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Standards Q&A: Interpreting ASME’s Post Weld Heat Treatment Requirements

Posted September 25, 2016 12:00 AM by reprendergast
Pathfinder Tags: ASME standards Welding

ASME Standards often require careful reading in order to interpret them correctly and engineers can be left with questions about some details. In this post we take a look at an engineer’s welding question related to a vessel’s heat treatment.

Question: My shop is constructing a Section VIII Division 1 vessel that uses SA-516 Grade 70 Normalized Plate Material. The Vessel is not exempted from Impact Testing. Can I use an existing PQR qualified with SA-516 Grade 70 as rolled plate to support the WPS I want to prepare to weld on this vessel?

Reply: The short answer to the above question is No.

UG-84(h)(2)(-b) says “be in the same heat treated condition” as one of the requirements to be fulfilled for the test plate material used to qualify the PQR with impact testing. Therefore a PQR qualified with SA-516 Grade 70 as rolled plate cannot support a WPS written to weld SA- 516 Grade 70 Normalized Plate Material.

Someone could potentially misinterpret the phrase mentioned above in quotes to be the post weld heat treatment (PWHT) instead of the heat treatment condition of the base material.

Note that Section IX does not list the base metal heat treatment condition as a supplementary essential variable. So this is a perfect example of a construction code invoking a supplementary essential variable in addition to the ones provided in Section IX.

Another subtle point to be noted here is that a PQR qualified in accordance with Section IX rules doesn’t need to show the base metal heat treatment condition in the PQR since it is not a supplementary essential variable in Section IX. However, in order to make the same PQR compliant with Section VIII Division 1 impact testing rules, base metal heat treatment condition needs to be recorded in the PQR either explicitly or by attaching a material test report of the test plate material used to qualify the PQR.

In summary, the absence of verifiable evidence about the base metal heat treatment condition can make the acceptability of an existing PQR meeting Section IX requirements questionable for Section VIII applications.


Editor's Note: This is a sponsored blog post by HSB Global Standards.

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