TECH

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DESteam distribution

1Contents

Introduction 2Steam distribution 2Steam system basics 2

Working pressure 4Determining the working pressure 4Pressure reduction 6

Pipeline sizing 7Effects of oversizing and undersizing pipework 7Pipeline standards and wall thickness 8Pipeline sizing on steam velocity 9Pipeline sizing on pressure drop 11Pipeline sizing for larger and longer steam mains 12

Steam mains and drainage 17Drain points 18Waterhammer and its effects 19Branchlines 21Branch connections 22Drop leg 23Rising ground and drainage 23Steam separators 24Strainers 26Mains drainage method 27Steam trap selection 28Steam leaks 29Summary 30

Pipe expansion and support 32Allowance for expansion 32Pipework flexibility 33Expansion fittings 36Pipe support spacing 40

Air venting 44Reduction of heat losses 46

Calculation of heat transfer 47Relevant UK and international standards 49Summary 51Appendix 1 - Sizing on pipeline capacity and pressure drop 52Further information 57Appendix 2 - Steam tables 58Appendix 3 - Conversion tables 60

2Introduction

Steam distribution

Steam systembasics

The steam distribution system is an important link between thecentral steam source and the steam user. The central steamsource may be a boiler house or a cogeneration plant. The sourcemust supply good quality steam at the required rate and pressure,and it must do this with the minimum of heat loss and maintenanceattention.

This guide will look at the distribution of dry saturated steam as aconveyor of heat energy to the point of use, for either process heatexchange applications, or space heating, and will cover the issuesassociated with the implementation of an efficient steamdistribution system.

From the outset, an understanding of the basic steam circuit, or'steam and condensate loop' is required. The steam flow in acircuit is due to condensation of steam which causes a pressuredrop. This induces the flow of steam through the pipes.

The steam generated in the boiler must be conveyed throughpipework to the point where its heat energy is required. Initiallythere will be one or more main pipes or 'steam mains' which carrysteam from the boiler in the general direction of the steam usingplant. Smaller branch pipes can then carry the steam to theindividual pieces of equipment.

When the boiler crown valve (the steam outlet from the boiler) isopened, steam immediately passes from the boiler into and alongthe steam mains. The pipework is cold initially so heat is transferredto it by the steam. The air surrounding the pipes is cooler than thesteam, so the pipework will begin to lose heat to the air.

As the steam is flowing to a cooler environment, it will begin tocondense immediately. On start-up of the system, the amount ofcondensate will be greatest as the steam will be used in heatingup the cold pipework - this is known as the 'starting load'. Oncethe pipework has warmed up, condensation will still occur asthe pipework loses heat to the surrounding air - this is known asthe 'running load'.

The resulting condensate falls to the bottom of the pipe and iscarried along with the steam flow and by gravity, due to thegradient in the steam main which should normally fall in thedirection of steam flow. The condensate will then have to bedrained from the lowest points in the steam main.

3When the valve on the steam pipe serving an item of steam usingplant is opened, steam flow from the distribution system entersthe plant and again comes into contact with surfaces cooler thanitself. The steam then gives up its energy in warming up theequipment (starting load), and continues to transfer heat to theprocess (running load) when it will condense into water(condensate).There is now a continuous flow of steam from the boiler to satisfythis connected load, and to maintain this supply more steam mustbe generated. In order to do this, more fuel is fed to the boiler andmore water is pumped into it to make-up for the water which hasalready been evaporated into steam.

The condensate formed in both the steam distribution pipeworkand in the process equipment is a ready made supply of useablehot boiler feedwater. Although it is important to remove thiscondensate from the steam space, it is a far too valuable commodityto be allowed to run to waste. The basic steam circuit should becompleted by returning all condensate to the boiler feedtank,wherever practicable.

Fig. 1 A typical steam circuit

Feedtank

Make-upwater

Boiler

Steam

Vat

Pan PanSteam

Vat

Condensate

Processvessel

Spaceheatingsystem

CondensateSteam

Feedpump

4The pressure at which the steam is to be distributed is partiallydetermined by the point of use on the plant needing the highestpressure.

It should be remembered that as the steam passes through thedistribution pipework, it will lose some of its pressure due toresistance to flow, and condensation from loss of heat to thepipework. Therefore allowance should be made for this pressureloss when deciding upon the initial distribution pressure.

To summarise these points, the following need to be consideredwhen selecting the working pressure:

Pressure required at the point of use.Pressure drop along the pipe due to resistance of flow (friction).Pipe heat losses.

Steam at a higher pressure occupies less volume per kilogramthan steam at a lower pressure. It therefore follows that if steam isgenerated in the boiler at a higher pressure than that needed byits application, and is distributed at this higher pressure, the sizeof the distribution mains will be smaller for any given mass flowrate.Figure 2 illustrates this point.

Working pressure

Determining theworking pressure

Fig. 2 Dry saturated steam pressure/specific volume relationship

0 1 2 3 4 5 6 7 8 9 10 11 12 13 140

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Pressure bar g

Sp

ecific

vol

ume

m/k

g

5Steam generation and distribution at a higher pressure will havethe following advantages:

Smaller bore steam mains are required, resulting in lowercapital cost of steam mains, for materials such as pipes,flanges, support work, and labour.Lower capital cost of pipe insulation.Drier steam at the point of use due to the drying effect ofpressure reduction.The thermal storage capacity of the boiler is increased, helpingit to cope more efficiently with fluctuating loads, reducing therisk of priming and carryover at maximum conditions.

Having distributed at a higher pressure, it will be necessary toreduce the steam pressure to each zone or point of use in thesystem in order to correspond with the pressure required by theapplication.

Please note, it is often thought that running a steam boiler at alower pressure than its design rated pressure will save fuel. Thislogic is based on more fuel being needed to raise steam to ahigher pressure and thus temperature.

Whilst this is marginally so, ultimately, the rate at which energy isused is determined by the connected load not the boiler. Hencethe same energy is used (say in kJs) by the load wether the boilerdelivers at 4 bar g, 10 bar g or 100 bar g. Hence the energysupplied by the burner is exactly the same.

Standing losses and flue losses increase, but these can be reducedby insulation and heat recovery technology, and can be consideredmarginal when compared to the advantages of distributing steamat high pressure.

6Pressure reduction

A separator is used before the reducing valve to remove waterfrom incoming wet steam, therefore allowing only dry saturatedsteam to pass through the reducing valve. This will be looked at inmore detail later.

If a pressure reducing valve is used, it is appropriate to fit a safetyvalve downstream to protect the steam using equipment. Shouldthe reducing valve fail, and allow the downstream pressure toincrease, the steam using equipment may be permanentlydamaged, and the possibility of danger to personnel may result.With a safety valve fitted, any excess pressure is bled off throughthe valve, to prevent this from happening.

Other items completing the pressure reducing valve station are:

The first isolating valve - to shut the system down formaintenance.The first pressure gauge - to monitor the integrity of supply.The strainer - to keep the system clean.The second pressure gauge - to set and monitor thedownstream pressure.The second isolating valve - to set the downstream pressureon no load conditions.

Fig. 3 A typical pressure reducing valve station

DP17

Separator

Strainer

Reducing valveSafety valve

Trap set

Steam

Condensate

Steam

The most common method for pressure reduction is to use apressure reducing station, similar to the one shown in Figure 3.

7Pipeline sizing

A natural tendency exists, when choosing pipe sizes, to be guidedby the size of connections on equipment to which they will beconnected. If the pipework is sized in this way, then the desiredvolumetric flowrate may not be achieved. The use of concentricand eccentric reducers can be used to correct this, enablingpipework to be properly sized.

Pipe sizes may be chosen on the basis of either:

Fluid velocity.Pressure drop.

In each case it is wise to check using both methods to ensure thatthe alternative limits are not being exceeded.

Oversizing of pipework means:

The pipes will be more expensive than necessary.A greater volume of condensate will be formed due to greaterheat loss.Poorer steam quality and ultimate heat transfer due to thegreater volume of condensate formed.Higher installation costs.

In a particular example, the cost of installing 80 mm pipework wasfound to be 44 % more than the cost of 50 mm pipework whichwould have had adequate capacity. The heat lost by the insulatedpipework was some 21 % more from the 80 mm line than it wouldhave been from the 50 mm. Any uninsulated parts would havelost some 50 % more from the 80 mm, than from 50 mm size. Thisis due to the extra surface area available.

Undersizing of pipework means:

Higher steam velocity and pressure drop creating a lowerpressure than required at point of use.Risk of steam starvation at point of use.Greater risk of erosion, waterhammer and noise due toincrease in steam velocity.

Effects of oversizingand undersizing

pipework

Fig. 4 Concentric and eccentric reducers

Steam

EccentricConcentric

Steam

8Probably the most common pipe standard in global use is thatderived from the American Petroleum Institute (API), where pipesare categorised in schedule numbers.

These schedules bear a relation to the pressure rating of the pipingand are eleven in number ranging from the lowest at 5 through 10,20, 30, 40, 60, 80, 100, 120, 140 to schedule no. 160. For piping150 mm nominal size and smaller, schedule 40 (sometimes called'standard weight') is the lightest which is specified. Only schedules40 and 80 cover the full range from 15 mm up to 600 mm nominalsizes and are the most commonly used schedule for steam pipeinstallations. For the purposes of this guide, reference will be topipework of schedule 80 (sometimes called 'extra strong').Tables of schedule numbers can be obtained from BS 1600which are used as a reference for the nominal pipe size and wallthickness in millimetres. Table 1 is an example of the bore sizesof different sized pipes, for different schedule numbers. In Europe,pipe is manufactured to DIN standards and DIN 2448 pipe isincluded in the table.

Pipeline standardsand wall thickness

For a 25 mm schedule 80 pipe, the internal bore diameter of thepipe is 24.3 mm, likewise a schedule 40 pipe has an internal borediameter of 26.6 mm.Pipes most commonly used are heavy grade carbon steel (standardlength 6 m) for steam mains and condensate lines.Another term which is commonly used for pipe thickness is 'Blueband and Red band'. These are referred to from BS 1387, (Steeltubes and tubulars suitable for screwing to BS 21 threads), andapply to particular grades of pipe, Red being heavy, commonlyused for steam pipe applications, and Blue being used as amedium grade, commonly used for air distribution systems. Thecoloured bands are 50 mm wide, and their positions on the pipedenote its length. Pipes less than 4 metres in length only have acoloured band at one end, while pipes of 4 to 7 metres in lengthhave a coloured band at either end.

Example

Pipe size (mm) 15 20 25 32 40 50 65 80 100 125 150Schedule 40 15.8 21.0 26.6 35.1 40.9 52.5 62.7 77.9 102.3 128.2 154.1

Bore (mm) Schedule 80 13.8 18.9 24.3 32.5 38.1 49.2 59.0 73.7 97.2 122.3 146.4Schedule 160 11.7 15.6 20.7 29.5 34.0 42.8 53.9 66.6 87.3 109.5 131.8DIN 2448 17.3 22.3 28.5 37.2 43.1 60.3 70.3 82.5 107.1 131.7 159.3

Table 1

Fig. 5 Pipe band locations

Single band.Up to 4 m in length

Double band.Between 4 m - 7 m in length

9If pipework is sized on the basis of velocity, then calculations arebased on the volume of steam being carried in relation to thecross sectional area of the pipe.

