Pipeline bends in buried pit to relieve stress
Pipeline bends in buried pit to relieve stress
(OP)
Hi,
we are installing an high WT 12" pipeline for gas injection (600 bar) with a differential temperature of around 80 degree celsius. To guarantee the compliance with allowed stress values, our engineering contractor is proposing to install the most critical bends into buried concrete pit in order to let the pipe free to move.
They said it's quite a common solution in cold place where thermal expansion is big and created stress are huge.
Any reference for this kind of application?
we are installing an high WT 12" pipeline for gas injection (600 bar) with a differential temperature of around 80 degree celsius. To guarantee the compliance with allowed stress values, our engineering contractor is proposing to install the most critical bends into buried concrete pit in order to let the pipe free to move.
They said it's quite a common solution in cold place where thermal expansion is big and created stress are huge.
Any reference for this kind of application?





RE: Pipeline bends in buried pit to relieve stress
OK, if the flat concrete floor extended the length of the pipeline, and there were no bends in the pipeline. Real world, the length of pipe buried in the soil will restrain the pipe. Even if there were thermal expansion Loops (U-bends or double-L bends in each pit), his plan only substitutes underground open pits with a sliding floor for standard (and cheaper and more easily maintained above-ground bends.
So a sketch of dwg or photo of his proposed plan. The concept appears wrong in principle and in economic terms.
RE: Pipeline bends in buried pit to relieve stress
Ganga D. Deka, P. Eng
Canada
RE: Pipeline bends in buried pit to relieve stress
Use of pits to relieve stress by allowing movement is a solution but is costly and complex to construct but I have installed one before now where no other solution worked reliably.
What do you mean by reference? Ask your engineering contractor and see what alternatives have been considered.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pipeline bends in buried pit to relieve stress
RE: Pipeline bends in buried pit to relieve stress
It's not really the stress in the pipe that's an issue, but either stress in the bends or also the amount of movement. If you get a lot of movement then you can get ratcheting where the soil fills in behind and then when you stop flowing it doesn't contract to the original shape and then next time expands some more and on and on.
Whilst looking for something else I came across this product / company who may be able to provide more information.
https://www.norseman.ca/en/node/52
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.