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Determining Material Spec
2

Determining Material Spec

Determining Material Spec

(OP)
We are expanding the chemical unit I’m working at to increase production. It’s going to be a combination of buying new equipment and using vessels that have been out of service.

There is this one particular vessel that we used only for about a year back in the 80s but it hasn’t been used since.

I did UT readings on it and there isn’t any signs of localized or general corrosion. Visually, it looks fine as well.

Issue is, I don’t know the material spec of it (i.e. SA-516) which is also needed to order to determine the allowable stress.

I spoke with a few contractors regarding this and here are some of the recommendations:

1. Use LIBS and convert the hardness of the metal into UTS. Contractor claims they are able to narrow down the spec this way.

2. One vendor said he doesn’t trust the recommendation above. Instead, he recommends the best I can do is do an FMR to determine the grain structure which will allow me to estimate the range of the UTS.

I’m not sure how to move forward with this and I’m having a hard time finding information on this.

Advice? Thoughts?

NOTE: I know some of you will just simply say to just buy a new vessel but unfortunately that is not an option. Long story short our spending is limited and there isn't much for someone at my pay scale to do about that.

RE: Determining Material Spec

Hello,

Base on my experiences neither of those options will definitively tell you the materials spec.

The first option is just an estimate (since you cannot directly relate metal hardness with tensile strength) and also take into account that you are only testing the harness of the surface of the material. As an example, since your vessel was already in operation you material integrity might be compromise at the surface and the hardness testing and might not be representative of the entire thickness of the material.

The second option is also dependent of in-service parameters, since your microstructure and grain structure might have been affected while in-service.

What I would recommend for a definitive answer is to section the vessel to get mechanical testing specimens (tensile maybe charpy as well)you can then use those samples to also do the two options above (hardness testing and microstructure identification but you would be able to do it through thickness which is much better). Then perform a weld repair on the vessel. This of course goes without saying that base on those results (mechanical, hardness and microstructure interpretation) you would need to adjust / control your weld repair on the vessel. Lastly, I am assuming these are CS so you could also do OES which will give you your carbon content.

Ultimately, your decision should be made on the combination of many of the options outlined above an not a single one of them.

Hope this helps.

RE: Determining Material Spec

(OP)
Thank you for the response

RE: Determining Material Spec

Please explain why you have no vessel paper records, drawings, or specifications regarding the info that you need.

Please explain why the pressure vessel has no identifying plate or mark that would lead you back to the original fabricator

Please tell us why you trust a contractor that will be paid by you..

Please tell us into which country that this dangerous pressure vessel will be installed ...

Looking forward to your response ...

MJCronin
Sr. Process Engineer

RE: Determining Material Spec

(OP)
@MJCronin:
It's not uncommon for my companies to have poor record retention programs back decades ago.

I have no idea why the info is missing or a nameplate.

This is in USA.

My hands are a bit tied here.

RE: Determining Material Spec

Rube
run and run past go, you are over your head.

RE: Determining Material Spec

(OP)
@mfgenggear: I may very well have to go back to management and tell them this pressure vessel cannot be fully vetted.

In regards to another user mentioning "dangerous pressure vessel" I want to stress that this vessel is not currently in operation and I'm merely asking for guidance on how to handle this. Ultimately, if I cannot safely determine what the required thickness is then it won't get installed.

Safety First

RE: Determining Material Spec

Rubie
Good response, pressure vessels are not my bag. But know enough to know, that your management is not legit. And don't get railroaded. Remember engineers can not use here say. It must certified, tested, and deemed safe.

RE: Determining Material Spec

I suggest you check out NB Synopsis: NB-370 and see what your state requires for PVs. They may have a copy of the data report...and they will definitely have to be on board with any plan you make for this vessel.

RE: Determining Material Spec

IMO, no vessel document, no talk.
As trying to save the Company face and $, you may not go anywhere for reservicing a pressure vessel if there is no formal document for backing up. And, it's nothing to do with your pay scale.

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