Fillet welded patch on piping

[Joss10]

This is my question:

What should be factor "E" (ASME B31.3 - Formula Design) after a fillet welded patch is installed in a process piping in order to arrest a leak.

Any input is appreciated.

 

[LittleInch]

Patches are not normally a good idea due to the inherent weld stress concentration of the fillet weld from pressure under the patch. They have been replaced by things like clock spring and other full circumference repair sleeves or clamps.

I don't believe factor E should be used for anything like this and this is at best only a short term repair operating at reduced pressure.

Has this repair been hydrotested?

Has this patch been designed / inspected by an inspector qualified to API 570?

8.1.4.1. of API 570 refers as does ASME PCC-2

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Joss10]

Hi,

Piping is to be hydrotested after NDT is completed.

We have to calculate new working pressure after the patch is installed.

Patch is in acc. with PCC-2 and inspected by API 570 certified inspector.

Regards.

 

[LittleInch]

ASME PCC-2 article 212 would appear to give you the means to certify that your design and welding of the patch allows you to maintain the same design pressure as the previous pipe. Also then backed up by the hyrotest.

Patches should though be removed at the earliest possible opportunity.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[racookpe1978]

What service?
pressure?
temperature?
original pipe wall thickness, new patch "wall" thickness?
Fillet weld throat thickness is only .707 pipe wall thickness (at best).

See, the original pipe weld is "equivilent" to a butt weld across the full thickness of the original pipe wall against internal pressure against both hoop stress and axial stress.
The repair patch is resisting the amount of hoop stress and axial stress as the original, but with fillet welds effective only for the thickness of the patch (at best!). Anf the fillet welds are much less efficient as butt welds. And, fillets are not NDE certified by a production pipe axial joint or field checked like butt weld joints.

Not a good idea.

 

[Dhurjati Sen]

Dear Joss10,

A "patch" is always a temporary repair. Never heard of a patch repair being hydro-tested, but learning is never-ending !!!

Inspection by an API certified guy makes everything sacrosanct, is it not?

Regards.

DHURJATI SEN

https://www.nace.org/people/dhurjatisen