For dry saturated steam mains, practical experience shows thatreasonable velocities are 25 - 40 m/s, but these should be regardedas the maxima above which noise and erosion will take place,particularly if the steam is wet.

Even these velocities can be high in terms of their effect onpressure drop. In longer supply lines, it is often necessary torestrict velocities to 15 m/s if high pressure drops are to be avoided.

By using Table 2 (page 13) as a guide, it is possible to select pipesizes from the steam pressure, velocity and flowrate.

Alternatively the pipe size can be calculated by following themathematical procedure as outlined below. In order to do this, weneed to define the following information:

Flow velocity (m/s) CSpecific volume (m3/kg) vMass flowrate (kg/s) mVolumetric flowrate (m/s) V = m(kg/s) x v(m3/kg)

From this information, the cross sectional area (A) of the pipe canbe calculated:

Volumetric flowrate (V)Cross sectional area (A) = Flow velocity m/sec (C)

i.e: p x D2 = V4 C

This formula can be rearranged to give the diameter of the pipe:

D = 4 x Vp x C

\ D = 4 x Vp x C

This will produce the diameter of the pipe in metres. It can easilybe converted into millimetres by multiplying by 1 000.

Pipeline sizing onsteam velocity

l

l l

l

l

l

l

10

Example It is required to size a pipeline to handle 5 000 kg/h of drysaturated steam a 7 bar g, and 25 m/s required flow velocity.

- Flow velocity (C) = 25 m/s- Specific volume (v) = 0.24 m/kg (from steam tables)- Mass flowrate (m) = 5 000 kg/h = 1.389 kg/s3 600 s/h

- Volumetric flowrate (V) = m x v= 1.389 kg/s x 0.24 m/kg

= 0.333 m/s

Therefore, using:

Cross sectional area (A) = Volumetric flowrate (V)Flow velocity (C)

p x D = 0.3334 25

D = 4 x 0.333p x 25

D = 0.130 m or 130 mm

An alternative method is to use Figure 6 (page 14) for calculatingpipe sizes by velocity. This method will work if you know thefollowing requirements; Steam pressure, temperature (ifsuperheated), flowrate and velocity. The example below will helpto explain how this method works.

Using the above example, it is required to size a pipeline tohandle 5 000 kg/h of saturated steam at 7 bar g. The maximumacceptable steam velocity is 25 m/s.

Method refer to Figure 6, page 14.Draw a horizontal line from the saturation temperature line at 7 bar g(point A) on the pressure scale to the steam mass flowrate of5 000 kg/h (point B). Now draw a vertical line to the steamvelocity of 25 m/s (point C). From C, draw a horizontal lineacross the pipe diameter scale (point D). A pipe with a bore of130 mm will suffice in this case.

Example

l

l l

l

11

Sometimes it is essential that the steam pressure feeding an itemof plant is not allowed to fall below a specified minimum, in orderto maintain temperature, thus ensuring that plant heat transferfactors are maintained under full load conditions. Here, it isappropriate to size the pipe on the 'pressure drop' method, byusing the known pressure at the supply end of the pipe and therequired pressure at the point of use.

There are numerous graphs, tables and even slide rules availablefor relating pipe size to pressure drop. One method which hasproved satisfactory, is the use of utilizing pressure drop factors.An example of this method is shown in the appendix at the end ofthis guide.

An alternative and quicker method to sizing pipelines on thebasis of pressure drop, is to use Figure 7 (page 15) if the followingvariables are known: steam temperature, pressure, flowrate andpressure drop requirements.

It is required to size a pipeline to handle 20 000 kg/h of superheatedsteam at 15 bar g pressure at 300C, and a pressure drop of0.3 bar/100 m.

Method refer to Figure 7, page 15.Draw a vertical line from 300C (point A) on the temperature scaleto 15 bar g (point B) on the pressure scale. From B, draw ahorizontal line to the steam flowrate of 20 000 kg/h (Point C). Nowdraw a vertical line to the top of the graph. Draw a horizontal linefrom 0.3 bar/100 m on the pressure loss scale (point D). The pointat which this line crosses the vertical line from point C (point E), willdetermine the pipe size required. In this case 200 mm.

Example

Pipeline sizing onpressure drop

12

These pipelines should be sized using the pressure drop method.Calculations usually consider higher pressures and flowratesand superheated steam. The calculation uses a pressure ratiobetween the total pressure drop and inlet pressures, which maybe utilised in Figure 8 (page 16).It is required to size a pipe to handle 20 tonnes of steam per hourat a pressure of 14 bar gauge and a temperature of 325C. Thelength of the pipe is 300 metres and the permissible pressuredrop over this length is 0.675 bar.

Note that the chart is in absolute pressure and for an exercise ofthis kind, it is sufficiently accurate to approximate that 14 bargauge equals 15 bar absolute.

First find the pressure ratio:

Ratio = Pressure dropInlet pressure (absolute)= 0.675

15

= 0.045

Method refer to Figure 8, page 16.From this point on the left hand scale, read horizontally to the rightand at the intersection (A) with the curved line, read verticallyupwards to meet the length line of 300 metres (B). At this point,extend the horizontal line across the chart to point C.

Now read from the base temperature line at 325C and extendvertically upwards to meet the 15 bar abs. pressure line (D).Read horizontally to the right to meet the line of 20 tonnes/h (E)and from this point, extend a line vertically upwards. The pipesize is indicated where this line intersects line B - C at point F.This shows a pipe size of 200 mm.

This procedure can also be reversed to find the pressure drop in aknown pipe size.

Example

Pipeline sizing forlarger and longer

steam mains

13

Pressure Velocity kg/hbar m/s 15mm 20mm 25mm 32mm 40mm 50mm 65mm 80mm 100mm 125mm 150mm 200mm 250mm 300mm

15 7 14 24 37 52 99 145 213 394 648 917 1606 2590 36780.4 25 10 25 40 62 92 162 265 384 675 972 1457 2806 4101 5936

40 17 35 64 102 142 265 403 576 1037 1670 2303 4318 6909 950015 7 16 25 40 59 109 166 250 431 680 1006 1708 27911 3852

0.7 25 12 25 45 72 100 182 287 430 716 1145 1575 2816 4629 620440 18 37 68 106 167 298 428 630 1108 1712 2417 4532 7251 1032315 8 17 29 43 65 112 182 260 470 694 1020 1864 2814 4045

1.0 25 12 26 48 72 100 193 300 445 730 1160 1660 3099 4869 675140 19 39 71 112 172 311 465 640 1150 1800 2500 4815 7333 1037015 12 25 45 70 100 182 280 410 715 1125 1580 2814 4845 6277

2.0 25 19 43 70 112 162 295 428 656 1215 1755 2520 4815 7525 1057540 30 64 115 178 275 475 745 1010 1895 2925 4175 7678 11997 1679615 16 37 60 93 127 245 385 535 925 1505 2040 3983 6217 8743

3.0 25 26 56 100 152 225 425 632 910 1580 2480 3440 6779 10269 1431640 41 87 157 250 375 595 1025 1460 2540 4050 5940 10476 16470 2295015 19 42 70 108 156 281 432 635 1166 1685 2460 4816 7121 10358

4.0 25 30 63 115 180 270 450 742 1080 1980 2925 4225 7866 12225 1730440 49 116 197 295 456 796 1247 1825 3120 4940 7050 12661 19663 2781615 22 49 87 128 187 352 526 770 1295 2105 2835 5548 8586 11947

5.0 25 36 81 135 211 308 548 885 1265 2110 3540 5150 8865 14268 2005140 59 131 225 338 495 855 1350 1890 3510 5400 7870 13761 23205 3224415 26 59 105 153 225 425 632 925 1555 2525 3400 6654 10297 14328

6.0 25 43 97 162 253 370 658 1065 1520 2530 4250 6175 10629 17108 2404240 71 157 270 405 595 1025 1620 2270 4210 6475 9445 16515 27849 3869715 29 63 110 165 260 445 705 952 1815 2765 3990 7390 12015 16096

7.0 25 49 114 190 288 450 785 1205 1750 3025 4815 6900 12288 19377 2708040 76 177 303 455 690 1210 1865 2520 4585 7560 10880 19141 30978 4347015 32 70 126 190 285 475 800 1125 1990 3025 4540 8042 12625 17728

8.0 25 54 122 205 320 465 810 1260 1870 3240 5220 7120 13140 21600 3321040 84 192 327 510 730 1370 2065 3120 5135 8395 12470 21247 33669 4685815 41 95 155 250 372 626 1012 1465 2495 3995 5860 9994 16172 22713

10.0 25 66 145 257 405 562 990 1530 2205 3825 6295 8995 15966 25860 3589040 104 216 408 615 910 1635 2545 3600 6230 9880 14390 26621 41011 5756015 50 121 205 310 465 810 1270 1870 3220 5215 7390 12921 20538 29016

14.0 25 85 195 331 520 740 1375 2080 3120 5200 8500 12560 21720 34139 4721840 126 305 555 825 1210 2195 3425 4735 8510 13050 18630 35548 54883 7653415 60 145 246 372 558 972 1524 2244 3864 6258 8868 15505 24646 34819

17.0 25 102 234 397 624 888 1650 2496 3744 6240 10200 15072 26064 40967 5666240 151 366 666 990 1452 2634 4110 5682 10212 15660 22356 42658 65860 91841

Table 2 Saturated steam pipeline capacities at specific velocities (schedule 80 pipe)

14

Fig. 6 Superheated and saturated steam pipeline sizing chart (velocity method)

B

C D

Steam

veloc

ity m/

s

Steam

flowra

te kg/h

50 % Vacuum

Steam pressure bar g

600500

15

10

2520

30

400

150175200250300

1251008070605040

150

5

100

102030

50100

200

500

1 000

2 000

3 000

2030

Steam temperature C100 200 300 400 500

200 0

00100 0

0050 00

020 00

0

30 00

010 0

005 000

10075

50

2030

10

50

532

10.5

0 bar g

710A

Pipe

dia

met

er m

m

The dotted line A, B, C, D refers to the example on page 10

Saturation temperature

curve

15

Fig. 7 Steam pipeline sizing chart (pressure drop method)

400300200100 500

1810

5

3Pr

essu

re lo

ss b

ar/1

00 m

2

1

0.5

0.20.3

0.1

0.05

0.030.02

0.01

50 % Vacuum

0 bar g0.5

12357

A

10B

2030

50

10075

Steam temperature C

Stea

m flo

wrat

e kg/

h

200 0

00

100 0

00

C

50 00

0

30 00

05 000

3 000

2 0001 0

00500300200100503

02010

20 00

0

10 00

0

Insid

e pipe

diam

eter

mm

60050040

030025020

015012510

08070605

040302

520

15

10

The dotted line A, B, C, D, E refers to the example on page 11

Steam pressure bar g

Saturation temperature

curve

D E

16

Figure 8 Pipe sizing chart for larger steam mains

0.8

0.60.7

0.50.40.3

0.2

0.090.1

0.080.070.060.050.040.03

0.02

0.010.0090.0080.0070.0060.0050.0040.003

Rat

io D

P =

Pres

sure

dro

p ba

rIn

let p

ress

ure

bar a

bs

100 200 300 400 500

110 120100

80706050403025

15

20

1086

54

3

2

1

Steam inlet press

ure bar abs

10 20 40

70

150

300

500

1 000

2 000

4 000

Pipe length m

7 000

15

30

50

100

200

400

700

1500

10000

50 70 100

150200

300400500750

Pipe diameter mm

F C

600

450

350

250

175

1258060

300

150

704020106421

200

10050301581.5 3 5

50003000

G = S

team

mas

s flow

rate

tonn

e/h

ED

Steam temperature C

B

A

0.9 4

6

810

15

20

30

40

60

80

150

Steam velocity m

/s

The dotted line A, B, C, D, E refers tothe example on page 12

100

200

17

In any steam main, some steam will condense due to radiationlosses. For example, a well lagged 100 mm line 50 m longcarrying steam at 7 bar, with surrounding air at 20C, will condenseapproximately 26 kg of steam per hour, when heated from cold.

