Performing NDT in lieu of hydrotest 1

[massad]

We have a waste heat boiler for new sulfur recovery unit. This equipment is in 3 sections. Boiler, reaction furnace and burner section. Boiler and reaction furnace are manufactured by one manufacturer and welded together and hydrotest at shop. Burner section is manufactured separately and hydrotested. At site first 2 sections are already erected on foundation and now the burner section is being erected. After erection both section need to be welded together so there will be one circumferential joint joining the burner section and boiler + reaction furnace section.

Now my question is that is it mandatory to perform hydrotest of this field weld joint. If we do so then the other parts will be rehydrotested , would this be a problem. Is there any way we can waive off hydrotest and perform other NDT testing only.

 

[macmet]

I believe you could also Xray the weld instead of doing a full hydrostatic test on it. I'm not sure how practical that would be for your application.

I have not seen this done before, but I have heard it brought up as an option a few times. I imagine someone here will have a direct reference for you.

 

[TGS4]

macmet is right that is may be able to be done. Talk to the Jurisdiction/AI.

Do NOT perform that final closure weld until you have agreement from the appropriate parties. In addition to post-weld NDE, there will likely be some additional in-process inspection that may need to be witnessed.

 

[chicopee]

Since you are welding pressure parts based on your statement that the two separate components are , I for one, would sure want to hydrotest the final product.

 

[metengr]

You need to review the contract documents and determine what was required as part of completion of the project. If the burner section is considered part of the waste heat boiler code boundary, the waste heat boiler cannot be considered completed until all components have been field assembled/fabricated and a final hydrostatic test is performed to consider the unit complete for code requirements. If the burner section is considered a separate part outside of the waste heat boiler, your contract documents or specification should outline what is required for final acceptance.

 

[Rich2001]

I have personally witnessed welds that have passed UT and RT that later failed during hydrotesting. Though the code or specification may allow it, being conservative I would recommend hydrotest. for example, if the wrong filler was used (lower strength) a sound (passing RT or UT) weld may be produced but would fail at pressure.


Richard

 

[LittleInch]

May sound stupid, but can you not flange the joining part? Pipelines often have this issue and it is generally accepted to have "golden" welds whereby at least two and sometimes 3 means or NDT are used, along with very close supervision and checking of the welding by the Welding inspector for correct materials, procedure, visual during the weld, then UT, X ray and MPI if possible. If you can do a leak test to design presusre before commissioning, that helpos as well.

I appreciate vessels are different, but that's my experience of these things.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[massad]

Thank you everyone for your response. I also personally feel that hydrotest should be done and this what I proposed to the client but now the contractor has raised 2 more concerns.

1) The equipment does not have drain nozzles, so how the hydrotest water will be drained?
2) The foundation design was on operating weight only, so if we fill the equipment with water the foundations will fail.

For 1st point I checked the drawings and visited the site also and found 4 No, 2" nozzles at the bottom of equipment, which I think can be used for draining the water.

For 2nd point I doubt the foundation is only designed for operating load, so I have requested the contractor to provide the design calculations for the foundation to verify the same. If this comes out to be correct then I think there is no way to do the hydrotest. So is this case can we go for pneumatic test instead of going for NDT.

Also a good point is mentioned above to contact the authorized inspector in this regards.

Thankyou.