CAPACITY CURING MANAGEMENT OF CONTINUOUS …

Pakistan Sugar Journal April-June, 2013 (2)

CAPACITY CURING MANAGEMENT OF CONTINUOUS CENTRIFUGAL MACHINES

Abdul Aziz Tahir**Technical Director, Ranipur Sugar Mills Limited, Ranipur

Over ViewThe Raw Massecuite CuringStation of Boiling House isthe most cost effectiveStation in the point of viewof Electrical, Operation andMaintenance cost heads. Bycontrolling these heads,meaning full saving can bemade which will ultimatelyshare the profitability of theproject. The Paper is thereview of activitiesperformed at continuouscentrifugal station. It focusedthe criteria for selection ofconti machine, its erection ,selection of the V belts andpulleys design for powertransmission, selection ofmachine rpm and nickelworking screens, start up andoperation precautions,necessary steps for capacitygaining, scheduled andpreventive maintenance,basket keeping, safetydevices, preventive measures

to avoid major break downof the machine, technicaldetails of different makebaskets, comparativecapacity test for differentmake machines, pay backperiod calculations for highcapacity new machine andcase study for 6000 TCDplant working with highcapacity conti machines.

The presentation details:1-Over view of a ContiMachine2-Selection of the type ofConti Machine3- Effect of rpm and BasketAngle4-Space and MechanicalStructure Requirement5-Installation/Erectionprecautions6-Selection of Nickelworking Screens7-Selection of V Belts typeand Pulley design for PowerTransmission

8-Start up Precautions9-Operational Parameters10-Massecuite FeedingArrangements11-Massecuite Conditioning12-Maximum Capacity Gain13-Essential Safety Devices14-Machine Maintenance15-Causes of Major MachineAccidents16-Precautions to Stop theMachine for over non cropPeriod17-Comparative TechnicalDetails of different MakeBaskets18-Comparative CapacityRun Data for DifferentMakes Machines19-Payback Period of HighCapacity local made Conti.Machine20-Case Study for ReplacingK1100 Conti Machines withSK125021-Machines for 6000 TCDPlant22-Recommendations

Over View of a Continuous Centrifugal Machine


2- Selection of the type ofConti Machine

It includes:

A-Curing Capacity Tons/hrwith given condition ofa. Massecuite type and its:i. Brixii. Purityiii. Temperatureb. Sugar Qualityi. Purity

B- Basket RPM

C. Basket Diameter andAnglei. Basket diameter at topii. Basket angle with respectto the tangential at the centreof basket (see at Sr. no. 17)

3- Effect of rpm and BasketAngleA-Rpm are selected withthe massecuite type, normalrecommended rpm andbasket angle with experienceare following:a. 1600/ 30º at A Massecuiteb. 1600 - 1800/ 30 º at BMassecuitec. 1800 - 2000/ 34 º at CMassecuite

B-high rpm beyond therecommended limit maycause:a. Crystal damageb. Reduce capacity curing

c. Decrease the V belts lifed. Decrease the bearing lifee- Ultimately risk operationof the Machine

C-Low rpm againstrecommended limits maycausea. Low quality sugarproductionb. More molasses circulationin the system

D-lesser degree basketagainst the recommendedangle may cause/require:a. Resistance to travel themassecuite/ sugar over thebasket screen.b. More power demand forcapacity run.

E-higher degree basketbeyond the recommendedangle may cause:a. Low quality sugarproductionb. More molasses circulationin the system

4- Space and MechanicalStructure Requirement

A- Make steel structureaccording to or nearest tothe Manufacturer Design.B-Weak Structure or overloaded structure may resultin:

a. vibration transmissionfrom one machine to otherb. reduction in bearing lifec. reduction in through put ofthe batteryd. Basket damage or majormachine accidentse. Constant life risk threat forthe operators

5- Installation/ ErectionPrecautionsa. That Machine isdynamically pre-balanced atdesigned rpm.b. The complete weldingpoint of the structurec. Horizontal left right “00”balance of the structured. “00” balance of the driveunit/ housing of the machinee. “00” balance of basket topring after fittingf. Very Important to notethat: Feeding Pug Millcenter, Feeding Pipe of pugmill, distributor of machine isvertically in line.g. Pug mill feeding pipediameter should not less than8 inches for K1100 Machineand 10 inch for 1200/K1250or equivalent makemachines.h. The length of feeding pipefrom main control valve tofeed control valve (Agartype) equal to basket length +1 ft. as shown in under givensketch.