This is probably less than 1 % of the carrying capacity of the main.Nevertheless it means, that at the end of 1 hour if not drained, themain would contain not only steam, but at least 26 litres of waterand progressively more with time.

So some provision must be made for draining off this water. Ifthis is not done effectively, problems such as corrosion andwaterhammer will set in, which will be covered later. In addition,the steam will become wet as it picks up water droplets, therebyreducing its heat transfer potential. Under extreme conditions ifwater is allowed to build up, the overall effective cross sectionalarea of the pipe is reduced, hence increasing steam velocityabove recommended limits.

Whenever possible the main should be run with a fall of not lessthan 100 mm in 10 m, in the direction of the steam flow. If thesteam main rises in the direction of flow, then the condensate willtend to be dragged uphill with the steam flow. Instead relaypoints may be installed allowing the pipe to fall in the direction offlow between the points. Refer to the Figure 9 for further details.

By installing the pipework with a fall in the direction of steam flow,both steam and condensate will run in the same direction. A drainpoint is needed at the foot of each relay, and the steam andcondensate will run in the same direction towards the drain points.The subject of drainage from steam lines is covered in the UKBritish Standard BS 806, section 4.12.

Steam mains and drainage

Fig. 9 Diagram of rising ground pipeworkRising ground

Trap setCondensate

Steam

Steam

18

The benefits of selecting the most appropriate type of steam trapfor a particular application will be wasted if condensate cannoteasily find its way to the trap. For this reason, careful considerationshould always be given to the size and situation of the drain point.

Consideration should also be given to what happens to condensatein a steam main at shut-down when all flow ceases. Due to gravitythe water will run along falling pipework and collect at the lowerpoints in the system. Steam traps should therefore be fitted tothese low points.

However, the amount of condensate formed in a large steammain under start-up conditions is sufficient to require the provisionof drain points at intervals of 30 m to 50 m, as well as at naturallow points.

In normal operation steam may flow along the main at speeds ofup to 145 km/h, dragging condensate along with it. Figure 10shows a 15 mm drain pipe connected from the bottom of a main toa steam trap. Although the 15 mm pipe has sufficient capacity, it isunlikely to catch much of the condensate moving along the mainat high speed. Such an arrangement will be ineffective. A morereliable solution for the removal of condensate is shown in Figure11. The drain line off-take should be at least 25 to 30 mm from thebottom of the pocket for steam mains up to 100 mm, and roughly athird to centre of the pocket for larger mains, allowing a spacebelow for any dirt and scale to settle. The bottom of the pocketmay be fitted with a removable flange or blowdown valve forcleaning purposes.

Steam mains diameters Drain pocketup to 100mm Bore same as main

depth at least 100 mm125, 150, 200 mm Bore 100 mm; depth at least 150 mm250 mm and above Bore half that of main

depth at least diameter of main

Drain points

Fig. 10 Incorrect Fig. 11 Correct

Steam trapPocketSteam trap

19

Waterhammer may occur when condensate is pushed along apipe by the steam instead of being drained away at the low points,and is suddenly stopped by impacting on an obstacle in thesystem. The build up of droplets of condensate along a length ofsteam pipework, as shown in Figure 12 eventually forms a 'solid'slug which will be carried at steam velocity along the pipework.Such velocities can be of 30 m/s or more. This slug of water isdense and incompressible, and, when travelling at high velocity,has a considerable amount of kinetic energy.

Waterhammer andits effects

When obstructed, perhaps by a bend or tee in the pipe, the kineticenergy of the water is converted into pressure energy and apressure shock is applied to the obstruction. (The laws ofthermodynamics, state that energy cannot be created or destroyed,but is simply converted into a different form). Commonly there is abanging noise, and perhaps movement of the pipe. In severecases the fitting may fracture with almost explosive effect, withconsequent loss of live steam at the fracture, providing a hazardoussituation.

Fortunately, waterhammer may be avoided if steps are taken toensure that the condensate in the pipework is not allowed tocollect along the pipework.

Avoiding waterhammer is a better alternative than attemptingto contain it by choice of materials, and pressure ratings ofequipment.

Common sources of waterhammer trouble occur at the low pointsin the pipework (See Figure 13). Such areas are:

Sags in the line.Incorrect use of concentric reducers and strainers. For thisreason it is better to fit strainers on their sides in steam lines.Inadequate drainage of steam lines.

Fig. 12 The formation of a 'solid' slug of water

Steam

Steam

Steam

20

To summarise, in order to minimise the possibility of waterhammer;

Steam lines should be arranged with a gradual fall in thedirection of flow, with drain points installed at regular intervalsand at low points.Check valves should be fitted after all traps which wouldotherwise allow condensate to run back into the steam line orplant during shut-down.Isolation valves should be opened slowly to allow anycondensate which may be lying in the system to flow gentlytowards, and through, the drain traps before it is picked up byhigh velocity steam. This is especially important at start-up.

Steam

Fig. 13 Potential sources of waterhammer trouble

Steam

Steam

21

Branch

Branchlines It is important to remember that branch lines are normally muchshorter in length than the steam mains. Sizing branches on thebasis of a given pressure drop is accordingly less convenient onshort lengths of pipe. With a main of 250 m length, a pressuredrop limitation of 0.5 bar may be perfectly valid, even though itleads to the use of lower velocities than might be expected. In abranch line of only 5 m or 10 m length, the same velocity wouldlead to values of only 0.01 or 0.02 bar. Clearly these areinsignificant, and it is usual to size branch lines on a higher steamvelocity. This may create a higher pressure drop, but with ashorter pipe length, this pressure drop will be acceptable.

Sizes are often selected from a table, like the 'Pipeline capacitiesat specific velocities' table (Table 2). When using steam velocitiesof 25 to 35 m/s where short branch connections to equipment arebeing considered, it should be noted that the accompanying rateof pressure loss per unit length can be relatively high. A largepressure drop can be created if the pipeline contains severalfittings like connections and elbows. Longer branch lines shouldbe restricted to a velocity below 15 m/s unless the pressure dropis also calculated.

Fig. 14 Branchline

Steam mainSteam Steam

Steam

22

Steam

Branch connections Branch connections taken from the top of the main carry thedriest steam. If taken from the side, or even worse from the bottomas Figure 15, they can carry the condensate from the main and ineffect become a drain pocket. The result is very wet steam reachingthe equipment. The valve in Figure 16 should be positioned asnear to the off-take as possible to minimize condensate laying inthe branch line, if shut-down for extended periods.

Fig. 15 Incorrect

Fig. 16 Correct

Steam

23

Low points will also occur in branch lines. The most common is adrop leg near to an isolating valve or a control valve. Condensatebuilds up in front of the closed valve, and will be entrained withthe steam when the valve opens again - consequently a drainpoint with a steam trap set is required at this point.

Drop leg

It is not uncommon for a steam main to run across rising ground,where the contours of the site make it quite impractical to lay thepipe with a natural fall, therefore the condensate must be inducedto run downhill against the steam flow. It is then wise to make surethat the pipe size is large enough, over the rising section, to lowerthe steam velocity to not more than 15 m/s. Equally, the spacingbetween the drain points should be reduced, to not more than 15 m.The aim is to prevent the condensate film on the bottom of thepipe increasing in thickness to a point where droplets are pickedup by the steam flow, Figure 18 below.

Rising groundand drainage

Fig. 17 Diagram of a drop leg

Fig. 18 Reverse gradient on steam main

30 - 50 m

Fall

Drop leg

Trap set

Steam main

Controlvalve

Isolation valve

Isolation valve

Steam Steam

Condensate

Steamvelocity40 m/s

Fall

Increasein pipediameter Fall

15 m15 m

Steamvelocity15 m/s

24

Modern packaged steam boilers have a high duty for their sizeand lack any reserve capacity to cope with overload conditions.Incorrect chemical feedwater treatment, TDS control and transientpeak loads can cause serious priming and carryover of boilerwater into the steam mains. The use of a separator to remove thiswater is shown in Figure 20. Selection is not difficult when using asizing chart. See Figure 19.

Determine the size of separator required for a flowrate of 500 kg/hat 13 bar g pressure.

1. Taking the pressure and flowrate, draw line A - B.2. Draw a horizontal line B - C.3. Any separator size curve that is bisected by the line B - C

within the shaded area will operate at near 100 % efficiency.4. Additionally, line velocity for any size can be determined by

dropping a vertical line D - E. (e.g. 18 m/s for a size DN32 unit).5. Also, pressure drop can be determined by plotting lines E - F

and A - F. The point of intersection is the pressure drop acrossthe separator, i.e.: 0.037 bar approximately.

Steam separators

Separator sizingchart example

Fig. 19 Separator sizing chart

CBD

A

EF

Steam pressure bar g

Sepa

rato

r size

Pressure drop across separator bar

DN150DN125DN100

DN80DN65DN50DN40 DN32

DN25

DN20

DN15

1 2 3 4 5 6 7 8 9 101112 16 18 20 22 24 25 5 10 15 20 25 30 35 40

10 000

5 000

2 000

1 000

500

200

100

502010

0.002

0.02

0.01

0.05 0.1

0.2

Flow velocity m/s

Stea

m flo

wrat

e kg

/h

25

Separators should be selected on the basis of the bestcompromise between line size, velocity and pressure drop foreach application.

As soon as steam has left the boiler, some of it must condense toreplace the heat being lost through the pipe wall. Insulation willnaturally reduce the heat loss, but the heat flow and thecondensation rate remain as small but finite amounts and ifappropriate action is not taken these amounts will accumulate.The condensate will form droplets on the inside of the pipe wall,and these can merge into a film as they are swept along by thesteam flow.

