89 8. Mechanical Fasteners 90 9. Bolting of Flange Joints 93

10. Pressure Vessel Testing 95

11. Sealants 96 12. Welding 97 13. Lapping & Scraping 99 14. Principles of Filtration 102

15. Reliability, Maintainability and Availability 104

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TABLES

_____________________________________________ Sl.No Contents Page No.

1. Compatibility And Pressure Temperature 106

Rating Of Commonly Used Gaskets and Elastomers

2. Gasket Pressure Temperature Limits 107 3. Recommended Gasket Compression For 107

Spiral Wound Metallic Gasket 4. Minimum Gasket Seating Stress 108 5. Torque Required To Produce Bolt Stress 109

6. Data For Use With Alloy Steel Stud Bolts 110 7. Nut Factor 111 8. Gasket Factor (M) For Operating Conditions 112 9. Nomenclature Of Mesh 113 10. Wire & Sheet Metal Gauges 114 11. Threading Taps 115 12. Standard Stainless Steels Composition (%) 116 13. Elastomers and their properties 117 14. Lubricant minimum viscosity 118 15. Viscosity conversion tables 119 16. Refrigerant P-T chart 121 17. Humidity chart 122 18 Vibration severity charts 123 19. Forged flanges table 125 20. Hardness conversion table 126 21. References 127

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Part-A – Mechanical Equipments

1. Pumps v Net Positive Suction Head is the gauge pressure at pump suction minus the gauge

vapour pressure of liquid corresponding to its temperature and velocity head at this point.

NPSH available should be > NPSH required. NPSH = HP - HVap + Hz - Hf HP = Pressure of fluid in suction tank. Hvap = Vapour pressure of fluid at pumping temperature. +Hz = Positive suction head when the water level is above the pump centre lines. - Hz = Suction lift when the water level is below the pump centre line. Hf = Friction losses in piping. v Cavitation: Bubbles are formed in the moving liquid at the eye of the impeller when

the pressure at any point falls less than the vapour pressure at the temperature. The bubbles are collapsed at the high pressure region and causing damage to the pump internals.

v Specific speed is the speed of an imaginary pump, identical with the given pump, which

will discharge one litre of water per second while it is being raised through a head of one metre.

N√ Q Where N = Speed of the impeller in rps Ns = ----------- Q = Discharge of the pump in M3/Sec. H3/4 H = Head, against which the pump has to work. Equipment (MAPS) Specific Speed LP Process water pump - 4900 HP Process water pump - 1400 . Transfer water pump - 58.8

v Location of Impeller:

a) Double suction impeller in the horizontal pump to be locked at the centre of total end ply.

b) In Single inlet impeller shaft to be locked with 1/3 of the total end ply movement from suction side.

v Methods of axial thrust balancing in pumps: a) Use of double Suction Impeller, b) Balancing hole in Impeller, c) Hydraulic balancing, d) Staggering of stages in multistage pumps, e) Pump out vanes.

v Wearing ring: a) Wearing ring clearance- 0.025 to 0.0375 mm (1to1.5 thou/inch.φ).and should not be

more than 0.075 mm (3 thou/inch.φ).

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b) Wearing ring clearance={0.25+(D-150) 0.001mm.)(D=Inner dia.of wearing ring in mm).

c) A general rule is to replace the wearing ring when the clearance has increased 100% above the original

v Priming: a) Never attempt to prime a centrifugal pump while it is running.

b) Pressure developed by the impeller of a Centrifugal pump is proportional to the density of the fluid. Therefore it will produce only a negligible pressure, if running in air, which may not suck water.

c) The specific weight of air is approximately 1/800 that of water. A centrifugal pump can produce only 1/800 of its rated liquid pressure. For every 1 meter, water has to be raised to prime a pump, the pump must produce a discharge head of air of approximately 800 meter. It is therefore apparent that the head required for a conventional Centrifugal pump to be self-priming and to lift a large column of water when pumping air is considerably greater than the rating of the pump.

v Direction of Rotation: a) Impeller rotates in the direction away from the vane curvature and always towards

the discharge nozzle. b) Newly installed motor, direction of rotation to be checked before coupling. This is

particularly important on vertical pumps to avoid unscrewing of shaft coupling. v Stuffing Box: a) Gland Leak--10 to 12 drops/minute (For Lubrication of packing)

b) Adjust the sealing liquid flow 3.8 to 7.6 litres/minute (usually sufficient) to ensure packing lubrication.

c) Examine the gland follower for general condition and fit. The inner radial clearance should be 0.4mm (0.015”) maximum and the outer radial clearance should be 0.25mm (0.010”) maximum to prevent the risk of cocking or touching on the shaft.

d) An average, gland packed shaft/sleeve needs replacement at least once in every year. e) It is estimated that the energy lost due to gland friction is usually upto 10% of the output

of the motor, whereas the mechanical seal consumes negligible power. v Canned Motor Pump: a) Pump and motor are integral, No coupling and no alignment is required. b) No external lubrication is required. c) No mechanical seal. No leak path. d) Very few parts. Rotor and impeller are the only moving parts.

e) Pump runs at negligible vibration and noise levels. No need for base plate or rigid foundation.

f) Pump can be used in fluids under vacuum conditions. g) Efficiency of Canned motor pump is about 26% whereas the conventional centrifugal

pump is about 80%. (or) more. i) Bearing indicator is provided to know condition of bearing. v Progressing cavity pump: The principle of a rotor (Similar to a single start thread)

turning inside a stator (Similar to a twin start thread of the same profile) – produces a flow directly related to rpm and by the diameter of the rotor. The series of `moving Cavities’ formed as a rotor (a larger rotor produces larger cavities increasing the

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capacity) per revolutions turns inside the stator produces a pumping action that required no valves and is therefore particularly suitable for pumping viscous, highly particulate, abrasive or fragile structured products.

The valve less PCP ensures pulse-free delivery v Turbine Pump: a) This pump has some Characteristics of both Centrifugal and positive displacement

pump. b) Pressurise depends on momentum given to liquid by spinning rotor. c) Overall efficiency is about 40 to 50%, but design simplicity overcomes the efficiency. v Characteristic of Centrifugal pump: (a) Loss in head, capacity and increase in power consumption are effect of reversed

mounted double suction impeller on performance, which is much severe than with a correctly mounted impeller that is running reverse.

(b) The capacity by a centrifugal pump varies as the speed and diameter of the impeller. (i.e.) Q2 = Q1 (N2/N1) and Q2 = Q1 (D2/D1)

(c) Head developed by a Centrifugal pump varies as square of the speed and diameter of the impeller. (i.e.) H2 = H1 (N2/N1)2 and H2 = H1 (D2/D1)2

(d) The brake Horse power varies as the Cube of the speed and diameter of the impeller. (i.e.) P2 = P1 (N2/N1)3 and P2 = P1 (D2/D1)3

(e) The capacity of the parallel pumps will have nearly the sum of the each capacity of pump and the head of Series pumps will have nearly the sum of the each head of the pump.

(f) In a multi stage pump, the head developed by each impeller, is the total head divided by the number of impellers.

v Double suction reduces the axial thrust of impeller & Double volute casing reduces the

radial thrust on impeller. v Slip: (a) In practice, the actual discharge is less than the theoretical discharge.

Difference between these two is known as slip of the pump. (b)Slip is the loss in capacity through clearance between the casing and the rotating element and capacity varies as the discharge pressure increases.

v Generally the suction line is larger than the pump discharge nozzle and for horizontal

pump eccentric reducers should be used. a) If the source of supply is below the pump centre line, the reducer should be installed straight side up.

b) If the source of supply is above the pump, the straight side of the reducer should be at the bottom. c) Installing eccentric reducers with a change in diameters greater than10 cm (4 inch.) could disturb the suction flow.

v Piping Strains:

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Cast Iron pumps are never provided with raised face flanges. If Steel suction and discharge piping is used, the pipe flanges should be of the flat face and not the raised face type. Full-face gaskets must be used with cast iron pumps.

v Operation of Centrifugal pumps at reduced flows: a) Power losses is the difference between the brake horse power consumed and the

water horse power developed represents the power looses in the pump, except for a small amount lost in the pump bearings are converted to heat and transferred to the liquid passing through the pump.

b) The pumps were to operate against completely closed valve, the power losses would be equal to the shut off brake horse power, all this power would go into the heating the small quantity of liquid contained in the pump casing.

c) For hot water pumps, as a boiler-feed service, it is generally advisable to limit the temperature rise to about 15oF (8oC). As a general rule, the minimum permissible flow to hold the temperature rise in boiler – feed pumps to the value is 30 gpm. For each 100bhp (9.13 m3/h per 100 kw) at shut off.

d) For cold water pumps, the temperature rise may be permitted to reach 50 or even 100oF (28 or 56oC).

v Following are the varies cases, when lantern ring & sealing liquid are used : a) A suction in excess of 5 meters. b) A discharge pressure less than 7 meters. c) Hot water (over1200c) being handled without adequate cooling. d) Muddy sandy or gritty water being handled. e) The liquid being handled is other than water such as acid, juice or sticky liquids. v Pumps head-capacity curves can be classified as follows:

a) Steady rising head characteristic- Rising head- capacity characteristic, meaning a curve in which the head rises continuously as the capacity is decreased.

b) Steep rising head characteristic-A rising head-capacity characteristic in which there is a large increase in head between that developed at design capacity and that developed at shutoff.

c) Drooping head characteristic- Drooping head characteristic, indicating cases in which the head-capacity developed at shutoff is less than that developed at some other capacities. This is also known as a drooping curve.

d) Flat head characteristic. A head capacity characteristic in which the head varies only slightly with capacity from shutoff to design capacity. The characteristic might also be either drooping or rising. All drooping curve have a portion where the head developed is approximately constant for a range in capacity, called the flat portion of the curve.

v There is no clear-cut distinction between flat head & rising head characteristics.

However as a rule of thumb, curves that shows a 150% increase in head from the capacities of peak efficiency & shut off are called “steep rising” curve; those showing a

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10 to 25% rise are called “steady rising” curves & those with no more than 10% increase are called “flat”.

v Key Facts of Pumps: a) Coupling misalignment tolerance – Max: 0.075mm (3 thou) for flexible for both Parallel

and Axial, Max: 0.05mm (2 thou) for rigid (Same as shaft run out) for both Parallel and Axial.

b) Special Flexible Love Joy Coupling – Misalignment tolerance parallel 0.4mm, angular 1o (max.).

c) Gap between flexible couplings is approximately – two to three mm d) 1/3rd of the total lift is required to set for lift to couple in the vertical pump e) During starting other than Radial flow Centrifugal pump, the discharge valve can be

partial (or) full open. f) Maintenance of pressure alone is not an indicator to know the condition of a pump.

Measuring the flow at a given pressure can identify condition of a pump whether good or bad.

g) Warm up the pump before starting and the ∆T to be within 38oC between the pump parts and the liquid handle.

h) Oil level should reach slightly higher than the center of the lowest rolling element when the bearing is not rotating.

i) The temperature of any bearing in a centrifugal pump should not exceed 70oC during the operation.

j) The diameter of the suction flange and discharge flange are selected to keep the liquid velocity about 2.75 to 3.0 m/se. and 5.5 to 7.5m/sec. respectively.

k) The radial clearance between the impeller and diffuser vane tips varies between 0.75 to 3mm depending upon the impeller size.

l) 75 to 90% of Kinetic energy is converted to Pressure energy by the diffuser ring. m) Maximum acceptable TIR of Shaft is 0.0125 mm /300 mm (½s thou /ft) of shaft length.

But it should not be more than 0.025 mm (1 thou) in 300mm (one ft.) of length. n) A reasonable safe value for the tongue clearance in volute casing, still allowing good

efficiency is 5 to 10% of the impeller radius. Smaller the clearance will give higher efficiency. However, it produces larger pressure pulsation and will lead to impeller failure.

o) Heat in put to the system because of the pump is 0.0102MWth per Ampere. Eg: BFP Pump heat addition to the system = 0.0102 * 240 Amps. = 2.248 MWth.

p) Use a precision level to level the base plate or sole plate, side-to-side, end-to-end and diagonally to within 0.05mm per 300mm (0.002 inch per foot).

q) Pump Shaft differential expansion (i.e.) ∆L = L *α * ∆t Where L = Shaft length in inch. α = Co-efficient of thermal expansion (for Steel, 6.5 * 10-6 inch. /inch. /deg. F). ∆t = temperature difference in deg. F r) 2 to 4% of BHP is usually taken as Mechanical losses , which include the frictional

losses in the bearing, stuffing boxes etc. v 1 ml is equal to 37 drops for servo mesh 257 oil, 39 drops for servo system 68- oil.

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2. Seals & Packing

Gaskets v FUNCTION: To provide a tight seal in a rigid joint by supplying the necessary

resiliency so that leakage pathways are blocked. v WHY THE GASKET? Most flat faces, which appears flat enough to the naked eye,

would on microscopic examination reveal irregularities on the surface with crests and valleys.

v Basic requirements of Gasket materials: 1. Impermeability- Resists flow of fluid through the material. 2. Ability to flow into joint imperfections when compressed. 3. Maintains a seal in spite of age, variation in temperature. 4. Resistance to attack by the fluids and gases that it must seal. v Selection of a Gasket: The factors to be considered for the selection of Gaskets are: 1. Compatibility of the Gasket material with the fluid. 2. Pressure and Temperature conditions of the System.

3. The relationship of total installation bolt force to gasket seating stresses and hydrostatic end force.

v Preservation of rubber / elastomers / rubber expansion joint:

Coated with talcum powder and wrapped with black polythene sheet (to prevent Ultraviolet rays passing through) and kept in AC Room.

v Y Factor: When High Gasket Seating stress is achieved at assembly, better sealing

performance is achieved. This is the `Y’ factor. Gasket Seating Load

Gasket Seating Stress Y (PSI) = --------------------- Gasket Seating Area v M Factor: The Gasket factor (or) Maintenance factor at operating condition is the ratio

between the Residual Gasket Seating stresses to the internal pressure. Gasket Seating Stress Y `M’ Factor = ----------------------- = ----- Internal Pressure P

Radial lip seals

v Test has shown that maximum Lip Seal life is obtained when the shaft sealing surface is 8 to 20 inches in roughness. If the shaft is too smooth, it will not support a film. If too rough, it wears the seal lip.

a) Radial lip seals (Dynamic and Static) are primarily used to retain lubricants and exclude contamination.

b) The Seal functions at temperatures from 15oC-205oC.

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c) Advantages of lip seals are low cost, small space requirements and simple installation.

d) Lip seals recommended only for non pressure service and perform best in good lubricating media.

e) Lip will have narrow contact area about 1/16” (1.6mm) wide which, under pressure, causes extreme local heating and wear.

f) Materials of lip seals are acrylates (-29 to 149oC), nitriles (-54 to 107oC), fluro elastomers (-40 to 204oC), Silicon (-60 to 77oC) and TEF Fluoro carbons (-84 to 204oC).

g) Lip type seal is quite sealing upto 3000 hrs.

Labyrinth Seal a) Labyrinth seals are used mainly in high-speed applications where relatively high leakage

rate can be tolerated and simplicity is necessary. b) It does not require lubrication or maintenance. c) Leakage flow through inclined, stepped labyrinth is about 40% that of straight labyrinth

for similar conditions. d) Labyrinth Seal (high quality bronze) designed for 1, 00,000 hrs. equals to 11.4 years

of continuous operation.

Felt v It consists of fibers-wool and used as sealing material for the following reasons: a) A very common seal for low shaft speed limit if only 610 mtr. per min. (2000 fpm). It

scans satisfactorily seal upto 1210 mtr. per min. (4000 fpm) where shafts are hard smooth finish and where ample lubricants is present.

b) Oil storage capacity is largely a function of density and about 78% of the volume of a felt seal serves as oil storage.

c) In dry state it filters 99 to 100% of 0.7 microns size particles. When saturated in lubricants, even smaller particles are trapped and retained

d) Maintain constant sealing pressure and offer low friction. e) The usual temperature limits of felt are -51 to 121oC synthetic fiber felts can withstand

upto 204oC. `O’ Ring

a) The nominal pressure limit for `O’ rings, based on typical mechanical clearance is 1500 Psi (105Kg/cm2) and with backup ranges 3000 Psi (210Kg/cm2).

b) Elastomers ensure elasticity and return of the material to its original shape when a load is removed. This property is known as resilience.

c) ‘O’ ring softer compounds provide better sealing ability as the rubber flows more easily into the groove. Descending order of the `O’ ring material is to be considered as more softness - Natural rubber, Nitrile, Viton, and Silicon etc.

d) Harder compounds are specified for high pressure, to limit chance of extruding into the groove, and to improve wear life for dynamic service. Similar consideration is given to the temperature applications.

e) Shore A hardness from 50-70 are the most suitable for most `O’ ring application. f) `O’ ring materials have a Co-efficient of thermal expansion 10 times greater than that of

Steel. (I.e. Nitrile CTE is 6.2 * 10-5/oF and Steel CTE is 7.0 * 10-6/oF).

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v ̀O’ Ring installation and design: a) The Volume of the seal housing should be approx. 25% greater than that of the corresponding `O’ ring to compensate for the high degree of thermal expansion or possible swelling of the elastomer. b) Radial deformation – External Sealing:

Care must be taken to ensure that the `O’ ring rest, firmly on the bottom of the groove. When installed, the `O’ ring can expand by up to 6%.

c) Internal Sealing: The inner circumference of the `O’ ring must rest on the bottom of groove. Compression of up to 3% is permissible.

d) Generally `O’ ring grooves are 25% to 50% more wide as the dia.of `O’ ring. e) Maximum linear compression (Squeeze) suggested by manufacturers is 30% for static

applications and 16% for dynamic seals (upto 25% for small cross section diameters). Additional Squeeze deteriorates the compound in high temperature application.

f) Elongation or stretch should not normally exceed 5% of the Inner Diameter after installation. Excess stretch causes reduction in cross section result in rapid deterioration in high temperature application.

g) Surface finish Cylinder bore and piston rod = 5-15 micro inch. (r.m.s)

Groove Surface = 20-40 micro inch (r.m.s)

v Do not use Carbon Tetrachloride as a cleaning solvent. It causes deterioration of rubber seals.

v Generally Recommended O-Ring Lubricants by NMAC: O-Ring Material Recommended Lubricant Silicone Fluorinated oil (Krytax) or water Fluorosillicone Fluorinated oil (Krytax) or water Fluoroelastomers (i.e., Viton) Silicone based fluid/grease Natural rubber Silicone based fluid/grease Neoprene Silicone based fluid/grease Nitrile (Buna-M) Silicone based fluid/grease Ethylene Propylene Silicone based fluid/grease Urethane Silicone based fluid/grease Butyl Silicone based fluid/grease v General Lubrication Guidelines by NMAC Static seals: The lubricant is only necessary to aid in assembly. When applying lubricant to stationary seals a very thin film is all that is needed. You should not even see the lubricant on the surface except for the polish it gives to the O-ring. Remember, in some cases a little water is an adequate lubricant. Use this to judge how much lubricant to apply. Sliding Seals: Sliding seals require more lubricant than static seals, but not much more. Rather than a film, sliding seals require a thin coating.

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Dry Lubricants: Sufficient lubricant should be applied to give a dull gray finish to the surface after the carrier has evaporated.

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Mechanical Seal

v The run out of the shaft/shaft sleeve (i.e.) shaft deflection and shaft whip should be

limited to 0.05mm max. v In mechanical seal, the seal faces are right angle to the shaft centre line, therefore in

conventional language; this is called as end face mechanical seal. v Mechanical seal should be selected when PV values exceeds 15,00,000

Where P = Pressure to be sealed in PSI, & V = Shaft speed in feet per minute. v The accuracy of 1 Light Band is 29.4 * 10-5(0.000294) mm or11.6 * 10-6 inches.

v Sealing surface flatness and finish are important factors for mechanical seals to reduce

leakage and wear of seal faces. Surface flatness is to be below three light bands (less than 40 µinch) and surface finish is to be less than 5 micro inch rms.

v Make sure that the seal seat is perpendicular to a shaft within 0.001 inch TIR.

(TIR is total change in indicator reading). v Replace bearing if end play exceeds 0.05mm (0.002”) or radial looseness is greater

than 0.1 mm (0.004”). v Replace the shaft with a new one if run out exceeds 0.05 mm (0.002 inch) TIR. v Corrosion Selection of the material of mechanical seal parts based on the fluid being handled. The

fluid is classified into two categories viz. Corrosive and Non-Corrosive with respect to SS 316. Here the criteria of classification are based on the corrosion rate of less than 0.05 mm (2 mils) per year.

When the corrosion rate is greater than 0.05mm per year, double seals that keep the hardware items of the Seal in a neutral liquid should be selected to reduce corrosion. Stationary seal, which is exposed to the corrosive liquid, should be constructed of corrosion - resistant materials such as Ceramic, Carbon and Teflon.

v PV Factor: It is the product of seal face pressure and a linear rubbing velocity of a

mechanical seal. The seal face pressure is calculated using the formula: Pface = PBox * Balance Ratio and PV = Pface * V (Kg/cm2 * m/sec.) Higher the PV value of seal pair will give a longer seal life. PV Limits for Common Seal face Combination Seal face Mating face Max. lb/in2 ft/s Bar/met/sec.

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Carbon Tungsten Carbide 1000000 350 Carbon Ni-Resist 850000 300 Tungsten Carbide Silicon Carbide 500000 170 Balancing ratio is the ratio of mating area of both rings above the balancing line to the

total mating area of both rings. It can also be defined as the ratio of closing area to the opening area.

OD2 - BD2 | Where OD = Seal face outside diameter, Balance Ratio = ------------- | ID = Seal face inside diameter& OD2 - ID2 | BD = Balance diameter of the seal

v Rotating seal compression head is upto 5000 ft. /min (5.4m/s), more than this, compression head is in stationary.

v Normally, the flat seal rings have different hardness values and the soft one is lower

then the hard one. v Unbalanced Seal design (more closing force) is for low pressure application and its

balance Ratio is 1.25 to 1.35

Seal ID (In)

Shaft Speed (rpm)

Sealing Pressure (Psig.)

½ to 2 Upto 1800 175

1801 to 3600 100 Over 2 Upto 1800

1801 to 3600 50 v Partially Balanced Seal

a) Balanced Seal design allows good lubrication film between seal-faces suitable for high pressure application and its balance Ratio is 0.75.

b) For flashing hydrocarbons, where fluids with a vapor pressure greater than atmospheric pressure at the Service temperature, the balancing ratio is 0.80 to 0.85.

v Fully Balanced Seal (Floating condition) closing force and opening force are equal.

Hence balancing ratio is 0.5. v To ensure that the seal faces are always positively loaded, balance ratio of a mechanical

seal must be above 0.56, in practice is normally kept at 0.7 to the balanced seals. MAPS PHT circulating pump seal’s balancing ratio is 0.65.

v Seal Type and Arrangement

a) Multispring seals are normally used for clear lubricating and non-corrosive fluids free from solids.

b) Single coil spring seals are used for abrasive slurries and crystallizing as well as solidifying liquids.

v Double and Tandem Seal

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Difference between them is that the double seal has a pressurised barrier fluid and tandem seal (Secondary seal serves as backup to primary) has non-pressurised barrier fluid.

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Packings

v Packing failure: Approximately 70% of packing failures result from human errors (i.e)

Unsuitable material selection, improper fittings, neglecting to test reassembled valve etc. v Compression packings are used to throttle leakage between a sliding, moving or rotating

parts and a stationary one. v Therefore Compression packing creates a seal, when squeezed, the packing flows

outward to seal against the bore of the box and inward against the moving shaft/stem. v Cotton grease lubricated packing to be used for Low temperature 93oC (200oF) and

Low speed pumps. v Asbestos graphite/Mica coated for High temperature and high speed pumps.

v End cutting 45o for valves and 90o for pumps.

Saggregation of packing while assembling is to be done as follows. 45o saggregation is to be done if more than 8 packing. 90o saggregation is to be done if more than 4 packing. 180o saggregation is to be done if less than 4 packing

v Endless packing for very high pressure. v Selection of packing depends on shaft size, material and hardness, shaft speed, pressure

and temperature on the stuffing box and PH of the fluid to be sealed. v Ensure proper location of Lantern ring while assembling. v Pump shaft TIR at gland location should be within 0.05 mm and should have smooth

finish. v Gland loading has to be done while the pump is in operation. Otherwise it may result in

Excess loading and lead to burning of packing after starting.

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3. Power Transmission Components v KEYS AND KEYWAYS The factor of Safety for calculating the key dimension is taken as 1.5 for steady torque and increased upto 2.5 for fluctuating torque. Eg: If torque is 1 Kgm, the key is designed to 1.5 kgm for Steady load. • Square Keys: a) If a Square key and the shaft were to be of the same material and of equal strength, the

length of the key would be 1.23 times the dia. of shaft. b) Parallel (non prestressed) keys are made Square (width = height) upto width = 38 mm

(1½ inch), the width = ¼ Dia. of Shaft. For larger key width, the key height is usually smaller than width.

c) The depth of the key way in the shaft and in the hub usually is equal to ½ height of the key.

• Rectangular Keys:

a) If a rectangular key and a shaft are made from the same material, for equal strength, the size of the key in general will be width of D/4 and a height of 3D/16 and length of 1.57D.

b) As per IS 2048 Depth of key way is 60% and 40% in the shaft and hub respectively. c) As per IS 2710 the depth of key way is 70% and 30% in the shaft and hub respectively. d) Key to hub top clearance is 0.2 to 0.5mm for key thickness of 2mm to 50mm thick. v Splined Shaft a) Compared with keys, splines have the advantages of self centering. b) For a given torque transmission, a splined shaft is less weakened than keyed shaft. Thus it can transmit higher torque. v As per BS 4506 the conicity of a conical shaft ends is1:10(corresponds to (d1-d2)/

(L/2) = 1/10} where d1 = major dia, d2 = dia at L/2 and L = length of conical shaft.

`V’ BELT v General: a) Generally less than 186.5 KW (250 HP) and for low speed application. b) ‘V’ belt drive has transmission loss about 5% and as such the prime mover has to cater for the same. c) ‘V’ Belt generally for short distance and medium torque transmission. Nominal dimensions of Standard `V’ belts Belt Section Top Width in mm Thickness in mm

A 13 8 B 17 11 C 22 14 D 32 19 E 38 23

d) Belt top width is approximately 1.6 times the height of belt.

