Hi everyone,

I'm making desicion on purchase of a compressor for a compressor station. It is in a compact system without enough room. Temps are around 160C and 900 # . What i have ever worked with was 3 times of NEMA. But i think it is not enough for this case. As all 4. Nozzles are going to be checked, an interstage scrubber exists. Has anyone have any experience on this kind of compressors,please? The reason of this plant is keeping pressure of a reduced pressure well.
Thanks

Can anyone answer my question please? I don't have platform experience with compact piping system.
Thanks

Exactly what is your question?

If you need compressor that can withstand more than 3 tomes NEMA, contact NP GE. They usually build robust compressors.

Regards,

Be sure to agree with the vendor the location for resolution of nozzle loads. It is common on a 4-nozzle machine to use a point on the shaft centr-line, midway between suction nozzles. Also agree the basis for the Dc value used in NEMA computations. It could be nozzle ID or nominal and it can make a big difference. Nominal will allow larger loads.

With regard to load limits, Norsok allows 4x NEMA SM-23 It has been applied in the Norwegian sector for years so all decent manufacturers are well aware of it. Check what was agreed by the Mechanical Engineer with the vendor.

Moverz and Danb,
Thank you.
I should explain more, the story is that our client wants to construct an offshore platform to keep the pressure which is already reduced, I have never worked on offshore and that compact system, the layout is not complete yet, but as the money talks, they want to buy it not more than 3 times of NEMA, i want to know if anyone has any experience of this case and know if it is achievable or not.
As long as I know about the manufacturer, they consider the largest size the resolution point.
I want to know if it has happened successfully already or any recomendation on analysis if I couldn't convince them to pay more money.
Thanks

Hi,

I suppose that with Class 900, expansion joints are not an option.

As you explain, and based on NEMA SM-23 (and API 617) the reference point is the center of the biggest flange.
NEMA is a turbine code, it states loads are to be resolved at "centrelines of the exhaust connection", the centre of the biggest nozzle is chosen as resolution point.


It can be difficult to reach 3 times NEMA, but if your process guys let you put elbows which add lots of flexibility you can reduce forces and moments. Try to block the movements of the piping in the same planes as the fixed feet of the equipment.

You can also be precise in your modeling: instead of "infinitely" rigid supports, try to take into account their rigidity. The same applies to the compressor or at least the supports of the compressor.
With CII beam modeling possiblities, this is an option I would try for such a case.

Remark: I would say that NORSOK _requires_ 4 times NEMA from the equipment manufacturer, not "allows"

Cy / Timi,

The resolution point at the biggest flange assumes either that there is a larger one, or that it's a two nozzle machine. Frequently 4 nozzle machines has two suctions of the same size. Thus it is common to use the shaft centreline, at the mid-point as I described fro 4 nozzles. Really it does not matter provided both the pipe engineer and equipment manufacturer use the same basis.

I have designed compressor piping 24" diameter with 1.5in wall to 1.85 x NEMA and worse before. It's not too difficult with decent routing, supports and restraints.

Forget expansion joints, 40 barG is about the limit for those.

Finally, Norsok ... I do strongly approve of the Norsok approach to allowable loads on all equipment. However, it REQUIRES nothing. It is advisory only.

Moverz,
Thank you for your helpful responses,
I start the job hopefully Iget the answer. Though I have never worked with these temp and conditions before.
I may come back and ask for help as I'm too young not experienced enough.
Thanks everyone for answers

Hi Moverz,

I finished my job with checking all cases including allignment, but there is a problem! I couldn't get answer without large loops for the two high temp nozzles, is it unussual? The compressor manufacturer did not approved loops.
Is it unussual with situation that I explained above to have large loops?

Hi Moverz,
I finished my job with checking all cases including allignment, but there is a problem! I couldn't get answer without large loops for the two high temp nozzles, is it unussual? The compressor manufacturer did not approved loops.Is it unussual with situation that I explained above to have large loops?
Regards