Pipe and Tubes

8/6/2019 Pipe and Tubes

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Pipes

Since the purpose with a pipe is the transport of fluids like water, oil and many other products, themost import pipe property is the capacity, or in reality, the inside diameter of the pipe. The nominaldiameter of a pipe is therefore related to the inside diameter.

If we take a look atASME/ANSI B 36.10 Welded and Seamless Wrought Steel Pipe, the insidediameter of a 2'' pipe schedule 40 is 2.067". The inside diameter of a schedule 80 pipe is 1.939". Both

inside diameters are close to 2". The outside diameters for both schedules are 2.375".

Since the outside diameter of a single nominal pipe size is kept constant, the inside diameter of a pipewill depend on the "schedule", or the thickness, of the pipe. The schedule and the actual thickness of apipe will vary with size of pipe.

It is common to identify pipes in inches by using NPS or "Nominal Pipe Size". The metric equivalent iscalled DN or "diametre nominel". The metric designations conform to International StandardsOrganization (ISO) usage and apply to all plumbing, natural gas, heating oil, and miscellaneous pipingused in buildings. The use of NPS does not conform to American Standard pipe designations wherethe term NPS means "National Pipe Thread Straight".

Nominal Bore (NB) may be specified under British standards classifications along with schedule (wall

thickness).

The tolerances are looser to pipes compared with tubes and they are often less expensive to produce.

STD, XS and XXS

To distinguish different weights of pipe, three long standing traditional designations are used:

y standard wall - STD

y extra strong wall - XS

y

double extra strong wall - XXS

The last two designations are sometimes referred to as extra heavy wall (XH), and double extra heavywall (XXH).

For all pipe sizes the outside diameter (O.D.) remains relatively constant. The variations in wallthickness affects only the inside diameter (I.D.).

Welded and Seamless Wrought Steel Pipe


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To distinguish different weights of pipe, it is common to use the Schedule terminology fromANSI/ASME B36.10 Welded and Seamless Wrought Steel Pipe:

y Light Wall

y Schedule 10 (Sch/10, S/10)


y Schedule 30 (Sch/30, S/30)y Schedule 40 (Sch/40, S/40)

y Standard Weight (ST, Std)


y Extra Strong (Extra Heavy, EH, XH, XS)






y Double Extra Strong (Double extra heavy, XXH, XXS)

Note that many of the schedules are identical in certain sizes.

Stainless Steel Pipe

For stainless steel pipes thru 12-inch, schedule numbers from Schedule 5S to schedule 80S are usedas published inANSI/ASME 36.19M Stainless Steel Pipe.

y Schedule 5S (Sch/5S, S/5S)




Tubes

The nominal dimensions of tubes are based on the outside diameter. If we look at Copper Tubes -ASTM B88 the outside diameter of a 2" pipe is 2.125", relatively close to 2".

The inside diameter of a tube will depend on the thickness of the tube. The thickness is often specifiedas a gauge. If we look at Copper Tubes - ASTM B88 the wall thickness of 0.083"of a 2" pipe is gauge14.

The tolerances are higher with tubes compared to pipes. Tubes are often more expensive to producethan pipes.


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Pipe Schedules

What is a pipe schedule?Pipes are designed to carry fluid, therefore their internal diameter is their critical

dimension. This critical dimension is referred to as the nominal bore, commonlyappreviated as NB. Obviously, for pipes containing pressurised fluids the wall thickness,and by implication the pipe's strength, is important. Wall thickness is expressed in

"schedules", refered to as pipe schedules.What Standards Govern Pipe Sizes?In the oil and gas and related down stream industries the the most common standards are- ASME/ANSI B 36.10 Welded and Seamless Wrought Steel Pipe, and

- ASME/ANSI B36.19 Stainless Steel Pipe

Does Pipe Schedule Change With Pipe Size?For all pipe sizes the outside diameter remains relatively constant. Therefore any

variation schedule i.e. wall thickness, affects only the inside diameter. As the schedulenumber increases, the wall thickness increases, and the actual bore is reduced.

