Figure 4-2 - Minimum Discharge Pressure/Check Valve - Gardner Denver AUTO SENTRY EAU99G Operating And Service Manual

Oil Level Gauge (Figure 1-2, page 3 and Figure 5-6, page 46) - This gauge is located on the oil
reservoir and indicates the oil level.
Minimum Discharge Pressure/Check Valve (Figure 4-2, page 25) - An internal spring-loaded minimum
pressure valve is used in the final discharge line to provide a positive pressure on the coolant system of
the compressor even if the air service valve is fully open to atmospheric pressure. This valve also
functions as a check valve to prevent back flow of air from the shop air line when the unit stops, unloads,
or is shut down.
The valve incorporates a spring-loaded piston which maintains approximately 65 psig in the oil reservoir.
When the air pressure on the upstream (reservoir) side of the valve rises above 65 psig, the spring is
overridden and the valve opens to full porting.
The valve does not require maintenance or adjustment. If the valve fails to function, check the valve stem
O-ring for sealing, valve orifices for restriction, or valve and valve seat for burrs and dirt.
To service the valve make sure all pressure is relieved, disconnect the unit from the power supply, lockout
and tagout, then unscrew the valve cap from the body. The internal parts will come out after the cap has
been removed. Repair kits are available from your local authorized Gardner Denver distributor.
Figure 4-2 – MINIMUM DISCHARGE PRESSURE/CHECK VALVE
Inlet Valve (FIGURE 1-4 page 2, and , page 26) - The Inlet valve restricts the inlet to control
Figure 4-3
delivery and closes to unload the compressor. At shutdown, the inlet valve closes to prevent the back
flow of air.
The inlet valve position is controlled by air pressure in its piston cylinder, which is controlled by the
"AutoSentry" through solenoid valves IVC and IVO. As pressure to the piston is increased, the valve
closes to restrict air flow and compressor delivery.
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