The water will also gravitate towards the bottom of the pipe, andso the thickness of the film will be greatest there. Steam flowingover this water film can raise ripples which can build up intowaves. If this build up continues, the tips of the waves will breakoff, throwing droplets of condensate into the steam flow. Theresult is that the heat exchange equipment receives very wetsteam, which reduces heat transfer efficiency and the working lifeof control valves. Anything that will reduce the propensity for wetsteam in mains or branch lines will prove beneficial.

A separator will remove both droplets of water from pipe wallsand suspended mist entrained in the steam itself. The presenceand effect of waterhammer can be eradicated by fitting a separatorin a steam main, and can often be a cheaper alternative thanaltering pipework to overcome this phenomenon.

Fig. 20 A typical cut section through a separatorCondensate to steam trap

Wet steam Dry steam

26

When new pipework is installed, it is not uncommon for fragmentsof casting sand, packing, jointing, swarf, welding rods and evennuts and bolts to be left inside. In the case of older pipework, therewill be rust and in hard water districts, a carbonate deposit. Fromtime to time, pieces will break loose and pass along the pipeworkwith the steam, to rest inside a piece of steam using equipment,which could prevent a valve from opening/closing correctly

The steam using equipment may also suffer permanent damagethrough wire drawing - the cutting action of high velocity steamand water passing through a partly open valve. Once wire drawinghas occurred, the valve will never give a tight shut-off, even if thedirt is removed.

Therefore, it is sensible practice to fit a simple pipeline strainer infront of every steam trap, meter, reducing valve and regulating valve.The diagram shown in Figure 21 shows a typical strainer in section.

Strainers

Fig. 21 A typical cut section through a strainer

Steam flows from the inlet 'A' through the perforated screen 'B' tothe outlet 'C'. While steam and water will pass readily through thescreen, the progress of dirt will be arrested. The cap 'D', can beremoved, allowing the screen to be withdrawn and cleaned atregular intervals. A blowdown valve can also be fitted to the cap'D' to facilitate regular cleaning.

Strainers however, can be a source of waterhammer trouble aspreviously mentioned. To avoid this problem strainers should beinstalled on their sides when they are part of a steam line.

CA

B

D

27

The use of steam traps is the most efficient method of drainingcondensate from a steam distribution system.

The steam traps used to drain the main must be suitable for thesystem, and have sufficient capacity to pass the amounts ofcondensate reaching them with the pressure differentials whichare present at any given time.

The first requirement is easily dealt with, the maximum workingpressure at the steam trap will either be known or can readily befound. The second requirement covering the amounts ofcondensate reaching the trap under working conditions, when onlythe heat losses from the line are leading to condensation of thesteam, may be calculated, or read with sufficient accuracy fromTable 3 (page 31).It should be remembered, that traps draining a boiler header mayat times be required to discharge water carried over from theboiler with the steam. A total capacity of up to 10 % of the boilerrating is usually thought reasonable. In the case of the other trapsfurther along the system, Table 3 page 31, shows that providingthe drain points are not further apart than the recommended 50 m,the condensate loads will normally be well within the capacity ofa 15 mm low capacity trap. Only in those rare applications of veryhigh pressures (above 70 bar), combined with large pipe sizes,will greater trap capacity be needed.

A little more care is sometimes needed when steam lines are frequentlyshut-down and started up. Amounts of steam condensed while thepipes are being warmed from cold to working temperature are alsolisted in Table 3 page 31. Since these are steam masses rather thansteam flowrates, the time allowed for the heating process must alsobe taken into account. For example, if a pipe is brought to workingpressure in 20 minutes, then the hourly rate will be 60/20, or 3 timesthe load shown in the table.

During the first part of the heating up process, the condensing ratewill be at least equal to the average rate. However, the pressurewithin the pipe will be only a little above atmospheric pressure,perhaps by 0.05 bar. This means that the capacity of the trap willbe correspondingly reduced. In those cases where start-up loadsare frequent, the DN15 steam trap with normal capacity may be amore appropriate choice

This also highlights another benefit of the large pipe-sized drainpocket, which, at start-up, can fill up with condensate when steampressure may not be high enough to push it away through thetrap.

Mains drainagemethod

28

The specification for a mains drain trap should give dueconsideration to a number of aspects.

The steam trap should discharge at, or very close to saturationtemperature, unless long cooling legs are used between thedrain point and the trap. This means that the choice is oftenbetween mechanical traps like float and inverted bucketpatterns, or thermodynamic traps.

Where mains are outside buildings and the possibility of frostdamage arises, the thermodynamic steam trap is pre-eminent.Even if the installation is such that water is left in the trap atshut-down and freezing occurs, the thermodynamic trap maybe thawed out without suffering any damage when it is to bebrought back into use.

Historically, on poorly laid out installations where waterhammermay be prevalent, float traps may not have been ideal due totheir susceptibility to float damage. Contemporary design andmanufacturing techniques, now produce extremely robust unitsfor mains drainage purposes. Float traps are certainly the firstchoice for proprietary separators. The high capacities whichare readily achieved, and the near instantaneous response torapid load increases, are desirable features.

Thermodynamic steam traps are also suitable, for draininglonger runs of large diameter mains, especially where linesare in continuous service. Frost damage is then less likely.

Typical steam traps which are used to drain condensate frommains are shown in Figure 22.

The subject of steam trapping is dealt with in more detail in thetechnical reference guide 'Steam Trapping and Air Venting'.

Steam trapselection

Fig. 22 Steam traps

Thermodynamic type Inverted bucket typeBall float type Thermostatic type

29

Leaking steam is all too often ignored. However, leaks can becostly in both financial and environmental senses and thereforeneed prompt attention to ensure the steam system is working at itsoptimum efficiency with a minimum impact on the environment.

For example, for each litre of heavy fuel oil burned unnecessarilyto compensate for a steam leak, approximately 3 kg of carbondioxide are emitted to the atmosphere.

Figure 23 illustrates the steam loss for various sizes of hole andthis loss can be readily translated into an annual fuel savingbased on either 8 400 or 2 000 hours of operation per year.

Steam leaks

Fig. 23 Steam loss through leaks

1 000

500400300200

100

50403020

10

543

1 2 3 4 5 10 14

12.5 mm10 mm

7.5 mm

5 mm

3 mm

Leakinghole

Stea

m le

ak ra

te kg

/h

Coaltonnes/year

Heavy fuel oilx 1 000 litres/year

Gasx 1 000 kWh/year

1 000

500400300200

100

50403020

10

54

8 400 2 000Hours per day Hours per year

8 400 2 000

1

2345

10

20304050

100

200 500400300200

100

50403020

10

5432

1

2345

10

20304050

100

0.5

Hours per year8 400 2 000

1 000

500400300200

100

50403020

10

5

5 0004 0003 0002 000

1 000

500400300200

100

50403020

Steam pressure bar (x 100 = kPa)24 hour day, 7 day week, 50 week year = 8 400 hours8 hour day, 5 day week, 50 week year = 2 000 hours

30

To summarise this section, proper pipe alignment and drainagemeans observing a few simple rules:

Steam lines should be arranged to fall in the direction of flow,at not less than 100 mm per 10 metres of pipe.Steam lines should be drained at regular intervals of 30-50 mand at any low points in the system.Where drainage has to be provided in straight lengths of pipe,then a large bore pocket should be used to collect condensate.If strainers are to be fitted, then they should be fitted on theirsides.Branch connections should always be taken from the top ofthe main so the driest steam is taken.

Separators should be considered before any piece of steamusing equipment ensuring that dry steam is obtained.Traps selected should be robust for the job to avoid the risk ofwaterhammer damage, and appropriate for their environment.(i.e. frost damage).

Summary

31

Steam Main size - mm -18Cpressure correction

bar g 50 65 80 100 125 150 200 250 300 350 400 450 500 600 factor1 5 9 11 16 22 28 44 60 79 94 123 155 182 254 1.392 6 10 13 19 25 33 49 69 92 108 142 179 210 296 1.353 7 11 14 20 25 36 54 79 101 120 156 197 232 324 1.324 8 12 16 22 30 39 59 83 110 131 170 215 254 353 1.295 8 13 17 24 33 42 63 70 119 142 185 233 275 382 1.286 9 13 18 25 34 43 66 93 124 147 198 242 285 396 1.277 9 14 18 26 35 45 68 97 128 151 197 250 294 410 1.268 9 14 19 27 37 47 71 101 134 158 207 261 307 428 1.259 10 15 20 28 38 50 74 105 139 164 216 272 320 436 1.24

10 10 16 20 29 40 51 77 109 144 171 224 282 332 463 1.2412 10 17 22 31 42 54 84 115 152 180 236 298 350 488 1.2314 11 17 23 32 44 57 85 120 160 189 247 311 366 510 1.2216 12 19 24 35 47 61 91 128 172 203 265 334 393 548 1.2118 17 23 31 45 62 84 127 187 355 305 393 492 596 708 1.2120 17 26 35 51 71 97 148 220 302 362 465 582 712 806 1.2025 19 29 39 56 78 108 164 243 333 400 533 642 786 978 1.1930 21 32 41 62 86 117 179 265 364 437 571 702 859 1150 1.1840 22 34 46 67 93 127 194 287 395 473 608 762 834 1322 1.1650 24 37 50 73 101 139 212 214 432 518 665 834 1020 1450 1.1560 27 41 54 79 135 181 305 445 626 752 960 1218 1480 2140 1.1570 29 44 59 86 156 208 346 510 717 861 1100 1396 1694 2455 1.1580 32 49 65 95 172 232 386 568 800 960 1220 1550 1890 2730 1.1490 34 51 69 100 181 245 409 598 842 1011 1288 1635 1990 2880 1.14

100 35 54 72 106 190 257 427 628 884 1062 1355 1720 2690 3030 1.14120 42 64 86 126 227 305 508 748 1052 1265 1610 2050 2490 3600 1.13

50 65 80 100 125 150 200 250 300 350 400 450 500 6001 5 5 7 9 10 13 16 19 23 25 28 31 35 41 1.542 5 6 8 10 12 14 18 22 26 28 32 35 39 46 1.503 6 7 9 11 14 16 20 25 30 32 37 40 45 54 1.484 7 9 10 12 16 18 23 28 33 37 42 46 51 61 1.455 7 9 11 13 17 20 24 30 36 40 46 49 55 66 1.436 8 10 11 14 18 21 26 33 39 43 49 53 59 71 1.427 8 10 12 15 19 23 28 35 42 46 52 56 63 76 1.418 9 11 14 16 20 24 30 37 44 49 57 61 68 82 1.409 9 11 14 17 21 25 32 39 47 52 60 64 72 88 1.39

