technical reference guide on steam distribution
TRANSCRIPT
TE
CH
NIC
AL
RE
FE
RE
NC
E G
UID
ESteam distribution
1
Contents
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 44
Reduction of heat losses 46Calculation of heat transfer 47
Relevant UK and international standards 49
Summary 51
Appendix 1 - Sizing on pipeline capacity and pressure drop 52
Further information 57
Appendix 2 - Steam tables 58
Appendix 3 - Conversion tables 60
2
Introduction
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.
3
When 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 Pan
Steam
Vat
Condensate
Processvessel
Spaceheatingsystem
CondensateSteam
Feedpump
4
The 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
Spe
cific
vol
ume
m³/
kg
5
Steam 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.
6
Pressure 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 valve
Safety 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.
7
Pipeline 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
8
Probably 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 80 100 125 150
Schedule 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 97.2 122.3 146.4
Schedule 160 11.7 15.6 20.7 29.5 34.0 42.8 53.9 66.6 87.3 109.5 131.8
DIN 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
9
If 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) C
Specific volume (m3/kg) v
Mass flowrate (kg/s) m
Volumetric flowrate (m³/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= V
4 C
This formula can be rearranged to give the diameter of the pipe:
D² = 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
●
● ●
●
●
●
●
Ö
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 m³/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 m³/kg
= 0.333 m³/s
Therefore, using:
Cross sectional area (A) = Volumetric flowrate (V)Flow velocity (C)
p x D² = 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
Ö
●
● ●
●
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 300°C, and a pressure drop of0.3 bar/100 m.
Method refer to Figure 7, page 15.Draw a vertical line from 300°C (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 325°C. 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 drop
Inlet pressure (absolute)
= 0.67515
= 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 325°C 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 9500
15 7 16 25 40 59 109 166 250 431 680 1006 1708 27911 38520.7 25 12 25 45 72 100 182 287 430 716 1145 1575 2816 4629 6204
40 18 37 68 106 167 298 428 630 1108 1712 2417 4532 7251 10323
15 8 17 29 43 65 112 182 260 470 694 1020 1864 2814 40451.0 25 12 26 48 72 100 193 300 445 730 1160 1660 3099 4869 6751
40 19 39 71 112 172 311 465 640 1150 1800 2500 4815 7333 10370
15 12 25 45 70 100 182 280 410 715 1125 1580 2814 4845 62772.0 25 19 43 70 112 162 295 428 656 1215 1755 2520 4815 7525 10575
40 30 64 115 178 275 475 745 1010 1895 2925 4175 7678 11997 16796
15 16 37 60 93 127 245 385 535 925 1505 2040 3983 6217 87433.0 25 26 56 100 152 225 425 632 910 1580 2480 3440 6779 10269 14316
40 41 87 157 250 375 595 1025 1460 2540 4050 5940 10476 16470 22950
15 19 42 70 108 156 281 432 635 1166 1685 2460 4816 7121 103584.0 25 30 63 115 180 270 450 742 1080 1980 2925 4225 7866 12225 17304
40 49 116 197 295 456 796 1247 1825 3120 4940 7050 12661 19663 27816
15 22 49 87 128 187 352 526 770 1295 2105 2835 5548 8586 119475.0 25 36 81 135 211 308 548 885 1265 2110 3540 5150 8865 14268 20051
40 59 131 225 338 495 855 1350 1890 3510 5400 7870 13761 23205 32244
15 26 59 105 153 225 425 632 925 1555 2525 3400 6654 10297 143286.0 25 43 97 162 253 370 658 1065 1520 2530 4250 6175 10629 17108 24042
40 71 157 270 405 595 1025 1620 2270 4210 6475 9445 16515 27849 38697
15 29 63 110 165 260 445 705 952 1815 2765 3990 7390 12015 160967.0 25 49 114 190 288 450 785 1205 1750 3025 4815 6900 12288 19377 27080
40 76 177 303 455 690 1210 1865 2520 4585 7560 10880 19141 30978 43470
15 32 70 126 190 285 475 800 1125 1990 3025 4540 8042 12625 177288.0 25 54 122 205 320 465 810 1260 1870 3240 5220 7120 13140 21600 33210
40 84 192 327 510 730 1370 2065 3120 5135 8395 12470 21247 33669 46858
15 41 95 155 250 372 626 1012 1465 2495 3995 5860 9994 16172 2271310.0 25 66 145 257 405 562 990 1530 2205 3825 6295 8995 15966 25860 35890
