Gardner Denver INTEGRA EFD99E, Operating And Service Manual

13-20-604   Page 26 

Never paint, lubricate or alter a relief valve.  Do not plug vent or restrict 
discharge. 

Operation of the unit with improper relief valve setting can result in severe 
personal injury or machine damage.  Ensure properly set valves are installed 
and maintained. 

Oil Level Gauge - 

This gauge is located on the oil reservoir and indicates the oil level.  See “Oil Level 

Gauge”, Figure 5-4, page 42, for how to read oil level. 

Minimum Discharge Pressure/Check Valve - 

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 an orifice which, when air is flowing through it, maintains pressure in the oil 
reservoir.  A spring-loaded piston valve senses air pressure on the upstream (reservoir) side of the valve. 
When the system pressure rises, the spring is overridden and the valve opens to full porting. 

Inlet Valve 

(Figure 4-1, page 24) 

- 

The Inlet valve restricts the inlet to control 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 
"AirSmart

®

" Control through the magnetic unloader solenoid valve.  When the top of the cylinder is 

pressurized, the inlet opens for full air delivery.  When pressure is relieved from the cylinder, the inlet 
valve closes to restrict air flow and compressor delivery. 

Magnetic Unloader Solenoid Valve 

(Figure 4-1, page 24) 

- 

This valve controls the position of the inlet 

valve in response to signals from the "AirSmart" Control.  When de-energized, pressure is relieved from 
the top of the inlet valve cylinder to unload the compressor.  When the solenoid valve is energized, 
reservoir pressure is supplied to the top of the cylinder to load the compressor. 

Check Valve 

(Figure 4-1, page 24) 

- 

This valve is normally closed while the compressor is loaded or 

stopped.  While running unloaded, it opens to admit a small amount of purge air to the compressor inlet.  
This reduces compressor knock, and provides enough air to pressurize the controls during startup. 

Blowdown Valve 

(Figure 4-1, page 24) 

- 

The blowdown valve is a two-way solenoid valve which is piped 

into the oil reservoir outlet ahead of the minimum pressure valve.  When the solenoid is de-energized, the 
valve opens and the coolant system is blown down.  When the solenoid is energized, the valve closes to 
allow the coolant system to pressurize. 

Purge Air Valve 

(Figure 4-1, page 24) – The purge valve is a two-way solenoid valve that admits purge 

air from the final discharge manifold to the compressor to counteract the oil knock that occurs in oil-
flooded rotary screw compressors when they are completely unloaded with pressure in the oil reservoir.  
This valve is controlled by the controller which allows air into the airend whenever the inlet valve closes. 

System Pressure Transducer 

(Figure 4-1, page 24) 

- 

This transducer is connected after the minimum 

pressure valve.  It converts the pressure in the plant air system into an electrical signal for use by the 
"AirSmart" control for modulation and control.