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550
CHAPTER 22
1955 Guide
temperatures. Piping should be insulated to the same thickness and stand ards as for steam at the same temperature.
Valves for high temperature water should be made with cast steel bodies
Table 8. Head Loss in Fittings'
(For turbulent flow)
Feet of Same Size Pipe Having Equal Loss9
Fittings
10 8 6 5 4 3 21. 2 11 l 1 1
Globe Valve.................. 340 270 200 170 135 105 83 70 55 45 36 28 21 Gate Valve.................... 7 5.75 4.5 3.5 3 2.2 1.7 1.5 1.2 1 0.8 0.6 0.5 90 Welding Elbow.... 11 8.5 6.5 5.5 4.5 3.5 2.6 2.2 1.8 1.5 1.2 0.9 0.7
45 Welding Elbow.... 7 6 4.5 3.6 3 2.4 1.7 1.5 1.2 1. 0.8 0.6 0.5 2234 Welding Elbow.. 5 4 3 2.5 2 1.6 1.3 1.1 0.9 0.7 0.6 0.5 0.3 Lateral1*........................... 26 20 16 13 11 8 6.5 5.5 4 3.5 2.8 2.2 1.6
Lateral9........................... 17 14 10 8.5 7 5 4 3.5 2.8 2.5 1.8 1.5 1.1 Welding Tee'................ 13 10 8 7 5.5 4 3.2 2.6 2. 1.7 1.4 1.2 0.8
Concentric
to
Reducers
\ 10 8 6 5 4 3
From
2 m m 1 Vi 'A
10 8 6 5 4 3 m 2 m m i
\ \
1
2.5 3
2.8
3.5
\ \
1.2
2
2.2 2.2
C )NTRAC TING
10
3.5
\ \
0.5
1.3
1.8
1.7
12
7.5
1.5
\ \
0.5
1.2
1.4
1.5
12
9.5
4.5
1.5
\ \
0.6
1.2
1.4
1.5
10
7
5
1.8
\ \
0
0.8 1
1
7.5 6
3.8
0.7
\ \
0
0.7 0.8 0.75
6
5
2.5
0.8
\ \
0
0.6|o.6 0.6
5
3.8 2.8 9
\ \
0
0.5
0.5 0.5
4
3
2
0.3
\ \
0
0 0.3
ElI LA itGEMG
3 2.5 1.25 0.5 \ 0 0.3
%
2.5 2
1.3 0.5
0
1c
Vo 2 1.8] 1 - 5 0.8_J\
* Compiled from data published by Tube Turns, Inc., a Division of the National Cyliod Used by permission.
b Water deflected through branch. 9 Water flowing straight through fitting. d For eccentric reducers, the values read for ooncentric reducers must be increased by 33J%9 Equivalent length of pipe having a Fanning friction coefficient of 0.006.
and stainless steel trim since these have proved far more satisfactory than bronze valves. Wedge-type gate valves are recommended for isolating an for use within the boiler house. For general use throughout the system, globe valves are preferred.
Hot Water Heating Systems
551
Valves combining flow control and regulation are preferable for high temperature water where heat balancing is necessary, since a small quan tity of this water contains a large quantity of heat. As high temperature water is more penetrating than low temperature water, leakage due partly to capillary action should not be ignored' because even a small amount of. leakage evaporates immediately. This slight leakage becomes noticeable only on the outside of the gland and spindle of the valve where thin de posits of salts are left after evaporation.
Control
The control of temperature is usually obtained by conventional means although it is common practice to place control valves on the outlet line of
Table 9. Properties, of Water (212 F to 400 F)
Temperature F
Pressure*
psia
Density Lb/CuFt
Specific Heat Btu/(lb)(F)
Total Heat Above 32 F
Btu/Lb*
Btu/CuFt
212
14.70
59.88
1.0055
180.00
10.760
220
17.19
59.66
1.0068
188.06
11.222
230
20.78
59.37
1.0087
198.15
11.764
240
24.97
59.17
1.0104
208.26
12.327
250
29.82
58.84
1.0126
218.39
12.856
260
35.43
58.62
1.0148
228.55
13.403
270
41.85
58.25
1.0174
238.74
13.912
280
49.20
58.04
1.0200
248.95
14.555
290
57.55
57.65
1.0230
259.20
14.942
300
67.01
57.41
1.0260
269.48
15.476
310
77.68
57.00
320
89.65
56.65
330
103.03
56.31
340 117.99 55.95
350
134.62
55.65
1.0296 1.0332 1.0368 1.0404 1.0440
279.80 290.17 300.59 311.05 321.55
15.955 16.444
16.931 17.407 17.899
360 153.01 55.19
370
173.33
54.78
380
195.70
54.36
390 220.19 53.96
400
247.25
53.62
1.0486 1.0532 1.0578 1.0624 1.0670
332.10 342.71 353.39 364.14 374.96
18.333 18.778 19.213 19.644
20.106
* Reprinted by permission from Thermodynamic Properties of Steam, by J. H. Keenan and F. G. Keyes published by John Wiley and Sons, Inc., 1938 edition.
the heat absorbing equipment where the temperatures are lower. In larger distribution systems means of controlling differential pressures be tween the flow and return mains are advisable.
With space and process heating, temperatures can be controlled within close limits by the use of two- and three-way mixing valves modulating or by-passing some of the high temperature water. Such controls are essential at heat exchangers or converters.
Boilers or Hot Water Generators
Almost any high pressure boiler can be used for high temperature water systems, but certain types as, for example, the water tube boiler, are more advantageous than others. Boiler selection is important and such proberns as frictional head loss, available water space, flue outlet, type of firing,