capacity control in reciprocating compressors

[Rahju]

Which system of capacity control in reciprocating compressors is more reliable?
1.- Hydraulically controlled variable-volume clearance pocket
2.-Stepless capacity control system that uses finger-type unloaders pneumatically actuated. The system unloads the valve for only a portion of its stroke.

Does anybody have experience with any or both systems?
It seems that the second system could have problems of leakage by the shaft of the unloader.
What are the benefits and the problems of each system?

Thanks a lot

[Grizzly]

I cannot think of a recip with type 2 described. (Never ever heard of a pneumatic system before?)
Could you suggest what comps have such a system.
Grizzly

[Rahju]

the Peter Brotherhood comps.

[NoNickName]

Dresser Rand, as it is called now, does not produce refrigeration compressors.

[Josip]

Hi, Rahju

Which system of capacity control in reciprocating compressors is more reliable?
1.- Hydraulically controlled variable-volume clearance pocket
2.-Stepless capacity control system that uses finger-type unloaders pneumatically actuated. The system unloads the valve for only a portion of its stroke.

Does anybody have experience with any or both systems?
It seems that the second system could have problems of leakage by the shaft of the unloader.
What are the benefits and the problems of each system?

Thanks a lot

Seems you are using those compressors for process gases like nitrogen (air), LNG or similar and probably they are oil free compressors which we are not using in refrigeration except Danfoss Turbocor centrifugal compressor ...

Sorry cannot help...


Best regards, Josip

[Rahju]

It is true,This compressor is used to compress hydrogen.


Thanks a lot for your kind answer,Josip.

[D.D.KORANNE]

Frequency drive could be a solution ............... How will u signal the compressor to lower the speed , a feedback device such as pressure transducer would be required . Compressor not part of refrigeration system hence further expertise will be needed from compressor manufacturer