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e) The standard angle between the sides of a `V’ belt is 40o. f) Belt life at temperature above 82ºC (180ºF) and below (51ºC) –60ºF is signification shortened. v CONSTRUCTION: Basically, a V-belt consists of five component sections. a) Load carrying section: It is in form of cords arranged in a single or multilayer construction. The cords may be made up of rayon, nylon, and steel or glass fiber. They perform the purpose of transmitting load through the belt. b) Cushion section: It keeps the cords of load carrying section bonded in position between top tensile section and bottom compression sections; it also absorbs some of the shock during varying load conditions. c) Flexible section: The top rubber section, above pitch line carries the tensile stresses as the belt flexes around the sheave. It also helps in positioning the tensile member for better alignment of the cords and equalizes cord tension under load. d) Compression section: The compression section located below the pitch line serves two functions. It is a platform for supporting the tensile section, and it transmits through its side walls the wedging pressure from the tensile section to the pulley groove. e) Cover or jacket: It serves as a protection of all other parts of the belt and prevents them from dust, moisture, grit, oil etc. v Sizing of `V’ Belts a) C-2032 (80”) - 50 indicates the belt cross section, the nominal pitch length and

match number. One unit above (or) below 50 match number represents a deviation of 2.5mm from nominal pitch length and the grading number will increase or decrease, as the length is more or less. For example C2032-51 and C2032-49.

b) “V” belt designated, as C240 will have 240 inches (6096 mm) is the length of belt. c) Belt pitch length is the length of the belt at the neutral axis of the belt. This neutral axis

is located approximately 2/3 of the distance from the bottom (narrow portion) to the top (wide portion) of the belt.

v Belt matching and Length Coding: (Fenner product)

a) Fenner produced belts upto 150” (3870mm) `PB’ construction belts does not have code number on the belts.

b) Above 150” (3870mm) belts needs to be fitted in matched sets. Make sure that the matched sets fall within the following limits. Belt pitch length Code Spread Below 3870mm (150”) No code 3871-9140mm (360”) 4 consecutive codes 9141mm and above 5 consecutive codes

c) After obtaining a correct matched set of belts, check the pulley for obvious signs of wear before fitting them.

d) PB (Precision Belts) is to be used instead of matched set of belts. v Slip in belt drive is difference between the linear speed of the rim of pulley and the belt

on it.

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v Belt tension check: A belt that is too loose will slip and cause heating and wear. A belt that is too tight may overload the bearings, leads to misalignment and can consume extra horse power.

a) With moderate thumb pressure i.e., 1 kgf applied to a belt at mid point between unsupported 1220 mm (48 ") length the deflection should be equal to its own thickness or Deflection 0.4 mm per 25 mm (1/64" per inch) span.

b) This method requires experience in getting the proper feel. Slap the belt sharply with the hand. A properly tensioned belt will feel springy and alive. If the belts were too tight or too loose it would not spring.

c) A quick check to determine if belt adjustment is proper may be made by observing the slack side of the belt for a slight bow when the unit is in operation.

d) Deflection -16mm per metre of Centre Distance Force at the centre of the belt should be given as follows

`V’ Belt Section A B C D E Kilogram (Kgf) force required at centre

1.0 to 1.5

2.0 to 3.1

4.1 to 6.1

7.1 to 10.7

12.2 to 18.3

v Pulley: a) Angle of belt contact on small pulley should have a) 150o for flat belt drives, b) 120o for ‘V’ belt drives b) Shaft axis out of parallelism should not be more than 0.5 mm / 100 mm run. c) Pulley off set should not be more than 1 to 2 mm per meter. d) Limit of cast Iron pulleys max. speed in rpm corresponding to 6500 fpm. (33m/s). e) Maximum efficiency is obtained at speed between 20 and 25m/sec. f) Pulley’s groove surface roughness Ra = 1.6µ for peripheral speeds upto 10m/sec. and Ra = 0.8µ for peripheral speeds over 10m/sec. v Due to increased bending and windage losses combined with the loss due to wedging

action, the efficiency of drive is about 3% lower than that for flat drives.

Pulley Dia. * 3.14 Belt RPM = ----------------------- * Pulley RPM

Belt Length v Aligning `V’ Belt drives: a) Ensure that the bearings on both machines are not damaged. b) Inspect the condition of belts that they are not cracked, glazed, stretched etc. c) Check for any `soft foot’ conditions between the machinery feet and base plate at all of the hold down bolts. d) Check the wear of the `V’ in the sheaves with an appropriate wear indicator. e) Ensure that the face out does not exceed 1 thou/6” of sheave diameter. f) Ensure that the radial (rim) run out does not exceed 0.125 mm (5 thou.). g) Run a straight edge on both the pulley faces and check the gaps at all the contact points with help of a feeler gauge, it should not be more than 0.025 mm (0.001”). Then rotate both the pulleys by half revolution and recheck the above gap. Make correction if necessary.

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h) If the center distance between the pulleys is more than 6 feet, use the straight edge /a taut wire or cord.

v HOW TO MAKE V-BELTS LAST LONGER: a) Keep aligned, b) Maintain correct tension, c) Replace V-belts in complete, d) Inspect sheaves regularly, e) Keep belts clear, f) Protect and store belts properly, g)

Check for correct position of belts in grooves v Foundation:

Thumb rule of Concrete weight is equal to three times of the machine weight for rotating machine and five times for reciprocating machine.

Coupling Alignment

v Objective of Accurate Alignment: a) Reduce excessive axial and radial forces b) Eliminate the possibility of shaft failure c) Minimize the amount of wear in the coupling d) Minimize the amount of shaft bending e) Reduce the power consumption v Causes of Misalignment: a) Soft foot (Leveling of foundation base) short or long leg of machine. b) Corrosion and Erosion of Foundation c) Pipe strain – Forces transmitted to the machine by pipe or support structure. d) Thermal Expansion – Most machines aligned in cold e) Machine vibration f) Direct coupled machines are not properly aligned. g) Poor workmanship. v Effect of Misalignment: a) Most experts agree that 50% of Machinary problems are caused by misalignment. b) Increases 2-17% power consumption. c) Causes vibration, which destroys the critical parts such as bearings, seals, gears,

couplings etc. v Recognition of Misalignment: a) Excessive radial and axial vibration b) Repetitive/Premature of bearing, seal, shaft and coupling elements. c) High casing temperature at or near the bearing or high discharge oil temperature. d) The Coupling is hot while running and soon after the Shutdown.

Face and rim method of Alignment v Checks before coupling alignment: a) Smoothness of coupling surfaces (Face & Rim) b) Trueness of coupling bore (Concentricity and angularity) by measuring face out and run

out.

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b) Difference in outside Diameters (OD) of the coupling halves c) Checking `Bracket Sag’: Whenever every mechanical brackets and dial indicators are

used to measure shaft positions, `bracket or bar’ sag must be measured and compensated for.

v Rim and Face method Alignment Calculation:

Radial Reading Radial Misalignment = ---------------- 2 Face dial Reading Angular Misalignment = ----------------------------- Distance traveled by the dial v Advantages & Disadvantages a) Can be used where one of the shafts cannot be rotated during alignment. b) Difficult to obtain accurate face readings if motor has axial float. v Reverse Indicator Method – Advantages & Disadvantages a) More accurate than face and rim b) Negligible effect of axial float of motor c) Could not be used on closed – coupled shaft where the distance between the

couplings is less than the diameter of coupling on which the dial is reading. d) Difficult to obtain reading on extremely long shaft.

v The suggested tolerances can be when the machinery manufacturer’s recommended tolerances are not available.

RPM OFFSET ANGULAR Upto 1000 0.13 0.10 1000-2000 0.10 0.08 2000-3000 0.07 0.07 3000-4000 0.05 0.06 4000-5000 0.03 0.05 v General Rule for Good Alignment a) Ensure Machine base and Machine bottom clean, free from rust and burrs. b) Use only clean shims. c) Check/Correct the condition of soft-foot before starting the alignment. d) Always use the correct tightening procedure of the holding down bolts/nuts. e) Determine the amount of indicator sag before starting the alignment. f) Always try to position the stem of the dial indicator perpendicular to the surface

against which it must rest. g) Lift the machine to the height absolutely required adding or removing shims. h) Use Jack bolts for horizontal offset and angular misalignment and to hold the machine

in place while shimming (If not, provide this for large machinery before starting the alignment).

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v Hot Alignment a) One way of achieving hot alignment is to premisalign by providing a calculated

misalignment between motor and fan in the cold condition. b) As a thumb rule, the thermal expansion of a Pedestal shall be approximately

1.0mm/1 meter/100oC rise. v Vibration Spectrum Analysis

a) Angular – Axial vibration at 1* RPM b) Offset – Radial vibration at 2 * or 3 * RPM

c) Harmonics (3*-10*) generates as Severity increases d) If the 2* amplitude more than 50% of 1* then coupling damage starts.

e) If the 2* amplitude more than 150% of 1* then the machine should be stopped for correction.

v Vibration Phase Analysis a) Angular – 180o phase shift in the axial direction across the coupling.

b) Offset – 180o phase shift in the radial direction across the coupling. 0o to 180o phase shift occur as the sensor moves from horizontal to the vertical direction of the same machine.

c) Skew – 180o phase shift in the axial or radial direction across the coupling.

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4, Bearings and Lubrication

Bearings v Journal bearing clearance is 0.025 to 0.0375/25.4 mm (1 to 1.5 thou/inch) dia. of shaft.

For proper operation it should never exceed 0.075/25.4 mm (3 thou/inch.) dia. of shaft. v Replace all bearings and running joints whose clearance has increased more than 100

percent of the original. v The rated life of a bearing changes inversely as cube of load. v Standard Bearing VS Precision Bearings. 6209 6209 YC 78 Standard Bearing Precision Bearing Bore Tolerance +0 +0 -0.0005” -0.0002” OD Tolerance +0 +0 -0.0006” - 0.0003” Width (Inner Ring and +0 +0 Outer Ring) -0.005” -0.005” Radial Run out (Inner Ring) 0.0006” max. 0.0002” max. Radial Run out (Outer Ring) 0.0014” max. 0.0004” max. v Bearing Fit:

a) Ring which rotate must have interference fit with shaft /housing. b) SKF’s recommendation for press fits is a minimum 80% metal-to-metal contact between mating parts for existing applications. New OEM (Original Equipment Manufacture) fits should have 95% metal-to-metal contacts.

v The inner and outer rings of rolling contact bearings are hardened (Rockwell C 60 to

65) Carbon Chromium steel (SAE 52100). The composition is carbon 1%, Chromium 1.5%, Iron 87%, Manganese 0.35%, Silica 0.3%, Phosphorus and Sulfur 0.025% each.

v Bearing Life: The life of a bearing is generally expressed in millions of revolutions. Life

of ball/roller bearing (L) is inversely proportional to the K power of the radial load (F). i.e. L α 1/Fk. For ball bearings the value of constant K is 3 and for roller bearings it is taken is 3.33.

v Minimum load required for bearing is Fm=0.02*C to avoid vibration because rolling

action. Where C = Basic Dynamic Load Rating. v Bearing failure: Improper lubrication - 43%, Improper mounting - 27%

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a) Contamination is also a leading cause of premature bearing failure. Hence relubrication, proper mounting and sealing are the critical actions to ensure that the bearing does not fail prematurely.

b) The grain structure changes, when the temperature exceeds 1200 C and hence hardness also changes. Loss of 2-4% hardness reduces the bearing life by 50%. Hardness of outer and inner ring is 54 to 59 HRC, and rolling element is 59 to 64 HRC.

c) Storage and handling: Bearing can be stored in their original packages for years provided relative humidity in the storeroom does not exceed 60% and there are no great fluctuations in temperature.

v Bearing Mounting:

• More than 60 mm bearing required temperature mounting • Oil bath heating is not advisable because a) Contaminated oil. b) Oil flashes risk is involved. c) Should use new oil all the time. d) Flash point of oil should have more than 200’c • Induction heater: a) Temperature mode: - cut off at 110’c and demagnetize with in 5 sec. b) Time mode: - cut off at 60 min.

v The raceways are accurately ground in the rings to a very fine finish (16µ inch or less). v If actual RPM is 70%of speed rating we have to go for C3 clearance bearings. v Ball bearings function on point contact. Thus suited for higher speeds and lighter loads

than roller bearing. v Roller bearings function on line contact. They take heavy loads including shock, but are

at lower speed. v Doubling the misalignment force reduce the lifetime to 1/8th, three times the force reduce

the lifetime to 1/27th of the original lifetime. v Preload- thump rule- rotate by ¼ turns loose after tight. Check by dial gauge also. v Angular contact ball bearings:

a) Designed to support combined radial and thrust loads or heavy thrust loads depending on the contact angle magnitude. Bearings having large contact angles can support heavier thrust loads.

b) Tandum mounted for one direction load,. c) Back to back for both direction load, more span and stiff arrangement. d) Face to face for both direction loads, less span, less stiff and can take slight misalignment. e) Angle of contact 32o for Double row ball bearing and 45o for single row ball bearing. v Double row self aligning ball bearing:

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a) Because of the large track radius in the outer ring load carrying capacity is less than single row rigid ball bearing and thrust load capacity is very small.

b) Self-aligning ball bearing can take misalignment up to 30 arcs from vertical centre line.

c) The Self aligning feature should not be abused, as excessive misalignment or thrust load (10% of radial) causes early failure.

v Single row deep groove ball bearing: a) Shield/sealed bearing will have reduction of speed factor by 0.7 and 25 to 30% of the space is filled with Lithium grease. b) Filling slots on both races provide larger number of ball can be inserted than standard

type bearings, which increase the load carrying capacity, but reduce thrust load. c) Ball size of a ball bearing is approximately equal to (outside dia. - inside dia.)/4

i.e. (D-d)/4. d) Inner and Outer race track radius is approximately 4% greater than ball radius to

achieve point contact. e) Normally used for radial and thrust (Maximum 2/3 of radial) loads. f) In deep groove ball bearing axial clearance is five times more of radial clearance. v Double Row deep groove ball bearing: a) This bearing provides heavy radial and light thrust loads (because of filling slot). b) It is approximately 60 to 80% wider than a comparable single row bearing. v Single row rigid roller bearing: a) It will take (approx.) twice the radial load of similar size ball bearing. b) The approximate length/diameter ratio of rolling elements ranging from 1:1 to 1:3. v Needle Bearings: a) The bearings have rollers whose length is at least 4 times their diameter. b) They are most useful where space is a factor and are available with or without inner race. v Compliant Bearing: a) Greater load carrying capacity than equivalent rigid surface bearing. b) Ability to tolerate misalignment, shaft bending, eccentricity, inadequate lubrication etc. c) Elastically deform equal to or more than the lubricating film due to fluid pressure

induced in the film. d) Tolerates sand and silt contamination without scoring the shaft. e) A Continuous coolant flow of two gallons (9.1 litres) of water per minute per inch.

(25.4mm) of bearing is recommended as a rough working rule. The flow of cooling water should restrict temperature rises to about 3oC (Maximum).

v The limiting speed of rolling element bearing in rpm, the oil lubricated bearings is 1.25

times higher and thrust bearings are 1.4 times higher than grease lubricated bearings. v Contamination is also a leading cause of premature bearing failure. Hence relubrication,

proper mounting and sealing are the critical actions to ensure that the bearing does not fail prematurely.

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v Large bearings are oil bath heated to 80 to 90oC above ambient temp, but should not

reach 120oC. v Kingsbury thrust bearing can take both directional thrust load whereas Mitchel thrust

bearing can take one directional thrust load. v Lead wire to measure the bearing clearance should not be more than 0.010” (0.25mm)

thicker than the estimated bearing clearance. v When D is the diameter of the journal, the frictional horse power increases by D2. v White Metal Bearing:

a) Tin base have better corrosion resistance easy for bonding, suitable for impact and reciprocating load.

b) Fatigue failure because of cyclic load, wiping because of bearing over load and insufficient rotational speed to form a film and loss of lubricant.

c) Thinner the babbit layer, the greater the fatigue resistance. Thicker layer provide good conformity and embed ability.

d) Tin base babbit standard eg: ASTM-B-23-Alloy-2 (Tin-90%, Antimony-7%, Copper-2% Lead - Traces) – Std.

Lubrication

v The first principle/right principle of lubrication is to put the right lubricant in the right place at the right time.

v 2Z, 2RS (shielded, sealed) bearings shelf life of lubricant is 5years. v A little water (0.02%) in the bearing oil can reduce rated bearing life by as much

as 48%. v Grease (servo gem 3, servo gem 2, LMM) lubrication bearings for normal speed and

low temp. application. v Oil for high speed and high temp. application. v Required film thickness is determined by1.Temperature, 2. Speed of rotation, 3.Load v Grease: Calcium soap (Ca) - up to 60oC Higher quality like calcium - lead soap upto 120oC Sodium soap (Na) - higher temp. Synthetic sodium grease - upto 150oC Lithium soap (Li) - higher temp. range than sodium soap Synthetic grease (ester, silicone) Offer low frictional resistance at low temp. even - 70oC

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v The upper and lower temp. limit for grease is approximately + 140oC and - 30oC. (General purpose).

v The percentage of the oil in grease is usually about 80%, but can range from 70% to

97%. v Grease consistency - means the degree of stiffness, which the grease possesses.

NLGI - National Lubricating Grease Institute. This is based on the degree of penetration achieved by allowing a standard cone to sink into the grease of a temperature of 25oC over a period of 5 seconds. Subsequent measurement of the depth of penetration is at each 1/10 of mm. Grease Classification according to temp. & load

Temp. appl. NLGI Index Low temp. grease (LT) -50 to 50oC 0 - 2 Medium temp. grease (MT) - 30 to 110oC 2 - 3 High temp. grease (HT) +150oC 3 EP grease (sulfur, clarion) - 30 to 110oC 2

v Quantity of grease is to be filled 2/3 volume of the left out volume inside the Plummer

block. v Relubrication Guidelines:

a) Regreasing quantity in grams | where D = Outer diameter of the bearing G = 0.005 D B | B = Width of the bearing

b) Normal grease guns discharges 5grams of grease in one stroke

v When Relubricating with new grease, make sure the old and new grease are

compatible. If there is uncertainty, try removing all traces of the old lubricant without using cleaning solvent.

Guide lines as per NTN for Pillow Block Bearing: dn value, Bore (mm) x speed (rpm)

Environmental Conditions

Operating Temperature, oF

Relubrication frequency Hr Period

40,000 and below Ordinary 5-176 1550-3000 6-12 months 70,000 and below Ordinary 5-176 1000-2000 3-6 months 70,000 and below Ordinary 176-212 500-700 1 months 70,000 and below Very dusty 5-212 100-500 1 wk-months 70,000 and below Exposed

to moisture 5-212 30-100 1 day-1 wk

v Oil life:

If operating temperature is with in 300 C- life is 30 years. Every rise in 100C- life reduces to half.

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60 to 700C -1 to 2 years. 1000C- only 3 months.

v Oil change time:

Up to 50 oC - once in year 100oC - once in quarter 120oC - once in month 130oC - weekly

v Oil Quantity: For high speed at high temperature application regular feeding of small

amount oil is required. For moderate and low speed bearings oil level to be maintained to the centre of the lowest ball or roller.

v Troubleshooting: Operating equipment has great tolerance for lubrication property

changes. Greases can change a penetration grade or two, oil may increase in viscosity by half or so, and most equipment will function serenely without a noticeable difference. But if there is equipment distress it may be indicated by: a) Temperature increase, b) Output decrease, c) Noise, d) Change in vibration pattern, e) Visual distress (leakage)

When any of these symptoms occur, corrective action must be taken. However, checking lubricants based on a preventive maintenance schedule is also a good idea.

The first line of surveillance with lubricants, or the first step in isolating troublesome components is simple on site testing. A lot can be learned from looking at and smelling the stuff. It is only when a flag is raised by these on-site tests that further examination (see “Lube Testing”), or a complete change out may be necessary. This, of course, is in addition to the change-outs required by scheduled maintenance or recommended by equipment supplier.

v SENSOR TESTS

APPEARANCE? Look at the oil in a clean, dry sample bottle. Clear and bright? Or hazy and cloudy, indicting water contamination? Suspended material? Is it typical of the product? Basically, how des it compare with the original? COLOR? This is useful for light-colored lubricants. How does the lube compare with the original? Dark? This could indicate oxidation, possibly at high temperatures. ODOR? Compare carefully with the original. Oxidized oils and greases have “burned” or pungent odors. The same is true of irradiated lubricants - Odors show up by 108 rads. CONSISTENCY CHANGES? Comparative tests can also be effective here. Just observing the flow in an inverted bottle will suffice for oils (make sure the temperature of the original and used oils are about the same). Greases are a lot more complex. Stirring the product with a knife or spatula gives an idea of consistency. Feeling the product between thumb and forefinger is also revealing. Remember ---- these are all

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relative tests – you must have a sample of the original grease or oil with which to compare the used product.

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5. Piping

v For forged Elbows: a) Radius of short radius elbow is 1 time the nominal pipe diameter. b) Radius of long radius elbow is 1½ times nominal pipe diameter. v HDPE pipe - High Density Poly Ethylene pipe and PVC pipe - Poly Vinyl Chloride pipe. ERW Pipe - Electric Resistance welded pipe – Cheaper. Seamless pipe - Manufactured by cold drawing, extrusion process, hot rotary piercing processes. No welding. v As per ASTM (American Society for Testing and Material). Pipes are

distinguished based on weight of pipe is given as follows.

Specification Size as per wt. Schedule No. Equivalent ASTM-A53 Standard (`S’) wt. Schedule - 40 Extra Strong (`XS’) wt. Schedule - 80 ASTM-A120 Double extra strong Schedule - 160 (`XXS’)

v Pipe weight per foot = 10.68(D-t) * t lbs D = Outside diameter of pipe in inch. t = Wall thickness of pipe in inch.

v Weight of standard piping material is as follows. Low Carbon Steel - 0.2833lb/cu.inch Austenitic Stainless steel (300 Series) - 1.02 lb/cu.inch

P (M ax.) v Schedule No. = --------- * 1000

S (Max.) P (Max.) = Maximum permissible internal fluid pressure in PSI.

S (Max.) = Maximum permissible allowable stress in PSI of the material. For e.g.: If maximum stress of pipe material is 15000 psi, and with a pipe of sch-40,

the max. Permissible fluid pressure will be 600 psi. 40= (P/15000)*1000

Therefore P=40*15=600psi. Grade A - Low Carbon Steel Grade B - Medium Carbon Steel

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Grade C - High Carbon Steel v Standard size of pipes: (For C.S & S.S): Diameter of 12” and less has a nominal size

and wall thickness varies as per Schedule No.

Nominal Pipe Size Nominal Outside Diameter

Sch. 40

Sch. 80

Inch mm Inch mm Inch mm Inch mm ½ 12.700 0.840 21.336 0.109 2.768 0.147 3.734 ¾ 19.050 1.050 26.670 0.113 2.870 0.154 3.912 1 25.400 1.315 33.401 0.133 3.378 0.179 4.547

1-1/4 31.750 1.660 42.166 0.140 3.556 0.191 4.851 1-1/2 38.100 1.900 48.260 0.145 3.683 0.200 5.080

2 50.800 2.375 60.325 0.154 3.912 0.218 5.537 2-1/2 63.500 2.875 73.025 0.203 5.156 0.276 7.010

3 76.200 3.500 88.900 0.216 5.486 0.300 7.620 3-1/2 88.900 4.000 101.600 0.226 5.740 0.318 8.077

4 101.600 4.500 114.300 0.237 6.020 0.357 8.560 5 127.000 5.563 141.300 0.258 6.533 0.375 9.525 6 152.400 6.625 168.275 0.280 7.112 0.432 10.973

v Over 12” is based on the actual outer diameter and wall thickness is specified. v Mild steel (M.S) Pipe sizes are graded as Light, Medium and Heavy. v The head loss due to pipe friction increases approximately as the square of the liquid

velocity in the pipe line. Hf1/Hf2 = (V1/V2)2 Where Hf1, Hf2 = Head loss due to the condition of 1 &2.

V1, V2 = Velocity of the fluid at condition 1 & 2. v Double the flow increases the head loss four times in the pipe. v Double the pipe size increases the internal area by four times. v The Co-efficient of expansion for any grade of Iron or Steel is approximately 0.000007

inch. degree F/inch length. For example, if the temperature of a steel pipe is raised by 400oF, its length will increase by about (400 x 7 = 2800) 0.28 inch/100 inch. length.

v Pipe Corrosion/Erosion wall thinning limit is 12.5%. v Pipe Bending: a) Bends whose radii range from 3 to 5 times, the nominal pipe diameter will offer the least

pressure drop. b) The minimum radius of Curvature in cold bending and hot bending without filler should be at least 4 and 3 to 3.5 times OD of the pipe respectively.

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c) Thinning: In every bending operation, the outer portion of the bend (extrados) stretches and the inner portion (intrados) compresses. The Codes require that the wall thickness at the extrados after bending be at least equal to the minimum wall thickness required for straight pipe. The wall thickness (schedule) should be selected accordingly.

c) Ovality: The degree of ovality is determined by the difference between the major and minor axes divided by the nominal diameter of the pipe.

Dmax - Dmin

Ovality = ---------------- * 100 Where Dmax = Maximum Diameter Original D Dmini = Minimum Diameter Where the bend is subjected to internal pressure, the pressure tries to reround the cross section by creating secondary stresses in the hoop direction. Some codes consider an ovality of 8% acceptable in this case. Where the bend is subject to external pressure, the pressure tries to collapse the cross section. The ASME B31.3 code recommends a 3% maximum ovality.

v Carbon steel piping is usable upto 482oC. But it is limited by strength consideration as,

above 425oC permissible working stresses fall so sharply that its use is no longer economic.

v Pickling is done to remove mild scale from the surface of components. Minimum inside

dimension of pickling tank shall be 7.8 - 9 meter long, 1 meter deep and 1.4 meter side. a) Picking of carbon steel pipes will be done with the concentration of acid approximately

15% by weight of H2SO4 and 0.10% of inhibitor corobit-1001 at 49 to 55oC for about 10 to 15 minutes. Neutralise with 2% Caustic Soda solution for about 5 to 10 minutes.

b) Degalvanising (removal of zinc coating) of G.I pipe ends for welding of GI pipes will be done with concentration of acid approximately 8% by weight of H2SO4 and 0.10% inhabitor Corobit. 80mm shall be dipped in the acid bath for about 45 - 50 minutes. Neutralise 2% NaOH solution for 5 to 10 minutes.

v Pipe Insulation: The reason for insulating the pipe is to minimize the heat loss from the surface. a) According to the U.S Department of Energy’s Best Practices Steam Program,

Mechanical insulations should be used on any surface over 120oF (49oC). b) Potential Saving from Insulation application and upgrades may reduce fuel consumption

any where from 3% to 13%, according to the U.S DOE’s Industrial Assessment Center Program.

c) Installation: Two prime considerations are “Whether the insulation is dry and snugly fitted and whether there is enough of it”, suggests Don Wulfinghoff, author of the Energy Efficiency Manual. v Types of Insulations: a) Expanded polystyrene type SE (Self extinguishing) used on cold carbon steel Piping, G-I ducting and cold stainless steel piping and equipment. Thermal conductivity or “K” value is 0.03526 Kcal/hr. m.oC. at 50oC mean test temperature.

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b) Mineral wool (No glass wool) used on hot carbon steel and stainless steel piping and equipments “K” value is 0.077 Kcal./hr. moC at 300oC mean test temperature. This is suitable for use upto 600oC. c) Calcium Silicate used for turbine and associated equipment. “K” value is 0.077 Kcal/hr.m.oC at 300oC mean test temperature. This is suitable for application upto 600oC. v The pipe supports shall be designed to allow free expansion and contraction of pipe

without causing excessive strains in pipe, anchors or supports. v Flanges: a) A flange with raised face should never be joined to one with a plain face. b) Flanges with 1/16” or ¼” raised face may be faced smooth or finished with concentric

or spiral grooves not over 1/32” deep, 16 per inch. for cast iron and 32 per inch. for steel.

c) Slip-on welding flanges limited service pressure is 300 psi d) The internal dia. of Socket weld flanges should be 1.5 mm (1/16 inches) larger than the outer diameter of pipe. e) Flange bolt holes - For ½” and 5/8” bolts, the dia. of holes should be 1/16” larger. For bigger size of bolts, the dia. of holes should be 1/8” larger than the dia. bolts. f) Pressure temperature Rating of Flanges: Standard flanges may be used at pressure above the rating pressure for working temperature below 850oF (455oC).

