I’m facing difficulties with pipe connections; what should I do when the wall thicknesses of different materials vary? ? Guidance from an experienced expert is needed! !
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This post was last edited by solsun on 2020-6-22 at 13:34. Currently, there are pipes and flanges that need to be welded together; they have the same outer diameter. The flange is made of P91 material, while the pipe is made of 12Cr1MoV. P91 allows for higher allowable stresses, which results in a difference in wall thicknesses. The inner diameters differ by about 11 units. If the standard groove-cutting method is used to reduce the pipe’s wall thickness, the stress calculations will not be valid. How should this welding be carried out? Can it be effectively connected together to reduce local stress? Additional note: The pipes are not made of P91 material, so the conditions for installing transition sections are not met
What about adding a transition section made of the same or similar material as P91?
There are no P91 pipes on site; now, internal and external surfacing is being considered, but stress issues need to be taken into account
You might consider replacing the flange; this way, the stress on the joint weld will be reduced
Construct as designed； Changes in materials require modifications.
For such problems, the only solution is to have the design modify the flange.
It’s better to use a flange of the same wall thickness grade
Find a designer to reconsider the flange and pipe fitting issues.
Is the pipe wall thickness much greater than the flange welding thickness? Generally, it is not allowed; moreover, the stress calculation here fails, so change the flange! The S value should have been specified during the design phase; let’s make the change now.