Centrifugal compressor pressure

[Serkancan]

Hi ,

We have an 5 stages centrifugal compressor 265 psig design pressure 13000 m3/h , isi possible to decrease the air pressure to 100 psig by omitting one or more stages from the compressor ?

regards,

 

[LittleInch]

Maybe.

Ask the vendor as you will need special dummy stages to maintain shaft balancing and dynamics.

It will be the higher pressure end you take off first. You might not get to exactly 100 psi unless you modify the last stage.

Or maybe get 5 smaller stages.

Got anything more ( vendor, model number, sectional drawing, that sort of thing.

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[rotw]

Exit volume flow will increase by a factor 2~3. Probably velocity will be around 80~100 m/s. Not as critical as it is for the inlet but something to investigate.

If you plan an escape, you must succeed as if you fail, you will be punished for trying. Never say or write down your plan. Heart is the only place where secrecy is granted.

 

[LittleInch]

The devil is in the detail alright and yes the increase in velocity could limit the flow.

You don't normally change down pressure.

Only the vendor can really tell you.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Serkancan]

Model is Centac 70- MX5

Regards,

 

[LittleInch]

Can you double check? Got any details.

It's not coming up on the IR website, but C700s are, but not matching your specifications

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Serkancan]

You can check the spec

Regards,

 

[rotw]

Looks like it is an integrally geared compressor with 5 pinions. Some speculative options I could think of:

Maybe you could investigate a change of HSS/LSS (pinion/bull gear) speed ratio by modifying the gear diameter ratio while still keeping same number of stages. By spinning at lower speeds, the stages flow coefficient will reduce, thus efficiency will decrease. Moreover all impellers will need to be changed because of resulting flow coefficient mismatch.

The other option is to "short cut" the flow path at the exist of some intermediate stage and then blind flange the following stages and equipment downstream.

I suppose that these units are pre-engineered, it might require engineering efforts and a feasibility study to be done by a consultant specialized in retrofit (if not done by the OEM).

If you plan an escape, you must succeed as if you fail, you will be punished for trying. Never say or write down your plan. Heart is the only place where secrecy is granted.

 

[LittleInch]

Looks pretty old... Do you know how old?

Is that all the info you have? 265psi looks like a design pressure, not an operating pressure. You need operating data / compressor curve.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

Generally speaking, for a new design, you should be able to get 100psig on a 3 stage centrifugal - I've assumed polytropic eff of 80% on all 3 stages, which should be possible for the volume rates you've got. With a 4 stage, it shouldnt be a problem. Compression ratios I get are 2.6 on stage 1 and approx 2.2 on stages 2 and 3. Intercooler temp is 45degC for all 3 stages, which should be possible for most climes. For an existing machine, how do you plan to "delete or make do without" 1 or 2 stages on a 5stage machine? Bypassing one or more stages by external piping modifications can result in rotor imbalance.