Checkout Current Transformers (CTs) and check resistance across each one while it is disconnected. All resistances should be within 10% of one another. Also do a diode test on the CT inputs on each compressor module. (The diode test is described in RTAA-SVB10B-EN.)
[pdf] Even with an air dryer, some moisture will still accumulate in the compressor system. That's why it's crucial to regularly drain the condensate. Most screw air compressors come with automatic drain valves, which are set to open at specific intervals to remove the accumulated water.
[pdf] As a kind of friction clutch that uses compressed air as manipulating power source, pneumatic-tyred clutch is widely used in such equipment as oil drilling rig and workover rig, and is also an important part of the drive systems of oil drilling rig and workover rig.
[pdf] 
