Key things to look out for Centrifugal Compressor Selection

[planck121]

Hello Gents,
Considering the senerio of being a project engineer on rotating machinery. What are the key things one should look out for during selection of centrifugal compressors. To name a few that I think critical are...

* The range of operation would be quite critical. Selecting a compressor based on a set of few operating points.

* Number of stages would be important too because the bearing span should be kept to a minium for a given speed to keep the critical speeds at a higher range and avoid dropping the criticals to lower speed.

*) Mach number and tip velocities at the blade should also be addressed and preferebly kept below a certain number (i.e Mach 0.95 and tip velocities below say 270m/s

* polytropic head per stage should be limited to a certain value

* Gas temperature should be below a certain value to avoid thermal issues....

What other key critical things should be looked into for compressor selection standpoint. Perhaps rotordynamic stability is important....

Thanks

 

[pmover]

. . . hire a skilled rotating equipment engineer. otherwise, you'll be sorry.

there are more factors to consider and evaluate than mentioned. the lack of data supplied by you leads one to conclude that you need the help.

good luck!
-pmover

 

[DLite30]

Take a look at the data sheets in API 617, that will give you a pretty thorough idea of most of the design parameters to be considered.

And it makes a huge difference how deep you want to delve in to the "design" aspects of the machinery, depending on if you're the end-user, packager, or the manufacturer, which are you?

 

[jbattershell]

selecting compressors for an application, you should leave many of those items listed above to the actual OEM. items such as number of stages, mach number, gas temperatures are to be figured out by the experts at the OEM. you need to be focused on getting the correct flow and pressure requirements for the application. knowing the process at your plant in and out will be the best preparation for selecting a compressor.

trying to fill out the first couple pages of the API-617 data sheet will give you a good idea of what you need to know about your process to help compressor OEM's properly size the equipment. in addition, you need to have a thorough understanding of what other types of equipment are needed on the compressor such as: what type of instruments, how many valves do you want supplied by the OEM, how much piping do you want the OEM to handle, how many coolers do you want the OEM to supply (all of them or only the intercoolers), how much redundancy do you want in your equipment and instruments?, do you want the OEM to include a control system or is your company doing that?, where is the location of the control room and do you want local control or only remote control of the equipment, and on and on.

take care,
John

 

[rakuday]

In addition to jbattershell's comments, first you should check if the proposed compressor meets your capacity requirements. Have you considered sufficient safety factor in stating your capacity for future growth (expansion plans) of the applications. Losses and leaks from the compressor to the point of application.

Also, check the energy efficiency of the compressors, this will greatly impact the life cycle cost of running the compressor.

 

[CaracasEC]

Vendor experience list with the same application is also an important parameter. Stability, pressure rise to surge are also important..