Pipe Schedule ChartsThe wall thickness associated with a particular schedule depends on the pipe size as canbe seen from the charts below for some of the more common sized carbon steel pipes

encountered.

Abbreviations used: NB - nominal bore, STD - Standard, EH - Extra Heavy, DBL EH -Double Extra Heavy.

2"NB OD = 2.375 inch (60.32 mm)Schedule 5 10 20 30

40

STD60

80

EH100 120 140 160

DBL

EH

ID (ins) 2.245 2.157 --- --- 2.067 --- 1.939 --- --- --- 1.689 1.503

ID (mm) 57.02 54.79 --- --- 52.5 --- 49.25 --- --- --- 42.9 38.18

3" NB OD = 3.5 inch (88.9 mm)

Schedule 5 10 20 3040

STD60

80EH

100 120 140 160DBLEH

ID (ins) 3.334 3.260 --- --- 3.068 --- 2.900 --- --- --- 2.624 2.300

ID (mm) 84.68 82.8 --- --- 77.93 --- 73.66 --- --- --- 66.65 58.42

4" NB OD = 4.5 inch (114.3 mm)

Schedule 5 10 20 3040

STD60

80EH

100 120 140 160DBLEH

ID (ins) 4.334 4.260 --- --- 4.026 --- 3.826 --- 3.624 --- 3.438 3.152


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ID (mm) 110.08 108.2 --- --- 102.26 --- 97.18 --- 92.05 --- 87.33 80.06

6" NB OD = 6.625 inch (168.275 mm)

Schedule 5 10 20 30

40

STD 60

80

EH 100 120 140 160

DBL

EHID (ins) 6.407 6.357 --- --- 6.065 --- 5.761 --- 5.501 --- 5.189 4.897

ID (mm) 162.74 161.47 --- --- 154.05 --- 146.33 --- 139.73 --- 131.8 124.38

8" NB OD = 8.625 inch (219.1 mm)

Schedule

5 10 20 3040

STD60

80EH

100 120 140 160DBLEH

ID (ins)8.407 8.329 8.125

8.071

7.981 7.813 7.625 7.4397.18

97.001 6.813 6.375

ID (mm) 213.54

211.56

206.38

205 202.72

198.45

193.67

188.95

182.6

177.83

173.05

161.93

10" NB OD = 10.750 inch (273 mm)

Schedul

e5 10 20 30

40

STD60

80

EH100 120 140 160

DB

LEH

ID (ins) 10.48

210.42 10.25

10.13

6

10.0

29.750 9.564 9.314 9.064 8.750

8.50

0---

ID (mm) 266.2

4

264.6

7

260.3

5

257.4

5

254.

5

247.6

5

242.9

3

236.5

8

230.2

3

222.2

5

215.

9 ---

12" NB OD = 12.750 inch (323.85 mm)

Schedule 5 10 20 3040

STD60

80EH

100 120 140 160DBLEH

ID (ins)

12.42 12.39 12.25 12.09

11.938

12.000

11.62

6

11.376

11.750

11.06

410.75 10.50

10.12

6---

ID (mm)315.47 314.7

311.15

307.1303.2

2

304.8

295.3288.95298.4

5

281.03

273.05

266.7 257.2 ---


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Ingress Protection

What does IP stand for?IP is an acronym for Ingress Protection

Why is Ingress Protection Important?Liquid and/or solid particle ingress into electrical equipment may not only be harmful to

the equipment, it may also be dangerous to the operator. Therefore when buyingelectrical equipment whether it be an electric motor, a light fiiting or an enclosure, it is

essential to know what degree of ingress protection the item offers.

Sohow is Ingress Protection quoted?An "IP" number, or as it is commonly known, an IP rating is used to specify the

environmental protection offered. The IP rating is composed of two numbers, the firstreferring to the protection against solid object ingress and the second against liquid

ingress. The higher the number the better the protection.