10 10 12 15 17 21 25 33 41 49 54 62 67 75 90 1.3812 11 13 16 18 23 26 36 45 53 59 67 73 81 97 1.3814 12 14 17 20 26 30 39 49 58 64 73 79 93 106 1.3716 12 15 18 23 29 34 42 52 62 68 78 85 95 114 1.3618 14 16 19 24 30 36 44 55 66 72 82 90 100 120 1.3620 15 17 21 25 31 37 46 58 69 76 86 94 105 125 1.3525 15 19 23 28 35 42 52 66 78 86 97 106 119 141 1.3430 17 21 25 31 39 47 51 73 87 96 108 118 132 157 1.3340 20 25 30 38 46 56 70 87 104 114 130 142 158 189 1.3150 24 29 34 44 54 65 82 102 121 133 151 165 184 220 1.2960 27 32 39 50 62 74 95 119 140 155 177 199 222 265 1.2870 29 35 43 56 70 82 106 133 157 173 198 222 248 296 1.2780 34 42 51 66 81 97 126 156 187 205 234 263 293 350 1.2690 38 46 56 72 89 106 134 171 204 224 265 287 320 284 1.26

100 41 50 61 78 96 114 149 186 220 242 277 311 347 416 1.25120 52 63 77 99 122 145 189 236 280 308 352 395 440 527 1.22

Table 3 Warm-up / running loads per 50 m of steam main

Note: Warm-up and running loads based on an ambient temperature of 20C, and an insulation efficiency of 80 %

Running loads per 50 m of steam main (kg/h)

Warm-up loads per 50 m of steam main (kg/h)

32

Material Temperature range C< 0 0 - 100 0 - 200 0 - 315 0 - 400 0 - 485 0 - 600 0 - 700

Mild steel 0.1-0.2 % C 12.8 14.0 15.0 15.6 16.2 17.8 17.5 Alloy steel 1 % Cr 0.5 % Mo 13.8 14.4 15.1 15.8 16.6 17.3 17.6 Stainless steel 18 % Cr 8 % Ni 9.4 20.0 20.9 21.2 21.8 22.3 22.7 23.0

Pipe expansion and support

Allowance for expansion

All pipes will be installed at ambient temperature. Pipes carryinghot fluids, whether water, or steam, operate at higher temperatures.It follows that they expand, especially in length, with an increasefrom ambient to working temperatures. This may create stressesupon certain areas within the distribution system, such as a pipejoints which could be fractured. The amount of the expansion isreadily calculated using the following equation, or read fromappropriate charts.

Expansion = L x Dt x a (mm)where: L = Length of pipe between anchors (m)

D t = Temperature difference Ca = Expansion coefficient (mm/mC) x 10-

Table 4 Expansion coefficients (a)

Find the expansion of 30 m of pipe from ambient (10C) to 152C(steam at 4 bar g)

L = 30 mD t = 152C - 10C = 142Ca = 15.0 x 10- mm/mC

\ Expansion = 30 x 142 x 15.0 x 10- mm

i.e. expansion = 64 mm

Alternatively, the amount of pipe expansion can be determined byusing Table 6 (page 40) to calculate the amount of expansionover 10 m of pipe for the different pipe materials. Expansioncharts like Figure 34 (page 41) are also an easy method fordetermining the amount of expansion.

Example

33

The pipework must be sufficiently flexible to accommodate themovements of the components as it heats up. In most cases thepipework has enough natural flexibility, by virtue of havingreasonable lengths and plenty of bends, that no undue stressesare set up. In other installations, it will be necessary to build insome means of achieving the required flexibility. An example ofbuilding in flexibility is when condensate is drained from a steammain drain trap to a condensate main. In this case, the differencebetween the expansion of the two mains due to the change intemperature or the pipes' material expansion rates must beremembered.

The steam main may be at a temperature very much above that ofthe return main, and the two connection points can move inrelation to each other during system warm up. Some flexibilityshould be incorporated in the steam trap piping so that branchconnections do not become over stressed. (See Figure 24).

The amount of movement to be taken up by the piping and anydevice incorporated in it can be reduced by the use of 'cold draw'.The total amount of expansion is first calculated for each sectionbetween fixed anchor points. The pipes are left short by half thisamount, and stretched cold, as by pulling up bolts at a flangedjoint, so that at ambient temperature, the system is stressed in onedirection. When warmed through half the total temperature rise,the piping is unstressed. At working temperature and having fullyexpanded, the piping is stressed in the opposite direction. Theeffect is that instead of being stressed from 0 F to +1 F units offorce, the piping is stressed from - F to + F units of force.

Pipework flexibility

Fig. 24 Flexibility in connection to condensate return line

Steam main

Condensate main

Steam Steam

Condensate

34

In practical terms, the pipework is assembled with a spacer piece,of length equal to half the expansion, between two flanges. Whenthe pipework is fully installed and anchored, the spacer is removedand the joint pulled up tight. (See Figure 25).

The remaining part of the expansion, if not accepted by the naturalflexibility of the pipework will call for the use of an expansion fitting.

Pipework expansion and support in practice, can therefore be classifiedinto the following three areas as shown in Figure 26 below.

The fixed point support (A) provides a datum position from whichexpansion takes place.

The variable anchor point (B) will allow free movement forexpansion of the pipework, while keeping the pipeline inalignment.

Fig. 25 Use of spacer for expansion when pipework is installed

Fig. 26 Diagram of pipeline with fixed point, variable anchor point and expansion fitting

Position after cold draw

Hot position

Half calculated expansionover length

L

Neutral position Spacer piece

Point AFixed

Point BVariableanchor

Point CExpansion

fitting

Point AFixed

Point BVariableanchor

35

Fig. 27 Chair and roller

Roller supports are an ideal method for supporting pipes, whileallowing them to move in two directions. For steel pipework, therollers should be manufactured from ferrous material. For copperpipework, they should be manufactured from non-ferrousmaterial. It is good practice for pipework supported on rollers tobe fitted with a pipe saddle bolted to a support bracket at notmore than 6 metre centres to keep the pipework in alignmentwhile expansion and contraction occurs.

Where two pipes are to be supported, it is bad practice to carry thebottom pipe from the top pipe using a pipe clip. This will causeextra stress to be added to the top pipe whose thickness has beensized to take only the stress of its working pressure.

All pipe supports should be specifically designed to suit theoutside diameter of the pipe concerned.

The expansion fitting (C) is one method of accommodating for theexpansion. These fittings are placed within a line, and are designedto accommodate the expansion, without the total length of the linechanging.

Fig. 28 Chair roller and saddle

36

Full loop (Figure 29)This is simply one complete turn of the pipe and should preferablybe fitted in a horizontal rather than a vertical position to preventcondensate building up. The downstream side passes below theupstream side and great care must be taken that it is not fitted thewrong way round. When full loops are to be fitted in a confinedspace, care must be taken in ordering, otherwise wrong handedloops may be supplied. The full loop does not produce a force inopposition to the expanding pipework as in some other types, butwith steam pressure inside the loop, there is a slight tendency tounwind, which puts an additional stress on the flanges.

This design is rarely used today due to the space taken up by thepipework, and proprietory expansion bellows are now readilyavailable. However large steam uses such as power stations orestablishments with large outside distribution systems still tendto use loop type expansion devices, as space is usually availableand cost is relatively low.

Horseshoe or lyre loop (Figure 30)When space is available this type is sometimes used. It is bestfitted horizontally so that the loop and the main are on the sameplane. Pressure does not tend to blow the ends of the loop apart,but there is a very slight straightening out effect. This is due to thedesign but causes no misalignment of the flanges. In other cases,the 'loop' is fabricated from straight lengths of pipe and 90 bends.This may not be effective and requires more space, but it meetsthe same need. If any of these arrangements are fitted with theloop vertically above the pipe then a drain point must be providedon the upstream side.

Expansion fittings

Expansion loops (Figure 30)A development of the Horse shoe loop, expansion loops arefabricated from lengths of straight pipes and elbows welded at thejoins. The amounts of expansion which can be accommodated insuch assemblies are shown in Figures 36 and 37 page 42.

Fig. 29 Full loop Fig. 30 Horse shoe or lyre loop

37

Sliding joint (Figure 32)These are sometimes used because they take up little room, but itis essential that the pipeline is rigidly anchored and guided, to themanufacturers' instructions, otherwise steam pressure acting onthe cross sectional area of the sleeve part of the joint tends toblow the joint apart in opposition to the forces produced by theexpanding pipework. Misalignment will cause the sliding sleeveto bend, while regular maintenance of the gland packing is alsoneeded.

Bellows (Figure 33)A simple bellows has the advantage that it is an in-line fitting andrequires no packing as does the sliding joint type. But it doeshave the same disadvantages as the sliding joint in that pressureinside tends to extend the fitting so that anchors and guides mustbe able to withstand this force.

Fig. 32 Sliding joint

Fig. 31 Expansion loop

Fig. 33 Bellows

Welded bendradius = 1.5 dia

Weld joint

2W

W

38

Bellows can incorporate limit rods which limit over-compressionand over-extension of the element. These may have little functionunder normal operating conditions, as most simple bellowsassemblies are able to withstand small lateral and angularmovement. However, in the event of anchor failure, they behaveas tie rods and contain the pressure thrust forces, preventingdamage to the unit whilst reducing the possibility of further damageto piping, equipment and personnel.

Where larger forces are expected, some form of additionalmechanical re-inforcement should be built into the device, suchas hinged stay bars.

There is invariably more than one way to accomodate the relativemovement between two laterally displaced pipes depending uponthe relative positions of bellows anchors and guides, but generally,axial displacement is better than angular which, in turn, is betterthan lateral. Angular and lateral movement should be avoidedwherever possible.

Figure 34 a, b, and c give a simple indication of the effects ofthese movements, but, under all circumstances, it is highlyrecommended that expert advice is sought from the bellowsmanufacturer regarding any installation.

Fig. 34a Axial movement of bellows

Shortdistance

Guides

Fixing point

Guides

Axial movement

Axial movement

39

Fig. 34b Small lateral and angular movement of bellows

Fig. 34c Angular and axial movement of bellows

Mediumdistance

Guides

Fixing point

Guides

limit rods

Smalllateral

movement

Smalllateralmovement

Smallangularmovement

Smallangular

movement

Longdistance

Fixing point

hinged stay bars

largeangularmovement

Axialmovement

largeangular

movement

40

Nominal pipe size (mm) Interval of horizontal run Interval of vertical runSteel / Copper metres metres

Bore Outside dia. Mild steel Copper Mild steel Copper12 15 1.0 1.215 18 2.0 1.2 2.4 1.420 22 2.4 1.4 3.0 1.725 28 2.7 1.7 3.0 2.032 35 2.7 1.7 3.0 2.440 42 3.0 2.0 3.6 2.450 54 3.4 2.0 4.1 2.465 67 3.7 2.0 4.4 2.980 76 3.7 2.4 4.4 3.2100 108 4.1 2.7 4.9 3.6125 133 4.4 3.0 5.3 4.1150 159 4.8 3.4 5.7200 194 5.1 6.0250 267 5.8 5.9

The frequency of pipe supports will vary according to the bore ofthe pipe; the actual pipe material (i.e. steel or copper); and whetherthe pipe is horizontal or vertical.

