hi, we have three oil injected rotary screw compressors of Atlas Copco GA37. in one of the compressor, we are facing the problem of loud grinding noise and high vibrations when compressor runs in unloaded condition after 35 seconds. during loading cycle compressor runs normal. we have given external air supply to loading solenoid instead of air from separator and compressor found running normal. but when air hose is again connected to separator, same problem observed. we replaced air filter, oil filter, oil separator, all sealing kits of inlet valve, sealing of minimum pressure valve but problem didn't resolve. if you can give any suggestion what else can be done.
thank you
ankit vyas