Standard Components
Operation
The Combination Backpressure or Sustaining ACV with Hydraulic
Check Feature is designed to permit flow when upstream pressure is
above the adjustable setpoint of the control pilot, and throttle toward
closed when upstream pressure falls below the adjustable setpoint,
and close drip-tight when downstream pressure becomes greater
than upstream pressure.
It is controlled by a normally closed control pilot designed to: 1) Open
(allowing fluid out of the main valve cover chamber) when upstream
pressure is above the adjustable setpoint, and, 2) Close (allowing
fluid to fill the main valve cover chamber) when upstream pressure
is below the adjustable setpoint. An increase in upstream pressure
causes the valve to modulate toward an open position. A decrease
in upstream pressure causes the valve to modulate toward a closed
position.
If downstream pressure becomes greater than upstream pressure,
downstream pressure is admitted to the main valve cover chamber,
closing the valve and preventing reversal of flow. Normal backpres-
sure or sustaining operation resumes when upstream pressure ex-
ceeds downstream pressure.
When the valve is installed “in line” on the discharge of a pump, it acts
as Backpressure Control Valve. When pump discharge pressure falls
below the pilot setting, the valve modulates toward a closed posi-
tion, increasing backpressure against the pump. The valve should be
specified to include the optional opening speed control when used for
Backpressure applications.
When the Model valve is located "in line" connecting two distribution
zones, the valve acts as a Pressure Sustaining Control Valve. When
pressure in the upstream zone falls below the pilot setting, the valve
modulates toward a closed position, sustaining pressure in the
upstream zone. The valve will close, if necessary, until upstream
pressure is above the pilot setting. The valve should be specified to
include the optional opening speed control and position indicator
when used for Pressure Sustaining applications.
1
X
X
X
Y/FC
4
4
2
P/L
CLOSES VALVE
OPENS VALVE
FLOW
(AOS)
3
1. Clear the line free of slag and other debris.
2. Install the valve so that the FLOW ARROW marked on the valve body/tag corresponds to flow through the line.
3. Close upstream and downstream isolation valves.
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 a pressure gauge at a location upstream of the valve.
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 – Main Valve (905GD – Single Chamber)
2 – Pressure Sustaining Control
3 – Adjustable Closing Speed
4 – Check Valve
X – Isolation Cocks
Installation
920GD-01 (Globe) Pressure Sustaining Control Valve with
Hydraulic Check Feature
2 IOM-A-ACV-920-01_620-01 2115
EDP# 1917052
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