Are there standards coveringthese ratings?The applicable European standards for ingress protection are:

- BS EN 60529 Specification of Degrees of Protection Provided by Enclosures- IEC 529 Specification of Degrees of Protection Provided by Enclosures

What are the numerical codes?

Ingress Protection Classification

First Number Second Number

IP Protection Provided IP Protection Provided0 No Protection 0 No Protection

1

Protected against solid

objects up to 50mm e.g.accidental touch by hands

1

Protected against vertically

falling drops of water e.g.condensation

2Protected against solidobjects up to 12mm e.g.

fingers

2Protected against directsprays of water up to 15 deg

from the vertical

3

Protected against solid

objects over 2.5mm e.g.

tools

3

Protected against direct

sprays of water up to 60 deg

from the vertical

4Protected against solidobjects over 1mm e.g. wires

4Protected against watersprayed from all directions -

limited ingress permitted

5Protected against dust -

limited ingress (no harmful5

Protected against low

pressure jets of water from


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deposit) all directions - limitedingress permitted

6Totally protected against

dust6

Protected against strong jetsof water e.g. for use on

shipdecks - limited ingresspermitted

7Protected against the affectsof immersion between 15cm

and 1m

8

Protected against long

periods of immersion underpressure

What dotheyuse outside Europe?In North America, the NEMA classification is used. NEMA (National Electrical

Manufacturers Association) is a US trade association representing the interests ofelectroindustry manufacturers of products used in the generation, transmission and

distribution, control, and end-use of electricity.

How does the IP and NEMA systems compare?The IEC and NEMA degrees of protection can not be fully compared as equivalent

ratings. The NEMA Standard includes tests for environmental conditions such asmechanical damage, corrosion, rusting, ice formation, etc. However the follwoing table

can be used as a guide:

NEMA Enclosure

Type Number

IEC

Classification1 IP 10

2 IP 11

3 IP 54

3R IP 14

3S IP 54

4 and 4X IP 56

5 IP 52

6 and 6P IP 67

Does NEMA produce standards?NEMA Standard Publication 250 and UL 40 Standard Publication both provide further

information on ingress protection ratings used in the US


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Thermocouple Types

What is a Thermocouple?A thermocouple consists of two dissimilar metals, joined together at one end, which

produce a small voltage when heated (or cooled). This voltage is measured and used todetermine the temperature of the heated metals. The voltage for any one temperature isunique to the combination of metals used.

Are There Standards Governing Types of Thermocouple?British Standards Specification, BS 1041, Temperature Measurement provides guidancefor the selection and use of devices for measuring temperature.

ASTM Standard E230 provides specifications for the common industrial grades,including letter designations.

Why are there differenttypes?

Thermocouples are available in different combinations of metals, usually refered to by aletter, e.g. J, K etc. Each combination has a different temperature range and is therefore

more suited to certain applications than others. Although it is worth noting that themaximum temperature varies with the diameter of the wire used in the thermocouple.

Summaryof Thermocouple Types

TypeConductor

Combination

Temperature Range

F C

BPlatinum 30% Rhodium /

Platinum 6% Rhodium2500 to 31001370 to 1700

E Nickel-chromium / Constantan 32 to 1600 0 to 870J Iron / Constantan 32 to 1400 0 to 760

K Nickel-chromium / Nickel-aluminum 32 to 2300 0 to 1260

N Nicrosil / Nisil 32 to 2300 0 to 1260

RPlatinum 13% Rhodium /

Platinum1600 to 2640 870 to 1450

SPlatinum 10% Rhodium /

Platinum1800 to 2640 980 to 1450

T Copper / Constantan -75 to +700 -59 to +370

Type BType B thermocouples can be used up to 1600C with short term excursions up to

1800C. They have a low electrical output, therefore are rarely used below 600C. In factthe output is virtually negligible up to 50C, therefore cold junction compensation is not

usually required with this type.

Type EType E thermocouples are often referred to as Chromel-Constantan thermocouples. They


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are regarded as more stable than Type K, therefore often used where a higher degree ofaccuracy is required.

