Check the isolation of the motor windings. Should be in the mage-ohms (you need an isolation tester / high voltage ohm meter for this). Check the voltage when the compressor is running. If the voltage drop significantly when the compressor starts/runs, you have a bad connection somewhere.
[pdf] Install the valve with proper positioning of the flow arrow. Support and align adjacent piping and the vale. Install lubricated flange bolts. Hands tighten, and then torque the bolts using the crossover flange bolt-tightening method to load the bolts evenly, and eliminate concentrated stresses.
[pdf] A drill pipe float valve, also recognized as a non-return valve, is a specialized valve installed in the bottom hole assembly (BHA) and its primary function is to serve as a check valve, permitting the downward flow of drilling mud through the drill string but preventing any unwanted fluid from flowing back up into the drill string.
[pdf] 