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6. Valves and Actuators

v Control Valve: Valves performing a regulation function are normally referred to as

Control valves. A Control Valve can be open or closed or at any position in between as determined by the Control scheme.

v Trim: Valve trim in general, is all removable parts of the valve in contact with the

process fluid. v Valve Characteristic: Relationship between the travel of the valve closing element and

the corresponding flow through the valve is called valve characteristics.

v Inherent flow characteristic: The flow through the valve is pressure dependant.

However the valve manufacturer does not know the pressure differential across the valve after it is installed in a system. That is why valves are tested by the manufacturers and flow characteristic produced at a constant pressure differential. This characteristic provided by the manufacturer is called inherent flow characteristic.

v Valve gain or Sensitivity: It is defined as the ratio of the change in flow to the change

in travel when there is a constant differential pressure across it. In reality the gain is the slope of the valve characteristic.

v Quick opening characteristic: The Quick Opening characteristic produces the

maximum change in flow at low valve travels with a nearly linear relationship. Further increases of Valve travel yield sharply reduced changes in flow so when a valve is reaching to the fully open position, the change in flow approaches zero. This type is used mainly for on-off service. The majority of gate valves have this characteristic.

v Linear flow characteristic: The linear flow characteristic produces flow directly

proportional to the Valve travel. The Valve gain will be constant at all flows. The linear characteristic valves can be kept approximately constant because this makes the flow-rate proportional to the valve travel.

v Equal percentage characteristic: The equal percentage characteristic also known as

parabolic produces equal percentage changes in the existing flow for equal increments of valve travel, when the valve plug, disc (or) ball is nearly closed and the flow rate is low, the change in flow will be small. At large flows/ openings, the change will be large. An equal percentage valve will exhibit a low gain at low flows and a large gain at large flows.

Valves with an equal percentage flow characteristic are generally used on applications where a large part of the pressure drop is normally absorbed by the system itself and a relatively.

Small part is available at the valve. These valves are also used where highly varying pressure drop conditions are expected.

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Modified parabolic characteristic: It falls between the equal percentage and linear characteristics. This characteristic also produces an increasing gain with increasing valve openings. Modified parabolic valves are sometimes substituted for equal percentage valves. Mainly butterfly, ball and plug valves and even some gate valves produce this type of characteristic. Some important points: • Valve opening increases the flow through the Valve and lowers the pressure on the

upstream side of the valve (because system friction losses increases with flow) • If the valve discharges to atmosphere, the discharge pressure stays constant. • If the valve discharges into a piping system, the discharge pressure tends to raise, again

because of the system friction losses. • The max. flow rate of steam or gas flowing through a given valve at a given position and

subjected to a given pressure differential increases with the valve inlet pressure because fluid density rises with pressure.

• Incorrect selection of a valve can lead to turbulent flow and cavitations. Turbulent flow will increase system pressure losses and can increase erosion in the system. Cavitation can severely damage valves and pipe work.

v Carbon and alloy steel valves, forged valves predominate in the smaller sizes, and cast

valves in the larger sizes.

v SAFETY&RELIEF VALVES: a) Generally Safety/Relief Valve blow off set pressure is 10% greater than the

Working pressure and Reseating pressure should be less than 5% of the set pressure. b) Safety Valves: Safety valves are designed to have a full opening pop action to provide immediate relief. Section VIII of the ASME Code requires these valves. Capacity, overpressure and blow down for safety valves are specified in the code. Safety valves are usually employed to relieve excessive pressure build-up, caused by gases (compressible fluids). Set pressure opening tolerances for Safety Relief Valves Up to 70 PSI + 2PSI 71 to 300 PSI + 3% of set pressure 301 to 1000 PSI + 10 PSI

> 1000 + 1% of set pressure Ø According to the Indian boiler regulations, the essential requirements of any Safety

valve is that its area should be sufficient to discharge the steam as quickly as it is generated with rise in pressure not more than 10% of the safety valve blow off pressure.

Ø The blow off pressure of a boiler safety valve is 106% of boiler working pressure. c) Relief Valve: Relief valves are used to relieve excessive pressure build-up

caused by no compressible fluids. These are designed to open slowly with increase in initial pressure. These valves do not have a code design.

Liquid – Relief valve reach their rated capacity at no more than 25% over pressure. Up to 70 PSI + 2 PSI

Ø 70 PSI + 3% of set pressure v Safety & Relief Valves In gas and vapour valves, static pressure opens the disc and

dynamic force keeps it open. The increasing fluid velocity creates this force in the

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conical nozzle below the valve disc and the bell-shaped underside of the disc, called the huddling chamber. The huddling chamber diverts the gas flow. The velocity of the mass of gas, and the diversion are proportional to the force that keeps the valve seat open. In Safety relief valves, an adjustable blow down ring protrudes into the huddling chamber.

v Checking seat tightness of safety relief valves: a) Raise the air pressure upto 90% of set pressure. b) Observe leak off bubbles through 5/16" tube fitted at discharge flange for air escape

through water cup. c) Permit up to 20 bubbles/minute, which is equal to 0.3 CFT of air in 24 Hrs. When it exceeds the limit, seat lapping required. v As per Manufacturer standard specification (MSS), the maximum permissible leak rate

during the seat test on gate, globe, and Angle valves and check valves is as follows. Hydrostatic test – 10cc) | per hour per 25 mm (1 inch) diameter of nominal valve Air test - 1/10SCF) | size.

v Check Valve: a) For vertical/horizontal installation manufacturer recommendation is to be followed for

check valves. b) Check valve and globe valve flow direction to be checked before installation.

c) Do not use a swing check valve on reciprocating liquid pumps, always use a vertical - lift type.

v Check the gland bush for general condition. The inner radial clearance should be

0.4mm (0.016”) maximum and the outer radial clearance should be 0.25mm (0.010”) maximum to never risk of cocking or touching on the stem.

v Check the clearance between bonnet and stem and if it is greater than 0.25mm (0.010”)

radially, then it is useful to employ a thin close clearance spacer ring in the bottom of stuffing box to prevent the risk of packing extrusion.

v Don’t use `F’ lever for Valve Operation. v Bellow Seal Valve: Bellows are made out of Inconel –600 and have been designed

for a minimum number of 5000 Cycles of operation. The normal travel of the valve will be 15% of the total length of the bellow.

v Diaphragm Valve: Generally limited to the operating condition of 10Kg/cm2 and

100oC and radiation level low to moderate. v Ball Valve: a) Valve goes from full open to full close in Quarter-turn of the stem. (A plug valve –too)

b) Visual Clarity: When the handle is parallel to the pipe the valve is open and when perpendicular, the valve is closed.

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c) Size: Vertical size of 1” ball value varies from 2¼” to 4” depending upon the manufacturer. A comparable gate and globe valve in the open position required from 8” to 14” and 5” to 12” respectively.

The vertical size of 1” plug valve is 4” to 7”. d) Weight: A 1” ball valve weighs between 3.5 to 10 Kg. (1.6 to 4.5 lb.) whereas

comparable conventional valves weigh between 8.8 to 94.6 Kg. (4 to 43 lb). e) Lubrication: A ball valve does not have to be lubricated. So it is easier to operate

automatically. f) Flow loss: Straight – through flow, reduce turbulence and minimise head loss. g) Limitations: Low pressure and low temperature application. Not recommended for

throttling service. v Hopkinson Valve:

a) Purpose of Belleville washes is for live loading of gland packing and compactness in size. Load Vs deflection after the pre-loading is constant.

b) Helium leak check to the stuffing box after the replacement of gland packing is done at 15 PSI pressure for half an hour and leak check probing is done at leak off point and at follower/stem area. Leak rate should be less than 10-4 Std.cc /sec.

Helium inter gasket hold test at 100 PSI. for half an hour is carried out to ensure Bonnet gasket leak tight joint. c) The valve shall not be operated if differential pressure across the seat exceeds 14 Kg/cm2. (Note: To be checked by its logic or torque development is more.) d) Belleville washer spring deflects axially under load may be used series or parallel arrangements to give lower or higher stiffness respectively. The spring is space saving and its non-linear characteristics can be altered considerably by varying the proportions.

v Actuators : The Valve actuators can be inactive for up to 99% of their working life. The only exception is control valve actuation, but even here the activity is rarely continuous.

a) Manually operated valves are shut off by the operators feeling. b) Electrical operated actuators torque switch gives the actuator to “feel” valve

tightness with much greater precision and repeatability than any man. c) Wedge gates, globe valves and Diaphragm valves are required torque (Seating)

Switch for closing limitation and position limit switch for opening. d) Parallel slide valves, plug and ball valves require open and close position limit

switches and torque switch for protection. e) Bufferfly valves: Non-seating type requires position limit both ways with closing

torque switch for protection. Seating type requires position limit for opening and torque limit for closing.

f) Back seating under power is not generally recommended. (if required, being achieved manually).

g) Limit switches are operated by valve stem moment or by counter mechanism drive. h) Torque switches are operated by the reaction force on the worm shaft in direct

proportional to the output torque. i) As the torque applied to the output shaft increases, the worm shaft moves axially,

compressing the spring pack in either direction to trip open or close torque switch. j) Backlash hammer blow is incorporated to assist unseating.

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7. Heat Exchangers

v The Overall efficiency of the plant depends largely upon the efficiency of the heat

exchangers. v Water velocity in the tube is limited approximately 8ft/sec. usually between 6.5 and

8ft/sec. Lower velocity (i.e.) less than 6.5 increases size and cost of equipment. Higher velocity limit is to reduce tube erosion and pumping cost. MAPS main condenser water velocity is 5ft. /sec.

v In general, roughening the surface or turbulent flow will increase the heat transfer Co-

efficient. v Tube diameter must be selected on the basis of thermal and space requirement. Smaller

will have higher heat transfer co-efficient and larger ones carry more circulating water at given velocity with less pressure drop.

v Tube length must be determined by 1) Space limitation (space must be provided for

pulling tubes 2) Initial cost 3) Pumping cost v Tubes will occupy between 20 to 25% of the cross section area of the condenser. v Thermal conductivity of one-inch thickness of a material is twelve times more than one-

foot thickness of same material. v Water has the highest thermal conductivity of all the non-metallic liquids. v Highest thermal conductivity gas is Hydrogen among all the gases and vapours. v Cooling Tower: a) Cooling Tower Approach is defined as the difference between the cold water

temperature (outlet water temperature) and WBT of in coming air. Higher the quantity of water will lower the cooling tower approach.

b) Cooling range is the difference between the hot water and cold water temperatures. c) Performance of cooling tower is measured in term of its efficiency

Twi-Two | where Twi = temperature of water in let, ? = -------------- | Two = temperature of water out let, Twi-Twba | Twba = wet bulb temperature of inlet air.

d) Method of heat transfer in Cooling Tower: In a cooling tower, finely divided water falls through an air stream whose wet-bulb temperature is below that of the water. The evaporation of a small portion of the water causes the air to absorb heat from the remaining water, due to the latent heat of the evaporating water. The evaporation of 1 lb of water absorbs about 1000 Btu. Thus, the evaporation of 1 lb of water cools 100 lb of water through a 10-degree cooling range. In addition, a small amount of sensible heat is transferred because of the temperature differential between the water and air (dry-bulb temperature).

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e) The performance of the cooling tower is independent of the dry-bulb temperature of the air and dependent only on the wet-bulb temperature of the air in contact with the water.

f) The forced draft fan is more efficient than the induced draft by about 3%, because some of the fan velocity pressure is converted to static pressure in the tower. g) The number of fan blades varies from two to six. In general, the greater the number of blades the smother the operation; however it trends to reduce the efficiency of the fan because of interference between blades. h) A two bladed fan because the air time which elapses blade passing is so great that the Air flow is actually reversed, causing the pulsation, vibrating the entire structure, where as with a six blade fan, the pulsation disappears entirely. v Efficiencies of different types:

Spray ponds - 40 - 50% Natural draft towers - 50 - 70% Mechanical draft towers - 60 - 80%

v Tube leaks checks are done by Hydro test (water level) 1 foot above from the top most

row, Helium test (during S/D) Vacuum hold test and Candle flame test (during on power in condenser).

v After eddy current testing of heat exchanger tubes, if the wall thickness reduces by 40%

of the original thickness, the tube shall be plugged. v Maximum 10% of tubes can be plugged in the heat exchangers without affecting the

performance. v Leaky tubes are plugged with taper plug / plugged with taper plug and welded depends

upon rating. v Rule of thumb for computing Condensing Rate for water heaters: Raising the

temperature of 100 gallons of water 1oF will condense one pound of steam.

v Heat flux is the amount of heat transfer per unit area per unit time. v Classification of Heat Exchangers: a) Shell and Tube type, b) Spiral type, c) Finned tube type, d) Plate type e) Double pipe type v Advantages of Plate type HXs: a) Low initial cost b) High Heat Transfer Co-efficient of both fluids (up to 3 Times than shell and tube type) c) Low fouling characteristics due to High turbulence. d) More than 2 fluids can be processed in a single unit. e) Compact with respect to Volume, Weight and Hold up f) Flexibility to Increase/Decrease capacity. g) Rapid starts up and fast response due to less hold up.

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h) Withstand Thermal Shocks i) Vibration free j) Cleaning is easy due to full access. v The Key points in HX: a) Usually the hot fluid flows through the tubes. b) The relative flow direction between the two fluids can be parallel, opposite and at

right angles to each other (transverse flow). c) Most efficient heat transfer takes place with the opposite or counter flow. d) Tube to tube sheet joints type selection depends upon the operating parameters,

nature of the fluids, service life and maintenance requirements. v Tube Pitches: The tube pitch is the shortest center to center distance between adjacent tubes. a) Tubes are laid out on either square or triangular pitch pattern. b) Steam condenser and oil coolers etc. have Square pitch and the outside of tubes

can be easily cleaned. c) Triangular pitch HX is able to accommodate more number of tubes in the same

inside pipe diameter. d) Modified triangular pitch provides the access for mechanical cleaning. v Baffles: a) Baffles induce turbulence and Zigzag path on shell side liquids and increases higher

heat transfer co-efficient results. b) The Center-to-Center distance between baffles is called the baffles pitch or baffles

spacing. c) The spacing is usually not greater than a distance equal to the inside diameter of the

shell or closer than equal to 1/5th of the inside diameter of the shell. v Fixed Tube Sheet HXs are normally provided with expansion joint on shell to take

care the thermal stress developed across the tube sheet. v 1-2 Pass HX in which the shell side fluid flows in one pass and the tube fluid in two

passes. v Pull through floating head eliminates the differential expansion problem and possible

to insert lesser number of tubes only, where number of tubes could have been inserted in place of the bolt circle wasted to bolt the tube sheet cover.

v U-bend Heat Exchanger:

a) Tubes can expand freely, eliminating the need for a floating tube sheet, floating head cover, shell flange and removable shell cover.

b) The smallest diameter at the U-bend can be formed without deforming the outside diameter of the tube at the bend has a diameter of three to four times the outside diameter of the tubing. This means it is necessary to omit some tubes at the center of the bundle is the greatest disadvantage.

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c) The main advantage is that the tube bundle can be taken outside of the shell for inspection and cleaning and for any other maintenance required.

d) Fewer tube replacement is not possible. Complete tube bundle has to be replaced. Also cleaning tube bundle from outside is very difficult due to compactness.

v For a given pressure drop, higher heat transfer co-efficient are obtained on the shell

side than on tube side. v Designations of conventional shell and tube type exchangers by NUMERS and

LETTERS have been established by the Tubular Exchange Manufacturer Association (T.E.M.A). a) Size of the shell and tube bundles shall be designated by numbers describing shell,

tube bundle diameters and tube lengths. i) Nominal Diameter shall be the inside diameter of the shell in inches, rounded off to the nearest integer or whole number.

ii) The Nominal length shall be actual overall tube length of straight tube. For U-tubes, the length shall be taken as the straight length from end of the tube to a tangent on the bend.

b) Type designation shall be by letters describing stationary head, shell (Omitted for bundles only) and rear head. c) Typical Examples

(i) Fixed tube sheet having stationary and rear heads integral with tube sheets, single pass shell, 17 inch inside diameter with tubes 16 ft. long. Size 17-192 Type NEW.

(ii) U-Tube exchanger with bonnet type stationary head, split- flow shell, and 19 inch inside diameter with tubes 7 ft. straight length. Size 19-84 Type BGU.

v Indication of Fouling or Chocking: a) The available terminal temperature difference at both ends of the heat exchangers will

clearly indicate the condition due to which the heat exchanger performance has deteriorated.

b) In parallel flow HXs, T1-t2 (hot) and T2-t1 (cold) increases means indication of fouling of tubes.

c) In counter flow HXs also T1-t2 (hot) increases and T2-t1 (cold) increases means indication of fouling of tubes.

Where T1 – Hot fluid inlet temperature | t1 - Cold fluid inlet temperature T2 - Hot fluid outlet temperature | t2 - Cold fluid outlet temperature

v Locating Leaks in the Tubes a) Reduction in performance of the HX. b) Loss of D2O and release of activity in case of D2O HXs. c) Contamination of the cooling medium as may be in case of oil coolers. d) Conductivity changes in condensate (DM water) in condenser due to mixing of circulating water with the condensate. v Cleaning of Tubes: a) Mechanical cleaning-Care should be taken not to damage the inside surface of tubes. b) Circulating hot water / oil / light distillates. c) Commercial cleaning compounds / Chemicals.

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d) High pressure water jet cleaning. e) Tubes should never be cleaned by blowing steam through the individual tubes. v PERFORMANCE FAILURES:

The failure of heat exchanger equipment to perform satisfactory function may be caused by one or more of the following factors. a) Excessive fouling. b) Air or gas binding resulting from improper piping installation or lack of vents. c) Operating condition differing from design conditions. d) Mal distribution of flow in the unit due to choking of inlet and outlet nozzles.

Generally the inlet nozzles are chocked more than the outlet nozzles. e) Excessive clearance between the baffles and the shell and or tubes, due to

corrosion. f) Improper thermal design.

v BASIC HEAT TRANSFER EQUATION:

Q = U A ∆ T Where Q = Heat transferred, BTU/hr.

U = Overall heat transfer, coefficient, BTU/hr/Square Foot/deg F. A = Square feet of heat transfer surface. T = Corrected logarithmic mean temperature difference deg F.

Of these quantities, A is the desired unknown; Q is unknown; T can be quickly and accurately calculated; U can be approximated from average values taken from coefficient tables. The equation can then be calculated for A.

v FOULING FACTORS:

A fouling factor (fouling resistance) is really a safety factor to avoid reduced performance or to avoid too frequent cleaning). A 25% increase in fouling factor may result in a 50% or more decrease in the performance of the heat exchanger.

v Scale formation in condenser:

Hard water cause scaling problems. When heated the minerals are left behind, which form a deposit on the heat exchanger surface. The heat transfer rating of the scale deposit is very much lower than metals. For instance, calcium carbonate has a heat transfer rate, which is 552 times less than copper.

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8. Compressor

v Equipment categorised based on pressure is upto 2 Psig for Fan, 2 to 10 Psig. for

blower and More than 10 Psig. for Compressor. v Compressor Valves: a) If, due to wear, the total indentation of valve plate and seat is over 0.2mm, the valve ring

and or the seat must be replaced. b) Valve plates can be lapped up to 20% of valve plate initial thickness. c) Kerosene leak check is to be done after assemble the suction and discharge valves.

The valve lift is to be between 2 to 2.5mm. d) Finger type valves are normally used for small units 3/4 to 5 HP size. e) More than 5 HP have concentric ring type valves. v If normal air delivery has dropped off or if oil consumption of the compressor is

considered to be excessive, piston ring broken or worn may be the one of the cause. v A general rule in determining of minimum oil consumption to be approximately twenty-

five horsepower hours for 28.35 gms. (one ounce). In other words, any compressor using more than 113.4gms (four ounces) of oil per one hundred horsepower hours would be called as not meeting commercial standards and would require corrective action.

v Compressor rings and oil rings are classed as different types. Make sure that the rings

are properly positioned which can be identified by the word `top', the letter `T', a dash (-), a dot (.) or a paint mark.

v Normally 10% of leakage in the pipelines will be allowed for piping and tool leakage. v Gate valves are used in airlines to reduce friction loss. v Usual limiting compression ratio per stage for various types of positive displacement

compressors in capacities up to 1000 cfm are

Type Max. Compression Ratio Piston 10 Vane 8 Liquid ring 5 Diaphragm (10cfm max.) 5 Screw 3 Two Lube 2

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v Compressor Capacity Regulation a) Small compressor upto 25 HP can have ON-OFF control when adequate air storage is

available and the air requirement is less than 75% of the compressor delivery capacity. b) Constant speed unloading is used when the demand for air is practically constant at the

capacity of compressor. c) Constant speed intake unloading (using Auxiliary Valve) d) Constant speed free air unloading (using unloader piston and suction valve). e) Recirculation by valve control method.

f) Clearance volume control usually in three or five steps, which decrease in volumetric efficiency and capacity.

g) Compressor motor unload current is 50% of full load current (Motor no load current is 40%).

h) Air storage receivers should be sized for about 9 - 18 Litres Capacity/ CFM of compressor capacity for effective demand side control.

v To establish the size of the storage tank for a given compressor capacity, the following

formula can be used. Compressor output (Cfm * Psia) Receiver Size (ft3) = ---------------------------------------- Output pressure (Psig. + Psia.) v Purpose of inter cooler is to reduce the air temperature, reduces specific volume of air

to be handled in the next stage, increases the volumetric efficiency and thus reduces the power input to the prime mover.

________ a) Inter cooler pressure (P2) = √P1 * P3 | Where P1 = Initial Pressure | P3 = Final Pressure

b) Each 10oF air temperature decrease in intercooler outlet result in 1% saving in power input.

v Each 10oF change in inlet air temperature to Compressor affects efficiency by 1%.

Colder temperature increases and warmer temperature decreases efficiency. v Every 2 PSIG of atmospheric pressure change increases or decreases 1% power draw v Most compressors deliver 4 - 5 CFM/HP at 100 PSIG. v The speed of compressors is controlled by the piston speed, which are normally about

5 metres/sec. for small machines and about 4 metres/sec. for larger ones. v Bore to Stroke ratio = 0.75 to 1.25 v Ratio of compression per stage seldom exceeds 7 usually average 2 or 3 on multi stage. v Advantages of multistage compression:

a) High volumetric efficiency for a given pressure ratio.

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b) Better mechanical balance and uniform torque. c) Lighter Cylinder. d) Reduce leakage losses e) Reduction in power required driving the Compressor. f) Effective lubrication is possible due to lower temperature range.

v Moisture Condensation a) As air is compressed and cooled, which reduces the volume of each kilogram of air, the

ability for it to contain water as vapour becomes less. Finally water vapour condenses and appears in the air in liquid state.

b) The temperature and the volume (not the pressure) determine moisture capacity of air. The moisture capacity increased as the temperature increases. E.g. 1000cfm of saturated air (i.e. 100% R.H) at 80oF will contain 1.57 lb of moisture. At 100oF it can contain 285 lbs.

c) Under average conditions, every 100 CFM of air compressed to 100 Psig. produces 20 gallons of condensate per day.

d) 1000 ft3 of air after compression can release 1.3 litres of water. e) A good after cooler cool the air within 15oF of the cooling water temperature and will

condense 90% of water vapour originally contained in the air as it enter the receiver tank.

f) Most water cooled after coolers will require cooling water about 3 gpm.per 100 CFM of compressed air at a discharge pressures of 100 Psig.

v Problems with water in compressed air a) Washes away required lubricant b) Forms rust and scale in pipes c) Increases wear maintenance and malfunctioning of pneumatic devices. d) Rusts sand blasted parts e) Obstruction in tiny copper tubes by copper oxide formation. v Sliding vane: a) A running sliding vane compressor gives off large amount of heat due to mechanical friction. Therefore, at compression above 1.5 the compressor casing is water-cooled. b) Generally machines for pressure above 50 psi are built as two stage units. v Screw compressor shows higher efficiency than sliding vane compressor due to

absence of mechanical friction. v Water ring type compressor: a) As a compressor it is not commonly used becomes

compressed gas will contain lot of moisture, hence mostly it is used as vacuum pump. b) Conventionally designed water ring vacuum pumps have efficiency of not over 50%

v Intake Pipe: Intake pipe size should be at least one size higher for every 10 ft. in length

keep intake air velocity below 2500 f.p.m. v Jacket Cooling: Jacket water pressure should never exceed 40 PSI, a much lower

pressure being preferred, to avoid any possibility of leakage. For water cooled system, cooling water will first go to inter cooler then carried to cylinder. This is to ensure that

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no sweating takes place on cylinder walls. Recommended water temperature at outlet is 260 C (800 F) to 370 C (1000 F)? (lukewarm).

v Capacity regulation of rotary compressor: Generally, sliding vane compressors are directly connected to electric motors running at 1450; 960; 735 rpm. Screw type compressors operate at a very high speed, as great as 15000 rpm when driven by gas turbines. Large conventionally designed screw compressors run at 3000 rpm. For regulation following methods can be adopted. a) ?Variable speed. b) ?Suction throttling. c) ?Bypass control. d) ?On-off control. v Absorbent: It is used to remove moisture in dryers. Adsorption is distinct from

absorption in that it is the process of adhesion of the molecules of the substance to the surface of the adsorbent. In MAPS Silica gel is used in Air Compressor dryer. Molecular Sieves used in D2O vapour recovery dryers. Crystalline Alumino Silicate (type AW-500, Pore size 2X10-8 inch) used in Calandria Vault and FM Vault dryers. Crystalline Sodium Alumino Silicate (Type 13X: Pore size 4 X 10-8 inch.) is used in boiler room dryers.

v Axial Flow Compressors a) In an axial flow compressor, the pressure rise takes place in both fixed and moving

blades. b) An axial flow compressor is suitable for high volume flow rates with a small pressure size. c) In case of axial flow compressors for minimum fluid friction and blade tip clearance

losses, the blades of an axial flow compressor are designed for 53% reaction. v Dew point temperature: a) The temperature at which water vapor starts condensing. b) This is the saturation temperature of the remaining moisture; there will be no further

condensation when the temperature is maintained above this dew point. c) Atmospheric dew point -12oF is equivalent to a pressure dew point of 35oF at 100 psig.

Air Compressor Terminology: a) Single Acting Compressors are those in which suction, compression and delivery of

a gas take place on one side of the piston and we have one cycle/revolution of crankshaft.

b) Double acting compressors are those in which suction, compression and delivery of a gas take place on both sides of piston and we have two cycles/revolution of crankshaft.

c) Single stage compressors are those in which the compression of air from the initial pressure to final pressure is carried out one cylinder only.

d) Multistage Compressors Compressions more than one cylinder. e) Ratio of Compression is defined as the ratio of absolute discharge pressure to

absolute intake pressure.

