User Guide

6 © Copyright 2008 TAC All Rights Reserved. F-24380-2
Steam Two-position
Two-position zone valves and direct radiation valves are normally sized using a minimum of
10% of inlet pressure (psig).
Proportional
Proportional control valves are normally sized using:
• For low pressure (15 psig or less), use ΔP of 80% of gauge inlet pressure.
• For steam pressures greater than 15 psig, use ΔP of 42% of absolute (gauge plus
14.7 psig) inlet pressure.
• When the C
v
required is between two valve sizes, select the larger size. Do not size
steam valves using a pressure drop greater than 42% of the absolute inlet pressure.
Steam Capacity
See Table-6 for steam capacity of VB-7211 series valves.
Table-6 Steam Capacity in Pounds Per Hour for VB-7211 Series.
C
v
Equation
Where:
C
v
= Coefficient of flow
Q = Lbs. per hour of steam
ýP = Differential pressure in psi (pressure drop)
P2 = Outlet pressure in psia (absolute) (P2 = Inlet pressure + 14.7 –
ΔP)
K = 1 + (0.0007 x °F superheat) (K = 1 for saturated steam)
Valve Body
Part Number
Cv
Rating
Differential Pressure (
ΔP in psi)
a
a
Values are for saturated steam (K = 1). Left column under each inlet pressure is for two-position control, and right column is for proportional control
2 psig Inlet 5 psig Inlet
10 psig
Inlet
15 psig
Inlet
20 psig
Inlet
25 psig
Inlet
30 psig
Inlet
35 psig
Inlet
0.2 1.6 0.5 4 1 8 1.5 12 2 14 2.5 16 3 18 3.5 20
VB-7211-0-X-1 0.4 2.2 5.9 3.7 9.5 5.8 14 7.8 18 9.7 20 12 23 13 26 15 29
VB-7211-0-X-2 1.3 7.1 19 12 31 19 45 25 57 32 66 38 76 44 86 50 95
VB-7211-0-X-3 2.2 123220523276439653112641297414584161
VB-7211-0-4-4 4.4 24 65 41 105 64 153 86 192 107 225 127 257 148 289 168 322
VB-7211-0-3-4 5.0 27 74 46 119 73 173 98 219 121 255 145 292 168 329 191 366
VB-7211-0-X-5 5.5 30 81 51 131 80 191 107 240 133 281 159 321 185 362 210 402
VB-7211-0-4-6 7.5 41 111 70 178 110 260 146 328 182 383 217 438 252 493 286 548
VB-7211-0-3-6 8.5 46 125 79 202 124 295 166 372 206 434 246 497 285 559 324 621
VB-7211-0-4-7 10 55 147 93 238 146 347 195 437 243 511 289 584 336 658 381 731
VB-7211-0-3-7
VB-7211-0-4-8
14 76 206 130 333 204 485 273 612 340 715 405 818 470 921 534 1024
VB-7211-0-3-8 16 87 236 149 380 234 555 312 699 388 817 463 935 537 1052 610 1170
VB-7211-0-4-9 20 109 295 186 475 292 694 390 874 485 1021 579 1168 671 1315 763 1462
VB-7211-0-3-9 22 120 324 204 523 321 763 429 962 534 1123 636 1285 738 1447 839 1608
C
v
=
QK
Q=
K
ΔP • P23
ΔP • P23C
v