Generally, pipe supports should be provided which comply withBS 3974, Part 1, 1974: 'Pipe hangers, slider and roller typesupports.'Some of the important points are as follows:

Pipe supports should be provided at joints in the pipe, i.e.bends, tees, valves, flanges and at intervals not greater thanshown in the next table, Recommended support spacing forsteel pipes. The reason for supporting at joints is to eliminatethe stresses in screwed or flanged joints.Where two or more pipes are supported on a common bracket, thespacing between the supports should be that for the smallest pipe.When an appreciable movement will occur, i.e. where straightpipes are greater than 15 metres in length, the supports shouldbe of the roller type as outlined previously.

The following table can be used as a guide when calculating thedistance between pipe supports for steel and copper pipework.

Pipe support spacing

Table 5 Recommended support for pipework

Vertical pipes should be adequately supported at the base, towithstand the total weight of the vertical pipe. Branches fromvertical pipes should not be used as a means of support for thepipe, because this will place undue strain upon the tee joint.All pipe supports should be specifically designed to suit theoutside diameter of the pipe concerned. The use of oversizedpipe brackets is not good practice.

41

Temperature MaterialsC C. steel 12 % Cr steel 18/8 s.s Ductile iron Coppermm/10m mm/10m mm/10m mm/10m mm/10m-30 -4.99 -5.05 -7.79 -4.54 -7.16-25 -4.44 -4.49 -6.92 -4.04 -6.38-20 -3.90 -3.94 -6.05 -3.53 -5.59-15 -3.35 -3.38 -5.19 -3.03 -4.79-10 -2.80 -2.82 -4.32 -2.52 -4.00-5 -2.24 -2.26 -3.46 -2.02 -3.200 -1.69 -1.69 -2.59 -1.51 -2.415 -1.13 -1.13 -1.73 -1.01 -1.61

10 -0.56 -0.57 -0.86 -0.50 -0.8015 0.00 0.00 0.00 0.00 0.0020 0.57 0.57 0.86 0.50 0.8125 1.14 1.13 1.73 1.01 1.6130 1.71 1.70 2.59 1.51 2.4235 2.29 2.27 3.46 2.02 3.2440 2.86 2.84 4.32 2.52 4.0545 3.44 3.42 5.18 3.21 4.8750 4.03 3.99 6.05 3.75 5.6855 4.61 4.56 6.91 4.28 6.5060 5.20 5.14 7.78 4.82 7.3365 5.79 5.72 8.64 5.36 8.1570 6.39 6.29 9.50 5.89 8.9875 6.98 6.87 10.37 6.43 9.8080 7.58 7.45 11.23 6.96 10.6385 8.18 8.03 12.09 7.50 11.4790 8.79 8.62 12.95 8.03 12.3095 9.39 9.20 13.82 8.57 13.14

100 10.00 9.78 14.68 9.10 13.97110 11.23 10.96 16.41 10.53 15.66120 12.47 12.13 18.13 11.64 17.35130 13.72 13.32 19.85 12.75 19.04140 14.97 14.50 21.58 13.86 20.75150 16.24 15.69 23.30 14.97 22.46160 17.52 16.89 25.02 16.60 24.19170 18.81 18.08 26.75 17.74 25.92180 20.11 19.29 28.47 18.89 27.65190 21.43 20.50 30.19 20.03 29.40200 22.75 21.71 31.91 21.18 31.15210 24.08 23.04 33.63 23.38220 25.42 24.28 35.35 24.58230 26.78 25.53 37.07240 28.14 26.78 38.79250 29.52 28.04 40.51260 30.90 29.30 42.23270 32.30 30.57 43.94280 33.70 31.85 45.66290 35.12 33.13 47.38300 36.55 34.42 49.09310 37.98 35.71 50.81320 39.43 37.01 52.53330 40.89 38.32 54.24340 42.36 39.63 55.95350 43.84 40.94 57.67360 45.33 42.26 59.38370 46.83 43.59 61.10380 48.35 44.93 62.81390 49.87 46.27 64.52400 51.40 47.61 66.23410 48.96 67.94420 50.32 69.66430 51.68 71.37440 53.05 73.08450 54.43 74.79460 55.81 76.49470 57.19 78.20480 58.58 79.91490 59.98 81.62500 61.38 83.33

Table 6 Thermal expansion of pipes (mm per 10 m)

42

Fig. 35 Expansion chart for mild steel pipe

bar g 1 2 3 4 5 7.5 10 15 20 25 30C 120 134 144 152 159 173 184 201 215 226 236

Temperature of saturated steam

50040030020050200

100

504030

20

10

510 20 30 40 50 100 200 300 500 1000

Temperature difference C

2000Expansion of pipe (mm)

Leng

th o

f pip

e (m

) 220 100

43

Fig. 36 Copper expansion loop

Fig. 37 Steel expansion loop

200175150125100755025200

10090807060

50

40

30

200.5 2.521.51

2WW

Maximum pressure 10 bar

3.5 43

W. metres

Expansion from neutral position (mm)

Nom

inal

pip

e siz

e (m

m)

W. metres

25

2.5 321.510.52530

40

5060708090

100

200

300

40050 75 100 200175150125

3.5 4 4.5 5

W2W

Maximum pressure 17 barMaximum temperature 260C

Welded bendsradius = 1.5 dia.

Expansion from neutral position (mm)

Nom

inal

pip

e siz

e (m

m)

W. metres

W. metres

44

Air venting

It is often overlooked that when steam is first admitted to a pipeafter a period of shut-down, the pipe is full of air. Further amountsof air and other non-condensable gases will enter with the steam,although the proportions of these gases are normally very smallcompared with the steam. Nevertheless, these gases willaccumulate within the pipe and in the steam spaces of heatexchangers when the steam condenses, unless steps are takento discharge them. The warming up of the steam system willbecome a lengthy business which will contribute towards a fall inplant efficiency.

A further effect of air in a steam system will be the effect uponpressure and temperature. Air will exert its own partial pressurewithin the steam space, and this pressure will be added to thepartial pressure of the steam in producing the total pressurepresent. Therefore, the actual steam pressure will be lower thanthat shown by the total pressure on a pressure gauge. The overalltemperature will also be lower than that suggested by the pressuregauge. In reality this is usually a marginal effect. Far moreimportant is the effect air has upon heat transfer. A layer of aironly 1 micron thick can offer the same resistance to heat as alayer of water 25 microns thick, a layer of iron 2 mm thick or alayer of copper 17 mm thick. Therefore it is of utmost importancethat air is removed from the system.

Automatic air vents for steam systems are nothing more thanthermostatic steam traps, fitted above the level of any condensateso that only steam, or air, or steam/air mixtures can reach them.They are usually best located at the ends of the steam mains andthe larger diameter branches as can be seen in Figure 37.

The discharge from the air vent can be piped to any safe place. Inpractice, it is often taken into the condensate line, where it is agravity line falling towards a vented receiver.

Fig. 38 Draining and venting at the end of a main

Steam

Condensate

Air

45

In addition to air venting at the end of a main, other parts of thesteam system which may require air venting are:

In parallel with an inverted bucket trap which is relatively slowto air vent on start-up.In awkward steam spaces such as at the opposite side towhere steam enters a jacketed pan.Where there is a large steam space, and a steam/air mixtureis to be avoided.

46

Reduction of heat losses

Once a steam main has warmed up, condensation will continueas heat is lost by radiation, the rate depending upon the steamtemperature, ambient temperature, and the efficiency of the systeminsulation.

If a steam distribution system is to be as efficient as possible, thenall appropriate steps should be taken to ensure that any heatlosses are reduced to the economic minimum. The mosteconomical thickness of insulation will depend upon severalfactors:

Installation cost.Value of the heat carried by the steam.Size of the pipework.Pipework temperature.

If the pipework to be insulated is outside, then the air velocity andpotential dampness of the insulation must be taken into account.

Most insulation materials depend on minute air cells for theireffectiveness, which are held in a matrix of inert material such asmineral wool, fibreglass or calcium silicate. Typical installationsuse aluminium clad fibreglass, aluminium clad mineral wool andcalcium silicate. It is important that insulating material is not crushedor allowed to become waterlogged. Adequate mechanicalprotection and water proofing are essential, especially in outdoorlocations.

The heat loss from a steam pipe to water, or to water saturatedinsulation, can be as much as 50 times greater than from thesame pipe to air. Particular care should be taken to protect steamlines which must run through waterlogged ground, or in ductswhich may be subjected to flooding.The need to insulate all hot parts of the system must be kept inmind. This includes all flanged joints on the mains, and also thevalves and other fittings. It was, at one time, common to cut backthe insulation at each side of a flanged joint, to leave access to thebolts for maintenance purposes. This meant about 0.3 m of pipewas deliberately left bare, in addition to the surface of the flangesthemselves. The total effect was as if some 0.6 m of pipe hadbeen left uninsulated at each joint. Fortunately, the availability ofprefabricated insulating covers for flanged joints and boxes toinsulate valves is now more widely appreciated. These are usuallyprovided with fasteners so that they can readily be detached toprovide access for maintenance purposes.

47

Temperature Pipe sizedifference 15 20 25 32 40 50 65 80 100 150

steam to air mm mm mm mm mm mm mm mm mm mmC W/m56 54 65 79 103 108 132 155 188 233 32467 68 82 100 122 136 168 198 236 296 41078 83 100 122 149 166 203 241 298 360 50089 99 120 146 179 205 246 289 346 434 601100 116 140 169 208 234 285 337 400 501 696111 134 164 198 241 271 334 392 469 598 816125 159 191 233 285 285 394 464 555 698 969139 184 224 272 333 333 458 540 622 815 1133153 210 255 312 382 382 528 623 747 939 1305167 241 292 357 437 437 602 713 838 1093 1492180 274 329 408 494 494 676 808 959 1190 1660194 309 372 461 566 566 758 909 1080 1303 1852

Note: Heat emission from bare horizontal pipes with ambient temperatures between 10Cand 21C and still air conditions

The calculation of heat losses from pipes can be very complexand time consuming, as heat transfer theory by conduction,convection and radiation need to be considered. The formulae forthese factors are all different, and assume that obscure dataconcerning pipewall thickness, heat transfer coefficients andvarious derived constants are easily available.

The derivation of these formulae is outside the scope of thisguide, but it may be said that further information can be readilyfound in any good thermodynamics textbook. To add to this, anabundance of contemporary computer software exists to providethis service for the more discerning engineer.

This being so, the commonplace solution to the problem caneasily be found by reference to Table 7 and a simple equation.The table assumes ambient conditions of between 10 - 21C, andconsiders heat losses from bare horizontal pipes of different sizeswith steam contained at various pressures.

Calculation of heattransfer

Table 7 Heat emission from pipes

Other factors can be included in the equation, for instance, should the pipebe lagged with insulation providing a reduction in heat losses to 15 % ofthe uninsulated pipe, then M is simply multiplied by a factor of 0.15.

