Document NEzBGV2Y4w3ZgJ2wJ2qM0Dp08

American Society of Heating and Ventilating Engineers Guide, 1932 Table 3. Constants for Various Lengths and Initial Pressures Steam Pressure Gage Lb. Constant bt Which to Multiply 1Capacity of any Pipe fob Lb. Gaos Steam Pressure to Obtain Capacitt op Same Pipe fob Pres 1sure in Col. ' Length of Pipe Ft. Constant by Which to Multiply 100Capacitt of Ft. Pipe to Obtain Capacity of Same Sized Pipe With Same' Pressure, 1 and Length as AGiven in Col;. Col. 1 CoL 2 Co!. A CoLB 0 X 2 5 10 IS 20 30 40 50 60 75 100 125 150 175 . 200 - 0.92 1.00 1.03 1.11 1.24 1.35 1.45 1.63 1.79 1.94 2.08 2.26 2.54 2.79 3.02 3.23 3.44 20 40 60 80 100 120 140 160 180 200 250 300 350 400 450 500 600 700 800 900 1000 1400 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 Table .4. Length in Feet of Pipe to be Added to Actual Length of Run-- Due to Fittings--to Obtain Equivalent Length Size op Pipe Inches St'd. Elbow Side Outlet Tee Gate Valve Globe Valve Angle Valve Length in Feet to be Added in Run 2 2H 3 3H 4 5 6 .7 8 9 10 12 14 5 16 7 20 10 26 12 31 14 35 18 44 22 50 26 55 31 63 35 69 39 76 47 90 53 105 2 18 9 3 25 12 3 33 16 4 39 19 5 45 22 7 57 28 9 70 32 10 82 37 12 94 42 13 105 47 15 118 ' 52 18 140 63 20 160 72 Example of length in feet of pipe to be added to actual length of run. 136 MEASURED LENGTH. - 0P.-0 4'6ATE VALXE. = S;0, \ 4-4'ELBOWS. - S6-0 | EQUIVALENT LEN6TH 193-0' 'Cl Chapter 9--Steam Heating. Systems and Pipe Sizes PIPE SIZES The principal factors upon which the determination of pipe sizes for steam heating depends, are: 1. The equivalent length of the run from the boiler, or source of steam supply, to the farthest heating unit. (See Table 4). 2. The initial pressure and the total pressure drop, which may be allowed, between the source of supply and the end of the return system. 3. The maximum velocity of steam allowable for quiet and dependable operation of the system. 4. Unusual conditions in the building to be heated. Equivalent Length of Run The length of run must not only include the actual linear feet of straight pipe, but also the proper allowance for fittings, valves and other items which cause drop in pressure. 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. 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. Initial Pressure; Pressure Drop * Theoretically there are several factors to be considered such as initial pressure and the pressure required at the end of the line, but it is most important that (1) the total pressure drop does not exceed the initial pressure of the system; (2) that the pressure drop is not so great as to cause high velocities and .in the case of counter-flowing condensate, to cause water hammer; (3) that there is a constant initial pressure; (4) that there is sufficient difference in level between the water line of the boiler and the lowest point of the steam main, dry return and heating units. It is recommended that all systems be designed for low initial pressure and a reasonably small pressure drop. Such systems will operate under higher pressures without difficulty. When a system is designed for high pressure with a relatively large pressure drop and then operated at a low pressure, it is apt to be noisy and to have poor circulation. It is recommended that the total pressure drop never exceed one-half of the initial pressure. This applies to cases where the condensate is flowing in the same direction as the steam, but in the case of counter flowing condensate the capacities should not exceed those shown in Tables 5 and 6. Maximum Velocity The capacity of pipe of a given size in any part of a steam or vapor heating system depends upon the quantity of condensation present, as well as upon the available pressure drop in the pipe. Where no water is ?present or where a limited quantity flows by gravity in the same direction as the steam the available pressure drop only need be considered. . Where water and steam flow counter to each other the velocity of the steam must not exceed certain values above which disturbance between 137