Suction line arrangement for centrifugal/reciprocating compressors

[JustSomeRoark]

Gents,

What are the requirements of the suction line of a centrifugal/reciprocating compressor? I have been having a discussion with a colleague about this and we would appreciate if someone could shed some light on the issue.

From his point of view, no pockets + free draining towards suction KOD is required, in order to prevent any potential condensate draining into the compressor when the machine is shutdown.

From mine, no pockets and maybe free draining (but not mandatory towards suction KOD) would suffice, considering that if the machine is shutdown and some liquid condenses, it may drain towards the KOD or the casing of the compressor, where it will be drained prior to startup. In fact, for top entry machines a (short) part of the suction line will definitely drain into the compressor, and in case of reciprocating machines with pulsation dampeners, any liquid that may condense in the dampener (its volume may be larger than the suction line) will actually be routed to the machine. I understand that the critical requirement is that no pockets exist where liquid may collect (and cannot be drained), leading to a slug occurring upon restart up of the machine. In summary, no pockets + free draining is required, but a high point may exist in the suction line.

Thanks for any feedback that may help to settle our discussion!

Regards.

 

[1503-44]

Some other considerations may apply if you have valves and stuff.

https://whatispiping.com/centrifugal-compressor-piping/

https://duckduckgo.com/?q=compressor+suction+piping+arrangement&t=brave&ia=web

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[shvet]

no pockets + free draining towards suction KOD is required

Design this kind of is less prone to human factor during detailed design, construction and operation while the cost is the same. There should be an argued reason to implement a less reliable design.

 

[JJPellin]

It is not so simple. I have seen recip and centrifugal machines run to destruction from liquid even with well designed suction piping. Process conditions, machine design and piping design are all important.

Johnny Pellin

 

[georgeverghese]

In a recip compressor, would expect the dampener would be free draining if it is to work as intended. If so, keep the bottom exit line from dampener to compressor as short as possible to prevent further condensation. Line from suction scrubber/KOD to top or side entry nozzle on dampener to free drain back to KOD.