40 104 216 408 615 910 1635 2545 3600 6230 9880 14390 26621 41011 57560
15 50 121 205 310 465 810 1270 1870 3220 5215 7390 12921 20538 2901614.0 25 85 195 331 520 740 1375 2080 3120 5200 8500 12560 21720 34139 47218
40 126 305 555 825 1210 2195 3425 4735 8510 13050 18630 35548 54883 76534
15 60 145 246 372 558 972 1524 2244 3864 6258 8868 15505 24646 3481917.0 25 102 234 397 624 888 1650 2496 3744 6240 10200 15072 26064 40967 56662
40 151 366 666 990 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 flo
wrate
kg/h
50 % Vacuum
Steam pressure bar g
600500
15
10
25
20
30
400
150175200
250300
125
100
80706050
4015
0
5
100
10
2030
50
100
200
500
1 000
2 000
3 000
20
30
Steam temperature °C100 200 300 400 500
200 0
00100 0
0050 00
020 00
0
30 00
010 00
05 000
10075
50
2030
10
50
532
10.5
0 bar g
710A
Pip
e di
amet
er m
m
The dotted line A, B, C, D refers to the example on page 10
Saturation tem
perature
curve
15
Fig. 7 Steam pipeline sizing chart (pressure drop method)
400300200100 500
18
10
5
3
Pre
ssur
e 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 g
0.512357
A
10B
2030
50
10075
Steam temperature °C
Ste
am fl
owra
te k
g/h
200
000
100
000
C
50 0
00
30 0
005 00
0
3 00
0
2 00
0
1 00
0
500300200100503020
10
20 0
00
10 0
00
Insi
de p
ipe
diam
eter
mm
60050040
030025020
015012510
080706050
40
3025
20
15
10
The dotted line A, B, C, D, E refers to the example on page 11
Steam pressure bar g
Saturation tem
perature
curve
D E
16
Figure 8 Pipe sizing chart for larger steam mains
0.8
0.60.7
0.5
0.4
0.3
0.2
0.090.1
0.080.070.06
0.05
0.04
0.03
0.02
0.010.0090.0080.0070.0060.005
0.004
0.003
Rat
io D
P =
Pre
ssur
e dr
op b
arIn
let p
ress
ure
bar a
bs
100 200 300 400 500
110 120100
8070605040
3025
15
20
10
8
65
4
3
2
1
Steam inlet pressure bar abs
10 2040
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
150
200
300400500
750P
ipe diameter m
m
F C
600
450
350
250
175
12580
60
300
150
704020106421
200
10050301581.5 3 5
50003000
G =
Ste
am m
ass
flow
rate
tonn
e/h
ED
Steam temperature °C
B
A
0.9 4
6
8
10
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 20°C, 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 pipework
Rising ground
Trap set
CondensateSteam
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
CB D
A
EF
Steam pressure bar g
Sep
arat
or s
ize
Pressure drop across separator bar
DN150DN125
DN100
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
0.050.1
0.2
Flow velocity m/s
Ste
am fl
owra
te k
g/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
500400300
200
100
50403020
10
543
1 2 3 4 5 10 14
12.5 mm
10 mm
7.5 mm
5 mm
3 mm
Leakinghole
Ste
am le
ak ra
te k
g/h
Coaltonnes/year
Heavy fuel oilx 1 000 litres/year
Gasx 1 000 kWh/year
1 000
500400300
200
100
504030
20
10
54
8 400 2 000Hours per day Hours per year
8 400 2 000
1
2
345
10
20
304050
100
200 500400300
200
100
504030
20
10
543
2
1
2
345
10
20
304050
100
0.5
Hours per year8 400 2 000
1 000
500400300
200
100
504030
20
10
5
5 0004 0003 000
2 000
1 000
500400300
200
100
504030
20
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 -18°Cpressure 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 1.14
120 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 20°C, 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
MaterialTemperature 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/m°C) x 10-³
Table 4 Expansion coefficients (a)
Find the expansion of 30 m of pipe from ambient (10°C) to 152°C(steam at 4 bar g)
L = 30 mD t = 152°C - 10°C = 142°Ca = 15.0 x 10-³ mm/m°C
\ Expansion = 30 x 142 x 15.0 x 10-³ 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 -½ F to + ½ 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
TemperatureMaterials
°CC. 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 30
°C 120 134 144 152 159 173 184 201 215 226 236
Temperature of saturated steam
50040030020050
200
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
) 220100
43
Fig. 36 Copper expansion loop
Fig. 37 Steel expansion loop
200175150125100755025200
100908070
60
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 si
ze (m
m)
W. metres
25
2.5 321.510.525
30
40
50
60708090
100
200
300
40050 75 100 200175150125
3.5 4 4.5 5
W2W
Maximum pressure 17 barMaximum temperature 260°C
Welded bendsradius = 1.5 dia.