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f) Free air is that which exists under the condition of pressure and temperature at the intake of compressor.

g) Displacement of compressor is the volume swept through by the first stage piston or pistons in cubic metre per minute. In double acting compressors, it is the volume swept through by both sides of the piston.

h) Actual Capacity of a Compressor is the quantity of gas actually delivered. It is expressed in cubic metre of free gasper minute. The actual capacity of a compressor is always less than its displacement.

i) Volumetric/Efficiency is the ratio of the actual capacity of a compressor to its displacement.

j) Standard Cubic feet per minute (SCFM). Flow of free air measured at a reference point and converted to a standard set of reference conditions. (eg: 1.03Kg/cm2a, 15oC and 0% relative humidity)

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9. Diesel Engine

v Governor: Any change in load causes change in speed. Power developed in DG depends upon the amount of fuel burned in the cylinder. So, Governor is a speed sensitive device that automatically controls or limits the speed of the engine by adjusting the amount of fuel injected to the engine.

v Governor can be operated in three modes. a) Isochronous : The Governor will maintain a constant speed for all loads within the

capacity of the engine (except the moment at the time of load change occurs). b) Droop mode : The engine can be parallel with other engine or infinite bus and the load

carried by the governor will be a function of the governor droop and speed setting. c) Auto Mode : The Operation of the engine is governed by the emergency transfer

system. The mode of operation is either droop or isochronous. d) Cetane Number: The percentage by volume of Cetane C16 H34(Cetane number 100)

in a blend with α - Methylnaphthalene C10H7CH3(Cetane number 0), indicates the ability of a fuel to ignite quickly after being injected into the cylinder of an engine. Fuel oil minimum requirement of Cetane number is 45 for locomotive engine.

e) Super charging: Purpose is to admit more air into the cylinder so that more fuel can be burned resulting increase in volumetric efficiency and the engine output is increased. The usual super charger pressure ratio is about 1.35 to 1.4.

v Dust particles in Industrial atmosphere can contain about 40 million in 1m3 of air. If the

air volume is reduced to 7 times to give 7 bar of air pressure, the concentration of dust particles would be 280 mppm3.

v Only 1/3 of fuel energy is available at crankshaft.

1/3 heat goes in engine cooling, 1/3 heat goes in exhaust and some heat is lost in friction and radiation.

v The difference between IHP and BHP of an engine is due to friction loss of the engine. v DIESEL FUEL OIL: a) The main chemical elements, which form the fuel, are "Hydro-carbons". Fuel oil is composed of 85% carbon and 15% hydrogen; it also contains some impurities like water, sulfur and ash. A good diesel oil should be free from mechanical impurities held in suspension, which may clog fuel strainers, filters and score fuel pump barrels and plungers. It should flow freely at ordinary temperatures, should be free from volatile elements that produce flammable gases and should have a high heat value (18,000 to 19,000 Btu per pound). b) Calorific value: The amount of heat produced during complete combustion of 1Kg or 1m3 fuel is known as calorific value of the fuel (Kj/Kg or Kj/m3).

Higher Lower Diesel - 46000 43250

Kerosene - 46250 43250 Petrol - 47000 43900

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v Fuel injector is like a spring loaded check valve with nozzles having fine holes of 0.006" to 0.008" dia.

v Crankshaft Design features: In majority of the cases, the crank pin length is at least 30% of its diameter, which itself is usually not less than 60% of the cylinder bore. The thickness of the crank web is usually about 20% of the cylinder bore size. The main journal diameter is bigger than the crank pin diameter and is usually 75% of the cylinder bore whereas its length is about half its diameter. The angles between crank-throws are selected from the consideration of smooth power output. In 6.cylinder in-line engines the angle is 120°, whereas for V.8 engines it is 90°. a) Journal finish – 20 micro inches. Or better is desirable.

b) Crank pins should be parallel with main journals within 0.025 mm (1 thou.) in 150 mm (6 inches). c) Crankshaft end clearance (end play) generally 0.004” to 0.008”. MAPS DG’s crankshaft end clearance is 0.014”. d) Using hollow pins and journals, large fillets and well blended sections and the removal of oil holes from critical areas, the air craft crank shaft deliver 20 bhp per pound of weight as compared to 1 bhp for the automotive crank shaft. e) Main bearing connecting rod bearing Clearance Normal value is 0.001” per inch of shaft dia. and should be with in1.5 times of normal value. f) In the absence of Manufacturer’s instructions, about bearing clearance, it is customary to use a minimum of 0.0005” to 0.001”/ inch dia for small shaft. Any clearance in excess of 0.005” on either main or connecting rod is usually regarded as reason for adjustment or the installation of new bearings. g) MAPS DGs connecting rod Big end and Main bearing clearance is 0.008” for 6” Shaft size. v Connecting rod crank pin bore and piston pin should be paralleled within 1 thou in 6

inch. both in Horizontal and Vertical position. Bore finish must be smooth enough (80 micro inches) to ensure proper bearing contact and heat transfer.

v Connecting rods are graded by weight, letters L or R and Cylinder No. Where a new

connecting rod is required, it is essential to quote the grade letter and Cylinder No. (As per the Station DG Manual).

v Connecting rod bolt locking washers should never be used twice.

v Ensure Cylinder No. and arrow mark on piston before assembling of piston to

connecting rod. v Bumper clearance/piston top clearance checking is done as follows. a) Place 1/16” soft lead wire on top of piston at two places and tightens the cylinder

head. b) Turn the engine a short distance on either side of TDC. Remove TDC, then

remove and measure both piece of wire and note the mean thickness of both.

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v The requirement of Chimney height above the roof of Diesel Engine is 0.2 * √KVA as per ISO 14001. This is applicable to > 50 KW diesel engine (KVA = KW/Power Factor).

v Crankcase ventilation: It is possible that the products of combustion may leak to the crankcase. They mainly contain Nitrogen, Carbon-di-oxide and Water. They may also contain traces of acid due to presence of sulfur in the fuel. The acid causes corrosion of engine parts. Crankcase ventilation is a remedial measure taken to avoid effect of acid on parts in its contact. A steady flow of air is carried through the engine crankcase, which carries away the products of combustion along with it. An exhaust fan is normally used for crankcase ventilation. a) Never open the door of a totally and closed crankcase until the engine is cooled off. Over-rich mixture of oil vapour may get ignited when the fresh air is admitted. v Frequently inspect the engine for leaks, loose fasteners, abnormal mechanical noises and

temperature. v Camshaft speed is half of the speed of Crankshaft. v The overload capacity of Diesel Engine is usually around 10%.

v Diesel engines have higher compression ratio (16:1 to 22:1) than gasoline engine (8:1)

because they relay on high compression to create heat for fuel ignition.

v Cylinder: a) Single cylinder engines: The maximum size of the single cylinder engine is restricted to about 500-600 ' c.c,' because of the higher unbalance forces, which become difficult to be balanced. Further the weight of the flywheel required becomes excessive for higher engine sizes. b) Two cylinder engines: This type of engine, apart from providing more power, gives more uniform torque and balancing possible is also better as compared to single cylinder engines. c) V-type: In this two cylinders are placed with their centre line at same angle to each other. Generally this angle is kept 60°. But in some instances angles from 40" to 90° have also been used. Its main advantage is that it can be made more compact, e.g. same crankcase as used in a single cylinder engine may be used here also. Further short crankshaft also means more rigidity, due to which the engine runs more smoothly at higher speeds. Besides, overall length and height of the engine are decreased. The weight/volume ratio is lower compared to an in-line engine. However, cost or manufacture is high and balancing more difficult. d) Water cooled engines: The inlet to the jacket is given from the bottom, water while flowing upwards gains heat from the cylinder and cylinder head, and is then removed from outlet provided at the top of head. e) The Quantity of water circulated is 1.5 litres /min. /HP corresponds to 8oC rise. f) Re-boring is done when the? cylinder is worn out 0.007" per inch of bore. Re-bore to 0.001 to 0.005" within the desired measure.

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v Firing Order: The firing sequence is arranged in a predetermined manner to give the

best engine performance in terms of uniform rotation, equally spaced power impulse and proper balancing.

v Altering Compression Ratio: a) It is possible to change the stroke slightly by regrinding the crank throws off centre. b) By adding or subtracting metal in the combustion chamber or on the piston. c) Easiest method is to install a thicker (or two) cylinder head gasket or milled or shaved off on gasket face.

v The material of which the combustion chamber is made and the efficiency of the cooling

system also has distinct bearing on the compression ratio that can be used in the given engine.

Example: Aluminium pistons and Aluminium cylinder heads can operate at higher compression ratio than could cast Iron or Steel.

v The mating surfaces of cylinder head surface and cylinder block surface should be flat

and true within 0.5 mm (020 inch). Measurement is made by means of a metal straight edge and feeler gauge strips.

v In general, it is customary to have clearance fit between solid skirt cast Iron piston to

cylinder to about 0.00075 to 0.001 inch per inch of diameter. v Piston rings & Oil rings:

a) Piston ring No.1 (Top ring) has a full face contact on cylinder end gap 0.004” per inch of piston diameter and generally side clearance is 0.0025”.

b) Piston ring No.2 (Second from top) is also compression ring but has a narrower contact surface and therefore the entire expansion force of the ring is concentrated on the narrow area in contact. The result is that the top ring will show fewer tendencies to wear the cylinder in the driest and hottest part and the second ring will seat more quickly to the cylinder wall even though it has more lubrication than the top ring.

Its End gap is 0.003” per inch. diameter and the same gap are for other rings. Its side gap is 0.003” and the same for other rings. c) When the side gap is more than 0.005” on any ring required replacement.

d) If the Compression pressure varies more than 20% between the different cylinders, it is usually assumed that the cylinders, rings or valves or all three are defective.

• Piston ring end gap kept in practice is when installed about 0.30 to 0.35 mm. The ring end gaps may be either straight butt type or tapered or seal cut type. Out of these butt type is most commonly on account of its cheapness.

• Ring width the trend is towards reducing ring width for a) Lower piston height and consequently lower engine height. b) Better resistance to ring flutter. c) Problems of ring inertia are reduced. Ring inertia is the tendency of the ring to continue its motion as the piston changes direction. The problem is particularly severe at high speeds.

v Cylinder Head Valve:

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The poppet valve derives its name from its motion of popping up and down. This is also called "mushroom valve" because of its shape, which is similar to a mushroom. It consists of a head and a stem. It possesses certain advantages over the other valve types because of which it is extensively used- in the engines : 1. Simplicity of construction, 2. These are self-centering, 3. These are free to rotate about the stem to new position. 4. Maintenance of sealing efficiency is relatively easier. Generally inlet valves are larger than the exhaust valves, because speed of incoming air is less than the velocity of exhaust gases which leave under pressure. Further because of pressure, the density of exhaust gases is also comparatively high. Moreover, smaller exhaust valve is also preferred because of shorter path of heat flow. Generally inlet valves and exhaust valves are 45% and 38% of the cylinder bore respectively. v Valves and valve seats: Take blue contact of seat and valve. It should be 100% and approximately 2 mm wide. If contact is not proper the valve and seat should be ground on a Valve grinder to a proper angle. They should be lapped in position after grinding. Check clearance of valve stem with valve guide. It should not be more than 0.125 mm for Intake valve and 0.150 mm for Exhaust valve.

v Air Motor: a) A drop of 10 Psi. at the inlet reduces the air motor’s output by 14%, a drop of 30

PSI. Could affect the output by as much as 45%. b) One of the major advantages of an air motor is in terms of its ability to come up to

full speed almost instantly. c) It is generally accepted rule that if a rotor blade losses 20% or more of its width, it

should be replaced. d) A helpful rule for the maintenance department would be that an Air tool should be

scrapped if its repair cost exceeds 50% of the cost of replacement.

v Air tool hose size: The correct size is usually one size larger than the inlet thread on the tool. About 60% of air tools returned for repair have reduced nipple inserted at the air inlet, which causes reduction of air power, and their use should be discouraged.

v Maintenance of Diesel Engine: The primary purpose of good maintenance is to obtain safe, reliable, and economical

operation. a) Pressure . Design compression and maximum combustion pressures must be

maintained. Ø Causes of loss of compression are leaky cylinder head valves, low scavenging air

pressure, obstructions in air intake lines or filters, leaky or sticky piston rings, and increased end clearance between piston top and cylinder head. It is best to limit the loss of compression pressure to within 20 psi of the recommended normal pressure, except that when it is due to normal wear of piston rings and cylinder liner, up to 50 psi may be tolerated.

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Ø Compression pressure, fuel-injection timing, condition of fuel-injection system, and fuel-oil characteristics affect combustion pressure . Combustion pressure should be kept within 25 psi of the normal.

b) Exhaust Temperature is a sensitive and direct indication of proper combustion. The most efficient performance brings the lowest temperature; irregularities or deficiencies of combustion always bring temperatures above normal.

c) Fuel consumption is a simple and sure overall measure of engine performance. Meters or measuring tanks may be used for checking consumption.

d) Lubricating-Oil Pressure Abnormally low lubricating oil pressure is dangerous; low-pressure shutdown devices or alarms are frequently used. Abnormally large pressure drop through the filter indicated clogging; low pressure drop indicated a break in filter medium. Rise in oil temperature indicates hot bearing; Watch for contamination from fuel oil, because this indicates poor combustion conditions. Water in the oil indicates leaks from jackets or head gaskets. Metal particles may be abnormal wear or breaking up of Babbitt in the bearings. Abnormal quantity of sludge may indicate poor combustion or unsatisfactory type of lubricating oil for the engine and service conditions.

e) General Observations . Any unusual sound or symptom must be promptly investigated. Whenever any inspection work is done on an engine, extend the inspection to cover other parts that can be conveniently inspected at the same time. Similarly, when maintenance work is done on one part or assembly, recondition all parts in the assembly fully, as well as in any other assemblies or parts that can be conveniently handled at the same time.

? Basic Engine Terminology: 1. Top dead centre (T.D.C.): This refers to the position of the crankshaft when the piston is in its topmost position i.e. the position closest to the cylinder head. 2. Bottom dead centre (B.D.C.): This refers to the position of the crankshaft when the piston is in its lowest position, i.e., the position farthest from the cylinder head. 3. Bore: Inner Diameter of the engine cylinder is referred to as the bore. 4. Stroke: Distance traveled by the piston in moving from T.D.C. to the B.D.C. is called 'stroke'. 5. Clearance volume: The volume of cylinder (including the combustion chamber} above the piston when it is in the T.D.C. position is referred to as 'clearance volume' (Vc). 6. Piston displacement : This is the volume swept by the piston in moving from T.D.C. to B.D.C. This is also called 'swept volume'. If 'd' is the cylinder bore and 'S' the stroke, the piston displacement, Vs is given by: Vs = p /4 d2 S 7. Engine Capacity: This is a total piston displacement or the swept volume of all the cylinders. If 'n' is the number of cylinders and Vs is the piston displacement. Then 'engine displacement' or 'engine capacity' Vd, is given by: Vd=Vs.n 8. Compression ratio: This indicates the extent to which the charge in the engine is compressed. It is defined as the ratio of the volume above the piston at B.D.C. to the volume above the piston at T.D.C. If 'g' is the compression ratio, then g = Vs+Vc Vc (For petrol engines, compression ratios are about 8 to 9.5: 1, whereas for diesel engines they vary from 16 to 22 : 1. ) 9. Power: It is the work done in a given period of time. Doing the same amount of

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work in a lesser time would require more power. 10. Horse Power (H.P.): This is the amount of energy required to do 4500 Kgm. of work in one minute. 11. Indicated horse power (I.H.P.): The power developed within the engine cylinders is called indicated horse power, This is calculated from the area of the engine indicator diagram. 12. Brake horse power (B.H.P.): This is the actual power delivered at the crankshaft. It is obtained by deducting various power loses in the engine from the indicated horse power. 13. Engine torque: It is the force of rotation acting about the crankshaft axis at any given instant of time. It is expressed in Newton-metres (Nm). v Data sheet of MAPS DG

a) Number of Cylinder - 16 b) Bore and Stroke - 9” X 10½” c) Crank shaft rotation - CCW (Facing power takes off end) d) Engine rated speed - 1000 RPM e) Rated BHP (Continuous) - 2496 f) Fuel pump Rack travel - 33mm+ ¼mm g) Air manifold pressure (100% load) - 22 PSI. h) Crank case Vacuum (100% load) - 0.5-1.0 inch. H2O i) Maximum allowable crank ) shaft Deflection ) - + 0.0015” j) Mech. Over speed Engine trip at - 1130 RPM k) Engine Lub oil pressure trip at - 18 PSI l) J.water temperature raises trip at - 195oF (90.5oC)

Engine Lub oil pressure alarm at - 20 PSI. m) J.water temperature alarm at - 185oF (85oC) n) Firing order is - 1R-1L-4R-4L-7R-7L-6R-6L-8R-8L-

(The engine cylinders are numbered 5R-5L-2R-2L-3R-3L from the free hand).

o) Puppet Valve Clearance - 0.034” p) Governor - Woodward EG governor r) Fuel oil consumption - 0.324lb/hr/BHP at 110% load 0.37lb/hr./BHP at 75% load 0.39lb/hr./BHP at 50% load

s) Jacket water cooling system (Capacity 450 gallons): Thermostatic (By metal) by pass valve maintain water temperature within 65oC to 70oC.

t) At ¾ rated load and full speed, the maximum difference between cylinder compression pressures should not exceed 100 PSI.

u) At full rated load and speed, the maximum difference between cylinder firing pressures should not exceed 150 PSI.

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10. Fans and Blowers

v Purpose of a “FAN” is to move a mass of gas or Vapour at the desired velocity. There is a slight increase in the gas pressure across the fan rotor or impeller & volute casing. However, the main aim remains to move air or gas without any appreciable increase in its pressure. The total pressure developed by fans is of the order of a few millimeters of water gauge.

v A “BLOWER” delivers the gas or air with an appreciable rise in pressure to overcome

some kind of resistance in the flow. In some applications they develop pressures of the order of 1000 mm W.G. or more.

v Fan shaft: a) Shaft, which operates below 70% of their critical speed, is considered Rigid Shaft. Above 70% considered flexible shaft. b) If fan is required to run above critical speed, it is better to design 20 to 30% above the critical speed. c) Generally fan shaft diameter is higher than Centrifugal pump shaft for the same BHP.

v SISW: Single Inlet Single Width impeller. Lock the impeller 1/3 movement from

suction side of the total end ply in volute casing. v DIDW: Double Inlet Double Width impeller. Lock the impeller center of Volute

casing of the total end ply. v Tolerance for Vibration:

a) “Balance Quality and Vibration Levels for Fans”, recognizes five different fan application categories (BV-, BV-2, BV-3, BV-4 and BV-5) for the required balancing grade during manufacturing of the fan (See table).

b) These balance categories are ordered from a less sensitive group (HVAC) to the most sensitive fans, which include those for petrochemical processes and computer chip manufacturing.

c) These values vary from balance Quality Grade G-16 (least stringent requirement) to balance Quality grade G-1.0 (Most stringent requirement).

d) Example: The expected free space vibration velocity for rotor balanced to G-2.5 is approximately 0.1 inch/sec. (2.5mm/sec).

v The position of fan wheel with respect to the inlet is important for noise and efficiency.

As a general rule operation as close as possible without actual striking is the correct positions.

v A damper at the fan inlet is most essential that all moving joints of these dampers be

carefully and thoroughly lubricated at least once each month. Observation may indicate the need for more frequent maintenance attention under severs conditions.

v Belt Guards:

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A V belt drive is a friction drive, and as such will generate heat, air should be allowed to circulate freely around all parts of the drive to help dissipate this heat. It is not good practice to completely enclose V-belt drives. Use open mask guards if possible.

Application categories and required balancing grade Application Examples Driver Power

Limits, kW (hp)

Fan application Category, BV

Balance quality grade for rigid rotors/impeller

HVAC Building ventilation and air conditioning

< 3.7 (5.0) > 3.7 (5.0)

BV-2 BV-3

G 16 G 6.3

Industrial processes and power generation

Bag house, scrubber, conveying boilers, combustion air, pollution control

< 300 (400) > 300 (400)

BV-3 BV-4

G 6.3 G 2.5

Petrochemical Processes

Hazardous gases, process fans

< 37 (50) > 37 (50)

BV-3 BV-4

G 6.3 G 2.5

Computer chip manufacturer

Clean room Any BV-5 G 1.0

Information adopted from AMCA Standard 204. `Balance Quality and Vibration levels for Fans’.

v Centrifugal Fan: Wide ranges, Less noise, more efficient, High pressure, Airflow variation is easy, Low specific speeds.

a) FORWARD CURVED BLADE FAN: The pressure rises from 100 % free delivery toward no delivery with a characteristic dip at low capacities. Horsepower continuously with increasing air quantity. b) BACKWARD CURVED BLADE FAN: The pressure rises constantly from 100% free delivery to nearly no delivery. There is no dip in the curve. The horsepower curve peaks at high capacities. Therefore, a motor selected to satisfy the maximum power demand at a given fan speed does not overload at any joint on the curve, providing this speed is maintained. Two modifications of the backward curved blade fan are the airfoil and backward inclined blade fans. c) RADIAL BLADE FAN: The pressure characteristic is continuous at all capacities. Horsepower rises with increasing in air quantity in an almost directly proportional relation. Thus, with type of fan the motor may be overloaded as free air delivery is approached. The radial blade fan has efficiency, speed and capacity characteristics that are midway between the forward curved and backward curved blade fans. It is seldom used in air conditioning applications because it locks an optimum characteristic. v Axial Fan:

Large volume of discharge, Higher noise level, High specific speeds. v Running Maintenance of Fans

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a) Condition monitoring by vibration reading. b) Regreasing as per Schedule/Experience c) Ensure proper condensate draining d) Plummer block (bearing) temperature should not exceed 55oC. on surface. e) Condition and tension of belts f) Free operation of inlet vanes/outlet damper and links regreasing. g) Current drawing of fan motor h) Noise level

Speed Control (Using Inverter) in Fan or Pump a) Can reduce the corresponding cube root reduction in power and can reduce the wear

and tear. c) Where the noise level is critical (Office, Hotels etc.) 15% reduction in speed gives a

55% reduction in noise.

v In a well-balanced and properly installed fan, the mechanical noise originating from bearings and vibration of various parts is not as prominent as the aerodynamically generated noise is due to the various flow phenomena occurring within the fan. The main causes of aerodynamically generated noise are: a) The flow at the entry and exit of the fan, i.e., Suction and exhaust noise, b) Rotation of blades through air or gas, c) Passage of blades through wakes, d) Turbulence of air, e) Shedding of vortices from blades, and f) Separation, stalling and surging. v Some definitions used in fan work * * From the National Association of Fan Manufacturers, Inc, (NAFM). STANDARD AIR DENSITY is 0.075 lb per cu ft at sea level (29.92 in. barometric pressure), dry air, and 70o F STANDARD FLUE-GAS DENSITY is 0.078 lb per cu ft at sea level (29.92 in. barometric pressure) and 70o F VOLUME handled by a fan is the number of cubic feet of air per minute (cfm) expressed at fan outlet conditions TOTAL PRESSURE of a fan is the rise of pressure from fan inlet to fan outlet VELOCITY PRESSURE of a fan is the pressure corresponding to the average velocity determined from the volume of airflow at fan outlet area

STATIC PRESSURE of a fan is total pressure minus the fan velocity pressure POWER OUTPUT of a fan is expressed in horsepower and is based on fan volume and fan total pressure.

POWER INPUT is measured horsepower delivered to fan shaft

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MECHANICAL EFFICIENCY of a fan is ratio of power output to power input

STATIC EFFICIENCY if a fan is the mechanical efficiency multiplied by the ratio of static pressure to the total pressure FAN OUTLET AREA is the inside area of the fan outlet (flange) FAN INLET AREA is the inside area of the inlet collar

v LAWS OF FAN PERFORMANCE: Fan laws are used to predict fan performance under changing operating conditions or fan size. They are applicable to all types of fans. Then fan laws are stated in Table-The symbols used in the formulas represent the following quantities. Q - Volume rate of flow through the fan, N - Rotational speed of the impeller, P - Pressure developed by the fan, either static or total, HP - horsepower input to the fan. D - fan wheel diameter. The fan size number may be used if is proportional to the wheel diameter. W - Air density, varying directly as the barometric pressure and inversely as the absolute temperature. Table - FAN LAWS VARIABLE CONSTANT NO. LAW FORMULA ---------------------------------------------------------------------------------------------------------------------------- Speed Air density 1. Capacity varies as the speed Q1/Q2 = N1/N2 Fan size 2. Pressure varies as the square of the speed P1/P2 = (N1/N2)

2 Distribution 3. Horsepower varies as the cube of the speed System HP1/HP2 =

(N1/N2)3 4. Capacity and Horsepower vary as the square of fan size Q1/Q2=HP1/HP2= (D1/D2) 2 ----------------------------------------------------------------------------------------------------------- Fan Size Air density 5. Speed varies inversely as the fan size. N1/N2 = D2/D1 Tip speed 6. Pressure remains constant P1 = P2 Air Density 7. Capacity varies as the cube of the size Q1/Q2 = (D1/D2) 3 Speed 8. Pressure varies as the square of the size P1/ P2 = (D1/D2) 2 9. Horsepower varies as the fifth power of the size HP1/HP2 = (D1/D2)5 ---------------------------------------------------------------------------------------------------------- Air Pressure 10.Speed, capacity and Horsepower vary inversely as the square root Density Fan Size of the densityN1/N2 = Q1/Q2 = HP1/HP2 = (W2/W1)1/2

Distribution 11.Pressure and Horsepower vary as the Density P1/P2 = HP1/HP2 System = W1/W2

12. Speed remains constant N1 = N2 -----------------------------------------------------------------------------------------------------------

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In addition to the restrictions noted in Table -application of these laws is limited to cases where fans are geometrically similar and where there is no change in the point of rating on the performance curves. Because of the latter qualification, fan efficiencies are assumed constant. Geometrically similar fans are those in which all dimensions are proportional to fan wheel diameter. The same point of rating for two fans of different size means that for each fan the pressure and air volume at the point of rating are the same fraction of shut-off pressure and volume at free delivery provided the rotational speed is the same in either case.

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11. Refrigeration

v One ton of Refrigeration is the absorption of heat at the rate of 12,000 B tu/hr. or 200 Btu/min. or 50K Cal./min.

v The rate of heat removal is 8000/24X60 = 55.5Kcal./min. In practice, 1 tonne of

refrigeration is taken as 50Kcal. /min. which is equal to 3.5KW. v Performance of Refrigerator is measured in terms of Co-efficient of performance.

