pipe bending

[fazel2]

Is there any criteria for wrinkle on the surface of pipe during bending of the pipe?
we are boiler maker and in bending of some pipes which we have purchased from Romania, we confront this defect.
according to our technology transfer documents , wrinkle is not acceptable. But I don't know the reason and in ASME SecI which is our construction code, I couldn't find any criteria for this defect.
I believe that this is very tight criteria to say that any wrinkle even if it is very small ,is a cause for rejection.

 

[metengr]

Does the wrinkle cause an out of roundness problem, reportable surfe indication or local region where the minimum wall is violated? If the answer to any one of the above is the reason for rejection.

 

[Duwe6]

ASME recognizes the Pipefitting Institute "PFI ES-24" for ovality and wrinkling tolerances. This spec is available from TechStreet.com for $65.

The reason a wrinkle is unacceptable is that it is a Stress Riser, and concentrates stresses in a manner that is not caclulatable. That wrinkle may never be a problem, but you cannot prove that with engineering calc's.

 

[fazel2]

Dear metenger
wrinkles don't cause out of roundness and pipes have been checked by ultrasonic thickness gage and no problem were reported.

Dear Duwe6
according to PFI ES-24, for our pipes maximum acceptable Buckle height is about 0.2mm ,but the actual wrinkle height in worst case is 1.5mm.

 

[DSB123]

fazel2,
You mention this is a problem with pipes you have bought from Romania. Does this mean that on other suppliers pipes you do not get the problem? If the answer is that this only occurs on the pipes from Romania then the solution would be to not buy pipes from the Romanian supplier/mill.

You say that PFI ES-24 limits the buckle height to 0.2mm but then say your wrinkle height is 1.5mm then since 1.5mm>0.2mm this is a reject!!!

 

[chicopee]

How do you bend your piping? Do you use a mandrel?

 

[fazel2]

we bend the pipes by induction heating and we don't use mandrel.

 

[Duwe6]

Try cold-bending on a mandrel "Pines-style" bender.