Document K6KdpM1rB0GDaKqRMvpeBL3ow

476 CHAPTER 23 1949 Guide the counter-flowing water may produce objectionable sounds, such aswater hammer, or may result-in the retention of water in certain parts of the system until the steam flow is reduced sufficiently to permit the water to pass. The velocity at which such disturbances take place is a function of (1) ,the pipe size, whether the pipe runs horizontally or vertically, (2) the' pitch of the pipe if it runs horizontally, (3) the quantity of condensate flowing against the steam, and (4) freedom of the piping from water pockets which under certain conditions act as a restriction in pipe size. Reaming Important : Three factors of. uncertainty always exist in determining the capacity of any steam pipe. The first is variation in manufacture, which appar-. ently cannot be avoided. The second is the care- used in reaming the ends of the pipe after cutting. The effect of both of these factors increases as the Table 3,, Comparative Capacity or Steam Lines at Various Pitches por Steam and Condensate Flowino in Opposite Directions* Pitch of Pipe in Inchee per 10 Ft. Velocityin Ft per Sec. .. 'f.i Pitch or Pipe a in. - ;H , 1 w.;. 1IN. 2 IN. .. , .3 IN. 4 IN. 5 IN..,. . . Capacity - Capacity / Max. Vel.- | Capacity '. Capacity : Max. Vel. j Capacity Max. Vel. | Capacity Max. Vel. . | Capacity - .InPSciihpzeee.s : :> a s *C X i >u i s. A(9 o ' - s >- s 2 Capacity Expressed In Square Feet E D R : : 25.0 12 30.3 14 37.3 18 40.4 19 42.5 20 46.1 21 47.5 22 49.3 23 1 45.8 12 52.6 15 63.0 17 ,70.0 20 75.2 22 83.0 23 87.9 25 90.2 26 1H 2 104.9 18 117.2 20 133.0 23 144.5 25 154.0 27 165.0 28 172.6 29 178.2 31 142.6 18 159.0 -21 181.0 23 196.5 25 209.3 27 224.0 28 234.8 30 242.6 31 236.0 19 263.5 20 299.5 23 325.5 25 346.$ 27 371.5 28 388.4 29 401.1 30 Capacity Expressed in Pounds per Hour H .. 6.3 1 11.5 J Mr .26.2 2 35.7 59.0 12 . 7.6 114 12 13.2 15 18 29.3 20 18 39.8 21 19 65:9 20 9.3 15.8 33.3 45.3 74.9 18 17 23 23 23 10.1 17.5 36.1 49.1 81.4 19 20 25 25 25 10.6 18.8 38.5 52.3 86.6 20 22 27 27 27 11.5 21 11.9 22 12.3 23 20.8 23 22.0 25 22.6 26 41.3 28 .43:2 29 44.6 31 jin56.0 28 58.7 30 60.7 31 92.4 28 97.1 29 100.3 . ` Data from Amekil'an Sociltt or H sating and Ventilating Enginkebs Research Laboratory. pipe size decreases. According to A.S.H.V.E. Research Laboratory tests,- eithey.of these factors, may affect the capacity'of a 1-in. pipe as much as 20 per cent.. The third factor is the uniformity in grading the pipe line,. All of the capacity tables given in this chapter include a factor of safety: However, the factor of safety referred to does not cover abnormal defects or constrictions, nor does it cover pipe not properly reamed. - Equivalent Length of Run All tables for the flow of steam in pipes, based on pressure drop, must allow-for the friction offered'by the pipe as well as for the additional resistance of the fittings'and valves. These resistances generally are stated in terms of straight pipe; in other words, a certain fitting will produce a-drop in pressure equivalent to so many feet1 of straight run of the same size of pipe. Table 4 gives the number of feet of straight pipe usually allbwed'for themOre conunon types of fittings and valves. .. In-all pipe sizing tables in this chapter the length of run refers to theequivalent Steam -Heating Systems and Piping 477 h length of run as. distinguished from the actual length of pipe in feet. The length of fun is hot usually-known at the outset; hence it may be necessary, to assume-some pipe size at the start. Such an. assumption; frequently is considerably in error'and a; more common aM-'practical method is to assume the length of run and to check this assumption after the pipes are sized.- ' For this purpose the length of run usually is taken as double the actual length of pipe. TABLES FOR PIPE SIZING FOR LOW PRESSURE SYSTEMS* Tables 5, 6, and 7 are based on the actual inside diameters of the pipe and the condensation.Of :J. lb (4 oz) of steam per square foot of equivalent direct radiation {abbreviated EDR) per . hour. The drops indicated are Table 4. Length in Feet op Pipe to be Added to Actual Length op Run-- Owing to Fittings^--to Obtain Equivalent Length ` Size of Pipe ..Inches- : " Length, in Feet to be Added to Run Standard Elbow Side Outlet Tee Gate Valve* Globe Valve* Angle Valve* . H - . 1-.. . .1H m 2 2H 3 3J4 4 5.... 6 8 10 . 12, 14 - 1.3 1.8 : 2:2 .. 3.0 3.5 4.3 5.0 6.5 : 8 9 11 13 17 s 21 27 30 : 3 0.3 , - .4 . .. 0.4 5: 0.5 6 0.6 7 0.8 8 1.0 11 1.1 13 1.4 15 1.6 18 1.9 22 2.2 27. . 2.8 35 - 3.7 - 45........ ...... 4.6 53 5.5 63 6.4 14 18 23 29 34 46 . 54 66 80 92 112 136 180 230 270 310 - 7 10 12 . 15 ; 18 22 27 34 40 4556 67 92: 112 132 152 Valve In full open position. ^Example of length in feet of pipe to be added, to actual length of run. Measured Length * 132.0 ft 4 in. Gate Valve * 1.9.ft 4--4 in. Elbows D 36.0 ft n lEquivalent'Length '*= 169.9 ft X '.... :......... H drops in pressure per TOO ft of equivalent length of run. The pipe is assumed to be well reamed; and: without unusual or noticeable defects,- Table 5 may be. used for sizing pipingJor steam heating systems by pre-determining the allowable or desired pressure drop per 100 equivalent feet of run and reading from the column for that particular pressure drop. This applies to all steam mains on both one-pipe and two-pipe systems, vapor systems, and vacuum systems. Columns B to G, inclusive, are used where the steam and condensate flow in the same direction, while Columns H and I are for cases where the steam- and condensate flow; in opposite1directions, as in risers and runouts that are not dripped. Columns J, K, and L are for one-pipe systems and cover riser, radiator valve and vertical connection sizes, and radiator and runout sizes, all of which are based on the