Installation/ Erection Precautions

6- Selection of Nickel Working ScreensStandard Screens High Open area screens

Mass:Type

Slot Size(W X L) mm

Openarea(%)

Thickness(mm)

Slot Size(W X L) mm

Openarea(%)

Thickness(mm)

A 0.09 X 2.70 11% 0.35 0.09 X 1.85 22.30 % 0.353B 0.06 X 2.67 8.00 % 0.35 0.06 X 1.82 14.70 % 0.33C 0.04 X 2.64

0.06 X 2.676.50 %8.00 %

0.350.35

0.04 X 1.800.06 X 1.82

9.70 %14.70 %

0.330.33

High open area screensare cost effective but;

Increase the machinecapacity or improvesugar quality at givencapacity.

Less slot distortion dueto shorter slot lengthmeans extended servicelife of the screen withgood performance.

Selection of Screen is amatter at C massecuitecuring station;

with high open area slotsize of 0.04 x 1.80 mm,low quality sugarproduction at reducedmachine capacity,slightly less molassespurity but more sugarloss due to high washingwater requirement.

low purity of C Sugarcaused low quality end

sugar production withmore load of molassescirculation in the system.

with high open area ofslot size of 0.06x1.82mm, good quality CSugar production withcapacity curing, slightlyhigh molasses purity butlesser sugar loss due tolesser demand of washingwater.


7- Selection of V Belts type and Pulley design for Power Transmission V-BeltsRequirement Calculation (Ref: DRB, Design Manual for Power Transmission Belts)

Machine TypeMotor PowerDrive rpm, n2/Driven rpm, nlCentral distance of V belts, mmOperating Hours per day

SK 125090 KW(120 HP)1470/2000150024

Step Procedures Results1 Calculate the design HP

Pd: = Pt X FsPd: Design Horse PowerFS: Service Factor {Table-No.4)

Pd = 120 X 1.30 = 156 HP

Pt: Rated Horse power

2 Select the right V-Belt Type V-Belt Type : C(Figure4)3 Select the pulley diameter

i. Minimum Pitch dia (Table No.3)ii. Find speed ratio

Dp: = 229 mm

4 Speed ratio (RS) = nl/n2 Rs. = 2000/1470 = 1.365 s. Calculate the pitch diameter of the larger pulley

Dp: = RS X dpDp: Pitch diameter of larger pulleynl= rpm of smaller pulley

Dp:= 1.36 X 229 = 311 mmDp: Pitch diameter of smaller pulleyn2= rpm of larger pulley

6 1 - Determine the V-belt lengthLp: = 2C + 1.57 x (Dp + dp) + (Dp - dp)' / 4CLp:= effective pitch lengthC= centre distance (chosen)2 - Calculate the exact centre distance of pulleys afterbelt length is determinedC = b+(b= - 2 X (Dp - dp)=)'/. / 4

Lp=2 X1500+1.57x(229+311)+(311-229)' /(4 X 155)LP = 3858.60 mm(Nearest standard length from figureNo.5)

C = 2%2.20 + (2962.2' - 2 x (311 -229)')'/, / 4

7. 1 - Determine tilt power per BeltSee table No. 11 basic horse power rating for C typebelts2 - Determine the arc of contactcorrection factor, From Table No.53 - Determine the lengthCorrection Table No.6

Pr = 16.93 + 0.35 = 17.28Arc Contact = 180 - 60 (Dp - dp) / CArc Contact = 180 - 60 x (311 - 229)1481.10 = 176.68Fo = contact correction factorFL = length correction factor = 1.01

8 Calculate the No. of tilts requiredNumber of belts = Pd (Pr + Fo + PL) Numbers of belts = 155 / (17.28 +

0.99 + 1.01) = 8.099. allowance /la = 40 mm, /I a = 75 mm Table

No.7)10. Summarize the V-belts derive design

1- Pitch diameter of smaller pulley, 220 mm2- Pitch diameter of larger pulley, 311 mm3- Centre distance = 1481 mm

4 - Belts to be used : CISO, 8 pes


TABLE-3 B V belts Dimensions (mm)

Table-4 C Minimum V-Belts Pulley Diameters (in mm)


Figure 2 and Table-5 D V belts Pulley Design Under mentioned is a V belts pulley design guide line with dimensions in mm.

Table-6 E Accurate and Wrong design Pullies


Table-7 F Problems, Causes and Solutions of V-Belts damaging

Problem Probable Cause SolutionForeign object in drive Provide Shield

• Worn or damaged Pulley• Lesser V belts than

requirement• Combination of different

makes V belts• Old and new V belts of

different sizes.

