User Guide

6 © Copyright 2008 TAC All Rights Reserved. F-26075-2
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)
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-7213 series valves.
Table-6 Steam Capacity in Pounds Per Hour for VB-7213 Series.
C
v
Equation
Where:
C
v
= Coefficient of flow
Q = Lbs. per hour of steam
ΔP = 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
C
v
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-7213-0-4-1 0.4 2.2 5.9 3.7 9.5 5.8 13.9 7.8 17.5 9.7 20.4 11.6 23.4 13.4 26.3 15.3 29.2
VB-7213-0-4-2 1.3 7.1 19.2 12.1 30.9 19.0 45.1 25.4 56.8 31.5 66.4 37.6 75.9 43.6 85.5 49.6 95.1
VB-7213-0-4-3 2.2 12.0 32.4 20.4 52.3 32.1 76.3 42.9 96.2 53.4 112 63.6 129 73.8 145 83.9 161
VB-7213-0-4-4 4.4 24.0 64.9 40.9 105 64.3 153 85.9 192 107 225 127 257 148 289 168 322
VB-7213-0-4-5 5.5 30.0 81.1 51.1 131 80.3 191 107 240 133 281 159 321 185 362 210 402
VB-7213-0-4-6 7.5 40.9 111 69.7 178 110 260 146 328 182 383 217 438 252 493 286 548
VB-7213-0-4-7 10 54.5 147 93 238 146 347 195 437 243 511 289 584 336 658 381 731
VB-7213-0-4-8 14 76.3 206 130 333 204 485 273 612 340 715 405 818 470 921 534 1024
VB-7213-0-4-9 20 109 295 186 475 292 694 390 874 485 1021 579 1168 671 1315 763 1462
VB-7213-0-4-10 28 153 413 260 666 409 971 546 1224 679 1430 810 1636 939 1841 1068 2047
VB-7213-0-4-11 40 218 590 372 951 584 1387 780 1749 970 2043 1157 2337 1342 2631 1526 2925
C
v
=
QK
Q=
K
ΔP • P23
ΔP • P23C
v