Document NG5EDy2n6rJdpRZ4LNyazMBBb

436 CHAPTER 23A ' - . .1948 Guide - Table 5 may be used for sizing piping for 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 inopposite directions, 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 critical velocities of the steam to permit the counter flow of condensate without noise. Return piping may be' sized with the aid of Tables 6 and 7 where pipe capacities for wet, ,dry, and vacuum return lines are shown for the pres sure drops per 100 ft corresponding to the drops in Table 5. It is cus tomary to use the same pressure drop on both the steam and return sides of a system. Example 8. What pressure drop should be used for the steam piping of a system if the measured length of the longest run is 500 ft and the initial pressure is not to be over 2-psi gage? Solution. It will be assumed, if the measured length of the longest run is 500 ft, that when the allowance for fittings is added the equivalent length of run will not exceed 1,000 ft. Then, with the pressure drop not over one half of the initial pressure, the drop could be 1 psi or less. With a pressure drop of 1 psi and a length of run of 1,000 ft, the drop per 100 ft would be Jfo psi, while if the total drop were Vi psi, the drop per 100 ft would be Mo psi. In the first instance the pipe could be sized according to Column D for Jfs psi per 100 ft, and in the second case, the pipe could be sized according to Column C for yii psi. On completion of the sizing, the drop could be checked by taking the longest line and actually calculating the equivalent length of run from the pipe sizes determined. If the calculated drop is less than that assumed, the pipe size is all right; if it is more, it is probable that there are an unusual number of fittings involved, and either the lines must be straightened or.the column for the next lower drop must be used and the lines resized. Ordinarily resizing will be unnecessary. TABLES FOR PIPE SIZING FOR HIGH PRESSURE SYSTEMS Many of the recent installations of heating systems for large industrial type buildings have been designed for the use of high pressure steam, that is, without the use of pressure reducing valves. Such systems usually involve the use of unit heaters or large built-up fan units with blast heating coils. Pressures on these systems Vary from 30 to 150 psi. Tem peratures are controlled by a modulating or throttling type thermostatic valve controlled by the air temperature in. the room, fan inlet or outlet. Tables 8 to 11 may be used for the sizing of steam and return piping for systems of 30 and 150 psi. pressure, at various pressure drops. These tables are based on Babcock's formula, and have been used as-the basis of design for a number of years. SIZING PIPING FOR ONE-PIPE GRAVITY SYSTEMS Gravity one-pipe air-vent systems in which the equivalent length of run does not exceed 200 ft should be sized by means of Tables 5, 6 and 7 as follows: 1. For the steam main and dripped runouts to risers where the steam and condensate flow in the same direction, use Ms'Psi drop (Column D). 2. Where the riser runouts are not dripped and the steam and condensate flow in opposite directions, and also in the radiator runouts where the same condition occurs, use Column L. Steam Heating Systems and Piping 437. Table 8. - Steam Pipe Capacities foe 30 tsi Steam Systems3 Capacity Expressed in-Pounds. per Hour (Steam and Condensate Flowing in Same-Direction) Pipe Size = Inches - -1-u IK ix 22J4 3 3)4 4 .. 5 16 8 10 .12 .X : 15 ,31 69 107 217 - 358 651 979 1.390 2.560 4.210 8,750 16,300 25.600 Drop in Pressure--Pounds per 100 Ft in Length ,x . 22 . 46 100 .154 _ 313 516 940 1,410 2.000 3,640 6,030 12,600 23,500 36,900 xV 31- ; 63 141 219 ' 444 730 1,330 . 2,000 2,830 . 5,230 8,590 17,900 33.200 52,300 X 38 77 172 267 543 924 1,630 2,450 3,460 . 6,400 10,400 21,900 40,600 64,000 1 45 89 : 199 309 627 . 1,030 1,880 ' 2,830 4,000 7,390 12,100 25,300 46,900 74,000 .2 63 125 , 281 437 886 1;460 2,660 4.000 5,660 10,500 17,200 - 35,100 66,400 104,500 Note: Steam at an average pressure of 30 psi is used a9 the baas for calculating the above table. 3. Forup-feed steam risers carrying condensate back from theradiators, use Column J. 4. For doom-feed systems the main risers of which do not carry any radiator con densate use Column H. 5. For the radiator valve size and the stub connection, use Column K. 6. For the dry return main, use Column V. - 7. For the wet returnmain use ColumnT. On systems exceeding an equivalent length of 200 ft, it is suggested that the total drop be not over psi. The return'piping sizes shoujd corres pond with the drop used on the steam side of the system. Thus, Where J^4-psi drop is being used, the steam main and dripped runouts would be -sized from Column C; radiator runoiits and undripped riser runouts frbm Column L; up-feed risers from Column J; the main riser on a down-feed System from Column C (it will be noted that .if Column H fs. used the drop would exceed the limit of M* psi); the dry return from Column R; and the wet return from Column Q. .With a Kz-psi drop the sizing woiild be the same as .for Ka psi except that the steam main and dripped runouts,would be sized from Column B, Table 9. Steam Pipe Capacities for 150 psi Steam Systems . Capacity Expressed in 'Pounds per Hour (Steam and Condensate Flowing in Same Direction) Pipe Size ' Inches H V -1 IX . 2lH 2X 3 3X 4" 56 8 10 12 . ' Drop in Pressure--"Psi per 100 Ft in Length X 29. 58 . 130 . 203 412 683 . .1,240 1,860 2.630 4.860 7,960 16,600 30.800 48,600 x 41 . . 82 \ * 185 287 583 . - 959 : 1.750 2,630 3,720 6.880 .11,300 23,500 43,400 68,800 x 58 .. 117 , 262 .407 825 1,360 2.480 3.720 5,260 9,730 16,000 33.200 61,700 97,300 x.: v 71 :>143 >320 . 497 1.010 1,650 3,020 4,550 61430 11,900 19,500 40,600 75,600 119,000 . 1 82 165 370 575 1.170 1,920 . 3,500 5,250 7,430 13,800 22,600 47,000 87.300 138,000 2. 116 233 523 813 1,650 2,710 4,940 7,420 10,500 19,500 31,900 66.400 123,000 194,000 5 184 , 369 , 827 ^ 1,290 * 2.600 .4.290 7,820 11,700 16,600 30,800 50,400 105,000 195,000 307,500 Note: Steam at an average pressure of 150 psi is used as the basis for calculating the above table.