B31.3 IMPACT Test clarification

[Flareman]

I need help clarifying an impact test issue

The background:
The design condition for a pipe is -50 degC
We are using A-671 pipe made using A-516 Gr 60, with mill and impact test certs.
The pipe passes through a bulkhead and also has some additional attachments.

The attachments are just guides and have no effective design loads in themselves. These were spec'd as A-36.

The bulkhead has other loads so it was spec'd as A-516 Gr70 (normalized was NOT spec'd) but the overall bulkhead design was done with a reduction factor of 0.42S. The final thickness is 5/8&quot;. From 323.2.2A we find -19 degC with a further reduction (from 323.2.2B) of 42 degC = -61 deg (< -50 degC) so this material does not need impact test.

The welding however, DOES need impact test and the PQR came back with a low value (8 ft.lb in the 516 Gr70 base metal) but good values (about 18 - 22 ft.lb) in the Gr60 and the weld metal.

The questions:
Is the PQR good or do I need to have it requalified?
If so what should we do to avoid having the same problem but not affect the WPS/PQR compatibility?
Can I use the same PQR to support the WPS for the A36 connections?

Did I miss something?

Thanks for your help

david

 

[bvi]

The pipe material I presume per your discussion was impact tested to qualify it for -61F. It was not qualified by the low stress exemption of Fig 323.2.2B. The pipe to pipe welding procedures then need to be qualified for the temperature by impact testing, since the assumption is the pipe has adequate toughness for full stress conditions. An alternative would be to show impact testing of pipe material is not required via 323.2.2B because the conditions of stress are low, in which case impact tests are not required as part of the weld procedure qualification. While I do not think you are clear on this, I am actually presuming you are able to qualify the pipe to pipe welds, which brings you to the next issue, the pipe to other attachements welds.

The requirements for welded attachments and their welds is really not addressed in ASME B31.3. There are no specific requirements, so it is really a gap. The requirements for attachment materials can be found in 321.1.4 and 321.3.2 and impact testing is not mentioned.

I would think, though, that despite the lack of ASME B31.3 requirements, a good practice would be to have impact tested weld procedures whenever you are welding to a pressure boundary that requires impact testing, whatever it is that you are welding to it. The rules in Section VIII, Div 1, para. UCS-67 provide for this.

You could have avoided the whole issue by qualifying the pipe with Fig 323.2.2B.