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American Society of Heating and Ventilating Engineers Guide, 1930
Table 3. Constants for Various Lengths and Initial Pressures
Steam Pressure
Gags
Lb.
Constant bt Which to Multiplt
Capacity op ant Pipe fob 1 Lb.
toGage Steam Pressure
Obtain
Capacity op Same Pipe poq Pres
sure in Col. 1
Length op
Pipe
Ft.
Constant by Which to Multiplt
Capacity op 100 Ft. Pipe to Obtain
Capacity op Same Smm Pipe With
Same Pressure, AND LENGTH AS Given in Col. A
CoL 1
0 i
2
5
10
15
20
30 40 50 60 75
100
125 150 175
200
CoL-2f
Col. A
0.92 '
20
1.00
-i 40
1.03 ,
60
1.11 1
1.24
80
100
1.35
120
1.45
140
1.63
160
1.79
180
1.94
200 `
2.08
250
2.26
300
2.54
350
2.79 3.02
400 450
3.23
500
3.44
600
700
800
900
1000
1400
Col. B
2.240 1.580 .1.290
1.120
1.000 0.912 0.841 0.793 0.741 0.710 0.632 0.578 0.538 0.500 0.477 0.447 0.407 0.378 0.354 0.333 0.316 0.267
6
Table 4. Length in Feet of Pipe to be Added to Actual Length of Run-- Due to Fittings--to Obtain Equivalent Length
Size op Pips Inches
St'd. Elbow
Side Outlet Tee
Gate Valve
Globe Valve Ancle. Valve
Length in Feet to be Added in Run
2 5 16
7 20
3 10 26
3H ' 4
12 14
31 35
5 18 44
6 22 50
7 26 55
8 31 63
9 35 69
io 39 76
12 47 90
14 53 105
2 18
3 25 3 33
4 39
5 45 7 57 9 70 10 82 12 94 13 .105
15 118 18 140 20. 160
9 12 16
19 22 28 32 37 42 47 52
63 72
Example of length in feet of pipe to be added to actual length of run.
tiCASUSCD LEHOTH. - BE'.-O'
HSFLWt :m
' EQUIVALENT LENGTH 193-0'
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Chapter 20--Piping for Steam Heating Systems
Example: What is the capacity of a 140 ft. 4 in. pipe with an initial pressure of 1 lb. and pressure drop of 2 oz. in the 140 ft.?
Solution: From Table 2 it is found that the capacity of a 100 ft. 4 in. pipe with 1 lb. initial pressure and 2 oz. pressure drop, is 3,475 sq. ft. Multiplying this value by 0.841 the constant for a 140 ft. length as given in Table 3 gives 2,922 the capacity for the given conditions.
Example: What is the capacity of a 140 ft. 4 in. pipe with 2 lb. initial pressure and a pressure drop of 2 oz.?
Solution; From Table 2 find 3,475, the capacity of the 4 in. pipe with 1 lb. initial pressure and 2 oz. pressure drop. Multiplying 3,475 by 1.03 the constant found in Column 2, Table 3, for 2 lb. initial pressure and this by 0.841 the constant found under Column B, Table 3, the constant for 140 ft. length all as given in Table 3 gives 3,010 as the capacity of the 4 in. pipe with 2 lb. initial pressure and a pressure drop of 2 oz. in the 140 ft. length.
Should lengths other than those given in Column A, Table 3, and under length of pipes in feet in Table 1 be desired the constant may be obtained, from the formula in Column 4, Table 1, and used the same as the con stants from Table 3.
Example: What would be the constant for 2,500 ft. of pipe to be used
either in Tables 1 or 3?
,
Solution: The \Y 2,500 = 0.2 or the constant to be used.
In determining the length of pipe used in any system, the actual length must be increased for the various fittings and valves, in determining the equivalent length before applying any of the tables given.
Gate valves are recommended in all cases where service calls for the valve to be either entirely closed or open. They should never be used for throttling. Angle and globe valves should be used for throttling, such as the by-pass valve in a pressure-reducing outfit.
Table 4 gives the allowance for fittings in feet of pipe to be added to the actual length of run to obtain the equivalent length.
SYSTEMS OF STEAM HEATING
The choice of gravity one-pipe, two-pipe, vapor or vacuum return line systems depends upon the requirements as ito first cost, convenience, quality of service and local conditions. Theoretically, gravity one and two-pipe and vapor and vacuum return line systems are substantially on a par as to heating efficiency; that is to say, the major portion of the heat delivered is, or should be, dissipated by the heating unit.
It is essential that any system circulate steam uniformly throughout the entire installation, as too often certain defective features of a system will require that heat be kept on longer or to a greater degree than would otherwise be required uniformly and satisfactorily to heat the building. This will result in waste and overheating. The one important thing to be remembered in connection with all systems is-that they shall circulate steam freely and uniformly to the heating units and shall remove and return the condensation noiselessly.
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