This is one of the Q&A topics I'm collecting about compressors and antisurge control. Will post them here from time to time to discuss with the community.
What's the difference between centrifugal and reciprocating compressor from the control system standpoint?
From time to time I receive requests for an advice or even a detailed design for reciprocating compressor automatics. I guess it's a good idea to describe here the difference between compressors and compressors.
The question can be stated a bit broader: what's the difference between dynamic and positive displacement compressors?. Dynamic compressors are centrifugal and axial. They operate by transferring momentum to the gas via a high-speed rotor (1). It's a device that has an open internal path. If you fix the shaft, you can blow it through from one side to another in both directions, no matter if it's axial or centrifugal. It compresses the gas by increasing its speed and then converting it to pressure in the diffuser. Positive displacement compressors are reciprocating, screw, vane and scroll types. They collect a fixed volume of gas within a chamber and compress it by reducing the chamber volume (1). A displacement compressor has some sort of a mechanical part inside that would block the internal passage and would not allow you to blow it through. That mechanical part can be a screw or a piston or any bent piece of metal of various shapes. It is something that's used for reducing the gas volume, thus increasing its pressure.
The foregoing basically means that a dynamic compressor can surge and a positive displacement one can't. A surge is a consequence of compressor stall. You can very briefly read about it here or more detailed in this Wikipedia article. When a stall occurs in the dynamic compressor, it suddenly has no force to resist the pressure raise it was creating all the way before. So, now the gas starts moving in a direction determined by the natural forces - from the area of higher pressure to the area of lower pressure, in this case, from discharge to suction. A positive displacement compressor is not prone to stall and it has an internal obstacle on a way of a reversed gas flow so it can't surge.
What I always have to answer is that a reciprocating compressor doesn't need any special treatment. Just consider it being a pump. You need to start and stop it properly, design safety valves and vibration measurements in the right places and make sure it's constantly sealed and lubricated. A volumetric flow rate of the gas in a positive displacement compressor is just a volume of its chamber multiplied by the number of the piston movements per minute (second, hour, whatever) or vane/screw rotation frequency. If you want to change the throughput, somehow you need to change the crosshead or shaft rotation frequency. That's about all you'd need to consider about positive displacement compressor automation.
Mechanically reciprocating compressor is a more complex device, but from the control automation standpoint it's way simpler than centrifugal compressor.
(1) a definition by MARKS' Standard Handbook for Mechanical Engineers