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spiousas (Mechanical) (OP)
12 Jul 07 13:24
I'm analyzing a pressure vessel from the sixties and I'm having several problems with the material's characterization. The material is a ASTM A212 Gr-B.

I made the charpy test of some samples and the reults aprove the code specification (ASME VIII from 1962 and from 2005)for use at low temperature.
My problem is that I have 100% of Brittle fracture in the test at working temperature of the vessel (-20°F).The codes, the new one and the old one, don't have conteplated this issue.

What have I do about it? Do I have to respect the code, and say that is allright, or do I have to take care about the probabilities of a catastrophic failure caused by the brittle fracture?

Thank you.

(sorry about my english)
metengr (Materials)
12 Jul 07 15:25
spiousas;
What is the lowest temperature the vessel is subjected to in service? Typically, SA 212 Grade B was used for drum applications in Section I years ago, and I find it difficult to believe that it would be used for lower temperature service.

If your pressure vessel normally operates well above ambient temperature the SA 212 would be acceptable. However, I would not even subject this material to an ambient temperature pressure test using 70 deg F water.

spiousas (Mechanical) (OP)
12 Jul 07 15:34
The lowest temperature in service is -20°F.

Thenk you.
metengr (Materials)
12 Jul 07 15:45
spiousas;
If you are telling me that you actually performed impact testing of plate samples from this vessel, and you have demonstrated brittle fracture behavior at -20 deg F, I would NOT recommend re-using this vessel at -20 deg F.

The implication with brittle fracture behavior at -20 deg F is that any stress riser, pre-existing flaw or service-induced crack will result in an unstable crack growth situation. There is nothing you can do to prevent brittle fracture, it is inherent with this material at -20 deg F.
unclesyd (Materials)
12 Jul 07 21:40
I have data from US Steel, circa 1966, that give the flowing information on A212 GrB.
ASTM A 201 and A 212 carbon steel grades made to fine grain practice were for many years the only carbon steels available for use at low temperature service - 50F.  These plates were supplied to meet ASTM A 300 (obsolete)standards of a Charpy keyhole impact value of 15 foot- pounds at a minimum temperature of - 50F. These plate were furnished in the heat treated condition.

A lot of our old process equipment where we used Anhydrous Ammonia at 6500 psig was made from 210 and 212. This was to cover the potential of autorefrigeration of the Ammonia
unclesyd (Materials)
12 Jul 07 21:44
Forgot to add the that I have always assumed that a Charpy fracture for low temperature service should have at least 50% shear failure.
metengr (Materials)
12 Jul 07 22:13
unclesyd;
Some of the SA 212 Grade B drum materials that I have experience with were so lousy in notch toughness that I would not even pressure test them today for fear of brittle fracture. We had some lower drum material, coarse grained junk that was tested at 70 deg F,  and the CVN was 8 ft-lbs.

Agree with the FGP provided it was specified. In reading the OP, spiousas may have been overzealous in noting brittle fracture if there is any shear fracture. My take is 100% brittle fracture means no shear on the fracture surface. The CVN may well be below 10 ft-lbs at -20 deg F.

I will temper my original response if we had CVN data to review.
stanweld (Materials)
13 Jul 07 9:14
SA-212 B could have been made to fine grain melting practice or not. Yours no doubt was not. I am not sure why you are testing the material from an existing vessel unless you are rerating it. Please note that SA-212 B was permitted to be used at -20 F without impact testing partially due to the 4:1 safety factor of the time. There are many old vessels in use today that are brittle at that operating temperature. Brittle failure may occur if you are changing the actual operating/service conditions of the vessel. If you are not changing the service conditions and the vessel has been operating for the past 40+ years, you should only be concerned if flaws have progressed.   

unclesyd (Materials)
13 Jul 07 22:58
I was just posting some background information, not recommending, on the use, of A201 and A212 in the fifties and early 60's. We were the always looking the physicals of any MOC that might be suspected of any possible hidden failure mode. It was a routine procedure to have equipment under a continual evaluation program. Our original equipment was fabricated in the early 50's and there was a lot of material used that was not the optimum for the intended service. A lot of the original equipment fabricated from A201 and A212 were replaced with the A516 materials that were just starting to be used. This materials was problem both from the code point of view and availability due to the Korean Conflict.

If any of our testing or inspections detected any deviation from from the original requirements and specifications there was not problem getting it changed out to a more appropriate material.

My boss at the time believed in getting a sample and doing a metallurgical evaluation on everything that didn't move. Getting, preparing, and preliminary evaluation of the samples fell on my shoulders. When I started work I made the mistake in listing photography as one of my hobbies. The only thing I hate is that the company tossed out all the metallographic glass plates (~2000).  

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