7 replies to this topic

[Ghasem.Bashiri]

Dear All

I have some Centrifugal Compressor to compress 1000 MMSCFD Natural Gas.
Is there any general rule or practice for Piping design in suction line of compressor from KO Drum to inlet of compressor. I mean No Pocket, Top entry, Slope to KO Drum or any other requirement.

I prefer some Code or Good Practice.

[Erwin APRIANDI]

Dear Ghasem.Bashiri

First, the size required for lines attached to compressor is determine by the gas velocity inside the lines, the gas velocity inside the lines must be limited to remain within acceptable vibration ranges. and in case of low suction pressure, the pressure drop may sometimes be a limitation, in this case, the pressure drop criteria will governed the line sizing.

Second, for the piping design for the suction and discharge line, no pocket is required.

Third, the minimum straight length of lines of suction and discharge line is defined at minimum 2D for suction and and 1D for discharge

Forth, in case of any check valve installed at the discharge of compressor, the valve shall be located close to the compressor discharge

That's all I know, anyone to add

Edited by erwin.apriandi, 25 August 2010 - 09:33 PM.

[Ghasem.Bashiri]

Dear all
For No pocket item, in which side? No pocket to KO Drum or No Pocket to Compressor inlet?
Also note to compressor Inlet nozzle that can be horizontal or vertical based on compressor model.
Also Load of Inlet line to compressor nozzle is another issue.
With these issues what is your proposal for Inlet line arrangement?
Ghasem Bashiri

[Erwin APRIANDI]

Dear Ghasem,

First, I hope you understand the term of no-pocket (I've attach some skecth for more understanding). The no-pocket requirement is between the outlet of suction scrubber to the inlet of compressor, and from the discharge of the compressor to the downstream equipment.

And yes, the compressor inlet nozzle will depend on the manufacturer standard, some of them having the inlet nozzle at the top, and some of them will be on side.

The issue of load on the inlet line will be resolved by a piping stress engineer, and this also will be a part of compressor package guarantee. We process engineers will only give our input in case of any problem occurring after the study or analysis.

Attached Files

•  Pocket.xls   29KB   333 downloads

Edited by Art Montemayor, 01 September 2010 - 06:52 AM.

[theleftcoast]

Hello erwin.apriandi,

Can you expand on the following section from your post:

First, the size required for lines attached to compressor is determine by the gas velocity inside the lines, the gas velocity inside the lines must be limited to remain within acceptable vibration ranges.

I don't know much about vibration caused by fluid flow in piping. Can you point me to a resource or add your comments about fluid flow related vibration calculations?

Thanks,
JT

[Erwin APRIANDI]

Dear JT,

understanding regarding to the pipe vibration you can find in piping design engineering handbook.
some handbook that I've read is : Piping and Pipeline Engineering Design, Construction, Maintenance, Integrity, and Repair By: George A. Antaki.

For the guideline of sizing the inlet and outlet line of rotating equipment, mostly some engineering company will have their own guideline. Which I can not share in this forum since it is a proprietary item

Hope This Help

[theleftcoast]

Hello again erwin.apriandi,

The book is available for preview on google books and is very helpful. Thanks!

Piping and Pipeline Engineering Design, Construction, Maintenance, Integrity, and Repair By: George A. Antaki

-JT

erwin,

1. A general guideline of not to exceed density x velocity ^2 value of 15000 (SI units) can be considered.
2. No pocket is definitely required.
3. Consider the suction line chemical cleaning requirement. Should be able to do that without disturbing the compressor flange. Hence removable spool at the compressor end is required (preferably with elbow). For the same reason, a removal spool with elbow can be though about with the suction KO drum. A high point vent can be considered.
4. Think about the instrumentation with the compressor suction line. In case, you are considering flow element (say venturi) in the suction line, think about liquid draining, (either by sloping or provide a drain) after chemical cleaning. Also these instruments require upstream and downstream straight lengths. This shall be marked with P&ID to communicate to piping.
5. Consider on leak testing the compressor suction piping during commissioning. You should be able to isolate the compressor with isolation valves so that the compressor need not be pressurised during leak testing. The compressor isolation shall be minimum distance to compressor.

Hope this helps you.

Arap