PARALLEL COMPRESSOR CONTROL - WHAT SHOULD BE CONSIDERED

This paper is concerned with the control systems for parallel compressors which found many applications in processing industries. Most common, perhaps, are refrigeration compressors in ethylene and propylene plants. Frequently three or more compressors are in parallel providing suction to a second pair of compressors in parallel. This configuration illustrates control problems which are uniquely associated with parallel compressors. In each set of compressors, one is a spare in standby having automatic startup controls. The discussion is presented under headings - main sources of problems and their consequences; objectives of control; control related to process demand (capacity); control related to surge protection; particularities of parallel compressors; anti-surge considerations; automatic start-up. The authors recommend that control systems for parallel compressors be designed by dynamic simulation done by a hybrid computer.