Restore Vessel to Service After Overpressure 1

[AlphaT]

I've got a situation in which a 304SST vessel was exposed to a possible overpressure. The vessel is vented, and designed to contain hydrogen deflagrations. In this situation, the vessel may have been exposed to a detonation, exceeding the vessel design by an unknown factor. There is no apparent deformation or damage. I am leaning toward re-hydro to verify strength and tightness, but there are some complication with the hydro and I'd like to hear any opinions on other options. Also, does anyone know of any specific code requirements which would apply? The vessel is ASME U-stamped.

 

[aybee]

I cant comment on the legal implications of the ASME u stamp and putting back into service.
what I would do would be to do a full survey.Doa full external and internal visual survey to knock out obvious damage look at the plate not just the welds ,..you dont say what temperature this vessel operates at
Check all cylindrical sections for bulging (strap the section. shine a torch up the sides..very good for detecting bulges)
make a template and check head dome/knuckle radius for deformation...if it hasnt bulged it hasnt yielded...the shell would mostlikely bulge before the head changed shape but you should check anyway.
Check all weld seams and nozzle connections inside and out for cracking use good NDT techniques.it may have stretched elastically and cracked...rather than yielded.
I think I would not hydro..its just had a "hydro" and if it didnt do any damage then its been proven. I would rather do a sensitive leak test , fill it with helium or some such gas and "sniff" all the weld seams

 

[chicopee]

Do a Hydro at 150% MAWP following an internal and external inspection by a competent inspector. Also get a copy of the manufacturers data sheet for construction details some of which may require closer inspection.

 

[AlphaT]

Thanks for your good advice. Your recommendations were in line with what I'd been considering. We are presently angling toward using inspection to verify the vessel wasn't damaged. It helps that the sequence of events to have had a detonation are extremely unlikely. Normally, I'd hydro the vessel, but in our case that would be extremely expensive (about $60,000 for post processing the water alone). After we took a good look at requirements for hydro testing this particular tank, it's actually not much more expensive to build and install a new one.

 

[dig1]

Have you talked to your local authorities? They will probably have something to say about restoring the vessel to service. I agree with many of the comments above but it may be decided by other issues.

NBIC might have some provisions which would help, but I couldn't find anything specific.

 

[AlphaT]

We do have an environmental group that has been involved in making sure that our recovery is approved by the appropriate local regulators (there are a number of regulations we have to navigate, most notably RCRA and NEPA). In addition, we're a federal contractor, so we've got a federal agency to satisfy. Based on the above, I absolutely agree that "other issues" may control our actual recovery procedure.

My emphasis is more on providing a justifiable techical basis for a recovery proposal. The actual decision on what path to take (inspection, rehydro, replacement, etc.) will be made by our managers, and will certainly involve consulting with the various interested agencies.

I did look through NBIC, but like you I didn't find anything that really seems to apply.