Understanding Surge Control for Centrifugal and Axial Compressors

Before the holidays, ModelingAndControl.comControl Talk blog’s Greg McMillan had another set of eBooks, Centrifugal and Axial Compressor Control Student Text and Instructor’s Guide. These books were originally published in 1983 and the copyrights were returned to Greg.

As described in the “About the Book” section, the text is geared for instrumentation and process control design engineers. The text describes:

…the surge phenomena and illustrates the effect of the operating conditions on surge. Covers various methods of throughput and surge feedback control. It explains the need for preprogrammed open-loop surge control and describes newly developed methods for implementation and coordination with feedback control.

Greg was recently asked by a colleague how surge control might be applied in automation systems like the DeltaV system. He responded:

DeltaV provides an excellent solution for nearly any control system that prevents surge by the manipulation of a control valve if you make the execution time of the module 0.1 to 0.2 seconds so that it is much faster than valve. Surge control valves have a response time of 1 to 5 seconds. Also, you should configure an open loop back in the DeltaV module because once a compressor gets into surge a feedback PI loop can’t get it out of surge no matter how fast it is due to the flow reversals every couple of seconds. The open loop back up is simply a CALC block in DeltaV that puts the PI in ROUT and increments the surge valve position when activated. When deactivated it returns the PI to its preferred mode. The trigger for activation is a crossing of a line between the actual surge curve and the surge controller set point allowing for some error in the knowledge of the surge curve. The clear point for deactivation is a point well to the right of the surge controller set point for at least a couple of seconds.

This set of eBooks joins his other freely available eBooks:

If your process includes centrifugal or axial compressors, you may want to take a look these latest additions to the eBook library.

Update: Thank you to the new, aspiring engineer for alerting me to the broken links. I’ve updated them. All of Greg’s free eBooks are available in the archived books section of ModelingAndControl.com.

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