• Replace the Pulleyii-iv Fit required no. ofbelts of same brand,same size and not mix oldand new ones.

i. Pulley diameter too small.ii. High temperature

i. Replace pulley withproper diameter Pulley.ii. Remove heat sourceand improve ventilation

8- Start up Pre-cautionsFollow the instruction laidout in the Instruction Manual,other wise or additions tothose also check that (Sr. No.A- H):A. Bearings are fully greasedB. Basket is fully tightenedwith housing unitC. Nickel working screensare fully tightened and sidesare overlapped according tothe direction of rotation andscreen holding clamps aretightened.D. No foreign material ispresent in the basket andmassecuite distributor.E. Top cover is placed and noair entering points left openin the casing or top cover.F. Rotation of the machinewith motor run.G. Machine is steam heatedto +/- 60ºCH. Feeding pipe contains nocooled massecuite.I. Steam up the feeding pipeof Pug mill at both side of themassecuite control valve toreduce the viscosity of thefeeding massecuite at thestart up and prevent the

massecuite from entering themachine, during massecuiteremoving from Pug millfeeding pipe , temporarilyblind the feeding pipe of themachine .J. Stop the steam heatingwhen feeding massecuite andmachine gained goodoperation temperature andmachine came in normaloperation.K. Close the feed controlvalve and open the Mainmassecuite Control valve.L. Start the machine, afterDelta run, start feedingmassecuite and notice theover all behavior of themachine at operatingconditions, after satisfaction,regulate the massecuite feedcontrol valve.M. Always use hot water of60- 65 C immediate after theagar control valve along withmassecuite feed to lubricatethe massecuite for ease ofequal distribution with in thedistributor.N. Very Important to regulateoperation of the machine forgood quality sugar

production at designedcapacity at recommendedAmpere of the Machine. Ifthere is problem withoperation at full load, checkand rectify it but do notleave it pending for next cropor compromise at reducedcapacity operation.

9- Operational Parameters.(Other than to listed above)

A. Use nozzle water spray atbasket to maintain Sugarquality with followingconditions: at distance not less than 50

mm water temperature 60-65 oC water pressure 2 kg/cm2 good spray is observed

with fish tail type nozzlesspraying at two points at180 degree to each other.

B. Avoid over washing thesugar crystals, better check isto maintain molasses brix, Ifat recommended molassesbrix sugar quality is notachieved then check otherparameters like:


machine rpm number of V belts and

tightening condition massecuite quality n/w screen condition internal cleaning of the

machine casing & distributor

C. Check and maintain: cleaning the machine casing

at defined intervals inspection of the sugar

quality hourly record the data for; feeding massecuite

temperature water spray temperature running Ampere of the

machine bearing temperature sugar and molasses quality

10-Massecuite FeedingArrangementsA-Drive less PressureFeeding BottleFeeding Bottle is installed onsingle or group of machinesa. Merits:i. Pressure feedingii. Drive lessiii. Maintenance freeb. De meritsi- Massecuite re-circulationthrough over flow line tomother Crystallizer damagethe sugar crystalsii. Transmit vibration to theMachine station as a part ofmassecuite pump deliveryline

B- Pug milla- Merits:i. work as pressure feedingbottle if installed asmentioned in Sr. No.5, figureNo.1ii. No massecuite re-circulationiii. Keep the massecuite inmotionb. De meritsi. chances of addition offoreign material if top of pugmill not properly coveredwith mesh screen.ii. more temperature loss ascompared to feeding bottleiii. stirrer power consumptionand maintenance cost.

11- Massecuite Conditioning:

Table-8Type ofMassecuite

FeedingTemp.

Cooling Re-heating Media and Temperature Range

A 60ºC i. open air crystallizer coolingB 55ºC • open air Crystallizer cooling to 60ºC.

ii. one step Vertical crystallizer or Werkspoor water cooling to 55ºCC 58ºC • open air Crystallizer cooling to 60º C

• V.C water cooling to 40º C• water re-heating to 58º C

12- Maximum CapacityGainMost of the parameters arelisted above, others are to:A- Control massecuitetemperature at not belowthan 55ºCB- Run machine at maximumrecommended AmpereC. Install Ampere meter infront of the Operator at eachmachineD. Install easy operativemassecuite feed control valveE. keep clean:a. Inside of the machinecasingb. N/W screen of theMachine

c. massecuite distributord. hot water spray nozzles

13- Essential safety Devicesof the MachineA. Vibration trip deviceB. Bearing TemperatureIndicatorC. Ampere Meter andoverload running electricaltrip device

14- Machine MaintenanceA. Scheduled MaintenanceEach machine should be stopweekly over a period forcheck up and maintenanceof:

i. Basket L-Key bolts andTop ring boltsii. cleaning of distributor,back liner and N/W screensiii. greasing the bearingsiv. inspection of the V. beltscondition

B- Preventive MaintenanceCheck and maintain record ofvibration limits of eachmachine running at full rpmwith no load. If vibration ofthe machine increases thelimits, immediately stop themachine and go throughcheck up and maintenance toget back the machine in thesame limits of vibration.