Heat extracted from cold body Refrigerating effect

COP = ----------------------------------- = ------------------- External Energy supplied Working Input

v External power required per tonne of refrigeration is equal to 3.5KW/COP

COP for Freon -11 is 5.09, Freon-22 is 4.66

v The minimum HP requirement per tonne of Refrigeration using R-11 is 0.9383 and R-22 is 1.0114.

v The Compressor ratio should be within Industry standards of 10:1. Higher

discharge pressure will develop more problems. v During compression in a vapour compression cycle when the refrigerant is super-

heated C.O.P is reduced. v Flooded evaporator will transfer about 50% more heat than direct expansion

evaporators because of good contact with evaporator surface. v Requirement of Air Conditioning is 1 TR/ 10m2 area. Approximately.

v Air conditioning a Theater 13.5 seats/TR.

v Factors of human comfort are achieved by controlling the temperature, relative

humidity and air motion. Best comfort for winter 40% R.H and 19oC room temperature Best comfort for summer 60% R.H and 22oC room temperature v Thermostatic expansion valves controls the flow of refrigerant into the evaporator in

an amount that exactly matches the evaporation rate of the refrigerant in the evaporator.

a) Thermostatic expansion valves act in response to the temperature of the suction gas as it leaves the evaporator, along with refrigerator pressure inside the evaporator.

b) The three forces that operate a thermostatic expansion valve are: • The pressure inside the remote bulb and power element. • The pressure inside the evaporator. • The pressure of the super heat spring.

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c) Thermostatic expansion valves are designed so that an increase of 4oF Super heat will cause the valve to completely open.

d) Thermostatic Expansion Valve Remote bulb installation. On suction lines smaller than 7/8” OD, the bulb may be installed on top of the line. On lines larger than 7/8” OD, the bulb should be mounted at about the 4 or 8-O’ clock position. It is preferred that the bulb is installed on a horizontal of the suction line. If it must be installed in a vertical position, the bulb must be installed so that the Capillary tubing extends from the top of the bulb.

v Liquids used in refrigeration normally 20 to 30% heavier than water. v Refrigerant cylinders are normally filled only about 74% liquid full at 80oF (27oC). v Handling of Refrigerant cylinders : a) Never allow a cylinder to be heated to 125oF (52oC). b) Never apply a flame directly to a cylinder.

c) Feasible plug begins to melt at 157oF, but the hydrostatic pressure created by this temperature exceeds the cylinder test pressure.

d) At room temperature pressure in the R-22 is about 150 Psig. and R-11 is about 2.5 Psig. And HFC134a is about 90 Psig.

e) Cylinder colour code R-11 is white at top, violet at middle and Grey at bottom half of cylinder, R-22 is grey at bottom half and violet at top half the cylinder and HFC-134a is light blue at top, violet at middle and grey at bottom half of cylinder.

v Characteristics of a Good Refrigerant: It should possess following characteristics.

a) Low boiling point and also low freezing point. b) High latent heat value and low specific value. c) No effect on moisture. d) Ability to operate on a positive pressure. e) Should be safe and nontoxic. f) Capacity to mix with oil. g) No corrosive effect on metals h) It should be cheap.

v A refrigerant is a fluid that absorbs heat by evaporating at a low temperature,

pressure and gives up that heat condensing at a higher temperature and pressure. a) R-11 Trichloro fluoro methane (CCl3F). Normal boiling point (+) 23.3oC. b) R-22 Chlorodifluoro methane (CHClF2). Normal boiling point (-) 41.3oC.

c) HFC - 134a Tetrafluoro ethane (CH2F CF3) Normal boiling point is (-) 26oC. Mineral oil and HFC-134a are not miscible. It requires that special oil to be used.

HFC134a operates at a moderate positive pressure, thus eliminating all draw backs of a negative pressure system.

d) Leak detection of R-11 and R-22 is accomplished with normal methods of soap bubble solution, halide torch, electronic leak detectors, fluorescent dyes and ultrasonic leak detectors.

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v Numerical Designations of Refrigerants: a) The first digit on the right is the number of fluorine atoms.

b) The second digit from the right is one more than the number of hydrogen atoms. c) The third digit from the right is one less than the number of carbon atoms.

Numerical Designation Chemical Name Chemical Formula R-11 R-12 R-22 R-134a

Trichloro fluoro methane Dichloro difluoro methane Chlorodifluoro methane Tetrafluoro ethane

CCl3F CCl2F2

CHClF2

CH2FCF3

134a, a- asymmetric Bonding.

v Refrigerant circulated lbs/min/ton for HFC 134a is 3.00 and for HCFC 22 is 2.78.

v HFC-134 a requires 3.17 cfm/ton, while HCFC-22 requires 1.83 cfm/ton of cooling. v OZONE LAYER AND GLOBAL WARMING

Ozone has the beneficial role of blocking some of the sun’s ultra violet rays. Too high an intensity of ultra violet rays could result in a greater incidence of skin cancer among the earth’s occupants.

Refrigerants are made of Carbon, Hydrogen, Chlorine and Fluorine elements. a) R-11 and 12 when released, it breaks down at upper atmosphere and chlorine combines with Ozone that exists there and depleting the Ozone concentration. b) R-22 when released to the atmosphere, most of it breaks down before reaching

the ozone layer. It has much less damaging to the Ozone layer. c) R-134a - It contains no ozone depleting chlorine. It has no phase out schedule

and will be available for the lifetime of the chiller. It has similar saturation properties to R-12 and it is the front-runner for a replacement of R-12.

v Ozone depletion potential (ODP) and global-warming potential (GWP) of several

refrigerants relative to R-11.

Refrigerant Formula ODP GWP R-11 R-12 R-22 R-134a Ammonia

CFCl3

CF2Cl2

CHClF2

CH2FCF3

NH3

1.00 1.00 0.055 0 0

1.00 3.20 0.3 0.31 0

v The concentration of natural chlorine in the stratosphere is about 0.6 parts per billion in

1985; currently it is 3.0 parts per billion levels and still raising.

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v About 50% of the predicated globle warming is attributed to the emissions of carbon di-oxide. R-11 & R-12 (CFCs) are responsible for about 15% to 20% of the gases.

v Each module of CFC gases gas approximately 20,000 times more impact on the global

climate than CO2. The control of CFCs more important than controlling CO2 in the preventing of global warming.

v Relative Humidity is the ratio between the mass of water vapour actually present in a

certain volume of air at any temperature and pressure and the mass required to saturate it under the same conditions.

Mass of water vapour actually present in air Relative Humidity (RH) = ---------------------------------------------- * 100 Mass of water vapour required saturating air Under same condition.

v Condenser: a) It is generally assumed that air-cooled condenser will have a condensing temperature of about 14oC (25oF) to 19.5oC (35oF) higher than the ambient temperature. b) Water cooled condensers generally operate with a condensing temperature that is lower than the surrounding ambient temperature. c) In Condenser the amount of heat is given up by the refrigerant must always equal to the amount of heat gained by the cooling medium. d) The amount of sensible heat removed in the condenser is very small when compared to the amount of latent heat removed. e) The condensers are specifically designed to hold the entire refrigerant charge. v The standard of ARI (Air conditioning and Refrigeration Institute) rating

condition is: a) Leaving chilled water temperature 440F (6.670c). b) Chilled water flow rate 2.4gpm/ton. c) Entering condenser water temperature 850F(29.440c) d) Condenser water flow rate 3.0gpm/ton. e) 0.0001 evaporator fouling factor and 0.00025 condenser fouling factor.

v Using the ARI design condition: a) The temperature change in the evaporate is found to be 100F (5.50C) the water

temperature entering the evaporator is than 540F (12.220C) b) The temperature change in the condenser for modern high efficiency chiller is found

to be 9.40F at 3gpm/ton.

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12. Turbine

v ̀U’ loops or expansion loop ensure flexibility of piping between chests and casing and ensures that the lateral stress due to pipe and casing expansion will be equalised from both sides of casing. Thus the stress on the turbine casing due to metal expansion is minimized.

v Where steam pressure is > 1000 PSI, the H.P Cylinder is generally of double shell

design. v The process of providing an arrangement, which will keep rotor speed as closers

constant, irrespective of load conditions is known as Governing of Steam Turbine. v Modern steam turbine, the rate of steam is nearly 4Kg/KWhr.and MAPS turbine steam

rate is nearly 5-6Kg/KWhr. v Steam consumption per hour at no load is 0.1 to 0.14 times the full load steam

consumption for condensing turbine. v Throttle Governing a) It is a simple governing system for Base Load Station. b) Outlet pressure of the Governor valve is lower than the inlet pressure (but enthalpy

remains the same) and hence steam flow is controlled. c) Losses in Steam energy and poor turbine efficiency at part load. v Turbine Losses The losses in a turbine may be divided into two groups – external and internal.

External losses are due to bearing friction and the power required to drive auxiliaries. Internal losses are a) Friction losses b) Leakage losses c) Leaving loss On modern turbines inter-stage leakage accounts for 0.5 to 1.0% loss if the seals are in

good condition. v Casings or Cylinders

The cylinder has to be extremely stiff in a longitudinal direction in order to prevent bending and to allow accurate clearance to be maintained between the fixed and moving parts of the turbine. The working pressure aspects demand thicker and thicker casing and the temperature aspects demand thinner and thinner casings. Design developments took place to take care of both pressure and temperature considerations. Three types of casing design: a) Single shell casing, b)Multiple (double) shell casing & c) Barrel type casing

v Functions of Governing System

a) Control the speed of the turbine when the generator is not synchronized to the grid. b) Control the unit load when TG is synchronized to grid. c) Protect the turbine against over speeding under certain abnormal condition.

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v Governor maintains a constant mean speed of rotation of crankshaft as closely as possible, over long periods during which the load on the engine may vary. It exercises no control on cyclical fluctuation of speed.

v Flywheel serves to limit the inevitable fluctuations of speed during each cycle that arise

from the fluctuations of turning moment of the crankshaft. It has no effect on the mean speed of rotation.

v Exhaust Annulus

a) The maximum blade length approximately 30” for 3600rpm shaft and 46” for 1800 rpm shaft. MAPS LP last stages blade length is 37.2”.

b) The length of blade is determining, the flow area for the steam at the exhaust end of the turbine.

c) The exhaust area and turbine efficiency is interrelated. (i.e.) within certain limits, when the exhaust area is greater the efficiency will be higher.

The last stage annulus) Generator output KW area required in inch2) = ------------------------------------------------- (Rough estimation) ) 1000 * Average exhaust pressure inch. Hg. Abs. v Impulse Turbine a) The pressure drop takes place at fixed blade/Nozzle.

b) Maximum efficiency of an impulse turbine is obtained when the blade speed is approximately half the speed of the steam.

Blade Velocity Velocity Ratio = ---------------- = 0.5 or exactly 0.48

Steam Velocity

v Reaction Turbine a) The pressure drop takes place both fixed and moving blade.

b) Maximum efficiency in reaction turbine is when the blade velocity is almost equal to steam velocity.

Velocity Ratio = Around 0.80 to 0.85 c) Since velocity ratio is high, only a small heat drop can be accommodated per

blade row, larger number of stages is required than impulse turbine. v Compounding a) The process of reducing the rotor speed by absorbing the energy in several stages

is known as compounding. b) In pressure compounding turbine, pressure drop takes place equally in the entire

nozzle, the velocity gained at nozzle is subsequently absorbed in the next moving blades.

c) In Velocity compounding the full pressure drop occurs in the Ist nozzle ring and pressure remain constant in the moving and fixed blades. The total velocity gained at 1st nozzle is absorbed in each moving blades.

d) In Pressure & Velocity compounding is a combination of both the previous methods. Less stage is necessary because of bigger pressure drop in between stages. Hence for a given pressure drop, the turbine will be shorter and the

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diameter of the turbine is increased at each stage to allow for the increasing volume of steam.

MAPS Turbine is Impulse (70%) Reaction (30%) and pressure compounding turbine. v Twisted Blades

The blade speed will vary from root to tip, the ratio of the blade to steam speed changes over the length of the blade. Reasons for impulse at bottom of blade and reaction at top of blade:

a) To accommodate change of velocity ratio. b) To confine steam moving radially out and to have steam flows parallel to the shaft,

towards the exhaust end. v Moisture in Steam will decrease efficiency because: a) The moisture moves slower than the steam and will strike the back of the blade and

retard its forward motion. b) The moisture reduces the quantity of steam actually doing work. c) Since it has an erosive effect on the blade, it is generally not allowed to be >

about 13%. d) This reduces the blade efficiency ½ % for each 1% moisture present in steam in

impulse turbine and 1-1/4 % for each 1% moisture present in Reaction turbine. v Shrouding: The strip of metal joining all blades together at the tips and adds

strength to the blades. It confines the steam within the space of the blades and thus reduces the leakage.

v Lacing wire to dampen vibration along the blades. The lacing holes are however

a source of weakness and the wires disturb the steam path. v Turbine Bearings:

a) Lead wire to measure the bearing clearance should not be more than 0.25mm (0.010") thicker than the estimated bearing clearance.

b) If L/D ratio of Journal bearings is > 0.5 place lead wire at two places on the Journal along its length.

c) Bearing clearance at the top is equal to the thickness of the wire, on the top of the journal, minus the average thickness of the lead wire on both sides of the parting plane.

d) General Thumb Rule of oil clearance of Journal bearings: 0.0375/ 25.4 mm (1.5Thou/inch.) dia for top clearance and side clearance is half of the top clearance.

e) The vertical clearance should not exceed 0.0015mm per mm dia. and when increases to 0.002 /mm per mm dia, the bearing shell should be replaced with a new one.

f) The minimum thickness of oil film depends upon details of design, but an average value is approximately ½ thou per inch radius of the shaft. For example, the minimum film thickness for 18 inch.(MAPS LP Turbine Journal) diameter shaft would be 4½ thou.

g) The general principle of alignment (assuming the coupling faces to be true with the shafts) is that, the shafts are aligned in such a way that a continuous curve is formed

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with their natural deflections from governor to exciter. The shaft will retain their natural deflection at any speed other than the critical speed.

h) Usual bearing temperature range from 1250F (510C) to 1600F (710C); occasionally the oil leaves at 1750F (800 C).

i) In barring gear full oil circulation is provided to the bearing to prevent overheat by conduction from turbine or generator rotor when shutting down since bearing metal tends to become plastic around 3000 F (1490 C).

v The governor is said to be hunting, when a governor is oversensitive, and the sleeve will

oscillate between two extreme when there is a slightest change of speed. v All Governor Pins should be just loose and never more than 0.125 mm (0.005").

TRAPS

v Function of Steam Trap is to send out the condensate, air and CO2 from the system

as quickly as they accumulate. a) Traps must drain condensate because it can reduce heat transfer and cause water

hammer. b) Traps should evacuate air and non condensable gases as quickly and completely as

possible to increase heat transfer and to reduce the corrosion effect. v Types of Steam Traps

a) Inverted Bucket Steam Trap operates on the difference in density between Steam and water.

b) Float and Thermostatic Steam Trap operated on both density and temperature principles. These traps have two valves. A thermostatic element opens one valve to vent accumulated air, while a floating ball controls the condensate discharge valve.

c) Thermostatic steam trap operates on a temperature differential and discharge condensate slightly below the steam temperature, used on application with very light condensate loads.

d) Thermodynamic Steam Traps (Controlled Disc Steam Trap) operates on the velocity principle. A cyclic rate of 15 to 20 times per minute indicates some wear on disc. A rapid machine – gun – like cycle suggests a failed disc that is blowing steam. i. This trap is efficient when the condensate load is between 5% and 50% of

steam trap capacity. ii. Vertically mounded Thermodynamic (disc) steam traps foiled at twice the rate

of those mounted horizontally. v The method of monitoring steam traps: 1) Temperature, 2) Sound, & 3) Visual v Function of Barring gear a) Eliminate the sag of the rotor and hence rubbing at glands is avoided. b) Eliminate hogging of spindles by providing uniform heating and cooling of rotor. c) Maintain oil film in between Journal and bearing and hence direct contact is prevented.

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v Critical Speed: The angular speed at which a rotating become dynamically unstable

with large lateral amplitudes, due to resonance with natural frequencies of lateral vibration of the shaft. MAPS TG Rotor combined critical speeds are 650, 1300, 1850 and 2650 rpms.

v Turbovisory Equipment: is necessary to ensure safe and satisfactory operation of the plant. Deviation of any reading gives advance warning to the operator so that appropriate action to be taken in time to prevent damage.

a) Differential Axial Expansion detects the axial clearance between moving and Stationary parts. Rotor expansion relative to the casing gives positive reading, rotor contraction gives negative reading. If it exceeds the limit, it causes rubbing of moving blades with fixed blades and rubbing of turbine gland labyrinths.

b) Shaft Eccentricity: Measurement gives warning of a bend shaft especially in low speed. At a higher speed the same type of information is measured as vibration.

v Oil Centrifuge Separator is one that is adjusted to continuously separate, discharge

oil and contaminants (water, solids and sludge’s). Contamination creates sticky operation of Governor Valves and reduces the bearing life. MAPS Oil Centrifuge bowl’s speed is 15,000 rpm and motor is 4.5 HP.

v Gas tightness test(Air holding test) for MAPS Generator: Leakage of gas in 24 hrs.

with respect to atmospheric pressure

925 {P1 - P2} | Where t = time in hrs. (24 hrs.) = ---- {--- - -----) | P1 & P2 - initial and final pressure in barometric. t {T1 - T2} | T1 & T2 -initial and final temperature in degree Kelvin.

| Permitted maximum leak rate in volume is 5% of the generator

| Volume (56m3).

v Gas Turbine a) The range of compression ratio in a gas turbine is 5 to 8. b) Overall efficiency of a gas turbine is less than Diesel cycle efficiency.

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PART-B - MECHANICAL GENERAL

1. Vibration and Balancing

v Motion of a machine or machine parts back and forth from its position of rest.

v Displacement, Velocity and Acceleration of a vibration is often referred to as the

“Amplitude” of vibration. Greater the amplitude, the more severe the vibration. v By knowing the frequency of the vibration, we can identify which part is at fault and

the nature of the problem. v Vibration velocity is a direct measure of vibration severity since it is the function of

displacement and frequency. It gives direct measures of machinery condition for the intermediate vibration frequencies 600 to 60000 CPMS.

VPeak = 52.36 * 10-6 (D) (F)2 VPeak = 3.87 * 103 (g)/F

Where VPeak = Vibration Velocity in mm/second D = Peak-to-Peak displacement in microns F = Frequency in Cycles per minutes. GPeak = 0.56 * 10-9 * (D) (F)2 GPeak = 10.69 * 10-6 * (V) (F) Where g = Acceleration due to gravity (980.665 cm/sec/sec) D = Peak to Peak Displacement in microns rms Value = 0.707 * Peak Value rms Value = 1.11 * Average Value Peak Value = 1.414 * rms value Peak Value = 1.57 * Average Value Average Value = 0.637 * Peak Value

Average Value = 0.90 * rms Value Peak to Peak = 2 * Peak Value v Where Stress is of major importance at very low frequencies (less than 600 CPM)

displacement measurement is important. v Acceleration is the function of displacement and frequency squared. v Generally acceleration measurements are recommended for vibration frequencies above

60,000 CPM. Velocity measurement also can be used.

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v Whenever the amplitude of axial vibration is greater than 1-1/2 times of the highest radial (horizontal or vertical), then misalignment or a bent shaft should be suspected.

v Faulty anti-friction bearings cause a high frequency vibration, normally several times the

rotating speed of the part but not an even multiple of shaft RPM. v Problem with sleeve bearings, which result in high levels of vibration or noise. v Phase is defined as the position of a vibration part at a given instant with reference to a

fixed point or another vibrating part. This is essential (a) in diagnosing specific machinery defects comparing the relative motion of two or more parts (b) allows us to balance the part quickly and easily without trial and error techniques.

v Unbalance is the unequal distribution of the weight of a part about its rotating centre line. v CAUSES OF UNBALANCE: There are many reasons that unbalance may be present in a rotor. The most common causes are following: a) Blow holes in castings, b) ?Eccentricity, c) ?Addition of keys and key-ways d) Distortion, e) ?Clearance tolerance, f) ?Corrosion and wear, g) ?Deposit built-up. v Balancing is the technique for determining the amount and location of this heavy spot so

that an equal amount of weight can be removed at this location or an equal amount of weight added directly opposite.

v Unbalance will be measured largest amplitudes in radial (horizontal or vertical) direction.

Overhauling rotor will have axial vibration also equals to radial amplitude. v Eccentricity is a common source of unbalance and can also result in reaction forces. v The amount of vibration is proportional to the amount of unbalance. v Centrifugal force due to unbalance actually increases by the Square of the rotor RPM

that result as unwanted vibration

v Unit for expressing unbalance is the product of the unbalance weight and its distance from the rotating centre line (i.e.) grams-centimeters etc.

v Force (F) Generated by unbalance is

F = 0.01 * (RPM/1000)2 * gram-centimeters

v For L/D ratios less than 0.5 and operating speed upto 1000 RPM single plane balancing is sufficient. Above 1000-RPM two plane balancing is often required.

v For L/D ratios greater than 0.5, two-plane balancing is usually required for operating

speed greater than 150 RPM.

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v Shafts should be designed to operate at a speed that is 20% above or below the critical speed. Shaft that operates above the critical speed should be balanced under operating conditions.

v Locate the test transducer as close as possible to the bearing with solid metal between

the bearing and the sensor. Vibration Due To Unbalance, the amplitude of vibration is proportional to the amount of unbalance present. Normally the largest amplitude will be measured in the radial (horizontal or vertical) direction; however, unbalance of an overhung rotor will often result in high amplitude in axial direction as well (as high as radial amplitude). Axial vibration is the best indicator of misalignment or a bent shaft. In general, whenever the amplitude of axial vibration is greater than one-half of the highest radial (horizontal or vertical), then misalignment of a bent shaft should be suspected. Eccentricity does not mean out-of-round, but means that the shaft (rotating) centerline is not the same as the rotor (geometric) centerline. Vibration Due To Faulty Antifriction Bearings: Anti-friction bearings, which have flows on the raceways, balls or rolls, will usually cause a high frequency vibration. This frequency is normally several times the rotating speed of the part but probably not an even multiple of shaft RPM. Vibration Due To Mechanical Looseness Mechanical looseness and the resultant “pounding” action causes a vibration at a frequency of twice the rotating speed (2 x RPM) and higher orders of the loose part. The vibration characteristic of mechanical looseness will not occur unless there is some other exciting force such as unbalance or misalignment to cause it. Vibration Due To Electrical Problems: Vibration caused by electrical problems is normally the result of unequal magnetic forces acting on the rotor or stator. These unequal magnetic forces may be due to: a) Rotor not round, b) Eccentric armature journals, c) Rotor and stator misalign (i.e. the rotor is not centered in the stator), d) Elliptical stator bore e) Broken bar, f) Open or shorted windings Vibration Due To Aerodynamic And Hydraulic Forces: Machines, which handle fluids such as air, water, gas, etc., will often have vibration and noise due to the reaction of the vanes or blades on the impeller striking the fluid. Vibration of this type is common on pumps, fans and blowers; and can be readily identified because the frequency will be equal to the number of vanes or blades on the impeller times the RPM of the machine.

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2. Shock Pulse Measurement

v 15% addition cost is required for break down maintenance without condition

monitoring. v SPM is a Trend monitoring instrument helps maintenance personnel to know about

surface condition and availability of Lubrication to take corrective action on anti-friction bearings.

v Using vibration analysis, by the time the bearing vibrate, shows large enough to be

deleted. In many cases, the bearing is closes to failure and provides very little warning time.

v It detects development of a mechanical shock wave caused by the impact between two

masses at the initial stage. v It magnifies the weak amplitude and high frequency shock wave and gives out sequence

of electric pulse proportional to the amplitudes of the shock waves. v Shock pulse is measured on decibels scale.

a) LR - Low Rate of occurrence (the value for the relatively small number of strong Shock pulse in the pattern).

b) HR - High Rate of occurrence (the value for the large number of weak shock pulse in the pattern).

v Bearing condition is evaluated based on the measured values, LR and HR and the

basic data input prior the measurement. v Good Bearings will have low HR value and difference between LR and HR (called

the delta value) will be smaller. (about 4). v Lack of Lubrication (Dry running) will have higher HR value and the delta value will

be smaller at initial stage. v Rolling interface surface deterioration or damage will have higher HR Value and delta

value will also be larger. v Cracked inner ring will have low HR value (as if good bearing) and large delta value. v By measuring the variations in the shock pulse patterns of undamaged bearings, the

SPM evaluate the effect of the lubricant film and display a LUB No., which is directly proportional to film thickness.

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3. Material Handling v EOT Crane: a) Before taking load on a Crane, ensure condition of limit switches by operating the

crane without load. b) If a Hook throat is stretched just 15% from original size, or is twisted more than 10

degree, any crack in the hook, do not use it, the hook shall be rejected. c) A clear space 18” wide must be maintained between any moving part of crane and

any stationary part or object. d) While operating mobile crane, vertical or lateral distance between any part of the

crane and any overhead power cable must be more than 6 metres. e) CO2 or DCP extinguishers should be kept in the cabin. f) Crane load test to be carried out once in twelve months as per the Atomic Energy

Factory (Factories) Rules 1996. Upto 20 Ton – Test load 25% excess More than 20T and Upto 50T - 5T Excess More than 50T - 10% Excess

g) Permissible crane beam centre deflection during load test is L/900, Where L = Span length. MAPS T/B Crane 28,000/900 = 31.11mm, S/B Crane 19,500/900 = 21.66mm h) In Cranes hoist mechanism, (equipped with two brakes) each brake should hold at

least 1½ times the rated capacity of the Crane. i) Hooks – Forged and heat-treated alloy steel. j) Limit Switches – One for over hoisting, one for over lowering and one gravity type limit

switch for preventing over hoisting. k) Major cause of break down in cranes and hoists is vibration, which are caused due to

frequent jerky starts of the whole bulk of the crane/hoist. Vibration hence loosens the fasteners and connections causes misalignment and break down.

v Checks before Crane Maintenance: a) Ensure Power Isolation. b) Suitable and Safe ladder or Scaffolding is provided for to access the crane. c) Ensure Lighting arrangement for carrying out the job. d) Basic tool kit and the maintenance manual/checks sheet are carried by the technicians

on to the top of the crane. v Manila ropes are available in the three grades:

Grade –I : Very light in colour, Grade-II : Slightly darker& Grade-III : Considerably darker.

v Synthetic Nylon Ropes: This is strong, roughly 2 times stronger than Manila, has

good abrasion resistance. v Wire Rope : a) Improved plow steel - A high Carbon steel with tensile strength of 2, 60,000

PSI. (i) Wire rope for Sling 6 * 19 (ii) Wire rope for Crane 6 * 37 (flexible). b) When we use 2 wire ropes the included angle should not exceed 90o.

