Try to turn the compressor by hand. It should be possible to turn it around. It should turn around smoothly, without any 'hickups' (be sure to completely shut down the air compressor!). Check the isolation of the motor windings.
[pdf] Displacement (m³/min): It refers to the volume of air discharged by the compressor per unit of time, also known as flow rate or volumetric flow rate. Discharge pressure (MPa): It indicates the pressure of the air at the compressor’s outlet, usually measured in megapascals (MPa).
[pdf] A screw air compressor is very similar to a human heart. While a human heart has tricuspid, pulmonary, mitral, and aortic valves, a screw air compressor has four critical valves namely air inlet, minimum pres.
[pdf] 
