Centrifugal Compressor

[asghar]

I have to develop specifications for procuring a cetrifugal compressor that should raise the Natural gas pressure from 25 psig to 400 psig.

A sample technical spec sheets would be of great help. Any other material or technical advice shall also be appreciated. The Natural Gas Sp. Gr. is 0.65

 

[1969grad]

Are you sure you want a centrifugal and not a recip? Compression ratio is 10.4 which is considerable for a centrifugal compressor.

For specs and data sheets see API 617 or 618.

 

[stewbaby]

Contact vendors such as Ingersoll-Rand, Kobelco, GE Power...and get a copy of there spec sheet and modify to fit your needs.

Try the Process Associates web site for a handy calculator to see if centrif is even feasible...

http://www.processassociates.com/process/rotating/centri_s.htm

 

[asghar]

1969grad and stewbaby,
This is what I have been asked that it should be a centrifugal compressor. I had made a run on the Processassociates and came up with 3 number of stages but the flow rate has decreased as the stages increased. I have a feeling that I made some boo-boo in runing this program and also this program seemed to be a preliminary type as compared to Ariel program available for reciprocating compressor. I wonder if a compatible program is available for centrifugal compressors.

1969Grad, I do not have a copy of API 617 or 618, incase anyone has, will appreciate of mailing me the spec sheet from it.

 

[TD2K]

You will be looking at a 3 stage centrifugal with intercooling. I ran some quick numbers and the dT is too high with a stage machine. Centrifugals are limited to 300F or so discharge temperature as a rule of thumb.

Have you got a copy of the GPSA Engineering data book? You shouldn't be sizing the compressor, leave that to the vendor. You can do some rough number crunching that will give you the number of stages, approximate discharge temperature and Hp required.

If your flow is decreasing as you add stages then the Processassociates program is using some sort of built-in correlation for their compressors. A vendor will be able to design their unit to add the dP you need at the flow you need.

 

[1969grad]

API specifications are copywrited which means you have to buy them. If your company can afford to buy the compressor then they can afford to buy the spec. It is the cost of doing business.

 

[1969grad]

Ran the processassociates program. First thing I noticed was the compressor head per stage: 39,000 (first), 42,000 (second) and 42,000 (third).

Each compressor wheel will develop about 12,000 feet of head so you can see how many wheels you will have for each stage.

To do this in one compressor means you are going to have to use a process type compressor with side streams in and out. If your flow rate is not constant then control is going to be a nightmare.

Alternately, you would have to have 3 compressors operating in tandum with a single driver or 3 separate compressors.

If your application is gas transmission then a process type compressor is not a good choice from an efficiency standpoint in addition to the above.

You do not give the flow rate to know if a process type compressor would fit as too small a volume will eliminate consideration of a centrifugal.

Looks more and more like a recip application to me.

 

[pmover]

asghar,

i highly recommend that you sondier hiring a skilled rotating equipment engr that will provide you the equipment that is needed.

as a minimum, defining the process fluid, process conditions, preparing specifications, and preparing data sheets is the first step in procuring a compressor.

yes, you can conduct preliminary sizing of compressor; however, the best and prudent decision is to allow the experts (manufacturers) design the compressor based on the stated process conditions. the mfg reps will gladly assist you with the preliminary sizing and selection; however, you or the responsible engineer must specify the process conditions to obtain the best equipment/solution.

based on pressure data you provided, td2k comments regarding intercooling are valid regardless of compressor type and this is a consideration for the mfg to know. what is more critical to know/specify is flow at stated temps and pressure for specified fluid.

bottom line recommendation, hire a skilled rotating equipment engr to handle the matter (there are plenty of them in houston). the skilled individual ought to be able to provide you preliminary and reasonably accurate results within a week or so.

oh, API 617 "...centrifugal compressors ..." spec is the std for specifying centrifugal compressors and the document and accompaning data sheets are not free. sorry! for purchase, try

http://www.api.org.

good luck!
-pmover

 

[Hookem]

If you have not sized a compressor in 33+ years, hire a consultant! API Specifications are the real go-by for production, transmission and plants, be they recip. or centrifugal. Centrifugal are very limited in compression ratios and in operating range flexibility. Recips are much better in both areas, but carry their own sets of challenges, not the least of which is pulsation and resonance, both with the piping, but also in the foundation.

 

[RotaryG]

Asghar,

Whichever compnay you work for, I am sure that your compnay has on its roles at least a junior rotary engineer! If not you must hire one. You also need to clearly define your predicament. Data provided by you is incomplete, hence the responses you get will either be generic or inaccurate for your need.




Regards,

Guru

"Evolution rather than Revolution"