Document by9Qo1b2w77D49pqw0bJeXZLk

412 CHAPTER 23 1946 Guide Table 1. Flqw of Steam in Pipes P -- loss in pressure in pounds per square inch. D = inside diameter of pipe in inches. L = length of pipe in feet. d = weight of 1 cu ft of steam. W = pounds of steam per hour. W P = 0.0000000367 ( 1 + W*L dD6 Pressure Col. 1 Pipe Size IN Ounces 5220Vl~P~ wo Nominal Actual Internal Diameter Internal Pipe Sq Inches Col. 2 1* Steam Press. Col. 3 v/------- op Pipe in Feet Col. 4 /loo v-- 0.25 65.28 1 1.049 0.864 0.536 -1.03 0.187 20 2.240 0.50 1.00 2 3. 4 92.28 130.5 184.6 226.0 261.0 IX m 2 2X 3 1.380 1.610 2.067 2.469 3.068 1.496 2.036 3.356 4.788 7.393 1.178 -0.53 0.190 1.828 0.0 0.193 3.710 6.109 0.3 0.195 1.3 6.201 11.183 2.3 0.207 40 1.580 60 1.290 80 1.120 100 1.000' 120 0.912 5 291.8 3X 3.548 9.887 16.705 5.3 0.223 140 0.841 6 319.7 4 4.026 12.730 23.631 10/3 0.248 160 0.793 7 345.3 iX 4^506 15.947 32.134 15.3 0.270 180 0.741 8 369.1 5 5.047 20.006 43.719 20.3 0.290 `200 0.710 10 412.7 6 . 6.065 28.886 71.762 30.3 0.326 250 0.632 12 452.0 7 7.023- 38.743 106.278 40.3 0.358 300 0.578 14 488.3 8 7.981 50.027 149.382 50.3 0.388 350 0.538 16 522.0 9 8.941 62.786 201.833 60.3 0.415 400 0.500 20 583.6 10 101020 78.854 272.592 75.3 0.452 450 0.477 - 24 639.3 12 12.000 113.098 437.503 100.3 0.507- 500 0.447 . 28 690.5 14 13.250 137.880 566.693 125.3 0.557 32 ' 738.2 16 15.250 182.655 816.872 150.3 0:603 40 825.4 Column 1 X 2 X 3 X 4 ' lb of steam 175.3 0.645 .48 904.1 pipe for a given condition. 200,3 0.685 80 1167.2 Example I: l. oz drop -- 2 tn. pipe ' -- 1.3 lb press. -- 100 ft equivalent length: 160 1650.7 130.5 X 3.710 X 0.201 X 1 = 97.2 lb per hour. 97.2 X 4b a 388.8 sq ft equivalent radiation. 320 .480 2334.5 ` 2859.1 .Table 1 does not allow for entrained water in low-pressure steam, condensation in covered pipe and roughness in commeraal pipe as found in practice. 600 700 `800 900 1000 1200 1500 2000 0.407 0.378 .0.354 0.333 0.316 0.289 0.258 0.224 Pounds per square inch gage = 2.Q4 in. Vacuum, Mercury Column. '' bThe factor 4 is the approximate equivalent in square feet of steam radiation of 1 lb of steam per hour. Steam Heating Systems and Piping 413 factor is the velocity permissible without interfering with the condensate flow. A.S.H.V.E. Research Laboratory experiments limit this to the capacities given in. Table 2 for horizontal pipes at varying grades. Maximum Velocity The capacity of a steam pipe in any part of a steam system depends upon the quantity of condensation present, the direction in which the condensate is flowing, and the pressure drop in the pipe. Where the quantity of condensate is limited and is flowing in the same direction as the steam,, only the pressure drop need be considered. When the con densate must flow against the steam, even in limited quantity, the ve locity of the steam must not exceed limits above which the disturbance between the steam and the counter-flowing water may produce object-1 ionable sounds, such as water hammer, or may. result in the retention of Table 2. Comparative Capacity of Steam Lines at Various Pitches for Steam and Condensate Flowing in Opposite Directions3 Pitch of Pipe in Inches per 10 Ft. Velocity in Ft per Sec. Pitch of Pipe M IN. M IN. 1 IN. 04 IN. 2 IN. 3 IN. 4 IN. 5 IN. ' C a p a c ity C a p a c ity M ax. Vel. C a p a c ity M ax. Vel. | C a p a c ity M ax. Vel. | C a p a c ity M ax. Vel. C a p a c ity C a p a c ity M ax. Vel. C apadly Pipe Size Inches V > .$ 2 "3 > > w a s 22 Capacity Expressed in Square Feet E D R H . 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 1A 104.9 18 117.2 20 133.0 23 144.5 25 154.0 27 165.0 28 172.6 29 178.2 31 lA 142.6 18 159.0 21 181.0 23 196.5 25 209.3 27 224.0 28 234.8 30 242.6 31, 2 236.0 19 263.5 20 299.5 23 325.5 25 346.5 27 371.5 28 388.4 29 401.1 30 Capacity Expressed in Pounds per Hour A 6.3 12 7.6 14 9.3 18 10.1 19 10.6 20 11.5 21 11.9 22 12.3 23 1 11.5 12 13.2 15 15.8 17 17.5 20 18.8 22 20.8 23 22.0 25 22.6 26 1A 26.2 18 29.3 20 33.3 23 36.1 25 38.5 27 41.3 28 43.2 29 44.6 31 1A 35.7 18 39.8 21 45.3 23 49.1 26 52.3 27 56.0 28 58:7 80 60.7 31 2 59.0 19 65.9 20 74.9 23 81.4 25 86.6 27 92.4 28 97.1 29 100.3 30 Data from American Society of Heating and Ventilating Engineers Research' Laboratory. 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 hori zontally, (3) the quantity of condensate flowing against the steam, and (4) freedom of the piping from water pockets which under certain con ditions 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 pipe size decreases. According to A.S.H.V.E. Research Laboratory tests, either 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.