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c) Increasing the angle between the legs of String increases the stress on each leg of sling even though the load is same and reduces the lifting capacity.

v Angle between the leg and tension in each leg are as follows:- 90o

– 0.707W, 120o – 1W, 150o – 1.93W, 170o – 5.74W, 175o – 11.4W, 178o – 28.65W, 180o – Infinity.

v The wire shall be rejected if any one or more of the following conditions observed.

a) The number of visible broken wires exceeds 10% of the total wires in a length equal to 8 dia.

b) Even one broken wire exists below, the metallic socket at the eye of the sling. c) The dia. of the rope is reduced by wear at any point by 10% of more. d) Rope is corroded at the base of a metallic socket or at any point. e) Formation of bird caging, kink, crush or jam. f) A wire rope becomes unserviceable when 5% or more broken wires are showing

in any of 10 diameters. v Chain Slings: Chains for material handling equipment’s are generally made of

carbon steel and small chain hooks are generally drop forged. The chain shall be rejected if any one or more of the following conditions observed.

a) Presence of any crack in welds areas or any other section of the link. b) Wear of the chain link is 10% of its normal diameter.

c) Stretch or elongation is more than 3% of its length. (Elongation should be determined by measuring the length of 10 or 20 links).

d) Bent twisted or damaged links and corrosion of chain links. e) Chains made up of iron of less than 5/16” dia. should not be used for lifting. v D – Shackles: The D-Shackles/Pins shall be rejected if any one or more of the

following conditions exist. a) Width between eyes should not vary. b) Bent or threads damage in pin or pin could not be screwed in all the way. c) Any cut mark/wear is 10% of its original diameter. v Eye Bolts:

a) The eyebolt should be rejected if any crack or damage of thread, which does not allow the bolt to screw in fully. b) Collarless Eyebolts are designed for vertical loads only. c) The shoulder type eyebolt has an angular strength several times greater than the conventional eyebolt. d) Ordinary drop forged steel eyebolt is designed only for vertical load. Shoulder or Collar type eyebolt hole should have enough depth, about 1.5 times of bolt diameter. During tightening collar should be in contact with plain surface, if not contacting with plain surface pack it with washers.

v Lifting Eye Bolts: a) Forged product should be used. b) Lifting at an angle from the shank’s centerline significantly reduces the lifting eye’s capacity. Even a 45o angle reduces capacity. In any case, never exceed a 45o angle. c) Rated capacity in Tons:

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Where `d’ is the shank diameter in inches with unaltered eye and threading. 4d 2 Zeroo angle – 4d 2 (app.), 45o = -----, &Over 45o is not recommended. 4

d) Lifting eye must never be altered by such means as grinding, machining or cutting. e) Ensure Snug seating of the shoulder of the lifting eye. Washer can be used to ensure

lifting eye. Washer can be used to ensure Snug seating as long as there is a 90% minimum threads engagement.

v The breaking strength divided by the actual total stress on the rope is known as the

“factor of safety” and should not be less than the values given in Table. MINIMUM SAFETY FACTORS FOR WIRE ROPE

Slings 8 Overhead electric hoist (small) 7 Overhead traveling cranes (small) 6 ½ Industrial truck cranes 6 Derricks 6 Overhead traveling cranes (large) 5 ½ Hoisting tackles 5

v Safe Working Loads: Safe working loads are to be arrived at by dividing the

minimum breaking load quoted by the manufacturer by appropriate factor of safety depending on the use. Factor of safety as below is recommended in relation to their diameter:

Dia of rope (mm) 12 14-17 18-23 24-39 40 & above Factor of Safety 12 10 8 7 6

It is also recommended that fiber ropes less than 12 mm dia should not be used for a sling or as part of a lifting appliance.

v Lifting Tackles: The load test for newly procured or repaired lifting tackles (except

wire rope) shall be carried out as follows. a) Upto 25 tons (SWL) - Test load is 2 X SWL Tons b) Above 25 Tons (SWL) - Test load is (1.22 X SWL) + 20 Tons

v Safe load in “tons”: When d is the dia in inches. a) Manila Rope (not accurate in sizes larger than 1”) - d2 b) Open Eye Hook - d2, d = dia. of eye c) Chain - 6d2, d = dia. of chain d) `D’ Shackle - 4d2, d = dia. of pin Safe load in tonnes for wire rope slings (6 Strands of 19 wires - New improved plough steel) under different loading condition. a) Single wire rope sling vertical lift - 6d2 say W tonnes. b) Sling or 2 Wire Ropes - Used at 120o included angle - W c) Sling or 2 Wire Ropes - Used at 90o included angle - 1.4 * W d) Sling or 2 Wire Ropes - Used at 60o angle - 1.73 * W

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v Noise Control:

a) The TLV of noise level is 90 dB (A). b) A person can work at 90dBA for 8 hours a day. The time of exposure will be

reduced by 50% for each 5dB (A) increase. c) No exposure in excess of 115dB (A) is to be permitted. d) The limit of audibility is 120 dB (A). e) Properly fitted Earplugs and Earmuffs can reduce the noise level by 30 to 40dB (A).

f) The audible frequency range is 20 to 20000 Hz.

v Forklift: a) Do not drive at a speed exceeding 28 kmph.

b) Keep the fork about 10-15 cm above the ground while driving. c) Forklifts should not be moved on ramps or grades exceeding 1 in 10.

v Working at Height

a) For working at height, above 4.5 meters a safety belt should be used. b) Welders should have safety belt more than 1.5-metre elevation.

c) The belt should be strapped to the upper trunk of the person and the free end hooked to a fixed structure above.

d) Proper working platform with suitable approach ladder should be provided if any work has to be carried out at a height of work more than 2.5 metres from the working floor.

I. Ladder

a) Erect the ladders in the “Four-up-one-out” position (The horizontal distance from the wall to the foot of the Ladder should be about a Quarter of the Ladder’s length). The Angle between portable ladders to the ground should not be less than 75o.

b) The ladder length should not exceed the following limit. Single Ladder - 20ft, Extension ladder - 50 ft. Step Ladder - 18ft and trestle ladder - 16 ft. c) Single ladders are used where the work required to be done is at a fixed height. The

length of a single ladder should not be more than 20 feet and the rungs should be placed 12 inches apart. The inside width between the side rails should be at least 111/2 inches for ladders up to 10 feet length, the width should increase by 1/4 inches for each 2 feet extension in length.

II. Scaffolding a) The recommended nominal bore of scaffolding tube is 40mm. b) The minimum thickness of Scaffolding plank should be 32mm for a span of 1 metre. It is 38mm. for 1.5 metre and 50mm for 2.6 metre. c) A railing of height 1 metre should be provided above scaffolds. d) Toe boards of 15 cm height are to be provided to prevent tools and other materials

from falling down and causing injury to people. e) Where the height is more than 3 times the base dimensions, it should be supported

against overturning. v Manual Material Handling

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a) Maximum weight an adult male worker allowed to lift is 55 Kg. b) Maximum weight an adult female worker allowed to lift is 30 Kg.

v Industrial safety permit is to be obtained for hazardous jobs such as a) Working at height above 2 metres

b) Entry into confined spaces (O2 allowable limit for working should be more than 19% Vol. /Vol. Normal value in atmospheric air = 21.8%).

c) Handling of Hazardous chemicals d) For welding & cutting jobs v Ozone is produced in the air where arc welding is done. It is a toxic gas. The

permissible limit (TLV) of exposure for Ozone is 0.1ppm. v Grinding a) Every abrasive wheel should be visually examined for breakage, cracks or any damage and for expiry date. b) The distance between the work rest and the wheel should not exceed 3 mm. c) Safety guard should cover ¾th of the grinding wheel. d) The wheel should be mounted on its shaft in such a way that the direction of the

thread of the securing nut tend to tighten itself while it revolves. v Storage of Cylinders :

a) Thin walled cylinders such as LPG and dissolved gas cylinders shall not be Stacked in horizontal position. b) The flammability limit of LPG is 3-10%. c) Use Ammonia torch to detect chlorine leak. d) Chlorine cylinder Hydro test is to be done once in two years. e) Since one volume of liquid chlorine when vapourised yield 460 volumes of gas,

hydrostatic rupture in containers, pipelines and other equipments may occur due to build up of excessive pressure.

v Climbing of Stack a) Early, in the morning (when Sun is not hot) b) No strong winds or rains c) 5 minutes rest after each stage d) Second person can climb after first person reach the next stage Climbing

down also can follow the same precautions. v Safety in Construction of work: All personnel should be removed to a safer

side, which are at least 150 metres away from the blasting point. v The cutting speed of Hacksaw should not exceed 60 strokes per minute.

v Gap between guard and accessible rotating parts, should be never larger than ½ an

inch. v Hand injury due to slippage of torsion tool is 25% of total accident in a year.

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4. Hydraulics v Pascal’s ((French Scientist) Law: Pressure applied on a confined fluid is transmitted

undiminished in all directions and acts with equal force on equal areas and at right angles to them.

v Joseph Bramah (British Mechanic) utilized Pascal’s discovery and developed

hydraulic press. He also decided that if a small force on a small area would create a proportionally larger force on a larger area, the only limit to the force a machine can exert is the area to which the pressure is supplied.

v Hydraulic means transmitting power by pushing on a confined liquid. Input and output

component of the system is called a pump and an actuator. v Advantages of Hydraulics a) Variable speed by varying the pump delivery or using a flow control valve. b) Variable force by varying the pressure using Relief Valve or Pressure Reducing Valve. c) Reversible. Actuators can be reversed instantly using four way valves. d) Small packages e) Can be stalled. Hydraulic Oil a) Non-Compressible. It will compress 0.5% at 1000 PSI pressure. It can transmit

power instantaneously. b) Greek word hydor means “water” and autos means “pipe”. c) Lubrication ability to the moving parts of the components. d) Pressure build up is 0.4 PSI/foot of oil column. Positive Displacement Pump a) Except for changes in efficiency, the pump output is constant regardless of pressure. b) The output is positively sealed from the inlet, so that whatever gets in is forced out the

outlet port. c) The sole purpose of a pump is to create flow; pressure is caused by a resistance to

flow. d) Most pump manufacturers recommend a vacuum not more than 2½-PSI pressure

difference to push the oil to the pump. e) In general for external gear pumps and for vane pumps as a “rule of thumb” never

exceed 7 inch. Hg. vacuum in the pump suction. Pressure drop through an Orifice a) When there is a pressure drop, there is a flow. b) Increase in pressure drop will always be accompanied by an increase in flow. c) When the pressure is equal on both sides, the oil is pushed equally both way and there

is no flow.

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v Pressure equals the force of the load divided by the piston area

F (i.e.) P = ---

A v Speed of an Actuator or motor rotates depends on its size and the rate of oil flow.

Volume/Time

(i.e.) Speed = --------------- Area

v Velocity in Pipes: a) General recommended velocity ranges at pump inlet line is 2 to 4 feet/sec. and

outlet/working line is 7 to 20 feet/second. Note: Very low velocity is recommended for the pump inlet line because very little

pressure drops can be tolerated there. b) Doubling the inside diameter of a line, Quadruples the crossectional area; thus the velocity is only one fourth as fast in the larger line. v Horse power in a hydraulic System:

a) Speed and distance are indicated by the gpm flow and force by pressure. b) If we assume an average efficiency is 80% power input required. Hp = gpm * PSI * 0.0007 Where 1 gallon = 231 Cubic inches

v General torque – Power formulas for any rotating equipment. 63025 * hp

Torque in inch pound = -------------- Rpm

v A hydraulic device, which uses the impact or kinetic energy in the liquid to transmit power, is called a hydrodynamic device.

v When a force applied to a confirmed operates the device liquid it is called a hydrostatic

device. v One atmosphere is equivalent to approximately 10.363 metre or 34 feet of water or

37 feet of oil or 29.92 (usually rounded off to 30) inches of Mercury. (2 inch. Hg = 1 PSI (Approx.).

v Flow is measured in two ways

(a) Velocity is the average speed of the fluid’s particles past at a given point per unit of time. (b) Flow rate is a measure of the volume of liquid passing a point in a given

Time.

v Daniel Bernoulli’s (Swiss Scientist) principle says that the sum of the pressure energy and Kinetic energy at various points in a system must be constant if flow rate is constant.

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v Four Primary purposes of the Hydraulic fluids

a) To transmit power b) To lubricate moving parts c) To seal clearances between parts

d) To cool or dissipate heat v Quality requirement of Hydraulic fluid

a) Prevent rust b) Prevent formation of Sludge, gum and varnish c) Depress foaming d) Maintain its own stability and thereby reduce fluid replacement cost. e) Maintain relatively stable body over a wide temperature range f) Prevent corrosion and pitting g) Separate out water h) Compatibility with seals and gaskets

v Viscosity: Is the measure of the fluid’s resistance to flow; or an inverse measure of fluidity. Unit – Centistokes (mm2/sec). A high viscosity is desirable for maintaining sealing between mating service. However, too high a viscosity increases friction, resulting in:

a) High resistance to flow b) Increased power consumption due to frictional loss c) High temperature caused by friction. d) Increased pressure drop because of the resistance.

And if the viscosity be too low: e) Possibility of Sluggish or slow operation f) Difficulty in separating air from oil in reservoir g) Internal leakage increases h) Excessive wear i) Pump efficiency may decrease, causing slower operation of the actuator j) Increased temperatures result from leakage losses. v Absolute Viscosity: Poise viscosity is defined as the force per unit of area

required to move one parallel surface at a speed of one centimeter per second past another parallel surface separated by a fluid film one centimeter thick.

Unit - Poise, Centipoise Shear stress Absolute Viscosity = ---------------- Rate of S-bear

v Kinematic Viscosity: The Co-efficient of absolute viscosity, when divided by the density of the liquid is called the kinematic viscosity. Unit - Stoke, Centistoke, Centipoises Centistoke = -------------- Density

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v SUS (Saybolt Universal Seconds) Viscosity: It is a Relative Viscosity is determined by timing the flow of a given quantity (60 milliliters) of a fluid through a standard orifice (0.176 cm. Diameter and 1.223 cm. long) at a given temperature. (100oF or 210oF). Ordinary, Viscosity tests are made with the oil at a temperature of 100oF. If more than 1000 seconds would be needed to empty the container because of thick oil, the oil would be heated to 210oF.

v Viscosity Index: Is an arbitrary measure of a fluid’s resistance to viscosity change

with temperature changes. A fluid that has a relatively stable viscosity at temperature extremes has a high viscosity index (VI). A fluid that is very thick when cold and very thin when hot a low VI has.

v Pour Point is the lowest temperatures at which a fluid will flow. For a thumb rule,

the power point should be 20oF below the lowest temperature to be encountered. v Oxidation Resistance (a) Oxidation or Chemical union with Oxygen is a serious reducer of the service life

of a fluid. (b) Oxygen readily combines with (petroleum oil) carbon and hydrogen. (c) Most of the oxidation products are soluble in the oil and additional reactions take

place in the products to form gum, sludge and varnish which plug orifices, increase wear and cause valves to stick.

d) When the maximum temperature of hydraulic system exceeds 150oF (65oC) oil oxidizes. The rate of oxidation approximately doubles with every 18oF (10oC) increase in temperature according to the characteristics of the fluid. Some fluid power research indicates that the working life of most oil is decreased by 50% for every 15oF rise in temperature above 140oF (60oC). Oxidation causes sludge to form, reduce clearance, creates more heat and causes corrosion.

v Emulsification: An emulsion is a mixture of oil and water is highly undesirable

because it has poor lubricating qualities. The process causes an emulsion (water enters the system and gets churned up with the oil) to form is called emulsification.

v Most of the Petroleum products (Hydro carbons) are approximately 85% Carbon

and 15% hydrogen. The difference between the products is determined by the size of the molecules and the arrangement of the atoms in those molecules.

v Rust and Corrosion Prevention a) Rust is the chemical union of iron (or steel) with Oxygen. b) Corrosion is a chemical reaction between a metal and a chemical usually an acid.

Acid results from chemical union of water with certain elements. c) Both rust and corrosion contaminate the system and promote wear. d) Rust and corrosion can be inhibited by incorporating additives that “plate” on the

metal surfaces to prevent their being attacked chemically. v Synthetic fluids are not compatible with the commonly used Nitrile (Buna) and

Neoprene seals.

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v Pressure and Flow Considerations a) Industry Standard recommended safety factors: Operating Pressure Factor of Safety 0–1000 PSI 8 to 1 1000-2500 PSI 6 to 1 Above 2500 PSI 4 to 1 Burst Pressure (BP) Factor of Safety (FS) = ---------------------------- Working Pressure (WP) b) Nomographic Chart can be used to select the pipe/tube internal size if the velocity and flow rate is known. G.P.M * 0.3208 Area (Sq. inch) = --------------------- Velocity (ft/sec.) v Seal Materials a) Natural rubber is seldom used as a sealing material because it swells and deteriorates

in the presence of oil. b) Synthetic rubbers (elastomers) are quite compatible with oil. Buna-N retains sealing properties from 40o to 230oF. It does swell in some synthetic

fluids. Viton for high temperature oil. Neoprene: Above 150oF neoprene is unsuitable as a sealing material because of a tendency to vulcanize or “Cook”. c) Silicone

It retains its shape and sealing ability to –60oF and is generally satisfactory upto 400 to 500oF.

At high temperature it tends to absorb oil and swell. This however, is no particular disadvantage in static application.

Silicone is not used in reciprocating seals, because it tears and abrades too easily. v Functions of Reservoirs a) Store house for the fluid until called for by the system. b) Place for air to separate out of the fluid. c) Permit contaminants to settle out. d) Dissipate any heat that is generated in the system. e) When filling the hydraulic oil into the system, a filter of less than 60µm(less than 220

mesh) should be used. v Baffle Plate a) Height of the Baffle plates is usually 2/3 of the height of oil level. b) Prevent local turbulence in the tank.

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c) Allows foreign material to settle to the bottom. d) Gives the fluid on opportunity to get rid of entrapped air. e) Helps to increase heat dissipation through the tank walls. v The pump suction strainer should be will below the normal fluid level in the tank

and at least 1 inch. from the bottom. v Reservoir Sizing Thumb Rule Tank Size (gallons) = Pump gpm * 2 or 3. v Accumulator Nitrogen Precharging

A range of 1/3 to 1/2 of the maximum hydraulic pressure will give good results on most applications.

v Three different classifications of the hydraulic valves. a) Direction Control to start, stop and reverse cylinders and motors. b) Volume Control to regulate rate of fluid or speed of an actuator. c) Pressure Control to regulate or limit force. v Hose Installation: Six basic rules of thumb to use when installing hose are:

a) Make it big (diameter) b) Make it long (generous, no tension) c) Never exceed the minimum bend radius d) Never install a twisted hose. (A slight twist in a hose can reduce its life by 70%). e) Protect hose lines that pass close to a heat exhaust manifold with a fire proof

boot or a metal baffle. f) Always use proper fittings

v Tubing’s are usually flared to 37 or 45 degree, depending on the fitting used.

v It holds particles of dirt and other foreign matter, which have abrasive effect causing

damage through excessive wear.

v Selection of Accumulator: For every 1% an accumulator is oil charged above the minimum system pressure, it will deliver 1 inch3 of oil for each gallon of its rated size.

a) A piston accumulator may be mounted in any position. b) The preferred mounting position for bag-type accumulator is vertically upright, although

they will operate in our position. v Function of Accumulator:

Act as an energy storage device, shock absorbers and pressure surge dampeners. v Recommended Reservoir Capacity is three times the flow rate in gallons per minute.

v Square or a rectangular tank has the largest heat transfer surface per unit volume.

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v Reservoir should contain additional space equal to at least 10% of its fluid capacity for thermal expansion of the fluid, gravity drain back during shutdown and still provides a free fluid surface for air separation.

v Relationship between Horse power, Torque and Speed

Torque (ft-lb) * Speed (rpm) HP = ----------------------------------- 5252 v Hydraulic systems for machine tools usually work in a temperature range from 100oF

(38oC) to 140oF (60oC). v Hydraulic fluid, which is normally mineral oil, usually has a specific gravity between 0.8

and 0.9, which means that its weight between 80 and 90% that of water. v Horse Power (a measure of the rate of work) involves three factors. Force, distance and

time (in hydraulics. Flow pressure and time). v 1 HP = 1 gpm at 1500 PSI (approx.) (1hp moves 33,000 lbs to the distance of 1ft in 1

min.) 1 HP = gpm * pressure * 0.00058 (100% efficiency) 1 HP = gpm * Pressure * 0.0007(85% efficiency)

v Rule of thumb estimates for heat generation:

a) Hydrostatic systems: 20 to 40% of input horse power goes to heat. b) 25 to 30% of input horse power goes to heat in torque converter systems (no

retarder). c) Pump and Cylinder systems: 15 to 25% of input hp goes to heat, plus any heat

restriction. Heat of restriction: gpm*psi (drop across restriction) * 0.00058 equals the amount of horse power going directly into heat.

d) Pump and Cylinder systems: 15 to 25% of input hp goes to heat, plus any heat restriction. Heat of restriction: gpm * psi (drop across restriction) * 0.00058 equals the amount of horse power going directly into heat.

v To find the capacity of a cooler when oil temperature drop across cooler and gpm

are known. gpm * temperature drop * 210 = Btu/hour capacity

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5. Engineering Materials

v Ferrous Materials: Those containing iron as principal constituent e.g., cast iron,

wrought iron and various types of steels. v Non-ferrous Materials: Those, which do not contain iron as principal constituent

e.g. Aluminium, copper, zinc etc. v Non-metals: Several non-metallic minerals, which are of considerable use in

various fields of engineering, are rubber, polystyrene, nylon etc. v Elastic Limit: It is the greatest stress a material can withstand without permanent

elongates when the load is removed the sample will return to its original length. v Yield Point: The stress at which appreciable elongation occurs without increase in

stress. v Ultimate Strength: Maximum stress needed to break a specimen.

v Modules of Elasticity: It is the ratio of stress to strain within the elastic limit. It is

a measure of stiffness. v Elongation: It is the ratio of the increase in gauge length to the original gauge

length expressed in percentage. v Ultimate Strain: The unit elongation (elongation per unit of length) at the specimen

breaking point. It is a measure of ductility. v Ductility and Brittleness: It refers to the ability of a metal to deform plastically

without fracturing. It is most commonly measured by means of elongation and reduction of area in the tensile test.

Final gauge – Original gauge length

% elongation = ------------------------------------------- * 100 Original gauge length Original area – Final area

% reduction of area = ------------------------------ * 100 Original area A material is generally classified as brittle if the percentage elongation is less than 5

in a gauge length of 50mm. v Poisson’s ratio: It is the ratio of the transverse to the longitudinal elastic strain in an

axial member, loaded on its longitudinal axis.

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v Stiffness: It refers to the ability of a metal to resist bending stretching, shortening and twisting. It is defined by the Modulus of elasticity. The modulus applies only within the elastic range-the range within which a metal will return to its original shape if the load is removed, it is the ratio of stress to strain.

v Indentation Hardness: In metal working, hardness means resistance of penetration.

It may, also include resistance to scratching, abrasions, or cutting. Indentation hardness is generally measured in terms of Brinell hardness number or Vicker’s pyramid number or Rockwell (Scale B or C) hardness number.

v Fatigue : It is a description of the behavior of metals under the action of alternating

(cyclic) loads as distinguished from the behavior under steady loads. Cyclic stressing may take place in bending, tension, compression, and torsion or in combination of these and may be found in such diverse applications as axles, connecting rods, springs etc.

v Impact Strength: It is the ability of a material to withstand on shock loading.

v Transverse Shear Strength: The value obtained by dividing the breaking load by the

transverse shear area. It is needed in the design of rivets, bolts, pin and other such components.

v Torsion: The twisting of materials by force, which turns one end of a bar about its

longitudinal axis while the other end, is either clamped in a rigid fixture or twisted in the opposite directions.

1) Low Carbon Steels - Carbon content below 0.15% 2) Mild Carbon Steels - Carbon contents 0.16% to 29% 3) Medium Carbon Steels - Carbon content 0.30% to 0.59% 4) High Carbon Steels - Carbon content above 0.60% to 1.70% 5) Cast Iron - Carbon content above 3% 6) Low alloy steels - Alloy content below 8% 7) High alloy steels - Alloy content above 8% 8) Stainless Steel - Above 12% Chromium v The corrosion rate of metals typically doubles with each 10oC increase in temperature. v Intergranular Corrosion: Localised attack occurring along the crystal boundaries of

a metal or alloy. v Stress Corrosion Cracking (SCC): Failure by cracking under the conjoint action of

a constant tensile stress, which is applied to residual, in certain chemical environments specific to the metal.

v Stress Relief Cracking: Cracking between metal grains in the heat affected zone of a

weldment during the exposure to high temperatures.

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v Creep: When a material is subjected to internal load within elastic limit at elevated temperature for a prolonged duration, a permanent set occurs. This progressive deformation of material is known as creep.

v EN (Emergency Number) Series Steels are coming under medium carbon steel range.

Can be hardened by heat treatment. Weight of metal:

a) 7.85 grams/cc or 7.85 Kg/Sq. Mtr./1mm thick for carbon steel. b) 40.833 lbs/Sq.foot of plate/1 inch. thick. c) 7.97 grams/cc for stainless steel. v Abrasives used for surface finishing and its size is given as grit size. Artificial

abrasives are silicon carbide, aluminium oxide, and boron carbide or boron nitride. Fine Aluminium oxide in powder with smaller particle 0.5micron or 0.0000197 inch. is used for fine finishing of surface.

v Admiralty Brass: It contains 71% Copper, 0.75% tin and 28% Zinc. Tin (additional

corrosion resistance) increases the hardness and strength but decreases the ductility. Used in MAPS LP Heater’s tubes.

v Aluminium Brass: It contains 76% Copper, 0.4% of Arsenic, 2% Aluminium and

remainder is Zinc-22%. Good corrosion resistance material. MAPS -Main condenser’s tubes and process water HX’s tubes material.

v Aluminium Bronze: It contains 5 to 10% Aluminium and remainder is Copper.

Addition of Aluminium to Copper increases the strength upto three times that of the original copper. MAPS - Main condenser and process water HX’s tube sheet material.

v Babbit Metal: It is a bearing metal of tin or lead base. Tin-antimony-Copper white

alloys used for machinery bearings. Connecting rod bearings has 86% tin, 5 to 6.5% copper, 6 to 7.5% antimony and 0.35% lead will have a compressive strength upto 20,000 PSI. Copper increases hardness and toughness in the alloy and rises the melting point. Antimony increases hardness of the metal and forms hard crystals, which improve the alloy as a bearing metal.

v Bronze : It contains 70 to 85% Copper, 5 to 10% tin and 5 to 25% lead with Zinc

below 0.50% (ASTM bearing bronze).

v Brass: It contains 70% Copper, 0.4% Arsenic and remainder is Zinc about 30%.

v Cupro Nickel: It is a high thermal conductivity and heat resistance material. a) 70/30 Cu.Ni. - At MAPS – Used in Moderator HX’s tubes material.

b) 90/10 Cu. Ni. – At MAPS - Used in HP Heater 5&6.

v Monel: It contains 30% Copper, 70% Nickel and 0.1% Cobalt.

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At MAPS - Used in boiler tubes. It is a chemical stability material and its melting point is 1500oC.

v Stellites: It contains 40 to 48% Cobalt, 30 to 35% Chromium and 12 to 19%

tungsten. v Zirconium Alloys generally have only small amount of alloying elements. To add

strength and resist the pick up of Hydrogen. a) Zircoloy - 2 contains 1.5% Sn, 0.12% Ferrous, 0.10% Chromium, 0.05%

Nickel and balance is Zirconium. Tensile strength is 68,000 PSI, elongation 37% and hardness Rockwell B89 and at 600oF. It remains strength of 30,000 PSI.

b) Zircoloy-4 contains 1.5% Sn, 0.22% Ferrous, 0.1% Chromium, 2% Niobium and balance Zirconium. (No Nickel) c) Zircaloy – 2.5%Nb : Zn 100ppm, Fe 1500ppm, Cr 200ppm, O – 900-1300ppm, Ni – 70ppm, Nb – 2.4-2.8%.Sn counteract the effect of N2 ,Cr, Fe, Ni(0.81-0.38%) reduces hydrogen pick up and stabilizes oxide film.

