Installing pipe supports onto a pressure vessel?

[acrmnsm]

20" diameter pipe, one of the supports has been specced by the piping designer as welded to the pressure vessel below (no actual relationship between the pipe and the pressure vessel) .
This strikes me as bit odd, but perhaps there is a good reason. Has anyone ever come across this before?

 

[RVAmeche]

Did the designer provide anticipated loads on the support? I'd be worried about it potentially causing issues with your vessel.

For a pipe that size it doesn't seem like a good idea, but I'm not sure if it's forbidden.

 

[XL83NL]

Arent tall columns (or towers), with large overhead or gas-out lines, sometimes supported on the top of the column?

 

[RVAmeche]

That's a good point. I haven't worked with a lot of columns, but I imagine there's an pipe anchor at the base of the column to limit it's growth/impacts on the vessel?

 

[acrmnsm]

Yeah the vessel has been designed and certified, and then the piping designer has added the support later. Its still in the design phase but he is adamant it is standard practice. I am only an observer but there is some consternation amongst the older pipers here.

 

[RVAmeche]

Ah, that's a bit of a different scenario. If you aren't the vessel manufacturer, I'd definitely provide the loads & support location to them and verify it's acceptable. If the vessel wasn't designed to accommodate that load, I'd be very wary.

 

[EngrPaper]

RVAmeche, its usually supported on the top and guided down the length of the column in order to prevent a buckling load on the pipe itself.

 

[Geoff13]

If your situation is like the picture posted by XL83NL, then it's pretty typical (including the pipe trunnion at the top support). As a vessel designer I would have been asking from day one how the piping coming off the top nozzle would be supported. In this case RVAmeche is right that you need to forward the loads to the vessel manufacturer to check both local and global strength.

However your words were "... no actual relationship between the pipe and the pressure vessel ..." which makes me think this is a different situation. It sounds like a pipe that's running past or near a vessel, and piping has decided to use the vessel as a convenient support. If I'm wrong in my understanding then ignore my comments.

This sounds like it could be a very bad idea. Obviously a 20" vapour pipe and a 20" product pipe would be very different loadings on the vessel.

The vessel will (usually) grow when operating due to the temperature and pressure. This will push/pull on the piping changing the loads. If piping has modelled the vessel as a rigid anchor (as they often do) the loads used to check the support and vessel will be meaningless. If the piping loads are high the vessel could deflect enough to also require re-running the piping analysis.

I had a situation where I went back and forth with the piping designers for weeks and weeks. They'd send me loads on the 3 large pipe supports they wanted. I send them back how much my structure (not a pressure vessel but similar) moved. They re-run the loads and send them back to me. I'd re-run the deflections. Etc. etc. etc. They asked for spring constants at the 3 locations. I sent them numbers to show the deflections were very non-linear to the imposed loads and thus couldn't be simplified in that way. For unrelated reasons the Owner cancelled the project before we came to a resolution.

I also suspect it's standard practice in real life refineries, and that I don't want to see what's been hung off my pressure vessels in the decades after construction.

 

[racookpe1978]

"Standard practice" meaning "I done it before, and nobody has made me analyze your pressure vessel as a vertical pipe support before, so I want to do it again because I don't want to build/pay for/design a proper pipe support and analyze that."

That the other pressure vessels have not failed does NOT mean it is "a proper practice."

Force the analysis and get the info (about this pipe and its proposed attachment and weld locations) to the vessel fabricator and designers.

 

[mk3223]

acrmnm,
....I am only an observer but there is some consternation amongst the older pipers here.

Instead of guessing why happened, one way to find out the truth is to verify with both Engineers who designed the vessel and pipe support in order to know if the piping load was included in the vessel design.

 

[acrmnsm]

Apologies, I missed this - the description by Geoff13 is correct

a pipe that's running past or near a vessel, and piping has decided to use the vessel as a convenient support

.
We have gone back to the vessel manufacturer who were mildly irritated that this had happened, they have re-analyzed the vessel with the pipe support and it no longer meets our spec. So they have requested that we either remove the support or the cannot supply the vessel.
I have made some friends. (Well I made friends amongst the older guys, the piper who made the initial support design gives me side eye..)

 

[RVAmeche]

Good outcome, thanks for sharing. It's concerning that the "piper" doesn't understand the concept of support forces, but it happens I suppose.

 

[Geoff13]

Thanks for letting us know how this was resolved. A little side eye is a small price to pay for a safe vessel.