Very High Weight on Supports

[micvanzyl]

Dear Friends,
I'm analyzing a 52" heavy walled (45mm thk.) gas export line with the design pressure of 100 bars.
Although I've tried so much to reduce the system weight applied on pipe supports, I'm not satisfied yet as I can't find the reason for such high loads in hydrotest (WW+HP) load case. I get the load arround 600,000N (HYD)/400,000(SUS) on some of the supports arround expansion loops. Specially I have one such a big load on a turnnion which is going to mount a 13m, 30" vertical riser of the system (connecting to the 52" horizontal line) which realy makes me worried.
I've checked for possible lift-offs and rectified all load unbalancies.
Please let me know your ideas...

 

[C2it]

A diagram would be helpful.

Are you not satisfied by the answers you got when you posted this same question on the Coade Forum yesterday ?

 

[micvanzyl]

However all active members here and in COADE forum have been always very helpful.
I'm not sure if I could manage to get them proper vision of my job and as you mentioned, a drawing can work best in my case.
Actually the file is in my company which I don't have access to at the moment.
I should be abale to supply one in the comming days.
Thank you

 

[SNORGY]

Double check the units for the fluid density.

I once entered 1000 kg/cm^3. Many "Piping Code Compliance Failed" messages later...

D'OH!

Doesn't sound like the case here though. If your vertical riser is expanding just enough to offload the next two supports either side in the 52"-D horizontal run, your dead load full of water might indeed be that high in some places.

Regards,

SNORGY.

 

[SNORGY]

The above said, expansion isn't included in the W+P1 case...

Are you running 60 feet between supports? I get something like 25.6 kN/m of pipe.

Regards,

SNORGY.

 

[micvanzyl]

Thank SNORGY you for your replies dear friends,

I've checked all load imbalancies in the supports and I don't have any lift-offs. The fluid density is not a concern here as you advised, because I'm having a gas service (With zero density) and the water weight for hydrotest is applied by the CII automatically in (WW+HP) load case.
The support span I'm using is 8 meters (~26 feet) but in some places where I have load problems (the expansion 3D loop and the risers) this 8m span can not be held. However, 8m span for such a big pipe is too small I guess.
I'll try to upload a drawing to get you and others clearer insight.
Thank you

 

[SNORGY]

I often find that the graphics animation output that CII provides is very illustrative towards honing in on how the system behaves.

Regards,

SNORGY.

 

[MJCronin]

For a heavy walled piping system with a massive 52" diameter, i would expect huge hydrostatic test loads.

I am afraid you have entered an area in piping design and stress analysis where temporary supports, just for the hydrotest, is the best solution.

Work with the field team, spot locations for temporaries, design them and then remove them after the hydro.