I. Specific properties of Nb are at high temperature a. Not affected by creep b. Not corroded by gases

II. Why Zr was selected?

a) Low neutron adsorption cross section b) Good corrosion resistance in high temp. water as long as oxygen content is less.

MECHANICAL PROPERTIES

v Tensile Strength: This is the ability of a material to withstand tensile (stretching) loads

without rupture occurring. The material is in tension.

v Compressive Strength: This is the ability of a material to withstand compressive (squeezing) loads without being crushed or broken. The material is in a compression.

v Shear Strength: This is the ability of a material to withstand offset or transverse loads

without rupture occurring. The river connecting the two bars shown is in shear whilst the bars themselves are in tension. Note that the river would still be in shear if the bars were in compression.

v Toughness: impact resistance: This is the ability of materials to resist shatter. If a

material shatters it is brittle (e.g. glass). If it fails to shatter when subjected to an impact load it is tough (e.g. rubber). Toughness should not be confused with strength. Any material in which the spread of surface cracks does not occur or only occurs to a limited extent is said to be tough.

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v Elasticity: This is the ability of a material to deform under load and return to its original

size and shape when the load is removed. Such a material would be required to make the spring shown.

v Plasticity: This property is the exact opposite of elasticity. It is the state of a material, which has been loaded beyond its elastic state. Under a load beyond that required to cause elastic deformation (the elastic limit) a material possessing the property of plasticity deforms permanently. It takes a permanent set and will not recover when the load is removed.

v Ductility: This is the term used when plastic deformation occurs as a result of applying

a tensile load. A ductile material combines the properties of plasticity and tenacity (tensile strength) so that it can be stretched or drawn to shape and will retain that shape when the deforming force is removed. For example, in wire drawing the wire is reduced in diameter by drawing it through a die.

v Malleability: This is the term used when plastic deformation occurs as the result of

applying a compressive load. A malleable material combines the properties of plasticity and compressibility. So that it can be squeezed to shape by such processes as forging, rolling and river heading.

v Hardness: This is the ability of a material to withstand scratching (abrasion) or

indentation by another hard body. It is an indication of the wear resistance of a material.

Processes, which increase the hardness of material, also increase their tensile

strength. At the same time the toughness of the material is reduced as it becomes more brittle.

Harden ability must not be confused with hardness. Harden ability is the ability of a

metal to respond to the heat treatment process of quench hardening. To harden it, the hot metal must be chilled at a rate in excess of its critical cooling rate. Since any material cools more quickly at the surface than at the center there is a limit to the size of bar which can cool quickly enough as its center to achieve uniform hardness throughout, this is the ruling section for the material. The greater its harden ability the greater will be its ruling section.

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6. Surface Finish and Flatness

Surface Finish Different process produce different degrease of finish on machined surfaces. These are graded from N1 an average height of roughness of 0.025µ, upto N12 roughness 50µ. a+b+c+...H Average height of roughness Ra = -------------

L Where a, b, c etc. = area on graph and L = Length of Surface.

Roughness Grade symbol

∇∇

∇∇∇

∇∇∇∇

Roughness valves Ra µm

25-50

8 – 25

1.6 – 8

0.025 - 1.6

Less than 0.025

1 Micro inch = 0.025 microns ____________________________ R.M.S = √ h12 + h22 + h33 + ………… + hn2 -------------------------------------------------------------- n Instruments used to measure surface finish is

1) Profile meter and 2) Comparator Flatness: All the points on the surface are lieing in the same plane. Instrument used is Monochromatic Light Optical Flat Checking Machine. Flange Surface Finish: a) Concentric serrated grooves 1/16” deep and 32 serration/inch for CAF gasket.

b) 80 micro inch is always preferable and 150 to 200 micro inch also acceptable for a Metallic gasket.

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7. Hardness Testing

v Hardness test on Material consists of pressing a hardened or point into a specimen

and measuring the size of the resulting indentation. v Rockwell method uses a ball or diamond cone. v Brinnel hardness number (BHN), the ball size is 10mm for most cases or 1mm for light

work. Load

BHN = ------------------------------------------ Spherical area of the indentation a) The tensile strength of a metal in pounds per square inch. is 500 times its brinell hardness. b) The Brinell and Vickers hardness values are practically identical upto a hardness of 300. c) In Brinell hardness the testing time of loading is 15 seconds. v Vicker’s pyramid method, which utilises a pyramidal point. (Pyramid indentor apex is

40o. v Shore Scleroscope measures the height of rebound of a hammer falling on the surface. v Shore durometer v Hardness of antifriction bearing i) Inner and Outer race is 55 - 58 HRC

ii) Rolling element is 58 - 63 HRC. Common Types of Hardness Tests, Inventors and Applications

-------------------------------------------------------------------------------------- Test Indentor Load Material Brinell 10mm ball 3,000 Kg Cast iron and steel Brinell 10mm ball 500 Kg Nonferrous alloys Rockwell A Brale 60 Kg Very hard materials Rockwell B 1/16” ball 100 Kg Brasses and low Strength steels. Rockwell C Brale 150 Kg High strength steels Rockwell N Brale 15-45 Kg Hard coatings, Superficial hardness Rockwell Y ½” ball 15-45 Kg Soft Coatings, Superficial Hardness Vickers Diamond 50g - 1 Kg All materials Pyramid Knoop Diamond 500 g All materials Pyramid -------------------------------------------------------------------------------------------------------------------

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8. Mechanical Fasteners v Surfaces are often serrated to achieve biting effect on the gasket, so that there is better

confidence of the deformation of the gasket. v The strain of the deformation of the gasket is often beyond the elastic limit. So, a gasket

is advocated to be considered as one-time use component. Sequence of tightening the fasteners helps ensure that the a) Surfaces are moved towards each other with proper orientation and location. b) The fasteners share equal load. c) Gaskets do not loose its flexibility.

v Mark or scribe a diagonal line down the side before the equipment is disassembled. It

helps to align the line during reassembly to ensure the components are in proper sequence.

v Always Bolt and nut threads are to be lubricated to reduce friction between the

threads and nut to washer so that maximum preload can be achieved. v Repeated unscrewing and tightening of steel nuts score threads. After 50 tightening, the

torsional resistance is approximately 100% greater than for the first tightening. After 200 tightening it is approximately 156% greater.

v Always use correct size spanner v Hexagonal head Flat to Flat is 1.5 times and Corner-to-Corner is 1.7 times of bolt size. v Socket head bolts are made of high tensile steel, head thickness is 1d and the dia. of

head is 1.6d when d is the out side or major diameter of thread. v Thickness of standard nut required is 0.8d and thickness of thin nut is 0.5d.

Thickness of plain washer is 0.15d. v A fine thread is suitable to joints subject to vibration. v The strength of fine threads of tapped hole is greater for sizes 1 inch and under. Strength

increases as the size decreases. v A Coarse thread is desirable where the hole is tapped in weaker materials, for example,

Cast iron, Aluminium and Magnesium alloys. It is stronger in size 1 inch. and over. v A higher bolt pre-load will lower the effect of the cyclic load on the total bolt load. v As a rule, the cyclic load in the bolt should be less than 25% of its yield strength. v The tightening of bolt should be followed as per bolt tightening sequence and should be

tightened in four steps, hand type, 1/3 torque, 2/3 torque and full torque.

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v Use torque wrench to ensure proper torque

v Combined load (Assembly load):

When system is in pressure, the internal pressure tends to force flanges apart and extrude gasket through the flange clearance space. Residual gasket stress is the stress remaining on the gasket at operating condition. Hence assembly load is hydrostatic end thrust + Residual gasket load.

πD2 | Where D = Inside Diameter of the gasket in inch. (i.e.) ------- * P + πD 2b.m.P | b = Width of the Gasket in inch. 4 | P = Pressure in PSI

| m = Recommended maintenance factor v Residual gasket load becomes zero for self-energizing type seals since value of `m'

factor is zero. v Commonly used gaskets are identified and their compatibility to different fluids and

pressure temperature ratings are given in Table-1. v Generally non metallic gaskets should not be considered above 555oC (850oF) and

below 18oC (65oF) or pressure in excess of 85 Kg/cm2 (1200 PSI). v Gasket material (have enough mechanical strength) is selected to withstand the pressure

and temperature of the fluid based. Refer Table-II for dimension less number. v Basically, the criteria fro proper gasket selection can be referred to as TAMP:

Temperature, Application, Media and Pressure. v ̀Y’ factor is the minimum gasket seating stress (varies with material, thickness, density

and gasket type) is required to flow the gasket into the flange surfaces. `Y' factor for different material and required surface conditions are given in Table-IV.

v ̀m’ factor is the ratio between the residual loads on gasket area to the internal pressure.

`m' factor for different material is given in Table-VII. v Nut factor is an experimental constant used to evaluate or describe the ratio between

the torque applied to a fastener and preload achieved. Table-VI lists nut factors for various lubricants.

v The torque value varies around 30% depending upon the cleanliness and lubrication of

the fasteners. Hence gasket manufacturers specify the compression of gasket rather than to the torque applied on bolts.

a) Spiral wound metallic gaskets can be compressed to 24% to 28% of its original thickness. Recommended gasket compression for spiral wound gasket is given in Table-III.

b) C.A.F joints can be compressed to 15 to 20% for getting a flow of gaskets for a 600 /1500 rating flange joints.

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v For torque values up to 125 lb-ft tighten the joint with a minimum of four tensioning

passes and over 125 lb-ft, use good mechanics judgment to increase a number of additional tensioning passes to avoid over compression of the gasket.

v Nuts are normally of softer material than the bolts. This ensures plastic yielding which

enables the nut thread to divide the load more evenly. v There is no strength grading system for small screws (< 1/4 inches.). Care must be

exercised when selecting pre load and torque. v Never use Torque wrench to loose the nut. __ v Diameter of rivets = 6√ t (unwin’s formula) where t is the thickness of plates

connected in mm. It should be rounded off to the Standard Value. Torque: Unit = lb-ft & Kg-m 1 Kg-m = 7.233 lb-ft 1 Kg-m = 9.81 Nm

1 lb-ft = 1.356 Nm 1 Nm = 0.74 lb-ft

1 HP = 33000 lb - ft = 4500 kg-m

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9. BOLTING OF FLANGE JOINTS

v PRELOAD is the tension force developed in the fastener when it is tightened against the joint.

v INITIAL PRELOAD is the tension created in a fastener when it is first

tightened, before the wrench has been disengaged from the nut. v RESIDUAL PRELOAD The remaining tension in a previously tightened

fastener after such factors as elastic interactions, creep etc. Have allowed the fastener to relax a little from its initially tightened condition.

v SHORT FORM TORQUE/PRELOAD EQUATION: The torque required to produce a desired pre-load is given by: t = kd fp Where t = torque, k = nut factor, d = nominal diameter & fp= pre-load

Equation gives the relationship between pre-load and torque. The two are related by the nominal diameter and the nut factor.

v NUT FACTOR (K) is an experimentally determined factor, which characterizes the

relationship between the torques, applied to the nut and the preload achieved. It accounts for the many variables affecting the relationship between torque and preload. As a result the nut factor is subject to wide variation, depending on the specific conditions under which it is measured.

v PRELOAD MEASURING METHOD: VARIATION ACCURACY RELATIVE COST Hand tight + 50 - 100 Low Torque wrench + 25 - 40 Low Turn - of - the nut + 15 Moderate Load indicating washer + 10 Moderate Fastener elongation + 3 - 5 High Strain gages + 2 - 5 Very high v Prying: External tension loads on a fastener are magnified by a lever action called

prying when the line of action of the external load does not lie along the axis of the fastener.

v Thread stripping is an insidious type of failure. It starts at the stressed thread and

gradually, the remaining threads “peel off” through the entire length of engagement. v ELASTIC INTERACTION is the process in which the previously tightened bolt will

relax somewhat when its neighbors in the joint are subsequently tightened is called elastic interaction.

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v FLANGE ROTATION is the outer edges of a raised face flange are pulled towards each other when the bolts are tightened. This distortion is called flange rotation.

v POINTS TO REMEMBER: a) Nuts are normally of softer material than the bolts. b) It is recommended to store a torque wrench with a torque setting above 20% of

maximum range c) Never use a torque wrench to loosen nuts. d) Use hardened washer between the turned element and the joint surface. e) Select a fastener that is long enough to allow a length of two thread pitches to

protrude beyond the nut face after tightening.

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10. Pressure Vessel Testing

v Hydro test is always safer than pneumatic test. v Pneumatic test result is more accurate than Hydro test. v Pneumatic test pressure is always less than Hydro test pressure. v Range of pressure gauge for leak test/pressure test 1.5 times to 4 times of test pressure. v Sensitivity of various leak test methods

By Hydro test - 10-2 Std.cc/sec By Bubble test in water ) - 10-4 Std.cc/sec

By Pneumatic test (Soap) ) By Ultrasonic test - 10-8 Std.cc/sec. By Helium test - 10-11 Std.cc/sec. v Acceptance leak rate in helium leak test

Mechanical Joint - 10-4 Std./sec. Welding - 10-6 Std./sec.

Fuel bundle - 10-8 Std./sec v To find leak in a gas service flange: Wrap a 2” wide marking tape around the flange;

pack a pin hole in the centre of the tape and apply soap water solution. If bubble or foam appears, the flange is leaking.

v As per the Indian Boiler Act 1923 a) A boiler means any closed vessel exceeding 23 Litres (5 gallon).

b) If any accident occurs, within 24 hrs, the accident report shall be sent to the Boiler Inspector.

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11. Sealants

Araldite hardeners to the resin ratio and Curing time v Using Hy 830 and Hy 850 (Hardeners)

Formula-1 Formula-2 Formula-3

-Parts by Weight -

Araldite Gy 250 100 100 100 (Base) Hardener HY 830 45 50 30 (Slow Curing) Hardener Hy 850 15 10 30 (Accelerated) Reactivity Average Slow Fast Pot life (Curing) At 30oC 1 ½ Hrs. 2 Hours ½ Hour Total quantity of two hardeners should be 60 parts per 100 parts of ARALDITE GY 250. Another combination using Hy 840 (Hardener)

Gy 250 - 100 parts by weight Hy 840 - 50 “

*******

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12. Welding

v Soldering and Brazing: a) In Soldering and Brazing, bonding takes place at a temperature below the melting

point of the metals being joined. b) Soft solder is a mixture of lead, tin and sometimes antimony (welding range less

than250oC). c) Silver solder is a alloy of Silver, Copper and Zinc (melting point about 700oC used

mainly for joining brass and copper). d) Above about 800oC, the process is called brazing and rod used for general work is

50% Copper and 50% Zinc. e) Borax is used as a flux in a brazing process. v Gas welding the heat produced melts the metal parts to be welded.

a) Oxyacetylene a flame temperature about 3300oC melts the metals, which fuse together to form a strong joint. Extra metal may be supplied from a filler rod and a flux may be used to prevent oxidation.

b) Keep Acetylene pressure less than 15 psi, so that the acetylene mixture does not flow back into oxygen cylinder.

c) In case of flame flash back, shut off the blow pipe oxygen valve first, then close acetylene valve.

d) Stainless steel (Chromium Oxide Lever has the higher melting point - 5500oC) can be cut by which has high flame temperature (more than 10000oC).

e) Capacity and pressure of Oxygen cylinder. Capacity Pressure O2 = 6.9m3 (244 ft3) - 100 Kg/cm 2

Ace = 7.8m3 (275 ft3) - 20 Kg/cm2

f) Acetylene is a colourless gas of the composition HC : CH. It contains 92.3% Carbon. When mixed with Oxygen as Oxyacetylene for flame cutting and welding, it gives a temperature of 3500oC. In air it is an explosive gas. The maximum explosive effect is with a mixture of 7.7% gas with 92.3% air.

v In Arc welding, the heat of fusion is generated by an electric arc (regulated low voltage

high current) struck between work pieces and welding rod. a) Bevel angle 37-1/2o (included angle 75o +5o) for C.S pipes b) Bevel angle 30o (included angle 60o +5o) for S.S pipes c) Root gap 1.5mm for socket weld joint d) While grinding SS pipe, Silicon Carbide wheels should not be used. e) Weaving length should not exceed 3 times the dia of electrode. v Welding Current a) 1 Amps for 1 thou dia of electrode

b) The thumb rule of minimum and maximum current (amps) is 40 times and 60 times of Electrode dia. in mm.

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v Socket Welding: a) Socket weld ends are generally used up to 2” dia. and butt weld ends for larger sizes. b) Socket weld connections are easily made up with less skill than for butt welds.

c) Failure to leave a small space when welding will produce very high stresses. When the weld metal contracts and pulls the pipe into the socket which leads to failure of weld joint and or can distort the seat of gate valve, so that they will not seat properly in service.

v Care to be taken during welding: a) Valve seats should be protected during welding from weld spatter. b) Valves should be kept as cool as possible to avoid body seat distortion.

c) PTFE seals of ball valves may require removal of seals to avoid damage from welding heat.

v Procedure qualifications are to demonstrate that the methods and practices used by a

manufacture or contractor for a given material will result in satisfactory welds. v Operator qualification is a series of tests to demonstrate the ability of an individual

operator to produce satisfactory welds under the specified conditions of his employer’s procedure.

v Welding procedure: Offset of the pipe should not be more than 20% of the pipe

thickness. v Preheating is desirable if the carbon content exceeds 0.35%, for pipe wall thicknesses

¾ inch. or over, or for alloy material. Preheats of 400 to 450 F for carbon steel, or 500F or higher for alloy material, are normally used.

v Stress relief is mandatory for wall thicknesses of ¾ inch. or greater for ordinary carbon

steels; and for thicknesses of 1/2 inch. and greater if carbon exceeds 0.35%, or for alloy steels. It is accomplished by slowly heating to the required temperature, holding that temperature for one hour per inch of wall thickness, and cooling slowly. Stress-relief temperatures used are 1100 to 1250 F for carbon steel, 1250 to 1325 F for carbon –molybdenum steel, and 1300 to 1350 F for chromium-molybdenum steel.

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13. Lapping & Scraping LAPPING: v The purpose of lapping is to secure a very smooth surface of a hermetic joint to achieve

leak tightness. a) For rough lapping, plates or Laps with longitudinal and transverse grooves are used. The grooves help in collecting excessive abrasive. These grooves are 1-2 mm deep and are spaced 10-15 mm from one another b) For fine lapping, a lap with an uninterrupted surface is used. c) Fine lapping reduces the surface irregularities to as little as 0.6-1.6 microns d) Extra fine lapping reduces the surface irregularities to as little as 0.16 – 0.4 micron. (1 micron = 0.001 mm). v A number representing the size of its abrasive particles expresses the grain size of

abrasive. The number corresponds to the mesh per inch of length of the screen, through which the particles will pass but be retained by the standard screen of finer size.

v For correctly specifying an abrasive following details should be given: a) ?Grain size or Mesh no, b) ?Material & c) ?Powder or paste v Following table gives an idea about comparison of Grit size, grain size: GRIT SIZE AVERAGE MICRON SIZE DESCRIPTION 220 60 COARSE 320 31 MEDIUM COARSE 400 22 MEDIUM 600 16 FINE 900 9 POLISH v Lubricant is used, according to the material of the particular lap. For cast iron laps,

benzine or kerosene is used, for steel laps machine oil, for copper laps alcohol, soda solution or machine oil. For laps made from copper-base alloys use is also made of machine oil mixed with an animal fat. The selected lubricant is very intimately mixed with abrasive powder to obtain a homogeneous mixture.

v Advantages of LAPMASTER are as follow: a) Identical part or parts of various shapes, heights and materials can be lapped simultaneously on one machine. b) Production is never interrupted to recondition lap plates. c) Simplicity in design with no obstructions makes loading and unloading easy and simple. d) Greater effective lapping area permits more parts per cycle. e) For greater production efficiency timing clock controls the lapping cycles. Automatic cycling permits pre-loading an additional work holder while machine is in operation. v Principle of LAPMASTER: The lapmaster is a versatile precision machine engineered to production lap flat surfaced within tolerances of one light band (0.0000116”) or finishes of less than 2 to 3 RMS micro inches with absolute uniformity.

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a) A heavy cast alloy lap plates revolves slowly under power. b) Large cast alloy adjustable conditioning rings are held in position and rotate freely on the lap plate to continually keep the plate flat and true. c) Work pieces may be placed inside the conditioning rings where they also rotate on the lap to create a cutting action, which forms a true flat surface. d) Fresh, sharp abrasive grains, suspended in suitable vehicle, are continuously fed on the lap plate and uniformly distributed under the work pieces during the lapping action. v MONO-CHROMATIC CHECKLIGHT: a) An optical instrument known as “Monochromatic Checklight” is used to measure surface flatness, the measurement unit being ‘Light bands’. It is the most accurate method of checking flatness and surface flatness up to 1 light band (i.e. 0.0000116” or 0.0002794 mm.) can be easily determined. b) It is an electrical instrument and operates on 230 V AC domestic supplies. The head of the instrument contains a vapor filled tube light. The tube is protected by an opalescent glass plate having a black line marked on it to work as reference during measurement. A platform is set below the light source and is used to keep the objects for flatness measurement. c) When switched ON, a little time lapse is required for the light to give full illumination. It gives a bright light of single “Yellowish- orange” color; all other colors of light get eliminated. Wavelength of light from this source is 23.2 millionth of an Inch. However since only half the wavelength is used in the measurement process, the increment measure is one half of 23.2 or 11.6 millionth of an Inch. v OPTICAL FLATS: Optical flats are used to measure surface flatness with help of Mono-chromatic checklight. They are made of fused Quartz; they have perfectly flat and parallel surfaces, have high resistance to abrasion and are superior due to their very low thermal expansion. For satisfactory service life the optical flats should be handled very carefully and kept clean. v HOW TO READ LIGHT BANDS: a) The lapped surface to be checked should be polished so that it reflects light. b) Clean the optical flat with a soft Tissue paper and rest it on the lapped and polished surface of the job. c) Adjust the job such that dark interference bands are visible beneath the optical flat and the reflection of the line marked on the glass becomes tangent to the curve of any interference band. d) The dark bands visible beneath the optical flat are not light waves, but they simply show the interference produced by reflection from two surfaces. These dark bands are used in measuring the flatness of the work. The band unit is 0.0000116”. This value indicates the level of work that has risen or fallen in relation to the optical flat, between the centres of one dark band to the centre of next dark band. e) The basis of comparison is the reflected line tangent to the interference band and parallel to the line of contact of work and optical flat. The number of bands intersected by the tangent line indicates the degree of variation from true flatness in terms of ‘Light bands’. f) View the optical flat at correct angle and correct distance. 80 to 90 degree is the correct angle to view seal faces. Viewing at 45 degree angle can produce a reading error of > 40%.

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SCRAPING: v Scraping is a process of surface finishing by which very thin layers of metal are removed

to improve sliding and guide surfaces with least possible friction loss in assemblies and the maximum possible closeness of fit.

v In fine scraping, metal only 0.01 mm thick is removed in one pass of the scraper. v In case of sliding contact bearings and other load bearing surfaces a minimum surface

contact of 80% is essential. v Depending on the purpose a part serves, the quality of scraping is judged by the number

of spots seen when a checking frames with in the space of 25x25mm. For example: a) Parts of metal cutting machines (beds, tables, carriages, tool slides etc.) should have 8- 16 spots, b) Test plates and rules 20-25 spots, c) Measuring tools and instruments 25-30 spots, etc. d) A minimum of 80% contact is essential in Plain bearings and split housing of rolling element bearings. e) In case of sliding contact bearings and other load bearing surfaces a minimum surface contact of 80% is essential. v Method of marking the surface: a)? A thin layer of Prussian blue is applied to the surface plate after cleaning with a clean linen rag folded over several times. b) ??Placing the work on the surface plate and slowly move across the plate. c)? After two or three circular movements are made over the plate, the work is carefully lifted. Surfaces, which are well prepared, will show high spots uniformly marked over the entire surface, a badly prepared surface will be non-uniformly spaced spots. At spots somewhat lower than the high spots the marking paint will tend to accumulate, but spots, which are still lower, will not be marked at all. d) Thus, as a result of the marking, the following spots will be seen on the surface: a. White spots, the lowest areas, which remain unmarked. b. Dark spots, areas, which are less deep and accumulate the marking materials. c. Grey spots, the highest areas and those left with a thin coat of the marking material. When the surfaces of large-sized objects which can not be disassembled or taken to a workplace is to be scraped; the surface plate or straight-edge must be coated with Prussian blue and then applied to the surface of the work. v Scrapers are made of carbon tool steel. The cutting point of the scraper is hardened

without tempering to a hardness of Rc= 60-65. Scrapers can be classified according to: a) ?No. of cutting ends: Single-ended and double-ended scrapers b) ?Shape of cutting edge: Flat, Three-square (Triangular) and Shaped (curved, hook bent end etc.) scrapers c) Design: Solid or Inserted tips. Single-ended scrapers are provided with handles, double-ended scrapers have no handles.

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14 .PRINCIPLES OF FILTRATION

1. Introduction: Filtration is the separation of particles from a fluid (liquid or gas) by passage of that fluid through a permeable medium. When the particles represent a significant proportion of the fluid, the process may be described as bulk solids collection. When the particles represent only a very small proportion of the total (0.015 or less), the process is called fluid clarification

2. Filtration Processes: Suspended solids are separated from fluids via three mechanisms; inertial impaction, diffusional interception and direct interception.

3. Inertial Impaction: Particles in a fluid stream have mass and velocity hence have a momentum associated with them. As the liquid and entrained particles pass through filter media, the liquid stream will take the path of least resistance to flow and will be diverted around the fiber. The particles, because of their momentum, tend to travel in a straight line and as a result, those particles located at or near the centre of the flow line will strike or impact upon the fiber and be removed.

4. Diffusional Interception: For particles that are extremely small (i.e. those with very little

mass), separation can result from diffusional interception. In this process, particles are in collision with the fluid molecules. These frequent collisions cause the suspended particles to move in a random fashion around the fluid flow lines. Such movement, which can be observed microscopically, is called “Brownian Motion”. Brownian motion causes these smaller particles to deviate from the fluid flow lines and hence increase the likelihood of their striking the fiber surface and being removed.

5. Direct Interception: While inertial impaction and diffusional interception are not as

effective in liquid service as in gas service, direct interception is equally as effective in both and is the desired mechanism for separating particles from liquids. In a filter medium, one observes not a single fiber, but rather an assembly of a large number of such filters. These fires define openings through which the fluid passes. If the particles in the fluid are larger than the pores or openings in the filter medium, they will be removed at a result of direct interception by the holes.

6. Aids to Liquid Filtration: It is possible to enhance a filter’s effectiveness in removing

particles from a liquid by several methods:

a) Electrostatic Deposition: Most particles carry a negative charge. Filter media often carry charges that can affect both particle removal efficiency and for particle retention efficiency of the filter. It is possible therefore to enhance the particle capture mechanisms of a filter by inducing a desired charge (usually positive) on the fiber.

b) Flocculation:

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Very fine size particles are difficult to filter. One way to enhance filterability is to cause them to flocculate into larger particles that are easier to filter and usually produce filter cakes within result in less pressure drop and, in consequence, an increase in throughout.