Expansion from neutral position (mm)
Nom
inal
pip
e si
ze (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 mm°C 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 10°Cand 21°C 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 - 21°C, 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
●
●
●
48
49
Relevant UK and Internationalstandards
Symbols have been used to indicate harmonised standards,technically equivalent standards, and related standards - º ; = and ¹respectively.
BS 10 Specification for flanges and bolting for pipes, valves andfittings.
BS 21 = ISO 7/1 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(¹ ISO 7005); Part 3 Section 3.2 Specification for cast ironflanges (¹ ISO 7005-2); Part 3 Section 3.3 Specification forcopper alloy and composite flanges (¹ 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 (¹ ISO 7005-2); Section 3.3Specification for copper alloy and composite flanges (¹ 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 1m³/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 m³/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
0.00016x 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
0.00020x 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
0.00025x 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
0.00030x 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
0.00035x 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
0.00045x 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
0.00055x 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
0.00065x 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
0.00075x 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
0.00085x 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
0.00100x 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
0.00125x 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
0.00150x 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
0.00175x 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
0.0020x 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
0.0025x 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
0.0030x 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
0.0040x 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
0.0050x 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
0.0060x 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
0.0080x 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
0.0100x 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
0.0125x 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
0.0150x 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
0.0175x 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
0.020x 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
0.025x 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
0.030x 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
0.040x 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
0.050x 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
0.06x 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 84.06 106.1 120.4 136.6 166.3 193.5 219.9 240.2 269.3 293.6 314.5
0.08x 21.08 62.28 134.8 245.2 402.1 872.8 1594 2599 5688 10249 16672 24518 36532y 44.11 61.02 76.28 86.69 98.49 123.5 139.8 159.1 194.9 224.7 255.2 276.8 313.5
0.10x 24.03 70.12 152.0 277.0 456.0 980.7 1804 2942 6424 11524 18879 27461y 50.29 68.70 86.01 95.67 111.7 138.7 158.2 180.1 220.1 252.7 289.0 310.1
0.12x 25.99 77.48 167.7 306.5 500.2 1079 1986 3236 7110 12700 20841y 54.39 75.91 94.90 105.9 122.5 152.6 174.2 198.1 243.6 278.5 319.0
0.15x 28.50 84.13 183.9 334.2 551.7 1195 2161 3494 7769y 59.64 84.42 104.1 115.4 135.1 169.0 189.5 213.9 266.2
0.20x 34.32 102.0 220.7 402.1 622.0 1427 2599 4217 9317y 71.82 99.93 124.9 138.9 162.1 201.9 228.0 258.2 319.2
0.25x 37.72 112.7 245.2 447.9 735.5 1565 2876 4668y 78.94 110.4 138.7 154.7 180.1 221.4 252.3 285.8
0.30x 41.37 122.7 266.6 487.3 804.5 1710 3126 5057y 86.58 120.2 150.9 168.3 197.0 241.9 274.2 309.6
0.35x 43.34 128.7 283.2 514.9 841.0 1802 32.61y 90.70 126.1 160.2 177.8 206.0 254.9 286.0
0.40x 49.93 147.1 323.6 588.4 961.1 2059 3727y 104.5 144.1 183.1 203.2 235.4 291.3 326.9
0.45x 50.31 150.0 326.6 600.2 979.9 2083y 105.3 146.9 184.8 207.3 239.9 294.7
0.5x 55.90 166.7 362.9 666.9 1089 23214y 117.0 163.3 205.3 230.3 266.7 327.4
0.6x 62.28 185.3 402.1 735.5 1201y 130.3 181.5 227.5 254.0 294.1
0.7x 63.07 188.8 407.6 750.9y 132.0 185.0 230.6 259.3
0.8x 72.08 215.8 465.8 858.1y 150.8 211.4 236.6 296.4
0.9x 73.28 218.4 476.6y 153.3 214.0 269.7
x = kg/h capacityy = m /s velocity with a volume of 1m³/kg
57
Further Information
This technical reference guide has been designed to give worksengineers or energy managers, an introduction into the subject ofsteam distribution. It is quite impossible to cover all aspects ofsteam distribution within these covers, as almost every installationis unique, and will have its own details where choices can bemade between several alternatives. It is not always apparentwhich will be the optimal solution.
