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Valve Sizing Information for Steam

Recommended Pressure Drops for Steam
Refer to specific valve data in this catalog for maximum allowable drops and close-off ratings.

A. Two Position Zone Valves and Direct Radiator Valves
Use a minimum of 10% of inlet pressure (psig).

B. Proportional Control Valves
Low pressure (15 psig or less): of 80% of gauge inlet pressure.

When Cv required is between two valve sizes and closer to the smaller valve size, re-size for Cv using 42% of the absolute inlet pressure as pressure drop. Use the valve that is larger than the calculated Cv .

For steam pressures greater than 15 psig: 42% of the absolute inlet pressure.

When Cv required is between two valve sizes, select the larger size.

Note: Do not size steam valves on higher system pressures using a pressure drop greater than 42% of the absolute inlet pressure.

Cv (Flow Coefficient) Determination
The Steam Capacity Tables or Slide Rule (refer to this and the following two pages) is based on the following formula:

Where:
Cv = Coefficient of flow
Q = Lbs per hour of steam
ΔP = Differential pressure in psi (pressure drop)
P2 = Outlet pressure in psia (absolute) psig + 14.7 = psia (absolute)
K = 1 + (0.0007 x ºF super-heat)
Note: K normally is 1 (K = 1 for saturated steam)

  

Other variations of the formula are:

Note: K normally is 1 (K = 1 for saturated steam).

These formulas can be used to calculate one of the quantities if the others are know.

Flow coefficients (Cv’s) for specific valve bodies are given on specification pages of this catalog.
STEAM CAPACITY IN POUNDS PER HOUR
Note: Table is based on saturated steam
Inlet Pressure 2 psig 5 psig 10 psig 15 psig 20 psig 25 psig 40 psig 50 psig 75 psig 100 psig
Cv / ΔP* (psi) 0.2 1.6 0.5 4 1 8 1.5 12 2 14 2.5 16 4 23 5 27 7.5 37 10 48
0.4 2.2 5.9 3.7 9.5 5.9 13.9 7.8 17.5 9.7 20.4 11.6 23.4 17.1 32.4 20.7 38.3 29.8 53 38.8 68
0.95 5.2 14 8.8 22.6 13.9 32.9 18.5 41.5 23 48.5 27.5 55.5 40.6 77 49.2 90.9 70.8 126 92.2 161
0.99 5.4 14.6 9.2 23.5 14.5 34.3 19.3 43.3 24 50.6 28.6 57.8 42.3 80.2 51.3 94.8 73.7 131 96.1 168
1.1 6 16.2 10.2 26.2 16.1 38.1 21.5 48.1 26.7 56.2 31.8 64.3 47 89.1 57 105.3 81.9 146 106.8 187
1.3 7.1 19.2 12.1 31 19 45.1 25.4 56.8 31.5 66.4 37.6 75.9 55.5 24.3 67.4 124.4 96.8 172 126.2 221
1.8 9.8 27 18.7 43 26.3 62.4 35.1 78.7 43.7 91.9 52.1 105.2 76.9 145.8 93.3 172.3 134.1 238 174.7 306
2.2 12 32.4 20.4 52 32 76 43 96 53 112 63.6 128.5 94 178 114 210.6 164 291 213.6 373
2.5 13.6 37 23 59 37 87 49 109 61 128 72 146 107 203 130 239 186 331 342 424
3.3 18 49 31 79 48 114 64 144 80 169 95 193 141 267 171 316 246 437 320 560
3.6 19.6 53 34 86 53 125 70 157 87 184 104 210 154 292 187 345 268 477 349 611
3.8 20.7 56 35 90 56 132 74 166 92 194 110 222 162 308 197 364 283 503 369 645
4.0 22 59 37 95 58 139 78 175 47 204 116 234 171 324 207 383 298 530 388 679
5 27 74 47 119 73 173 98 219 121 255 145 292 214 405 259 479 372 662 485 848
5.5 30 81 51 131 80 191 107 240 1334 281 159 321 235 446 285 526 410 728 534 934
6 33 89 56 143 88 208 117 262 146 306 174 351 256 486 311 574 447 795 582 1018
6.2 34 91 58 147 91 215 121 271 150 317 179 362 265 502 321 593 462 821 602 1052
7.4 40 109 69 176 108 257 144 324 180 378 214 432 316 599 384 708 551 980 718 1256
7.5 41 111 70 178 110 260 146 328 182 383 217 438 320 608 389 718 559 994 728 1273
8.2 45 121 76 195 120 284 160 359 199 419 237 479 350 664 425 785 811 1086 796 1392
8.5 46 125 79 202 124 295 166 372 206 434 246 497 363 689 441 814 633 1126 825 1443
9 49 133 84 214 131 312 176 393 218 460 260 526 385 729 466 861 670 1192 874 1528
10.5 57 155 98 250 153 364 205 459 255 536 304 613 449 851 544 1005 782 1391 1019 1782
11 60 162 102 262 161 381 215 481 267 562 318 643 470 891 570 1053 819 1457 1068 1867
15 82 221 139 357 219 520 293 656 304 766 434 876 641 1215 777 1436 1117 1987 1456 2546
16 87 236 149 380 234 555 312 700 388 817 463 935 684 1296 829 1531 1192 2120 1553 2716
17.4 95 257 162 414 254 603 340 761 422 889 503 1016 743 1409 902 1665 1296 2305 1689 2954
25 136 369 232 594 365 867 488 1093 607 1277 723 1460 1068 2025 1296 2393 1862 3312 2427 4244
35.8 195 528 333 851 523 1241 699 1565 867 1828 1036 2091 1529 2900 1856 3427 2667 4742 3475 6077
40 218 590 372 951 584 1387 780 1749 970 2043 1157 2337 1709 3240 2073 3829 2980 5299 3883 6790
45 245 664 418 1070 657 1560 878 1967 1092 2298 1302 2629 1923 3645 2332 4307 3352 5961 4368 7639

