ABSA – Impact Test Information on the Drawing
File:PVE-4711, Last Updated: Aug. 03/2011, By: LB
ABSA requires impact test information to be put on fabrication drawings whenever impact testing is a requirement of the design. This is information that is not usually put on a drawing, but if it is left off, the ABSA review process will be put on hold until it is added.
Removed from ABSA’s web site:
Identify which pieces of material must be impact tested and the temperature(s) at which the impact tests are conducted.
Identify whether production impact tests must be conducted for specific welds and the temperature(s) at which the impact tests are conducted.
For materials not impact tested, identify, by reference to the correct Code paragraph, the reason why this material is not being impact tested.**
It is highly preferable that the acceptance criteria (absorbed energy values or lateral expansion) for the impact tests be identified on the drawing since these change with material thickness and strength level.
This information is required to be on the Manufacturer’s Data Report and must be communicated by the designer to the shop in some fashion. The means of communication might be notes on the drawing, separate instruction sheets that are referenced on the drawing (and submitted to ABSA with the drawings) or some equally positive means.
** This is also a requirement for all vessels that do not require impact testing, for all jurisdictions in Canada
Why ABSA Cares
As mentioned above, ABSA has stricter drawing requirements for minimum temperature information than other provinces, and reviews minimum temperature calculations in more depth. The graph above shows why. Fort McMurray winter air temperatures drop to negative 40 degrees C (also -40 degrees F).
Should You Care?
Assuming your vessel is not headed for Alberta, should you care about this? An actual example from our jobs: We designed a pressure vessel with a SA-350 LF2 class 1 forging greater than 3″ thick. The vessel was designed to -20 deg F. LF2 material comes from the mill already impact tested to -50 deg F. – therefore it meets the code requirements – or does it?
SA-350 LF2 Class 1 material is impact tested to -50 deg F. The average minimum absorbed energy for three test specimens is 15 ft-lb, the minimum absorbed energy is 12 ft-lb (15 avg, 12 min). The minimum yield strength of the material is 36 ksi. Per Fig UG-84.1 The required average impact test requirements rises from 15 to 18 ft-lb because the material is greater than 2 inches thick. The minimum required is 2/3 the average or 12 ft-lb (18 avg, 12 min).
The test requirement from the SA-350 standard is no longer adequate! However, this portion of the code has gone through many revisions and updates which have disguised the intent of the rules and left us only with a mess of code passages to follow. Note c on the bottom of figure UG-84.1 exempts this material from the requirements of figure UG-84.1. So the material tested to the SA-350 standard is acceptable!
We can hope for code rules that make sense, but instead with each revision we get more rules that contradict and confuse. How does your company deal with this tortured mess of requirements? Putting the impact absorbed energy requirements on the drawing is one way to make sure that the code requirements are considered during the design cycle and met during production.