The proposed presentation will show the steps involved in the design and implementation of a reliable and cost-effective surge control system for centrifugal compressors. The paper highlights the basics of surge control system design, instrumentation, and guidelines for a controls retrofit and field testing. Surge and choke control as they pertain to the Cracked Gas Compressor, Propylene Compressor, and Ethylene Compressor will be addressed. Special attention will be given to process upsets that can cause surge and choke events in the compressors, and how a properly-designed control system can ameliorate the impacts caused by these upsets. Events such as a furnace shut-down can cause the Crack Gas Compressor to shut-down if the surge and performance control system is not adequately designed. A trip of the Propylene Compressor can cascade to the Ethylene Compressor and shut it down unless its Compressor Control System can use appropriate feed-forward signals to prevent that occurrence. Proper algorithms provide handles for the compressors to ride through upsets, rather than have overreactive control responses that lead to shut-downs or cause process instability.
Actual design and implementation of surge control systems will be illustrated with two successful field installations: 1) A turbomachinery surge control system for a gas fractionation plant with refrigeration applications done as an integrated control system, and 2) A surge control and loadsharing control system for two parallel mixed-refrigeration compressors in an LNG plant.
This tutorial content is meant to target rotating equipment, reliability and instrumentation engineers, and process engineers working in ethylene plants as well as other industries that make use of centrifugal and axial compressors. The material covered will be technical in nature, and it will be a good source of training material for new engineers, and a refresher for experienced engineers.