Recommended safe limit ofvibration for machine basketis less than 1.0 mm per sec.

15- Causes of MajorMachine AccidentsA- Loosen/ thread slippingof the L-Key boltsa. Always use L-Key Bolts ofHigh tensile material and do notcompromise on MS bolts.b. Replace the bolts if threadloosen and once at the startof the season.B-Loosen the top ring boltsa. Always check and tightenthese bolts during schedulemaintenance.C- Loosen the N/W screenfrom Screen holder ringD- Damaging the N/WscreenE- Choking of the Feeddistributor of the BasketF- Cold start of theMachine with coldmassecuite in the feeddistributor.

G- Initial high vibrationreading of the Basketduring start upH- Cold feeding of themassecuite during startrun.I- Stuck off bearings due tono greasing etc.

16. Precautions to stopMachine:A- for interval, duringoperation:a. complete empty and steamwash the massecuite feedingpipe of Pug mill.b. close tightly themassecuite main controlvalve, no leakage shouldobserve after its closure.c. blind the feeding pipe ofthe machined. steam wash the machine toclean any massecuite andsugar crystals adhering theinternal parts of the machine.e. Insure the distributor isfree of massecuite or foreignmaterial

f. shut off the machine andmade it power off from themain control panel.B-Permanent for over noncrop perioda. Properly grease thebearingsb. close/blind all openings ofthe machine casingc. made few manual turns ofthe basket twice a week.

17- Basket KeepingA- Mark the relevant positionof L-key bolts of drive unitwith basket after completionof rotary balancing of thebasket.B- Open the basket after thecompletion of the campaignand keep it body free atbalanced position.C- Re-fit the same basket insame machine with samedrive unit at the samerelevant marked position.This is experienced exercisewhich cut off more than 50% rebalancing expenses ofthe basket for next crop run.

17- Comparative Technical Details of different make Baskets(Installed at Ranipur Sugar Mills)


17- Table-9 Comparative Technical Details of different make Baskets(Installed at Ranipur Sugar Mills)

18- Table-10 A Comparative Capacity run Data for different make Machines(at Ranipur)

Sr.No.

Particulars SBK-1250/30o FCB-1250/30o

value Unit value Unit1 Liner Used

Open area 22.30 % 22.30 %Machine rpm 1600 1600

2 Motor installed 90 Kw 90 Kw3. Absorbed AMP

On load run 55 604. Absorbed AMP on full load 150-155 150 -155 %5. A-Massecuite cured 160 MP 120 MP6. Curing time 8 Hrs 8 Hrs7. Curing temperature 60 oC 60 °C8 Flow rate 20 M3/Hr 15 M3/Hr

Achieved 30 T/Hr 22.50 T/Hr9. A-Massecuite characteristics

Brix 95.00 95.20Purity 83.50 83.80

10 a-Heavy molassesBrix 83.90 84.70Purity 62.57 63.40

11 a-sugarBrix 99.90 99.90Purity 97.88 97.49Colour 651 ICUMSA 706 ICUMSA

Remarks:-a. Other conditions of wash water temperature etc kept constant and flow rate adjusted

according to sugar quality in both cases,b. Massecuite flow rate maintained at equal absorbed amperes in both cases.


Table-10 B


A-Total Electric operational cost saving for the Season (Rs.) 8,445,600.0Maintenance Saving Cost:1-Maintenance Cost for 10 Nos. K-1100 machines

@ Rs.215,900* per season (Rs.) 2,159,000.02-Maintenance Cost for 5 Nos. SK-1250 machines

@ Rs.265,650* per season (Rs.) 1,328,250.0B-Total Maintenance Cost Saving for 5 Nos. Sk1250 Machines (Rs.) 830,750.0C-Total Saving Cost per Season (Rs.) 9,276,350.0

* Cost per Machine, Ref Table No. 11

21- Recommendations:

A-Always select right machine for right massecuite.B-Take necessary care for its erection and start up.C-Take all good measures for capacity gaining.D-Operate machine at full capacity to save electric power and maintenance cost.E-Avoid major break downs by adopting condition monitoring and preventive maintenance practices.F-Control maintenance expenses by training personals and adopting good operation and maintenancepractices.G-Keeping Managerial checks over junior staff of the station, after all this is your own machine station.

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CAPACITY CURING MANAGEMENT OF CONTINUOUS …