Clean out door stress relief

[Moersleutel]

We have a fixed roof tank with a flush type clean out door, which is required to be stress relieved in accordance with API 650.

The problem is that the tank fabricator installed the door into the tank without completing all the welds, but stress relieving was however performed on the incomplete section. Now I believe we have to apply another round of stress relieving after the completion final welds on site.

Thermal stress relieving is impractical at the project site, would it be possible to satisfy API 650 by applying acoustic / vibrating stress relieving?

Any suggestions to save this without having to replace the clean out door section?

Thanks

 

[JStephen]

You could remove the cleanout door section, stress relieve it, and then reassemble.

Check if App. A has any exemptions applicable to the tank.

 

[JoeTank]

Which welds were completed at site?

Joe Tank

 

[Moersleutel]

The section was not fabricated into a shell section, so all welds related to the connection to the shell was not finalised. The pad, nozzle, flange was completed and the pad to 40mm floor insert was tack welded.

We cannot use Appendix A due to the nozzle neck of 20mm and the floor insert of 40mm, I am not familiar with the design to know why the neck is so thick.

The fabricator did not want to install the prefab section due to fears of peaking and banding. There are some serious QA/QC issues, as the QCP was set up correctly, but implemented incorrectly.

 

[JoeTank]

I think Mr Stephen has stated the obvious solution to your problem.

Joe Tank

 

[Moersleutel]

Thanks, I did not think there was a way out of it!

Any comments on the vibration stress relieving?

 

[JoeTank]

Vibratory stress relief is not permitted by API-650. Only thermal stress relief is acceptable.

Joe Tank