We have tried to cover the most often found areas where thesealternatives exist, but it may well be that we have omitted mentionof the options available in any particular part of an installationbeing considered. In such cases, on the spot advice is alwaysgladly given by our team of regional engineers, or by telephone orletter from our head office as required.
58
Specific enthalpy SpecificPressure Temperature volume
Water (hf) Evaporation (hfg) Steam (hg) steambar kPa °C kJ/kg kJ/kg kJ/kg m3/kg
absolute0.30 30.0 69.10 289.23 2 336.1 2 625.3 5.2290.50 50.0 81.33 340.49 2 305.4 2 645.9 3.2400.75 75.0 91.78 384.39 2 278.6 2 663.0 2.2170.95 95.0 98.20 411.43 2 261.8 2 673.2 1.777
gauge0 0 100.00 419.04 2 257.0 2 676.0 1.6730.10 10.0 102.66 430.2 2 250.2 2 680.2 1.5330.20 20.0 105.10 440.8 2 243.4 2 684.2 1.4140.30 30.0 107.39 450.4 2 237.2 2 687.6 1.3120.40 40.0 109.55 459.7 2 231.3 2 691.0 1.2250.50 50.0 111.61 468.3 2 225.6 2 693.9 1.1490.60 60.0 113.56 476.4 2 220.4 2 696.8 1.0880.70 70.0 115.40 484.1 2 215.4 2 699.5 1.0240.80 80.0 117.14 491.6 2 210.5 2 702.1 0.9710.90 90.0 118.80 498.9 2 205.6 2 704.5 0.9231.00 100.0 120.42 505.6 2 201.1 2 706.7 0.8811.10 110.0 121.96 512.2 2 197.0 2 709.2 0.8411.20 120.0 123.46 518.7 2 192.8 2 711.5 0.8061.30 130.0 124.90 524.6 2 188.7 2 713.3 0.7731.40 140.0 126.28 530.5 2 184.8 2 715.3 0.7431.50 150.0 127.62 536.1 2 181.0 2 717.1 0.7141.60 160.0 128.89 541.6 2 177.3 2 718.9 0.6891.70 170.0 130.13 547.1 2 173.7 2 720.8 0.6651.80 180.0 131.37 552.3 2 170.1 2 722.4 0.6431.90 190.0 132.54 557.3 2 166.7 2 724.0 0.6222.00 200.0 133.69 562.2 2 163.3 2 725.5 0.6032.20 220.0 135.88 571.7 2 156.9 2 728.6 0.5682.40 240.0 138.01 580.7 2 150.7 2 731.4 0.5362.60 260.0 140.00 589.2 2 144.7 2 733.9 0.5092.80 280.0 141.92 597.4 2 139.0 2 736.4 0.4833.00 300.0 143.75 605.3 2 133.4 2 738.7 0.4613.20 320.0 145.46 612.9 2 128.1 2 741.0 0.4403.40 340.0 147.20 620.0 2 122.9 2 742.9 0.4223.60 360.0 148.84 627.1 2 117.8 2 744.9 0.4053.80 380.0 150.44 634.0 2 112.9 2 746.9 0.3894.00 400.0 151.96 640.7 2 108.1 2 748.8 0.3744.50 450.0 155.55 656.3 2 096.7 2 753.0 0.3425.00 500.0 158.92 670.9 2 086.0 2 756.9 0.3155.50 550.0 162.08 684.6 2 075.7 2 760.3 0.2926.00 600.0 165.04 697.5 2 066.0 2 763.5 0.2726.50 650.0 167.83 709.7 2 056.8 2 766.5 0.2557.00 700.0 170.50 721.4 2 047.7 2 769.1 0.2407.50 750.0 173.02 732.5 2 039.2 2 771.7 0.2278.00 800.0 175.43 743.1 2 030.9 2 774.0 0.2158.50 850.0 177.75 753.3 2 022.9 2 776.2 0.2049.00 900.0 179.97 763.0 2 015.1 2 778.1 0.1949.50 950.0 182.10 772.5 2 007.5 2 780.0 0.185
