All,

I'm now doing pipe stress analysis connected to 3 stages reciprocating compressors. What i'm doing for checking nozzle loading at Compressors is calculate 3 stages separatly in term of NEMA check as follows:

1. Nozzle inlet TO 1st stage and nozzle outlet FROM 1st stage (combine)
2. Nozzle inlet TO 2nd stage and nozzle outlet FROM 2nd stage (combine)
3. Nozzle inlet TO 3rd stage and nozzle outlet FROM 3rd stage (combine)

Should all 3 inlet nozzles and 3 outlet nozzle be checked together in 1 calculation in term of NEMA check and combine all of them together. So, I add 3 nozzles inlet and 3 nozzles outlet at NEMA CII software.

appleapple,
Is your analysis for flexibility and nozzle loading based on thermal expansion and loading?

or

Is your analysis for acoustical and mechanical vibration and the proper location of "Hold-Downs"?

If you have the nozzles in the same compressor case (body) you have to combine them. If not, you will check them separately.

Regards,

I don't think you need to check the nozzle load against NEMA. NEMA is for centrifugal compressor (1xAPI617=1.85xNEMA). For reciprocating compressor, acoustic pulsation/mechanical response analysis is main concern which will be conducted by the vendor. The vendor will be providing allowable nozzle load at the interface (usually flange).

Regards

Job,

My analysis is for flexibility/stress and nozzle loading check..

danb,

Thanks for sharing, i think so, if nozzles located in the same case/body, i have to combine all of them.

Hello All,

I have a 3 stages Centrifugal compressor. But API 617 CAESAR's module is only for 2 stages. Can I set it up for 3????
Or I should do it all by hand??

Thanks!

Ohhhh, I was thinking. Can I use the NEMA module and consider the 1.85 factor???

Is your compressor a conventional layout with three machines on the same shaft and driver or not ?

Assuming that it is conventional and your 3 stage compressor has three pedestals, albeit on the same frame, they are separate units in terms of NEMA and should be considered as 3 separate calculations.

If it is actually one machine with six nozzles, then sharpen your pencil and warm up the old Casio.

Actually, 'Pipemill' software handles six nozzles in its NEMA calc.

By the way Alessandro, you should have started a new thread with your question.

I see that Caesar's NEMA SM23 module seems to be able to handle even more, but I think that the best thing to do is to ask the vendor about the allowable.

HEHEHE, you are right Moverz, I will start a new thread.
Do you mind copying your previous answer there??

Dan,

The vendor attached a nomogram based and that suggest to use API617 or 1.85 NEMA

Then use NEMA with a factor of 1.85

Instead of sharpen my pencil and warm up the old casio, I am creating an excel worksheet to compare this values, against CAESAR's NEMA module, considering the 1.85 factor.

Will let you know what happens...cheers!

Sorry, I've been busy.

I used NEMA’s CAESAR analysis module using the 1.85 factor and compare to the excel spreadsheet based on API617, I got the same values. Send the loads to Elliot for evaluation and everything workout just fine.