Where:M = Rate of condensation (kg/h)Q = Heat emission (W/m) (as Table 7)L = Effective length of pipe, allowing for flanges and fittings(m)hfg = Specific enthalpy of evaporation (kJ/kg)f = Insulation factor. e.g.: 1 for bare pipes

0.15 for good insulation

M = Q x L x 3.6 x fhfg

l

l

l

48

49

Relevant UK and Internationalstandards

Symbols have been used to indicate harmonised standards,technically equivalent standards, and related standards - ; = and respectively.

BS 10 Specification for flanges and bolting for pipes, valves andfittings.

BS 21 = ISO 7/1 ISO 7/2 Specification for pipe threads for tubesand fittings where pressure tight joints are made on the threads.BS 806 Specification for design and construction of ferrous pipinginstallations for and in connection with land boilers.

BS 1306 Specification for copper and copper alloy piping systems.

BS 1387 Specification for screwed and socketed tubes andtubulars and for plain end steel tubes suitable for welding andscrewing to BS 21 pipe threads.

BS 1560 Circular flanges for pipes, valves and fittings (Classdesignated); Part 3 Section 3.1 Specification for steel flanges( ISO 7005); Part 3 Section 3.2 Specification for cast ironflanges ( ISO 7005-2); Part 3 Section 3.3 Specification forcopper alloy and composite flanges ( ISO 7005-3)BS 1600 Dimensions of steel pipe for the petroleum industry.

BS 1965 Specification for butt welding pipe fittings for pressurepurposes.

BS 1710 Specification for identification of pipelines.

BS 2779 = IS0 228/1 and ISO 228/2 Specification for pipe threadsfor tubes and fittings where pressure tight joints are not made onthe threads.

BS 3600 Specification for dimensions and masses per unit lengthof welded and seamless steel pipes and tubes for pressurepurposes.

BS 3601 Specification for steel pipes and tubes with specifiedroom temperature properties for pressure purposes.

BS 3602 Specification for steel pipes and tubes for pressurepurposes: carbon and carbon manganese steel with specifiedelevated temperature properties.

BS 3603 Specification for carbon and alloy steel pipes and tubeswith specified low temperature properties for pressure purposes.

50

BS 3604 Steel pipes and tubes for pressure purposes: ferriticalloy steel with specified elevated temperature properties.

BS 3605 Austenitic stainless steel pipes and tubes for pressurepurposes.

BS 3799 Specification for steel pipe fittings, screwed and socketwelded for the petroleum industry.

BS 3974 Specification for pipe supports.

BS 4504 Part 3 Section 3.1 Specification for steel flanges; Section3.2 Specification for cast iron flanges ( ISO 7005-2); Section 3.3Specification for copper alloy and composite flanges ( ISO 7005/3).

51

To summarise what has been covered within this TechnicalReference Guide, it is appropriate to finish with a check list whichcan be used to ensure that a steam distribution system will operatewith optimum efficiency.

Are steam mains properly sized?

Are steam mains properly laid out?

Are steam mains adequately drained?

Are steam mains adequately air vented?

Is adequate provision made for expansion?

Can separators be used to improve steam quality?

Are there leaking joints, glands or safety valves?

Can redundant piping be blanked off or removed?

Is the system sufficiently lagged?

Summary

52

Appendix 1 - Sizing on pipelinecapacity and pressure drop

The following is relevant to the section titled ' Pipeline sizing onpressure drop'. The example demonstrates the theoretical methodfor calculating the pipe size using pressure drop.

Suppose we have a boiler supplying a heater battery as inFigure 38 below.

Example

The length of travel from the boiler to the heater battery is known,but we must allow for the frictional resistance of the fittings interms of equivalent pipe length.

If the size of the pipe was known, the resistance of the fittings could becalculated. As this size is not yet known, an addition to the equivalentlength is made based on experience. If the line is over, 100 metreslong and a fairly straight run, then the proportional allowance forfittings would be 10 %. A similar straight run, but a shorter length oftravel would rate an allowance more in the region of 20 %.

One further allowance has to be made and that is for heat lossesfrom the pipe. The heater battery requires 270 kg/h of steam,therefore the pipe must carry this quantity plus the quantity of steamcondensed by heat losses from the main. The size of the main is yetto be determined so the true calculations cannot be made but,assuming that the main is insulated, it may be assumed reasonableto add 1 % of the steam load per 30 m of travel as heat losses. Thisequates to 3.4 % per 100 m, i.e. in this instance, 3.4 % of 270 kg/hper 100 m multiplied by the pipe length, the calculation would be:

3.4 x 270 kg/h x 150 m = 14 kg/h due to heat losses100 100 m

Total steam load = 270 kg/h + 14 kg/h = 284 kg/h

Fig. 39 Boiler - Heater battery

150 m + 10 % equals 165 m

Heater battery at 6.6 bar g270 kg/h

Boiler at 7 bar g284 kg/h

53

Returning to the equation,

From the pressure factors for pipe sizing table (Table 8 page 54)P1 at 7.0 bar g = 56.38P2 at 6.6 bar g = 51.05Length L = 165 m

Therefore, F = P1 - P2 = 56.38 - 51.05 = 0.0323L 165

Follow down the left-hand column of the pipeline capacity andpressure drop factors table (Table 9), and it will be found that thenearest two readings around our requirement of 0.0323 are 0.030and 0.040. The reading 0.040 implies a pressure drop to a finalpressure lower than 6.6 bar and, therefore, we should choose thenext lower factor nearest to our requirements, in this case, 0.030.Alternatively, It is bad practice to size any pipe up to the limit of itscapacity as it is always important to have some leeway tocompensate for any errors in design. Therefore the next lowestfactor is chosen. Readings can also be interpolated withreasonable accuracy, however, the table does not conform to astraight line graph, so interpolation cannot be absolutely correct.

From 0.030, follow line x (volume of steam), and it will be seenthat a 40 mm pipe will carry only 229.9 kg/h and a 50 mm pipe willcarry 501.0 kg/h. Obviously the pipe will have to be of 50 mm boredue to its larger capacity.

Having sized the main using the pressure drop method, we cancheck to see if we are still within the limits of our required steamvelocity. This will involve using the velocity factor (y) line of Table 9,which is based on a steam volume of 1m/kg.

Our diagram (Figure 38), shows 284 kg of steam passing through a50 mm pipe. Referring to Table 9, and scanning the 50 mm pipecolumn, it will be seen that where this quantity of steam is beingcarried, the velocity factor (y) by interpolation is approximately 40.

54

Steam at 7 bar g has a volume (as shown in Table 8 page 54) of0.24 m/kg, so the true velocity of the example system using a 50mm pipe is:

y = True velocity x 1

40 = True velocity 0.24

True velocity = 40 x 0.24

\ True velocity = 9.6 m/s

It may be thought that this velocity is low in comparison withmaximum permitted velocities, but it must be remembered that thesteam main has been sized to limit pressure drop, whereasmaximum permitted velocities are usually accommodated by ahigh pressure drop.

55

Pressure Volume Pressure Pressure Volume Pressure Pressure Volume Pressurebar m3/kg factor bar gauge m3/kg factor bar gauge m3/kg factor

0.05 28.192 0.0301 2.15 0.576 9.309 7.70 0.222 66.310.10 14.674 0.0115 2.20 0.568 9.597 7.80 0.219 67.790.15 10.022 0.0253 2.25 0.660 9.888 7.90 0.217 69.290.20 7.64 9 0.0442 2.30 0.552 10.18 8.00 0.215 70.800.25 6.204 0.0681 2.35 0.544 10.48 8.10 0.212 72.330.30 5.229 0.0970 2.40 0.536 10.79 8.20 0.210 73.880.35 4.530 0.1308 2.45 0.529 11.40 8.30 0.208 75.440.40 3.993 0.1694 2.50 0.522 11.41 8.40 0.206 77.020.45 3.580 0.2128 2.55 0.515 11.72 8.50 0.204 78.610.50 3.240 0.2610 2.60 0.509 12.05 8.60 0.202 80.220.55 2.964 0.3140 2.65 0.502 12.37 8.70 0.200 81.840.60 2.732 0.3716 2.70 0.496 12.70 8.80 0.198 83.490.65 2.535 0.4340 2.75 0.489 13.03 8.90 0.196 85.140.70 2.365 0.5010 2.80 0.483 13.37 9.00 0.194 86.810.75 2.217 0.5727 2.85 0.477 13.71 9.10 0.192 88.500.80 2.087 0.6489 2.90 0.471 14.06 9.20 0.191 90.200.85 1.972 0.7298 2.95 0.466 14.41 9.30 0.189 91.920.90 1.869 0.8153 3.00 0.461 14.76 9.40 0.187 93.660.95 1.777 0.9053 3.10 0.451 15.48 9.50 0.185 95.41

1.013 1.673 1.025 3.20 0.440 16.22 9.60 0.184 97.18bar gauge 3.30 0.431 16.98 9.70 0.182 98.96

0 1.673 1.025 3.40 0.422 17.75 9.80 0.181 100.750.05 1.601 1.126 3.50 0.413 18.54 9.90 0.179 102.570.10 1.533 1.230 3.60 0.405 19.34 10.00 0.177 104.400.15 1.471 1.339 3.70 0.396 20.16 10.20 0.174 108.100.20 1.414 1.453 3.80 0.389 21.00 10.40 0.172 111.870.25 1.361 1.572 3.90 0.381 21.85 10.60 0.169 115.700.30 1.312 1.694 4.00 0.374 22.72 10.80 0.166 119.590.35 1.268 1.822 4.10 0.367 23.61 11.00 0.163 123.540.40 1.225 1.953 4.20 0.361 24.51 11.20 0.161 127.560.45 1.186 2.090 4.30 0.355 25.43 11.40 0.158 131.640.50 1.149 2.230 4.40 0.348 26.36 11.60 0.156 135.780.55 1.115 2.375 4.50 0.342 27.32 11.80 0.153 139.980.60 1.083 2.525 4.60 0.336 28.28 12.00 0.151 144.250.65 1.051 2.679 4.70 0.330 29.27 12.20 0.149 148.570.70 1.024 2.837 4.80 0.325 30.27 12.40 0.147 152.960.75 0.997 2.999 4.90 0.320 31.29 12.60 0.145 157.410.80 0.971 3.166 5.00 0.315 32.32 12.80 0.143 161.920.85 0.946 3.338 5.10 0.310 33.37 13.00 0.141 166.500.90 0.923 3.514 5.20 0.305 34.44 13.20 0.139 171.130.95 0.901 3.694 5.30 0.301 35.52 13.40 0.135 175.831.00 0.881 3.878 5.40 0.296 36.62 13.60 0.133 180.581.05 0.860 4.067 5.50 0.292 37.73 13.80 0.132 185.401.10 0.841 4.260 5.60 0.288 38.86 14.00 0.130 190.291.15 0.823 4.458 5.70 0.284 40.01 14.20 0.128 195.231.20 0.806 4.660 5.80 0.280 41.17 14.40 0.127 200.231.25 0.788 4.866 5.90 0.276 42.35 14.60 0.125 205.301.30 0.773 5.076 6.00 0.272 43.54 14.80 0.124 210.421.35 0.757 5.291 6.10 0.269 44.76 15.00 0.122 215.611.40 0.743 5.510 6.20 0.265 45.98 15.20 0.121 220.861.45 0.728 5.734 6.30 0.261 47.23 15.40 0.119 226.171.50 0.714 5.961 6.40 0.258 48.48 15.60 0.118 231.541.55 0.701 6.193 6.50 0.255 49.76 15.80 0.117 236.971.60 0.689 6.429 6.60 0.252 51.05 16.00 0.115 242.461.65 0.677 6.670 6.70 0.249 52.36 16.20 0.114 248.011.70 0.665 6.915 6.80 0.246 53.68 16.40 0.113 253.621.75 0.654 7.164 6.90 0.243 55.02 16.60 0.111 259.301.80 0.643 7.417 7.00 0.240 56.38 16.80 0.110 265.031.85 0.632 7.675 7.10 0.237 57.75 17.00 0.109 270.831.90 0.622 7.937 7.20 0.235 59.13 17.20 0.108 276.691.95 0.612 8.203 7.30 0.232 60.54 17.40 0.107 282.602.00 0.603 8.473 7.40 0.229 61.96 17.60 0.106 288.582.05 0.594 8.748 7.50 0.227 63.39 17.80 0.105 294.522.10 0.585 9.026 7.60 0.224 64.84 18.00 0.104 300.72

