Compressor Operation and Capacity Control
Starting Reciprocating Compressors
The work of compression is actually done in less than 180° of each rotation. Therefore, rotating inertia must be built into the power train to obtain a uniform power draw from the prime mover. The stored energy must be put into the system before compression starts; otherwise the prime mover will be overloaded.
The compressor is unloaded to start, either by suction valve unloading or through a valve bypass from discharge back to suction.
A popular means of suction ...