Nozzle thermal displacement

[Dj364]

Hello every one,
I have received old existing drawings ( turbine/compressor).
I have to set turbine nozzle initial ( thermal) displacements in my analysis.
I am reading on drawing " center of gravity". this point is shown on the compressor side. ( turbine and compressor have the same foundation).
My understanding is, the center of gravity means the anchor point from where I shall refer all the nozzles thermal displacement.
Just to be sure, Please confirm if I am right.
Your help will be very well appreciated.
Thanks in advance.
Dj.

 

[BigInch]

Center of gravity is used for lift rigging and foundation design ONLY and has nothing to do with thermal analysis.

Use shaft centerlines for calculations of lateral expansions. Longitudinal expansions can be calculated from an on-skid thermal anchor, if one has been placed by the mfgr.

http://virtualpipeline.spaces.msn.com

 

[Dj364]

Thanks BigInch,
The Dwgs I have, don't show any anchor point.For vertical expansion, I Assumed it from the level grade ( package/skid mounted 1.6m). it s important for me, because I am putting a spring hanger just close to the nozzle, therefore the thermal displacements affect the thermal movement of the spring (travel).
for longitudinal movement as well, is important because the height of center line piping is at 1.8m .
I have asked about the anchor point, they (client) don t have further informations.
Is my assumption correct for vertical displacement?
Thanks again,
Kind Regards.

 

[BigInch]

Oops, I didn't say anything about vertical, but yes you're right to use the base plate as the reference for vertical expansion.

For longitudinal expansion, without any defined anchor point, you might be able to set a reference at the centerline of (or maybe the centroid) of the main anchor bolts.

http://virtualpipeline.spaces.msn.com

 

[DSB123]

Dj364,
I would ask the Client to provide the information for the thermal displacement of the turbine or revert to the Manufacturer. It's normal for the thermal displacement of the nozzles to be on the drawings but if they are not then you need to ask because you do not know the temperature distribution within the equipment body and could overestimate/underestimate the thermal movements.
You say you are replacing a spring close to the turbine. In the original installation the probability is that the last thing done was to adjust the springs/supports (with spring un-blocked) until the piping aligned with the turbine nozzle, thereby minimising the equipment loads at installation and ensuring that un-anticipated variations in weight are accommodated. Is this being done during replacement of the springs?
Another point is are you sure that there was no cold pull used in the original installation (which could now be partly/totally relaxed) which needs to be considered for equipment loads?

 

[JohnBreen]

DJ,

By the way, there is a very good manual that was written by General Electric that provides pipe design guideines for designing piping for medium and large turbines.

I have seen in the past on one of the discussion forums that it was offered as an electronic file. You might be interested in looking around the Internet to see if you can get this manual.

Regards, John