The fluid used as a source of actuating power against the underside of the unloader power element piston of the refrigeration compressor capacity control mechanism illustrated is obtained from where? GS-RA-13 Illustration GS-RA-13: the U.S. Coast Guard has not released this illustration.
Official USCG Answer & Rule Citation
Correct Answer: Option D — discharge of the compressor lube oil pump
Hydraulic capacity control mechanisms on reciprocating compressors utilize high-pressure lube oil discharge from the compressor internal oil pump to act against the underside of unloader pistons, moving them to lift suction valve plates and disable cylinders.
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