Standard Components
Operation
The Combination Pressure Reducing and Pressure Sustaining
Automatic Control Valve (ACV) is designed to automatically reduce
a fluctuating higher upstream pressure to a constant lower down-
stream pressure regardless of varying flow rates, and will throttle to
sustain a minimum upstream pressure. It is controlled by a normally
open, pressure reducing pilot designed to: 1) Open (allowing fluid
out of the main valve cover chamber) when downstream pressure is
below the adjustable setpoint, and 2) Close (allowing fluid to fill the
main valve cover chamber) when downstream pressure is above
the adjustable setpoint. A decrease in downstream pressure causes
the valve to modulate toward an open position, raising downstream
pressure. An increase in downstream pressure causes the valve to
modulate toward a closed position, lowering downstream pressure.
The normally closed sustaining pilot remains open when upstream
pressure is above the adjustable setpoint, and modulates toward
a closed position if upstream pressure falls below the setpoint. As
the sustaining pilot closes, fluid is directed into the main valve cover
chamber, allowing the valve to modulate toward a closed position,
raising upstream pressure. Normal pressure reducing operation
resumes when upstream pressure is above the sustaining pilot
setpoint, and downstream pressure is below the reducing pilot set-
point.
1
X
X
X
Y/FC
4
2
3
AOS
CLOSES VALVE
OPENS VALVE
FLOW
P/L
Start-up of an automatic control valve requires that proper procedures be followed. Time must be allowed for the valve to react to
adjustments and the system to stabilize. The objective is to bring the valve into service in a controlled manner to protect the system
from damaging over-pressure.
1. Prior to installation, flush line to remove debris.
2. Install valve so the flow arrow matches flow through the line, and gauges to monitor valve inlet and outlet pressures. A Position
Indicator can be installed to provide visual indication of valve position and operation without disassembly.
3. Install isolation valves upstream and downstream of the main valve.
4. Open the isolation ball valves in the control tubing if so equipped. Failure to open these will prevent the valve from functioning
properly.
5. Install pressure gauges at locations upstream and downstream of the valve.
Note:
If using butterfly valves, ensure valve disc does not contact the main valve.
6. Provide adequate clearance for valve servicing and maintenance. Refer to valve servicing dimensions on next page.
7. Avoid installing valves 6" and larger in the vertical position (main valve stem horizontal). Automatic Control Valves (ACVs) are
designed for horizontal in-line installation, with the cover facing up (main valve stem vertical). Slow operation or premature stem and
guide wear may occur if valve is not installed according to factory recommendations. Consult factory for detailed engineering review
prior to ordering if valve is to be installed other than horizontally in-line.
8. If valve is equipped with a pilot control system, extra precautions should be made during installation to protect the piping circuit
from damage. Only remove the pilot control system from the valve if necessary. Tubing and fittings should be kept clean and
replaced exactly as removed. Consult appropriate hydraulic schematic to ensure proper re-assembly.
9. After installation, vent entrapped air from valve cover and pilot system by following instructions on Technical Bulletin.
1 – Main Valve (905GD - Single Chamber)
2 – Pressure Reducing Control
3 – Pressure Sustaining Control
4 – Fixed Orifice
X – Isolation Cocks
Installation
912GD (Globe) Pressure Reducing Control Valve with Pressure
Sustaining Feature
2 IOM-A-ACV-912_612 2115
EDP# 1917034
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