Note - Constantan is Copper-Nickel.

Type J

Type J thermocouples degrade rapidly in oxidising atmospheres above 550C. Theirmaximum continuous operating temperature is around 750C though they can with standshort duration excursions to 1000C. They are generally not used below ambient

temperature due to condensation forming on the wires leading to rusting of the iron.Note - Constantan is Copper-Nickel.

Type KType K are the most widely used thermocouples in the Oil & Gas, and refining industriesdue to their wide range and low cost. They are occasionally referred to as Chromel-

Alumel thermocouples. Note that above about 750C oxidation leads to drift and the needfor recalibration.

Type NType N thermocouples can handle higher temperatures than type K, and offer betterrepeatability in the 300 to 500C range. They offers many advantages over Type R & S at

a tenth of the cost, therefore prove to be popular alternatives.

Type RType R thermocouples cover similar applications as Type S but offers improved stability

and a marginal increase in range. Consequently, Type R tend to be used in preference toType S.

Type SType S thermocouples can be continually at temperatures up to 1450C. They can withstand short duration excursions up to 1650C. They need protection from high

temperature atmospheres to prevent metallic vapour ingress to the tip resulting inreduction of emf generated. Protection commonly offered is high purity recrystallised

alumina sheath. For most industrial applications, thermocouples are housed in athermowell.

Type TType T thermocouples are rarely used in industrial applications, and lend themselvesmore to use in laboratory situations.

Wire Sizes

Cables Wires and ConductorsA wire is a single rod of metal with a small ratio of diameter to length.

A conductor is a wire suitable for carrying an electric current.


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A stranded conductor is a conductor made up of a group of wires. These wires are usuallytwisted together.

A cable is either a single stranded conductor or a combination of conductors insulatedfrom one another (a mutlti-core cable). Cables in the oil and gas and petrochem industries

are generally always insulated and often protected with an armoured sheath. In general,

stranded conductors are more flexible and less susceptible to fatigue-failure than solidwires.

Cable SizingWires can carry only a limited amount of current safely. If the current flowing through a

wire exceeds the current-carrying capacity of the wire, excess heat is generated. This heatmay be great enough to burn off the insulation around the wire and start a fire. An

increase in the diameter, or cross section, of a wire conductor decreases its resistance andincreases its capacity to carry current.

Other reasons for choosing an increased cross sectional area of wire is to limit volt dropalong its length.

LimitationsWires and cables are made in standard diameters. When selecting cables it is commonselect the next standard size up from that calculated.

The terminals (e.g. Weidmuller, Phoenix etc) into which the cable or wire will terminateare made to accomadate a range of sizes. Be aware of any limitations this may place on

your selection.

DimensionsWire diameters are often specified in American Wire Gausge (AWG) rather than in mm

or inches. The charts below give dimensions of common diameters and the correspondingAWG.

Solid Bare Copper Wire

AWG NominalDiam

(mm)

CrossSection

(mm2)

10 2.6 5.23

11 2.3 4.155

12 2.05 3.29

13 1.83 2.63

14 1.63 2.07

15 1.45 1.651

16 1.29 1.3

17 1.15 1.039

18 1.02 0.816

Stranded Tinned Copper Wire

AWG Stranding

No/AWG

NominalDiam

(mm)

CrossSection

(mm2)

