Increasing Compressor Balancing Line Size

[MQM90]

Dear All,

I am confused that if a compressor balancing line size is changed and modified from 3 inches to 6 inches what more I can check after performing the stress / flexibility analysis.

I was thinking regarding the process checks like high velocities and pressure drop, but these have already been checked by Process Engninnering Department.

Any suggestion regarding mechanical checks ?

Line temperature is 105 deg
Line pressure is 158 kg/cm2g

Appreiciate your comments please.

Osama Nusrat Ali

 

[BigInch]

The requisition, construction spec, time of delivery and the welding and hydrotesing.

**********************
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[MQM90]

Hi BigInch

I meant any experience as follows:

1. Common sizes for balancing lines ?
2. Recommended support type for balancing lines or no supports are recommended on balancing lines ?
3. Type of weld connection not be used ?
4. Any additional thing that is to be avoided ?

Osama Nusrat Ali

 

[BigInch]

1 & 2 Depends on type of compressor, length of pipe, flowrate. Some support may be needed on recip compressors, but not on centrifugals.

Pipe lengths with naturally resonant frquencies should be avoided with recips. With recips it is often better to avoid equal support spacings as well.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[MQM90]

Hi BigInch,

My compressor is centrifugal and there are existing weight type supports installed. According to your reply it seems the centrifugal compressor lines shouldnt encourage for supports. So should i check my piping without supports ? Moreover it is my idea that a balancing line shouldnt be more than 4".

Please advice.

Osama Nusrat Ali

 

[MQM90]

Waiting for somebody to rule out my issues?

Osama Nusrat Ali

 

[pmover]

MQM90,

you need to direct your request for changing the centrifugal compressor balance line size to the compressor manufacturer.

you also need to provide a justification for requesting the change.

"process checks" and "high velocities" are not not a valid concern for making changes to balance piping size changes.

you need to understand the purpose of the balance piping system on a centrifugal compressor. multistage centrifugal compressor rotors typically have thrust forces that need to addressed and this is done by installing a balance line and a balance drum. these components counteract the thrust forces created by the impellers, thus minimizing thrust forces.

hope this helps.
-pmover

 

[MQM90]

Thankyou very much pmover.

Can i confirm one more thing.

My compressor manufacturer is not very cooperative, but i am trying to check that a 6 inches balancing line can solve their issues or not ? My process guys have accept the line size and have their concerns. I have also checked its flexibility.

Is there other thing particularly regarding its size to be checked under flexibility ?

Osama Nusrat Ali

 

[pmover]

MQM90,

the equipment seller or compressor mfg determines the requirements (i.e. size, etc.) for the equipment being manufactured (i.e. balance line). any equipment failure or malfunction resulting from an improper balance line size or flexibility is the responsibility of the designer (i.e. compressor mfg), not the operator unless a deliberate misuse is done by the operator (cannot imagine why).

i do not understand "Is there other thing particularly regarding its size to be checked under flexibility ? " if asking if there are other issues/concerns regarding the balance line size and flexibility, i am not aware of any.

good luck!
-pmover

 

[MQM90]

Thankyou pmover.

This was a great help atleast i am sure that the requirements related to line sizes to be sorted with compressor mfg.

pmover, i want to confirm do you have some experience that centrifugal compressor of multistage type, is checked for all its intermediate nozzle connections or simply the main inlet and outlet connections are checked against API 617.

Osama Nusrat Ali

 

[pmover]

all compressor nozzle connections have load limits (external forces & moments) that are not to be exceeded and the load limits are hopefully provided in the purchase agreement (api617 or otherwise). the responsible design piping engineer (stress analysis) needs to ensure the piping system external loads do not exceed the limits as agreed to in the purchase agreement, whether or not per api617 or otherwise.

good luck!
-pmover