Table 8 Pressure factors for pipe sizing

56

Table 9 Pipeline capacity and pressure drop factorsPipe size in mm

Factor 15 20 25 32 40 50 65 80 100 125 150 175 200 225 250 300F

0.00016 x 30.40 55.41 90.72 199.1 360.4 598.2 890.0 1275 1755 2329 3800y 4.30 4.86 5.55 6.82 7.90 9.16 10.05 10.94 11.94 12.77 14.54

0.00020 x 16.18 34.32 62.77 103.0 225.6 407.0 662.0 1005 1437 1966 2623 4276y 3.96 4.85 5.51 6.31 7.72 8.92 10.13 11.34 12.33 13.37 14.38 16.36

0.00025 x 10.84 17.92 38.19 69.31 113.2 249.9 450.3 735.5 1108 1678 2183 2904 4715y 3.74 4.39 5.40 6.08 6.92 8.56 9.87 11.26 12.51 14.40 14.85 15.92 18.04

0.00030 x 11.95 19.31 41.83 75.85 124.1 271.2 491.9 804.5 1209 1733 2390 4172 5149y 4.13 4.73 5.92 6.65 7.60 9.29 10.79 12.31 13.65 14.87 16.26 17.39 19.07

0.00035 x 6.86 12.44 20.59 43.76 80.24 130.01 285.3 519.2 845.3 1279 1823 2497 3346 5406y 3.88 4.30 5.04 6.21 7.04 7.96 9.77 11.38 12.94 14.44 15.64 17.00 18.34 20.69

0.00045 x 3.62 7.94 14.56 23.39 50.75 92.68 150.9 333.2 604.6 979.7 1478 2118 2913 3884 6267y 3.54 4.49 5.03 5.73 7.18 8.13 9.24 11.42 13.26 15.00 16.68 18.18 19.82 21.29 23.99

0.00055 x 4.04 8.99 16.18 26.52 57.09 103.8 170.8 373.1 674.2 1101 1663 2382 3281 4338 7057y 3.96 5.09 5.59 6.49 8.08 9.10 10.46 12.78 14.78 16.85 18.77 20.44 22.32 23.78 27.01

0.00065 x 4.46 9.56 17.76 29.14 62.38 113.8 186.7 409.8 739.9 1207 1823 2595 3597 4781 7741y 4.37 5.41 6.13 7.14 8.82 9.98 11.43 14.04 16.22 18.48 20..58 22.27 24.47 26.21 29.62

0.00075 x 4.87 10.57 19.31 31.72 68.04 124.1 203.2 445.9 804.5 1315 1977 2836 3908 5172 8367y 4.77 5.98 6.67 7.77 9.62 10.88 12.44 15.28 17.64 20.13 22.32 24.34 26.59 28.35 32.02

0.00085 x 5.52 11.98 21.88 35.95 77.11 140.7 230.2 505.4 911.8 1490 2240 3215 4429 5861 9482y 5.41 6.78 7.56 8.80 10.91 12.34 14.09 17.32 19.99 22.81 25.29 27.59 30.13 32.13 36.29

0.00100 x 1.96 5.84 12.75 23.50 38.25 81.89 148.6 245.2 539.4 968.5 1579 2403 3383 4707 6228 10052y 4.10 5.72 7.21 8.12 9.37 11.58 13.03 15.01 18.48 21.24 24.17 27.13 29.03 32.02 34.14 38.47

0.00125 x 2.10 6.26 13.57 24.96 40.72 87.57 159.8 261.8 577.9 1038 1699 2544 3634 5035 6655 10639y 4.39 6.13 7.68 8.62 9.97 12.39 14.02 16.03 19.80 22.76 26.01 28.72 31.19 34.26 36.48 40.71

0.00150 x 2.39 7.35 15.17 28.04 45.97 98.84 179.3 295.1 652.8 1172 1908 2896 4091 5631 7493 11999y 5.00 7.20 8.58 9.68 11.26 13.98 15.72 18.07 22.37 25.70 29.21 32.69 35.11 38.31 41.08 45.92

0.00175 x 2.48 7.51 16.30 29.61 49.34 103.4 188.8 311.1 686.5 1270 2017 3046 4291 5921 7852 13087y 5.19 7.36 9.22 10.23 12.08 14.63 16.56 19.05 23.52 27.85 30.88 34.39 36.83 40.28 43.04 50.08

0.0020 x 2.84 8.58 18.63 33.83 56.39 118.2 215.8 355.5 784.6 1451 2305 3482 4904 6767 8974 14956y 5.94 8.40 10.54 11.68 13.81 16.72 18.93 21.77 26.88 31.82 35.28 39.31 42.09 46.04 49.19 57.24

0.0025 x 3.16 9.48 20.75 37.25 61.30 132.0 240.5 391.3 881.7 1556 2456 3819 5422 7544 10090 16503y 6.61 9.29 11.74 12.86 15.01 18.67 21.09 23.96 30.21 34.12 38.97 43.11 46.53 51.33 55.31 63.16

0.0030 x 3.44 10.34 22.5 40.45 66.66 143.4 262.0 429.8 924.4 1701 2767 4183 6068 8275 11033 18021y 7.20 10.13 12.73 13.97 16.33 20.29 22.98 26.32 32.29 37.30 42.36 47.22 52.08 56.30 60.48 68.97

0.0040 x 4.17 12.50 26.97 48.55 80.91 173.1 313.8 514.9 1128 2040 3330 5051 7208 9905 13240 21625y 8.73 12.25 15.26 16.77 19.82 24.49 27.52 31.53 38.65 44.73 50.97 57.02 61.86 67.39 72.58 82.76

0.0050 x 4.71 14.12 30.40 54.92 90.23 196.1 354.0 578.6 1275 2305 3727 5757 8189 11278 14858 24469y 9.86 13.83 17.20 18.97 20.10 27.74 31.05 35.43 43.68 50.54 57.05 64.76 70.28 76.73 81.45 93.64

0.0060 x 5.25 15.69 35.80 60.31 99.05 215.8 392.3 647.3 1412 2250 4148 6277 9072 12406 16476 26970y 10.99 15.37 20.26 20.83 24.26 30.53 34.41 39.63 48.38 55.92 63.50 70.86 77.86 84.40 90.82 103.21

0.0080 x 6.08 18.34 39.23 70.12 116.2 251.5 456.0 750.3 1648 2976 4879 7355 10543 14417 19173 31384y 12.72 17.97 22.20 24.22 28.46 35.58 40.00 45.95 56.46 65.26 74.69 83.03 90.48 98.09 105.1 120.1

0.0100 x 6.86 20.64 44.13 79.44 130.4 283.9 514.9 845.9 1863 3334 5492 8336 11867 16280 21576 35307y 14.36 20.22 24.97 27.44 31.94 40.16 45.16 51.80 63.83 73.11 84.07 94.11 101.8 110.8 118.28 135.1

0.0125 x 7.35 22.20 47.28 81.00 140.1 302.1 547.3 901.9 1983 3589 5867 8844 12697 17426 23074 37785y 15.38 21.75 26.75 27.98 34.31 42.74 48.00 55.22 67.94 78.70 89.81 99.84 109.0 118.5 126.5 144.6

0.0150 x 8.27 25.00 53.33 95.62 157.2 342.0 620.6 1020 2230 4045 6620 10022 14251 19584 25974 42616y 17.31 24.49 30.18 33.03 38.50 43.38 54.43 62.46 76.40 88.70 101.3 113.1 122.3 133.2 142.4 163.09

0.0175 x 8.58 26.39 55.78 100.4 165.6 360.4 665.1 1073 2360 4291 6994 10512 15017 20595 27461 44194y 17.95 25.85 31.56 34.68 40.65 50.99 58.34 65.70 80.52 94.09 107.1 118.7 128.9 140.1 150.5 169.1

0.020 x 9.80 30.16 63.75 114.7 189.3 411.9 760.1 1226 2697 49.04 7993 12014 17163 23538 31384 50508y 20.51 29.55 36.07 39.62 46.36 58.27 66.67 75.01 92.41 107.5 122.3 135.6 147.3 160.01 172.0 193.3

0.025 x 10.99 33.48 70.73 127.3 209.8 459.7 834.6 1367 2970 5422 8817 13296 19332 26357 34750 56581y 23.00 32.80 40.02 43.97 51.39 65.03 73.20 83.70 101.7 118.9 135.0 150.1 165.9 179.3 190.5 216.5

0.030 x 12.00 36.78 77.23 137.9 229.9 501.1 919.4 1480 3264 5884 9792 14481 20917 28595 37697 62522y 25.11 36.03 43.70 47.63 56.31 70.89 80.64 90.62 111.8 129.0 149.9 163.5 179.5 194.5 206.6 239.3

0.040 x 14.46 44.16 93.17 169.2 279.5 600.7 1093 1790 3923 7710 11622 17457 25254 34571 45604 75026y 30.26 43.23 52.72 58.44 68.46 84.98 95.87 109.6 134.4 155.9 177.9 1971.1 216.7 235.2 250.0 287.1

0.050 x 16.43 49.53 104.4 191.2 313.8 676.7 1231 2020 4413 8042 13044 19370 28441 39229 51489 85324y 34.38 48.52 59.08 66.04 76.86 95.73 108.0 123.7 151.2 176.3 199.7 218.7 244.1 266.9 282.3 326.5

0.06 x 18.14 52.96 115.7 210.8 343.2 750.3 1373 2231 4855 8827 14368 21282 31384 43152 57373y 37.96 51.88 65.47 72.81 84.06 106.1 120.4 136.6 166.3 193.5 219.9 240