Brittle Fracture assessment

[MikeG7]

I am asked to evaluate an existing vessel that has seem many years of service for brittle fracture. The minimum design metal temperature is not changing.

I am not sure if it is required to be done because I have researched this topic a bit and it is advised in API-653 (5.2.2) that brittle fracture is a concern for initial testing of a low temperature vessel, re-rating, or reconstruction - none of which are expected.

If an analysis were to be done for brittle fracture, what is the applicable guideline? Is it API-653 or API-579, as I am not familiar with these standards and their applicability and if they overlap on the issue of brittle fracture.

 

[Duwe6]

Investigate the records and see what the actual metal was that your tank was built from, and what the MDMT is.
Look up in 650 what the temperature zone that tank is in.
If zone > material MDMT, you are done. Write a memo documenting your findings.

Some times our job really is that simple.

 

[MikeG7]

Ok Duwe6 thanks,will investigate that route. This is a cryogenic vessel in stainless steel 304 @ -320 deg F.

I'm still interested to know when to apply API-653 and API-579 and if they overlap in terms of brittle assessment.

 

[Duwe6]

Then you really do have a trivial exercise. Quote ASME that SA-240 Type 304/304L remains ductile at -320°F. Simple.
FYI - Brittle Fracture is one of the few Catastrophic failure mechanisms. Usually tanks & vessels just leak. With Brittle Fracture, there can be the Big Boom that destroys plants and adjacent communities. Insurance carriers always want to know about any Catastrophic failure mechanisms; probably why your investigation is being done.

 

[JStephen]

Just as a side note- API-653 is intended mainly for API tanks, and wouldn't normally be used for ASME vessels.