What are the parts of refrigeration compressor?

The parts of a hermetic (sealed) reciprocating compressor is as follows; motor, crankshaft, bearings, valves, and pressure relief valve and piston(s). there are other smaller parts that can be named but these are the main players.

The hermetic scroll compressor is a little different than the reciprocating compressor because it uses an orbiting scroll and a stationary scroll to compress the refrigerant instead of pistons. This is why a scroll compressor cannot run "backwards". The scroll compressor also has an oil pick up tube which differs from a reciprocating compressor.

Now a "semi-hermetic" compressor is build like a small engine. It has an oil pump, reed valve plate, unloaders, pistons, bearings, etc.

A screw compressor is in a class all to itself.