Grinding on shell of PWHT pressure vessel 1

[pingpong1973]

Dear Experts,

I want to take of a name plate of a pressure vessel to allow for UT scanning under it.

The vessel is PWHT and could therefore not be welded on without the right procedures and/or PWHT. What about the grinding? Is inducing heat by grinding a problem and should any special precautions be taken?

Thanks for any help.

Jarno

 

[vesselfab]

how are you going to replace the name plate?

grinding off is ok as long as AI is ok with it

 

[metengr]

Grinding is acceptable to remove tack/fillet welds as long as you make sure you take as little base metal off as possible and blend the surface smooth.

 

[pingpong1973]

Thanks for your answers.

At this stage we left the stubs that were welded to shell. So we did not actually grind on the shell surface. This does however still leave some of the area in accessible for UT.

There are 2 stubs left which are fillet welded all around and would require quite a bit of grinding to be removed and ground flush with the shell.

Still don't know whether I am allowed to that without any heat treatmenr or special precautions.

How big is the chance for grinding cracks and would we need to do PT afterwards?

The name plate will be tack welded back to the saddle support leg.


Thanks in advance for more input.

 

[metengr]

pingpong1973;
I would carefully grind the remaining fillet legs flush with the shell OD surface and perform a final Liquid Penetrant or wet fluorescent MT exam for final acceptance of the blend ground areas. Grinding cracks should not occur.

 

[fegenbush]

pingpong1973,

In addition to what metengr said about ensuring the quality of the exterior surface post grinding, I would like to add that you will need to reattach the nameplate unless you are decommissioning the vessel. If you are decommissioning the vessel, you have nothing to worry about, else, I would remove the nameplate, grind smooth (per metengr's advice), test as necessary, attach name plate bracket (will require R-1 or R-2 form, per your quality manual), and PWHT the entire vessel (if possible, the weld area at minimum). All work should be performed under the advisement of your local AI, and with their approval. They are the final word on the interpretation of the applicable code to your vessel.

I hope this has been helpful.

Fegenbush