7. Filter Types: In recent years it has become increasingly common to classify filters and filter media “depth type” or “surface type”.

Characteristics of Filter:

Among the more important factors it must be taken into consideration when choosing a filter for a particular application are the size, shape and hardness of the particles to be removed, the quantity of the particles, the nature and volume of fluid to be filtered, the rate at which the fluid flows, whether flow is steady, variable and/or intermittent system pressure and whether that pressure, compatibility of the medium with the fluid, fluid temperature, properties of the fluid, space available for particle collection, and the degree of filtration required.

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15.RELIABILITY, MAINTANABILITY AND AVAILABILITY

Reliability: Reliability of a unit (or product) is the probability that the unit performs its intended function adequately for a given period of time under the stated operating conditions or environment. Reliability is always a function of time.

Maintainability: Maintainability can be defined as the probability that failed equipment is restored to operable condition in a specified time (called `down-time’) when the maintenance is performed under stated conditions. Availability is another measure of performance of maintained equipment. It integrates both reliability and maintainability parameters and depends on the number of failures that occur and on how quickly any faults are rectified. Quality: Quality of a device is the degree of conformance to applicable specifications and workmanship standards. Reliability Parameters Failure rate: Failure may be defined as the termination of the ability of an item to perform its required function. Failure rate is expressed as failures for the given time. A lower failure rate is indicative of higher reliability. Mean time between failures: MTBF is a basic measure of reliability for an item. MTBF is the total time that an item is designed to last (or) the total operating time in a given period divided by the number of failures that have occurred. This parameter is known as the mean time between failures, or MTBF. MTBF = 1/Failure rate Mean time to fail (MTTF): MTTF is the mean operating time between successive failures. Mean time to Repair (MTTR) : MTTR is the mean Repair time between successive operation.

Reliability can be described in various forms as follows:

Inherent Reliability: The probability that a device will perform its specified function, determined on the basis of a statistical analysis of failure rates and other characteristics of the parts and components which comprise the device. Inherent Reliability is a function of Equipment, Design and Manufacture.

Use Reliability: The probability that a device of known inherent reliability will perform its prescribed mission for a specified time when subjected to field human engineering factors

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and maintenance practices. It depends on equipment operation, maintenance and environment. Operational Reliability: The probability that a device of known inherent and use reliability will perform its mission for the required time when utilized in the manner and for the purpose intended. Operational reliability is the reliability obtained under actual working conditions and is obtained as a product of inherent and uses reliability. Reliability of a System The reliability of a system composed of a number of elements is governed by their functional arrangement, which could either have Series, Parallel (or) mixed configuration. Principles used to ensure a high degree of Reliability in a Safety Systems

• Redundancy • Diversity • Independence • Periodic Testing • Fail Safe Systems • Reporting to AERB

Techniques to enhance System Reliability

• Parts improvement method • Effective and Creative Design • System Simplification • Use of Operational Components • Structural Redundancy • Maintenance and Repair

********

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LIST OF TABLES

TABLE-1

COMPATIBILITY AND PRESSURE TEMPERATURE RATING OF COMMONLY USED GASKETS AND ELASTOMERS

Sl. Type Pressure Temp. Service/Application No. (Kg/cm2) oC 1. CAF Champ 54 } 140 540 Steam, Oxygen, oils,

Klinger-100 (Non Metallic)} Petroleum distillate 1000 (Metallic) } fuels, Solvents.

2. CAF Champ 20 } 35 380 Steam, Water Klinger – 232 } 3. CAF Firefly 201 E 19 380 Steam, water, gases, Alkalis 4. CAF Champ 59 oil} 150 540 Oils, Solvents, Klinger-80E } Refrigerants

5. CAF Champ 60 Acid 150 210 Acids and Chemicals 6. Neoprene rubber 10 130 Excellent resistance to Weather ageing,

Moderate resistance to oil. Water, Refrigerants, Silicate Lubricants, Petro oils. Not Recommended for, Phosphate Easter fluids.

7. Buna - N 10 120 Good resistance to fuels, solvents, silicon fluids, abrasion, D2O, Water Grease, Petroleum oils. Not Recommended for Hydro Carbons (CTC), strong Acids, Auto Brake fluids. 8. Leather fold paper 10 100 Cold water/Oil 9. Rubberized cork 120 Oil 10. PTFE 10 250 Alkali/Acids. Not

Recommended for oils. 11. Lead Sheets 10 200 Chlorine.

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TABLE-II

A typical thumb rule is used in the form of a multiplication factor for limitation of gasket material as per table below.

GASKET PRESSURE TEMPERATURE LIMITS MATERIAL MAXIMUM MAXIMUM P*T TEMP. IN Psi * oF oF 1. Rubber 15,000 300 2. Fiber Sheets 40,000 250 3. Woven asbestos rubberized Sheet 1, 25,000 400 4. C.A.F 2, 50,000 850 5. Metallic > 2, 50,000 depend on type

TABLE-III

RECOMMENDED GASKET COMPRESSION FOR SPIRAL WOUND METALLIC GASKET

(AN EXTRACT FROM CATALOGUE OF M/S. JAMES WALER & CO. LTD)

-----------------------------------------------------------------------------------------------------------------------------

Nominal thickness Compressed thickness ------------------------------------------------------------------------------------------------------------ 3.2 mm (.125 inch) 2.4/2.6 mm (.095/.105 inch) 4.5 mm (.175 inch) 3.2/3.4 mm (.125/.135 inch) 6.4 mm (.250 inch) 4.6/4.8 mm (.180/.190 inch) 7.3 mm (.285 inch) 4.7/4.9 mm (.185/.195 inch)

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MINIMUM GASKET SEATING STRESS – IV

Material INCH Stress Surface Psi (y) Choice-I Choice-II ------------------------------------------------------------------------------------------------------------ RUBBER SHEET 1/32 and up 200 Compressed asbestos FLAT 1/64 3,000 Concentric All other types 1/32 2,000 serrated 1/16 1,600 1/8 1,200 TEFLON 1/64 14,000 80 rms All other types Virgin FLAT 1/32 6,500 (1/16 concentric 1/16 3,700 serrated) 1/8 1,600 Glass-filed FLAT 1/64 14,000 (all other 1/32 11.000 thickness) 1/16 6,000 1/8 3,000 FLAT MATERIAL FLAT Aluminium 1/32 & 20,000 Concentric 80 rms or less Copper 1/16 45,000 serrated Carbon Steel 68,750 Monel 81,250 Stainless 93,750 METAL (ASBESTOS FILLER) Aluminium Corrugated 1/8 2,000 150 rms Concentric Copper Steel and only 2,500 serrated Stainless corded 3,000 Monel 4,000 Lead Plain 1/8 only 500 80 rms or less 150 to 200rms Aluminium metal 2,500 Copper Jacket 4,000 Carbon Steel 6,000 Nickel 6,000 Monel 7,000 Stainless Steel 10,000 Stainless Steel 0.125 & 3,000 to -do- -do- Spiral wound 0.175 30,000

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TABLE - V

TORQUE REQUIRED TO PRODUCE BOLT STRESS (FROM CRANE VALVE CATALOGUE)

The torque or turning effort required to produce a certain stress in bolting is depending upon a number of conditions, some of which are:

Diameter of bolt Type and number of threads on bolt. Material of bolt. Condition of nut bearing surfaces. Lubrication of bolt threads and nut bearing surfaces.

The tables below reflect the results of many tests to determine the relation between torque and

bolt stress values are based on steel bolting well lubricated with a heavy graphite and oil mixture. It was found that a non-lubricated bolt has an efficiency of about 50 percent of well-lubricated bolt and also that different lubricants produce results varying between the limits of 50 and 100 percent of the tabulated stress figures.

Load in pounds on bolts and stud bolts when Torque loads are applied Data for use with machine bolts and cold rolled steel stud bolts. Nominal No. of Diameter Area Stress Diameter Threads root of at ------------------------------------------------------------ of bolts per inch thread Root 7,500 psi 15,000 psi 30,000 psi. Inches Inches of thread ---------------------------------------------------------- Sq. inch Torque Comp. - Torque Comp. - Torque Comp. ft.lbs. lbs. ft.lbs. lbs. ft.lbs. lbs. ¼ 20 .185 .0271 1 203 2 405 4 810 5/16 18 .240 .0452 2 338 4 675 8 1350 3/8 16 .294 .0683 3 510 6 1020 12 2040 7/16 14 .345 .0935 5 698 10 1395 20 2790 1/2 13 .400 .1268 8 945 15 1890 30 3780 9/16 12 .454 .162 12 1215 23 2430 45 4860 5/8 11 .507 .202 15 1515 30 3030 60 6060 ¾ 10 .620 .302 25 2265 50 4530 100 9060 7/8 9 .731 .419 40 3143 80 6285 160 12570 1 8 .838 .551 62 4133 123 8265 245 16530 1-1/8 7 .693 .693 98 5190 196 10380 390 20760 1-1/4 7 1.064 .890 137 6675 273 13350 545 26700 1-3/8 6 1.158 1.054 183 7905 366 15810 730 31620 1 ½ 6 1.283 1.294 219 9705 437 19410 875 38820 1 5/8 5 ½ 1.389 1.515 300 11363 600 22725 1200 45450 1 ¾ 5 1.490 1.744 390 13080 775 26160 1550 52320 1 7/8 5 1.615 2.049 525 15368 1050 30735 2100 61470 2 4 ½ 1.711 2.300 563 17250 1125 34500 2250 69000

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DATA FOR USE WITH ALLOY STEEL STUD BOLTS Nominal No. of Diameter Area Stress Diameter Threads root of at ------------------------------------------------------- -- of bolts per inch thread Root 30,000 psi 45,000 psi 60,000 psi. inches Inches of thread ---------------------------------------------------------- Sq. inch Torque Comp - Torque Comp - Torque Comp Ft.lbs. lbs. ft.lbs. lbs. ft.lbs. lbs. ¼ 20 .185 .027 4 810 6 1215 8 1620 5/16 18 .240 .045 8 1350 12 2025 16 2700 3/8 16 .294 .068 12 2040 18 3060 24 4080 7/16 14 .345 .093 20 2790 30 4185 40 5580 ½ 13 .400 .126 30 3780 45 5670 60 7560 9/16 12 .454 .162 45 4860 68 7290 90 9720 5/8 11 .507 .202 60 6060 90 9090 120 12120 ¾ 10 .620 .302 100 9060 150 13590 200 18120 7/8 9 .731 .419 160 12570 240 18855 320 25140 1 8 .838 .551 245 16530 368 24795 490 33060 1-1/8 8 .963 .728 355 21840 533 32760 710 43680 1-1/4 8 1.088 .929 500 27870 750 41805 1000 55740 1-3/8 8 1.213 1.155 680 34650 1020 51975 1360 69300 1 ½ 8 1.338 1.405 800 42150 1200 63225 1600 84300 1 5/8 8 1.463 1.680 1100 50400 1650 75600 2200 100800 1 ¾ 8 1.588 1.980 1500 59400 2250 89100 3000 118800 1 7/8 8 1.713 2.304 2000 69120 3000 103680 4000 138240 2 8 1.838 2.652 2200 79560 3300 119340 4400 159120 2 ¼ 8 2.088 3.423 3180 102690 4770 154035 6360 205380 2 ½ 8 2.338 4.292 4400 128760 6600 193140 8800 257520

2 ¾ 8 2.588 5.259 5920 157770 8880 236655 11840 315540 3 8 2.838 6.324 7720 189720 11589 284580 15440 379440 ------------------------------------------------------------------------------------------------------------------------

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Table – VI – NUT FACTOR Reported Nut Factors for Various Materials and Lubricants Metal/Lubricant Minimum Nut

Factor Mean Nut Factor

Maximum Nut Factor

As Received Alloy or Mild Steel Fasteners

0.158 0.2 0.267

As Received Stainless Steel Fasteners

- 0.3 -

Cadmium Plate (Dry) 0.106 0.2 0.328 Copper Based Anti -Seize

0.08 0.132 0.23

Cadmium Plate (Waxed) 0.17 0.187 0.198 Fel-Pro C54 0.08 0.132 0.23 Fel-Pro C670 0.08 0.095 0.15 Fel-Pro N 5000 (Paste)

0.13 0.15 0.27

Machine Oil 0.10 0.21 0.225 Moly Paste or Grease 0.10 0.13 0.18 Never-Seize (Paste) 0.11 0.17 0.21 Neolube 0.14 0.18 0.20 Phos-oil 0.15 0.19 0.23 Solid Film PTFE 0.09 0.12 0.16 Zinc Plate (Waxed) 0.071 0.228 0.52 Zinc Plate (Dry) 0.075 0.295 0.53

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TABLE-VII

GASKET FACTOR (m) FOR OPERATING CONDITIONS

Gasket Material Gasket Factor (m) Self-Energizing Types

`O’ Rings, Metallic, Elastomer other gasket types considered as self-sealing

0

Elastomers without fabric or a high percentage of asbestos fiber: Below 75 Shore Durometer 75 or high shore Durometer

0.50 1.00

Asbestos with a suitable binder for the operating conditions

1/8 thick 1/16 thick 1/32 thick

2.00 2.75 3.50

Elastomers with cotton fabric insertion 1.25 Elastomers with asbestos fabric Insertion, with or without wire reinforcement

3-PLY 2-PLY 1-PLY

2.25 2.50 2.75

Vegetable fiber 1.75 Spiral-wound metal, asbestos inserted

Carbon Stainless Steel or Monel

2.50 3.00

Corrugated metal, asbestos inserted

Or Corrugated metal, jacketed asbestos filled

Soft Aluminium Soft Copper or brass Iron or soft steel Monel 4-6% chrome Stainless Steels

2.50 2.75 3.00 3.25 3.50

Corrugated metal Soft Aluminium Soft Copper or brass Iron or soft steel Monel 4-6% chrome Stainless Steels

2.75 3.00 3.25 3.50 3.75

Flat metal jacketed asbestos Filled

Soft Aluminum Soft Copper or brass Iron or Soft steel Monel 4-6% Chrome Stainless Steels

3.25 3.50 3.75 3.50 3.75 3.75

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TABLE-VIII

NOMENCLATURE OF MESH

No. of Mesh Per English inch = 25.4mm

SWG

Diameter of Wire MM

Size of Opening

MM MICRONS

Approx. %

Open Area

4

6

8

10

12

14

16

18

20

24

30

40

50

16 18

16 18

18 20 24 26

20 22 24 26 28

24 26 28

26 28 30

25 26 28

24 26 28

30 32

26 28 30

32

32 33 34

36 38

1.626 1.219

1.626 1.219

1.219 .914 .559 .457

.914 .711 .559 .457

.3759

.559

.457 .3759

.457

.3759

.3150

.508

.457 .3759

.559 .457

.3759

.3150

.2743

.457 .3759 .3150

.2743

.2743

.2540

.2337

.193 .1524

4.7238 5.1308

2.6072 3.0142

1.9559 2.2609 2.6159 2.7179

1.6259 1..828

9 1.9809 2.0829 2.1640

1.5576 1.6596 1.7407

1.3572 1.4383 1.4992

1.0795 1.1305 1.2116

.8520 .9540

1.0351

.9550

.9957

.6013

.6824

.7433

.5723

.3607

.3810

.4013

.315 .3556

361 381 401

315 356

55.4 65.3

38.0 50.7

37.9 50.7 67.9 73.3

41.0 51.8 60.8 67.2 72.6

54.1 61.4 67.6

55.9 62.8 68.2

46.2 50.7 58.3

36.4 45.6 53.7

56.5 61.5

32.1 41.4 49.1

45.6

32.3 36.0 39.9

38.4

No. of Mesh Per English inch = 25.4mm

SWG

Diameter of Wire MM

Size of Opening

MM MICRONS

Approx. % Open Area

60

80

100

120

140

160

180

200

220

300

35 38

40 41

42

42 44 45

44 45 46

45 46 47

46 47

47

48

----

.1930 .1524

.1219 .1118

.1016

.1016 .0813 .0711

.0813 .0711 .0610

.0711 .0610 .0508

.0610 .0508

.0508 .0406

.04

.045

.036

.2303 .2709

.1956 .2057

.1524

.1101 .1304 .1406

.1001 .1103 .1204

.0876 .0977 .1079

.0801 .0903

.0762 .0864

.06

.055

.056

.050

230 271

196 206

152

110 130 141

100 110 120

88 98

108

80 90

76 86

60 55 56

50

29.8 41.2

37.9 42.0

36.0

26.6 37.5 43.6

29.8 36.2 43.3

29.6 37.0 45.2

33.2 42.0

36.0 46.2

36 30 42

34

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TABLE-IX

WIRE & SHEET METAL GAUGES

SHEET WIRE GAUGE NO.

(BS/SWG) INCH MM INCH MM

50. 0.0012 0.030 0.0010 0.025 49. 0.0013 0.034 0.0012 0.030 48. 0.0015 0.039 0.0016 0.041 47. 0.0017 0.043 0.0020 0.051 46. 0.0019 0.049 0.0024 0.061 45. 0.0021 0.055 0.0028 0.071 44. 0.0024 0.061 0.0032 0.081 43. 0.0027 0.069 0.0036 0.091 42. 0.0030 0.078 0.0040 0.102 41. 0.0034 0.087 0.0044 0.112 40. 0.0038 0.098 0.0048 0.122 39. 0.0043 0.109 0.0052 0.132 38. 0.0048 0.122 0.0060 0.152 37. 0.0054 0.137 0.0068 0.173 36. 0.0061 0.155 0.0076 0.193 35. 0.0069 0.175 0.0084 0.213 34. 0.0077 0.196 0.0092 0.234 33. 0.0087 0.221 0.0100 0.254 32. 0.0098 0.249 0.0105 0.274 31. 0.0110 0.279 0.0116 0.295 30. 0.0123 0.312 0.0124 0.315 29. 0.0139 0.353 0.0136 0.345 28. 0.0156 0.397 0.0148 0.376 27. 0.0174 0.443 0.0164 0.417 26. 0.0196 0.498 0.0180 0.457 25. 0.0220 0.560 0.0200 0.508 24. 0.0247 0.629 0.0220 0.559 23. 0.0278 0.707 0.0240 0.610 22. 0.0312 0.794 0.0280 0.711

SHEET WIRE GAUGE NO. (BS/SWG)

INCH

MM INCH MM

21. 0.0349 0.886 0.0320 0.813 20. 0.0392 0.996 0.0360 0.914 19. 0.0440 0.118 0.0400 1.016 18. 0.0495 1.257 0.0480 1.219 17. 0.0556 1.412 0.0560 1.422 16. 0.0625 1.588 0.0640 1.626 15. 0.0699 1.775 0.0720 1.829 14. 0.0765 1.994 0.0800 2.032 13. 0.0982 2.240 0.0920 2.337 12. 0.0991 2.517 0.1040 2.642 11. 0.1113 2.827 0.1160 2.946 10. 0.1250 3.175 0.1280 2.946 9 0.1398 3.551 0.1440 3.658 8 0.1570 3.988 0.1600 4.064 7 0.1764 4.481 0.1760 4.470 6 0.1981 5.032 0.1920 4.871 5 0.2225 5.652 0.2120 5.385 4 0.2500 6.350 0.2320 5.893 3 0.2804 7.122 0.2520 6,401 2 0.3147 7.993 0.2760 7.010 1 0.3532 8.971 0.3000 7,620 0 0.3964 10.070 0.3240 8,230

0.2 0.4452 11.310 0.3480 8,839 0.3 0.5000 12.700 0.3720 9,449 0.4 0.5416 13.760 0.4000 10,160 0.5 0.5883 14.940 0.4320 10.973 0.6 0.6250 15.880 0.4640 11.786 0.7 0.6666 16.930 0.5000 12,700

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THREADING TAPS

v Tap drill Size: a) (Size of the tap in inch * 7/8) – 1/32. b) D - 1.1328P (For with worth threads), c) Size of tap in mm – (1.23 * pitch), d) “Rule of thumb” = Outside diameter * 0.8.

v English tap drill: Subtract the inverse of the pitch, (in threads/inch) from the bolt diameter. The

number is close enough, with in 0.006 inch. e.g., bolt diameter is 0.500” and thread pitch is 13 TPI. The calculated Tap-Drill Diameter is 0.500 - 0.077 = 0.313 i.e., 5/16”.

v The required length of a tapped hole depends upon the material. Length of threaded bolt portion = CD inch.

Where C = 1.0 for steel, 1.5 for cast iron, 2.0 for bronze and aluminium. D = Dia. of Stud/Bolt.

TOP - Figures indicate T.P.I BOTTOM - Figures indicate Tapping Drill Size in MM

BA 47.5 deg. METRIC 60 deg.

SIZE

BSW 55deg.

BSF 55 deg.

BSP 55 deg.

UNC 60 deg.

UNF 60 deg.

NPT

60 deg.

SIZE TPI SIZE (mm)

PITCH (mm)

1/8” 40.00

2.55 - 28.00

8.00 - - 27.00

9.30

10.00 72.6

0 1.40

3.00

0.50 2.50

5/32” 32.00 3.20

- -

- -

- - - -

9.00

65.10

1.55

4.00

0.70 3.30

3/16” 24.00 3.70

32.00 4.00

- 11.80

- 5.10

- 5.50

- -

8.00

59.10

1.80

5.00

0.80 4.20

¼” 20.00 5.10

26.00 5.30

19.00 11.80

20.00 5.10

28.00 5.50

18.00 12.00

7.00

52.90

2.05

6.00

1.00 5.00

5/16” 18.00 6.50

22.00 6.80

-

18.00 6.60

24.00 6.90

- -

6.00

47.90

2.30

- 8.00

1.25 6.80

3/8” 16.00 7.90

20.00 8.30

19.00 15.25

16.00 8.00

24.00 8.50

18.00 15.50

- 5.00

43.10

2.65

- 10.00

1.50 8.50

7/16” 14.00 9.30

18.00 9.70

- -

14.00 9.40

20.00 9.90

- -

- 4.00

38.50

3.00

- 12.00

1.75 10.20

½” 12.00 10.50

16.00 11.10

14.00 19.00

13.00 10.80

20.00 11.50

- -

- 3.00

34.80

3.40

- 14.00

2.00 12.00

9/16” 12.00 12.10

16.00 12.70

- -

12.00 12.20

18.00 12.90

- -

- 2.00

31.40

4.00

- 16.00

2.00 14.00

5/8” 11.00 13.50

14.00 14.00

14.00 21.00

11.00 13.50

18.00 14.50

- -

- 1.00

28.20

4.50

18.00

2.50 15.50

¾” 10.00 16.25

12.00 16.75

14.00 24.50

10.00 16.50

16.0 17.50

14.00 19.40

- 0.00

25.40

- 20.00

2.50 17.50

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122

5.10 7/8” 9.00

19.25 11.00 19.75

- -

9.00 19.50

14.00 20.40

- -

- -

- -

22.00 -

2.50 19.50

1” 8.00 22.00

10.00 22.75

11.00 30.75

8.00 22.25

12.00 23.25

11.50 31.00

- -

- -

24.00 -

3.00 21.00

v The thread form (using tap) more than 60% does not increase the strength significantly. Normally 55% to 75% is sufficient. Generally Table recommends tap drill usually 75% thread height.

Composition of Standard Stainless Steels Composition (%)

Type

UNS Number

C

Mn

Si

Cr

Ni

P

S

Other

Austenitic Types 201 S20100 0.15 5.5-7.5 1.00 16.0-18.0 3.5-5.5 0.06 0.03 0.25 N 304 S30400 0.08 2.00 1.00 18.0-20.0 8.0-10.5 0.045 0.03 -

304L S30403 0.03 2.00 1.00 18.0-20.0 8.0-12.0 0.045 0.03 - 310 S31000 0.25 2.00 1.50 24.0-26.0 19.0-22.0 0.045 0.03 - 316 S31600 0.08 2.00 1.00 16.0-18.0 10.0-14.0 0.045 0.03 - 347 S34700 0.08 2.00 1.00 17.0-19.0 9.0-13.0 0.045 0.03 (3.0-2.0 Mo)

10X%c min Nb+Ta

Ferritic Types 450 S40500 0.045 1.00 1.00 11.5-14.5 - 0.04 0.03 0.1-0.3 A1 430 S43000 0.12 1.25 1.00 16.0-18.0 - 0.04 0.03 - Martensitic Types 410 S41000 0.15 1.00 1.00 11.5-13.0 - 0.04 0.03 - 420 S42000 0.15 1.00 1.00 12.0-14.0 - 0.04 0.03 - 431 S43100 0.20 1.00 1.00 15.0-17.0 1.25-2.50 0.04 0.03 - Precipitation Hardening Types 17-

4PH S17400 0.07 1.00 1.00 15.5-17.5 3.0-6.0 0.04 0.03

17-4PH

S17700 0.09 1.00 1.00 16.0-18.0 6.5-7.75 0.04 0.03

3.0-5.0 cu;0.15-0.45 (Nb+Ta)

0.75-1.5Al

Resistance of Standard Types of Stainless Steel to Various Classes of Environments

Type Mild Atmospheric

and Fresh Water

Atmospheric Industrial

Marine

Salt water

Mild

Chemical Oxidizing

Reducing

Austenitic Stainless Steels 201 X X X X X 304 X X X X X 310 X X X X X 316 X X X X X X X 347 X X X X X

Ferritic Stainless Steels 405 X X 430 X X X X

Martensitic Stainless Steels

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123

410 X X 420 X 431 X X X X

Precipitation hardening Stainless Steels 17-4PH X X X X X 17-7PH X X X X X An “x” notation indicates that the specific type is resistant to the corrosive environment. Adopted from ASM Metals Handbook Vo.3, 9th Edition (40)

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References 1. Industrial Refrigeration Hand Book, Author – Wilbert F. Stoecker, USA 2. Mechanical Engineer’s Hand Book Second edition, Edited by Myer Kutz, Myer

Kutz Associates inc. 3. Rules of Thumb for Mechanical Engineers. J. Edward Pope, Editor 4. Marks Standard Hand Book for Mechanical Engineers – Tenth Edition Eugene A. A. Vallone. Theodore Baumeister 111 MCGRAW – HILL International Editions 5. Mechanical Equipments T.M 2.1A, NTC, MAPS 6. Vibration and Shock pulse measurements Training Manual 146 NTC, MAPS 7. Instruction Manual Diesel Generating set, MAPS. Diesel Locomotive works, Varanasi. 8. Workshop Manual Rust on Diesel Engine, Pune. 9. Good bolting practices. NMAC – Nuclear Maintenance Application Centre. 10. Major Process Equipment Maintenance and repair. Heinz P. Bloch. Fred K. Geitner. 11. Hand book of Condition Monitoring – A. Davies (ed.) UK. 12. Fundamentals of Refrigeration Billy C. Langley, Dalmar Publishers, USA. 13. Material Hand Book – George S. Brady 14. Mechanical Engineer’s Hand Book. By Harold A. Rothbart. Edition-in-Chief MCGRAW – Hill Book Company. 15. Mechanical Engineer’s Data Hand Book, J. Carvill, Reed Educational and

Professional Publishing Ltd. 1993. 16. Fluid Power Trouble Shooting Second Edition, Anton H. Hehn. *******