12 7/20 2.44 3.61

12 19/25 2.36 3.07

12 65/30 2.41 3.27

14 7/22 1.85 2.26

14 19/26 1.85 1.93

14 42/30 1.85 2.06

16 7/24 1.52 1.42

16 19/29 1.47 1.216

16 65/34 1.5 1.3


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19 0.912 0.653

20 0.813 0.514

21 0.724 0.412

22 0.643 0.322

23 0.574 0.259

24 0.511 0.203

25 0.455 0.163

26 0.404 0.127

27 0.361 0.102

28 0.32 0.08

29 0.287 0.064

30 0.254 0.051

31 0.226 0.0432 0.203 0.032

33 0.18 0.025

34 0.16 0.02

35 0.142 0.016

36 0.127 0.013

37 0.114 0.01

38 0.102 0.008

39 0.089 0.006

40 0.079 0.005

18 7/26 1.22 0.891

18 19/30 1.24 0.957

18 42/34 1.2 0.819

18 65/36 1.2 0.845

20 7/28 0.89 0.504

20 19/32 0.94 0.612

20 42/36 0.914 0.533

22 7/30 0.762 0.352

22 19/34 0.787 0.38

24 7/32 0.61 0.226

24 19/36 0.61 0.239

24 42/40 0.584 0.201

26 7/34 0.483 0.1426 19/38 0.508 0.153

28 7/36 0.381 0.071

28 19/40 0.406 0.093

30 7/38 0.305 0.056

Armoured Cable Glands

Why DoWe Use Cable Glands?- To firmly secure cable entering a piece of equipment

- To maintain the ingress protection of the piece of equipment (minimum of IP54 for 'e'and 'n' type enclosures. Where the enclosure wall thickness is less than 6mm a sealing

washer or thread sealant will be required to maintain IP54 protection)- To maintain earth continuity between a piece of equipment and any armouring in the

cable- To ensure containment of an internal explosion in flameproof equipment

Is there a British Standard forCable Glands?The Code of Practice for selection, installation and inspection of cable glands used inelectrical installations is covered in BS 6121-5 1989 Mechanical cable glands.


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Selecting Cable GlandsItems to consider when selecting a cable gland for a particular installation include:- Possibility of electrolytic action between the gland and the enclosure. Shortened

lifetime for the glands and the cable entries can result if incompatabile materials selected.

The most common materials used are brass, stainless steel and plastic. Material choiscewill influence cost.- Degreee of Ingress Protection required. See our page on IP ratings.

- Certification of gland for use in Hazardous areas- Normal or barrier gland required

- Size of cable being terminated- Size of cable entry on peice of equipment

What is a BarrierGland?Barrier glands are similar to normal glands, except a compound sealant material is usedto ensure the inside of the cable is gas tight as well as the outside.

When Should a BarrierGland be Used?BS EN60079-14 Electrical Apparatus for Explosive Gas Atmospheres Part 14 - ElectricalInstallations in Hazardous Areas (other than Mines) provides a selection process for

deciding if a barrier gland is required. There are various options to consider, however ifthe hazardous gas require IIC apparatus, or if the volume of the enclosure is greater than

2 litres then it is likely you will need to use a barrier gland. IIC apparatus is generallyassociated with Hydrogen.

Gable Gland SizingA rough gland sizing table is provided below, however reference should be made to theBritish Standard referenced above.

NominalConductorArea (mm

2)

Numberof cores

1 2 3 4 5 7 10 12 19 27 37 48

1.5 -- 20S 20S 20S 20S 20S 20 25 25 25 32 32

2.5 -- 20S 20S 20S 20 20 25 25 25 32 41 40

4 -- 20S 20S 20 20 20 25 25 32 40 -- --

6 -- 20 20 20

This chart is forguidance only.

Consultrelevant British Standards beforemaking final selection.

10 -- 20 25 25

16 -- 25 25 25

25 -- 25 25 3235 -- 25 32 32

50 20 32 32 40

70 25 32 40 40

95 25 40 40 50

120 25 40 50 50

150 32 50 50 63


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185 32 50 50 63

240 40 50 63 63

300 40 63 63 75

400 50 63 75 --

Colour coding applies to the shoulder (curved part) of the cylinder and is used to identify theproperties of the gas in the cylinder.Two consecutive bands may be used to depict a gas that has more than one property.

** The colour of the cylinder is only an indication; always read the label to identify a cylinder's

contents.

Acetylene Helium

Air Hydrogen

Ammonia Nitrogen

Argon Nitrous Oxide

Carbon Dioxide Oxygen

Chlorine Oxygen (Medical)

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