Valve: Function of Valves used in Electric Screw Air Compressor.

in screw air compressor various types of valves used.Such as Oil Check Valve,Safety Valve,Minimum Pressure Valve,By Pass Valve,Air Discharge Valve
There are various types of valves used in engineering field. The types of valves and its functions are covered in coming posts. This post will give you information about valves used in screw air compressor. For the perfect operation of Screw Air Compressor some valves are fitted inside the compressor unit. These valves have to perform different function as per requirement of the screw compressor. The education about below valves plays the vital role while servicing or trouble shooting and rectification of the compressor. Details about various Valves are as below.
01) Oil Check Valve
The function of this valve is to stop the supply of oil immediately running through the system after stopping the Air Compressor. Hence Oil is not accumulated in Air End during next starting. This Valve remains opens when Compressor is running both in load and unload condition. During Unloading Condition, opens slightly to supply sufficient Oil to Air End. (As there is no air pressure developed during unload condition, there was no heat generation and no extra cooling effect required)
02) Safety Valve
As name denotes this  is used for the safety of compressor and the manpower working nearby unit. The Safety Valve is adjusted to 10% higher than the Maximum Unloading Pressure (Check from name plate or Purchase Order). This can adjust by tightening the Pressure Transformer, tightening the pressure transformer inwards will increase the blow-off pressure setting and vice-versa (keep Delivery Valve open). Start closing the Delivery Valve till Safety Valve Blowing. Note the Air pressure at which Safety valve Blows, replace the cap and lock it.
03) Minimum Pressure Valve (MPV)

It is of extreme importance that Air Pressure is developed in the Air Receiver as soon as the Compressor is started, since this Air Pressure Circulates the Lubricating Oil to the Compressor unit through the Oil Cooler, Filters, Strainers etc. Here MPV plays important role and holds the required pressure. The function of MPV is to maintain Air Pressure of 4 Kg/cm square in the Air-Oil Receiver at load or unload condition.

04) By Pass Valve

This  is fitted in Oil Line between Receiver and Oil Cooler. When Oil Temperature is less than 80 degree centigrade, Oil Cooler is By-Passed and Oil flows directly from Receiver to Oil Filter. A Thermostat is fitted in By-Pass Valve to sense the temperature of oil. One Ball Valve is also fitted in Oil Line near By-Pass Valve. If this  is closed, Oil will always pass through Oil Cooler. If Thermostat fails to function, the problem can be temporarily solved by closing the Ball Valve.

05) Air Discharge Valve

This Valve opens when the Air at Discharge Port of Air End is more than Receiver Pressure. This Valve Remains closed during Unloading Condition when Receiver Pressure is more than Pressure at Discharge Port. Scavenging Air is absorbed through Intake Valve during Unloading Condition to make up for Air Venting out through Unloader Body. Mixture of Oil and Scavenging Air is passed through this Valve during Unloading Condition.

I hope the information above will help you to better understand the use of valves.


Some another useful posts…

Compressor: How Screw Compressor Works?

Compressor: Classification of Air Compressor

Compressor: Types of Air Compressor