10.00 1 000.0 184.13 781.6 2 000.1 2 781.7 0.17710.50 1 050.0 186.05 790.1 1 993.0 2 783.3 0.17111.00 1 100.0 188.02 798.8 1 986.0 2 784.8 0.16311.50 1 150.0 189.82 807.1 1 979.1 2 786.3 0.15712.00 1 200.0 191.68 815.1 1 972.5 2 787.6 0.15112.50 1 250.0 193.43 822.9 1 965.4 2 788.8 0.14813.00 1 300.0 195.10 830.4 1 959.6 2 790.0 0.14114.00 1 400.0 198.35 845.1 1 947.1 2 792.2 0.13215.00 1 500.0 201.45 859.0 1 935.0 2 794.0 0.12416.00 1 600.0 204.38 872.3 1 923.4 2 795.7 0.11717.00 1 700.0 207.17 885.0 1 912.1 2 797.1 0.11018.00 1 800.0 209.90 897.2 1 901.3 2 798.5 0.10519.00 1 900.0 212.47 909.0 1 890.5 2 799.5 0.10020.00 2 000.0 214.96 920.3 1 880.2 2 800.5 0.099 421.00 2 100.0 217.35 931.3 1 870.1 2 801.4 0.090 622.00 2 200.0 219.65 941.9 1 860.1 2 802.0 0.086 823.00 2 300.0 221.85 952.2 1 850.4 2 802.6 0.083 224.00 2 400.0 224.02 962.2 1 840.9 2 803.1 0.079 725.00 2 500.0 226.12 972.1 1 831.4 2 803.5 0.076 826.00 2 600.0 228.15 981.6 1 822.2 2 803.8 0.074 027.00 2 700.0 230.14 990.7 1 813.3 2 804.0 0.071 4
Appendix 2 -Steam tables
59
Specific enthalpy SpecificPressure Temperature volume
Water (hf) Evaporation (hfg) Steam (hg) steambar kPa °C kJ/kg kJ/kg kJ/kg m3/kg
28.00 2 800.0 232.05 999.7 1 804.4 2 804.1 0.068 929.00 2 900.0 233.93 1 008.6 1 795.6 2 804.2 0.066 630.00 3 000.0 235.78 1 017.0 1 787.0 2 804.1 0.064 531.00 3 100.0 237.55 1 025.6 1 778.5 2 804.1 0.062 532.00 3 200.0 239.28 1 033.9 1 770.0 2 803.9 0.060 533.00 3 300.0 240.97 1 041.9 1 761.8 2 803.7 0.058 734.00 3 400.0 242.63 1 049.7 1 753.8 2 805.5 0.057 135.00 3 500.0 244.26 1 057.7 1 745.5 2 803.2 0.055 436.00 3 600.0 245.86 1 065.7 1 737.2 2 802.9 0.053 937.00 3 700.0 247.42 1 072.9 1 729.5 2 802.4 0.052 438.00 3 800.0 248.95 1 080.3 1 721.6 2 801.9 0.051 039.00 3 900.0 250.42 1 087.4 1 714.1 2 801.5 0.049 840.00 4 000.0 251.94 1 094.6 1 706.3 2 800.9 0.048 541.00 4 100.0 253.34 1 101.6 1 698.3 2 799.9 0.047 342.00 4 200.0 254.74 1 108.6 1 691.2 2 799.8 0.046 143.00 4 300.0 256.12 1 115.4 1 683.7 2 799.1 0.045 144.00 4 400.0 257.50 1 122.1 1 676.2 2 798.3 0.044 145.00 4 500.0 258.82 1 228.7 1 668.9 2 797.6 0.043 146.00 4 600.0 260.13 1 135.3 1 666.6 2 796.9 0.042 147.00 4 700.0 261.43 1 142.2 1 654.4 2 796.6 0.041 248.00 4 800.0 262.73 1 148.1 1 647.1 2 795.2 0.040 349.00 4 900.0 264.00 1 154.5 1 639.9 2 794.4 0.039 450.00 5 000.0 265.26 1 160.8 1 632.8 2 793.6 0.038 651.00 5 100.0 266.45 1 166.6 1 626.9 2 792.6 0.037 852.00 5 200.0 267.67 1 172.6 