Inlet Pressure 2 psig 5 psig 10 psig 15 psig 20 psig 25 psig 40 psig 50 psig 75 psig 100 psig
Cv / ΔP* (psi) 0.2 1.6 0.5 4 1 8 1.5 12 2 14 2.5 16 4 23 5 27 7.5 37 10 48
56 305 826 521 1331 818 1942 1093 2448 1359 2860 1620 3271 2392 4536 2903 5360 4171 7418 5436 9506
65 354 958 604 1545 949 2254 1268 2842 1577 3320 1881 3797 2777 5265 3369 6221 4842 8611 6310 11034
70 381 1032 651 1664 1022 2427 1366 3061 1698 3575 2025 4089 2911 5670 3628 6670 5214 9273 6795 11882
75 409 1106 697 1783 1095 2601 1463 3279 1820 3830 2170 4381 3204 6075 3887 7179 5587 9935 7280 12731
85 463 1253 790 2021 1241 2947 1658 3716 2062 4341 2459 4966 3631 6885 4406 8136 6332 11260 8251 14429
100 545 1475 930 2377 1460 3468 1951 4372 2426 5107 2893 5842 4272 8101 5183 9571 7449 13247 9707 16975
115 627 1696 1069 2734 1680 3988 2244 5028 2790 5873 3327 6718 4913 9316 5961 11007 8566 15234 11163 19521
145 790 2138 1348 3447 2118 5028 2829 6340 3518 7405 4195 8471 6195 11746 7516 13878 10801 19208 14075 24613
170 926 2507 1580 4042 2483 5895 3317 7433 4124 8682 4918 9931 7263 13771 8811 16271 12663 22519 16502 28857
200 1090 2949 1859 4755 2921 6935 3902 8744 4852 10214 5786 11684 8544 16201 10366 19143 14898 26494 19414 33950
235 1281 3465 2184 5587 3432 8149 4585 10275 5701 12002 6799 13729 10040 19036 12180 22493 17505 31130 22812 29891
275 1499 4055 2556 6538 4016 9536 5366 12024 6672 14044 7956 16065 11749 22277 14254 26321 20484 26429 26695 46681
350 1907 5161 3253 8321 5112 12136 6829 15303 8491 17875 10126 20447 14953 28352 18141 33500 26071 46264 33975 59412
425 2316 6267 3950 10104 6207 14737 8292 18582 10311 21705 12296 24828 18157 34427 22028 40678 31658 56300 41256 72143
440 2398 6488 4090 10461 6426 15257 8585 19238 10675 22471 12730 25704 18798 35642 22806 42144 32775 58287 42712 74689
640 3488 9437 5949 15215 9347 22192 12487 27982 15527 32685 18516 37388 27342 51844 33172 61257 47672 84781 62126 108639
680 3706 10027 6321 16166 9931 23579 13268 29731 16498 34728 19673 39725 29051 55084 35245 65085 50652 90080 66009 115429
1125 6131 16589 10457 26746 16430 39010 21950 49187 27294 57454 32547 65722 48063 91131 58310 107678 83799 149029 109206 190967
1150 6267 16958 10689 27340 16796 39788 22438 50280 27900 58731 33271 67182 49131 93156 59606 110071 85661 152341 111633 195210
1750 9537 25805 16267 41604 25558 60682 34145 76513 42457 89373 50629 102234 74764 141760 90705 167499 130354 231823 169876 297059
1850 10082 27280 17196 43982 27019 64150 36096 80885 44883 94481 53522 108076 79036 149860 95888 177070 137803 245070 179583 314034
2600 14169 38339 24167 61812 37972 90157 50730 113677 63079 132783 75220 151890 111078 210614 134762 248855 193669 344422 252388 441345
2650 14442 39076 24632 63001 38703 91890 51706 115863 64292 135337 76667 154811 113214 214665 137353 253641 197394 351046 257241 449832
3400 18529 50136 31604 80831 49656 117897 66339 148654 82488 173640 98365 198625 145256 275419 176227 325426 253260 450398 330045 577143
4500 24524 66356 41828   65722   87802   109175   130189                  
5400 29429 79628 50194   78866   105362                          
7000 38148   65066   102234                              
10000 54498   92952                                  
Last Updated Wednesday, July 26, 2006

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