Product Overview

Schneider Electric 839 North Perryville Rd. Rockford, IL 61107 1-888-444-1311 www.schneider-electric.com
F-27649-2 September 2013
© 2013 Schneider Electric. All rights reserved.
VB-7200 Two-Way Globe Valve Bodies
Venta
12
Sizing for Steam
Two-position
Two-position zone valves and direct radiation valves
are normally sized using a minimum of 10% of inlet
pressure (psig).
Proportional
For low pressure (15 psig or less), use DP of 80% of
gauge inlet pressure.
For steam pressures greater than 15 psig, use DP
of 42% of absolute (gauge plus 14.7 psig) inlet
pressure.
Maximum recommended differential pressure
in open position. Do not exceed recommended
differential pressure (pressure drop), as integrity
of parts may be affected. Exceeding maximum
recommended differential pressure voids product
warranty.
When the Cv 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.
Actuator must be rated to provide close off pressure.
Do Not Exceed the MAXIMUM Recommended
Pressure Drop Of the Valve
Additional Valve Sizing Information
• CA-28 Control Valve Sizing, F-13755
• Valve Selection Chart Water, F-11080
• Valve Selection Chart Steam, F-11366
For more information, download
these documents from our website.
Other forms of this formula are:
Cv (Flow Coefficient) Determination
The valves’ steam capacity is based on the following
formula:
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 Table Instructions
To Select the approproate valve Cv from the Table:
1. Determine if control is two position or proportional and use left column under Differential Pressure
for two position control or the right column under inlet pressure for proportional control.
2. Select table column with the available Inlet Pressure to be maintained.
3. Go down to the desired pounds of Steam Per Hour.
4. Select the closest valve Cv flow coefficient from the left hand column.
Valve / Actuator Selection Guides with Close
Off Pressure Ratings.
• Linked Globe Valve Assemblies Selection Guide
(Rack) F-26752
• Linked Globe Valve Assemblies Selection Guide
(Linear) F-27252
• Forta/Globe Valve Selection Guide F-27490
• Globe Valve Catalog (Pneumatic / Geartrain) F-27414
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