1 619.0 2 791.6 0.037 153.00 5 300.0 268.84 1 178.7 1 612.0 2 790.7 0.036 454.00 5 400.0 270.02 1 184.6 1 605.1 2 789.7 0.035 755.00 5 500.0 271.20 1 190.5 1 598.2 2 788.7 0.035 056.00 5 600.0 272.33 1 196.3 1 591.3 2 787.6 0.034 357.00 5 700.0 273.45 1 202.1 1 584.5 2 786.6 0.033 758.00 5 800.0 274.55 1 207.8 1 577.7 2 785.5 0.033 159.00 5 900.0 275.65 1 213.4 1 571.0 2 784.4 0.032 560.00 6 000.0 276.73 1 218.9 1 564.4 2 783.3 0.031 961.00 6 100.0 277.80 1 224.5 1 557.6 2 782.1 0.031 462.00 6 200.0 278.85 1 230.0 1 550.9 2 780.9 0.030 863.00 6 300.0 279.89 1 235.4 1 544.3 2 779.7 0.030 364.00 6 400.0 280.92 1 240.8 1 537.3 2 778.5 0.029 865.00 6 500.0 281.95 1 246.1 1 531.2 2 777.3 0.029 366.00 6 600.0 282.95 1 251.4 1 524.7 2 776.1 0.028 867.00 6 700.0 283.95 1 256.7 1 518.1 2 774.8 0.028 368.00 6 800.0 284.93 1 261.9 1 511.6 2 773.5 0.027 869.00 6 900.0 285.90 1 267.0 1 501.1 2 772.1 0.027 470.00 7 000.0 286.85 1 272.1 1 498.7 2 770.8 0.027 072.00 7 200.0 288.75 1 282.3 1 485.8 2 768.1 0.026 274.00 7 400.0 290.60 1 292.3 1 473.0 2 765.3 0.025 476.00 7 600.0 292.41 1 302.3 1 460.2 2 762.5 0.024 678.00 7 800.0 294.20 1 311.9 1 447.6 2 759.5 0.023 980.00 8 000.0 295.96 1 321.5 1 435.0 2 756.5 0.023 382.00 8 200.0 297.66 1 330.9 1 422.5 2 753.4 0.022 684.00 8 400.0 299.35 1 340.3 1 410.0 2 750.3 0.022 086.00 8 600.0 301.00 1 349.6 1 397.6 2 747.2 0.021 488.00 8 800.0 302.61 1 358.8 1 385.2 2 744.0 0.020 890.00 9 000.0 304.20 1 367.8 1 372.7 2 740.5 0.020 292.00 9 200.0 305.77 1 376.8 1 360.3 2 737.1 0.019 794.00 9 400.0 307.24 1 385.7 1 348.0 2 733.7 0.019 296.00 9 600.0 308.83 1 394.5 1 335.7 2 730.2 0.018 798.00 9 800.0 310.32 1 403.2 1 323.3 2 726.5 0.018 3
100.00 10 000.0 311.79 1 411.9 1 310.9 2 722.8 0.017 8102.00 10 200.0 313.24 1 420.5 1 298.7 2 719.2 0.017 4104.00 10 400.0 314.67 1 429.0 1 286.3 2 715.3 0.017 0106.00 10 600.0 316.08 1 437.5 1 274.0 2 711.5 0.016 6108.00 10 800.0 317.46 1 445.9 1 261.7 2 707.6 0.016 2110.00 11 000.0 318.83 1 454.3 1 249.3 2 703.6 0.015 8112.00 11 200.0 320.17 1 462.6 1 237.0 2 699.6 0.015 4114.00 11 400.0 321.50 1 470.8 1 224.6 2 695.4 0.015 0116.00 11 600.0 322.81 1 479.0 1 212.2 2 691.2 0.014 7118.00 11 800.0 324.10 1 487.2 1 199.8 2 687.0 0.014 4120.00 12 000.0 325.38 1 495.4 1 187.3 2 682.7 0.014 1
60
Appendix 3 -Conversion tables
Table 3 LengthFrom - To millimetre centimetre metre kilometre inch foot yard milemillimetre 1 0.1 0.001 - 0.0393 7 - - -
centimetre 10 1 0.01 - 0.393 701 0.032 808 - -
metre 1 000 100 1 0.001 39.370 1 3.280 84 1.093 61 -
kilometre - - 1 000 1 - 3 280.84 1 093.61 0.621 371
inch 25.4 2.54 - - 1 0.083 333 0.027 778 -
foot 304.8 30.48 0.304 8 - 12 1 0.333 33 -
yard 914.4 91.44 0.914 4 0.000 914 36 3 1 0.000 568
mile - - 1 609.344 1.609 344 - 5 280 1 760 1
Table 4 AreaFrom - To cm² m² km² in² ft² yd² acre mile²cm² 1 0.000 1 - 0.155 0.001 076 0.000 119 6 - -
m² 10 000 1 0.000 001 1 550 10.763 9 1.195 99 0.000 247 1 -
km² - 1 000 000 1 - - - 247.105 0.386 102
in² 6.4516 0.000 645 - 1 0.006 944 0.000 772 - -
ft² 929.03 0.092 903 - 144 1 0.111 111 0.000 023 -
yd² 8 361.27 0.836 127 - 1 296 9 1 0.000 206 6 -
acre - 404.86 0.004 040 7 - 43 560 4 840 1 0.001 562
mile² - - 2.589 987 - - - 640 1
Table 5 MassFrom - To kg tonne lb UK cwt UK ton US cwt US tonkg 1 0.001 2.204 62 0.019 684 0.000 984 0.022 046 0.001 102
tonne 1 000 1 2 204.62 19.684 1 0.984 207 22.046 2 1.102 31
lb 0.453 592 0.000 454 1 0.008 929 0.000 446 0.01 0.000 5
UK cwt 50.802 3 0.050 802 112 1 0.05 1.12 0.056
UK ton 1 016.05 1.016 05 2 240 20 1 22.4 1.12
US cwt 45.359 2 0.045 359 100 0.892 857 0.044 643 1 0.05
US ton 907.185 0.907 185 2 000 17.857 1 0.892 857 20 1
Table 6 Volume and capacityFrom - To cm³ m³ litre (dm³) in³ ft³ yd³ UK pint UK gall US pint US gallcm³ 1 - 0.001 0.061 024 0.000 035 3 - 0.001 760 0.000 22 0.002 113 0.000 264
m³ - 1 1 000 61 023.7 35.314 7 1.307 95 1 759.75 219.969 2 113.38 264.172
litre (dm³) 1 000 0.001 1 61.0237 0.035 315 0.001 308 1.759 75 0.219 969 2.113 38 0.264 172
in³ 16.387 1 - 0.016 387 1 0.000 578 7 0.000 0214 0.028 837 0.003 605 0.034 632 0.004 329
ft³ 28 316.8 0.028 317 28.316 8 1 728 1 0.0370 37 49.830 7 6.228 83 59.844 2 7.480 52
yd³ 764 555 0.764 555 764.555 46 656 27 1 1 345.429 168.178 4 1 615.793 201.974
UK pint 568.261 0.000 568 3 0.568 261 34.677 4 0.020 068 0.000 743 1 0.125 1.200 95 0.150 119
UK gall 4 546.09 0.004 546 1 4.546 09 277.42 0.160 544 0.005 946 8 1 9.607 6 1.200 95
US pint 473.176 0.000 473 2 0.473 176 28.875 0.016 71 0.000 619 0.8326 74 0.104 084 1 0.125
US gall 3 785.41 0.003 785 4 3.785 411 231 0.133 681 0.004 951 6.661 392 0.832 674 8 1
61
Table 7 PressureFrom - To atmos mm Hg m bar bar pascal in H 2O in Hg psi
atmos 1 760 1 013.25 1.0132 101 325 406.781 29.921 3 14.695 9
mm Hg 0.001 315 8 1 1.333 22 0.001 333 133.322 0.535 24 0.039 37 0.019 337
m bar 0.000 986 9 0.750 062 1 0.001 100 0.401 463 0.029 53 0.014 504
bar 0.986 9 750.062 1 000 1 100 000 401.463 29.53 14.504
pascal 0.000 009 9 0.007 501 0.01 0.000 01 1 0.004 015 0.000 295 3 0.000 145
in H20 0.002 458 3 1.868 32 2.490 89 0.002 491 249.089 1 0.073 556 0.036 127
in Hg 0.033 421 25.4 33.863 9 0.033 863 9 3 386.39 13.595 1 1 0.491 154
psi 0.068 046 51.714 9 68.947 6 0.068 948 6 894.76 27.679 9 2.036 02 1
Pascal = 1Nm²Table 8 Volume rate of flowFrom - To l / s (dm³/s) l / h m³ / s m³ / h cfm ft³ / h UK gall / m UK gall / h US gall / m US gall / h
l / s (dm³/s) 1 3600 0.001 3.6 2.118 882 127.133 13.198 14 791.888 4 15.850 32 951.019
l / h 0.000 278 1 - 0.001 0.000 588 0.035 315 0.003 666 0.219 969 0.004 403 0.264 172
m³ / s 1 000 3 600 000 1 3 600 2 118.88 127 133 13 198.1 791 889 15 850.3 951 019
m³ / h 0.277 778 1 000 0.000 278 1 0.588 578 35.314 7 3.666 15 219.969 4.402 863 264.171 8
cfm 0.471 947 1 699.017 0.000 472 1.699 017 1 60 6.228 833 373.73 7.480 517 448.831
ft³ / h 0.007 866 28.316 8 - 0.028 317 0.016 667 1 0.103 814 6.228 833 0.124 675 7.480 517
UK gall / m 0.075 768 272.766 0.000 075 8 0.272 766 0.160 544 9.632 62 1 60 1.200 95 72.057
UK gall / h 0.001 263 4.546 09 - 0.004 546 0.002 676 0.160 544 0.016 667 1 0.020 016 1.200 95
US gall / m 0.063 09 227.125 0.000 063 1 0.227 125 0.133 681 8.020 832 0.832 674 49.960 45 1 60
US gall / h 0.001 052 3.785 411 - 0.003 785 0.002 228 0.133 681 0.013 878 0.832 674 0.016 667 1
Table 9 PowerFrom - To Btu / h W kcal / h kW
Btu / h 1 0.293 071 0.251 996 0.000 293
W 3.412 14 1 0.859 845 0.001
kcal / h 3.968 32 1.163 1 0.001 163
kW 3 412.14 1 000 859.845 1
Table 10 EnergyFrom - To Btu / h Therm J kJ Cal
Btu / h 1 0.000 01 1 055.06 1.055 251.996
Therm 100 000 1 - 105 500 25 199 600
J 0.000 94 - 1 0.001 0.238 8
kJ 0.947 8 0.000 009 478 1 000 1 238.85
Cal 0.003 968 3 0.003 968 3 x 10- 5 4.186 8 - 1
Table 11 Specific heat capacityFrom - To BTU / lb°F J / kg°C
Btu / lb°F 1 4 186.8
J / kg°C 0.000 23 1
62
Table 12 Heat flowrateFrom - To Btu / ft²h W / m² kcal / m²hBtu / ft²h 1 3.154 2.712
W / m² 0.316 9 1 0.859
kcal / m²h 0.368 1.163 1
Table 13 Thermal conductanceFrom - To Btu / ft²h °F W / m² °C kcal / m²h °C
Btu / ft²h °F 1 5.678 26 4.882 43
W / m² °C 0.176 110 1 0.859 845
kcal / m²h °C 0.204 816 1.163 1
Table 14 Heat per unit massFrom - To BTU / lb kJ / kg
Btu / lb 1 2.326
kJ / kg 0.429 9 1
Table 15 Linear velocityFrom - To ft / min ft / s m / sft / min 1 0.016 666 0.005 08
ft / s 60 1 0.304 8
m / s 198.850 3.280 84 1
Temperature conversion
Can be achieved by using the following formulae:
°F = (°C x 1.8) + 32
°C = (°F - 32)
1.8
63
64
CM Issue 2TR-GCM-03
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