Welding Procedure qualification for Low Temp. Carbon Steel Piping 2

[engineermat]

This is a question about the impact test carbon steel piping (Low Temp. Carbon Steel). The fabrication code for Low Temperature Carbon Steel is B31.3. The vendor is planning to use a 0.5" thick pipe to qulify the piping thickness range from 0.25"-0.75".

According to ASME IX QW-403.6, the minimum base metal thickness qulified is the thickness of test coupon T or 0.625" (5/8"), whichever is less. That is 0.5". Therefore, the thickness range 0.25"-0.5" is not qualified.

But the vendor pointed out the the qualified thickness range can based on fabrication code B31.3 Table 323.3.1 which indicates that qualifed thickness range is T/2 to T+0.25".

In this case, what is the minimum qulified thickness: 0.25" or 0.5"? Please advise.

 

[metengr]

engineermat;
Impact test requirements and qualification range for weld procedure specifications qualified by impact testing are two different issues. For impact test requirements the code of construction governs, if applicable. Since B31.3 is applicable, impact test requirements stated in Table 323.2.1 only applies to the range of material thickness for testing (3 coupons), not the weld procedure qualification range for impact qualification. This defaults back to Section IX.

The ans. is 0.5" min thickness.

 

[engineermat]

metengr:

Thanks for you reply

If B31.3 is not used for the qulification, what is the range T/2 To (T/2 + 0.25") used for?

 

[stanweld]

I can state catagoricaly that literally tens of thousands of welds subject to low temperature impact testing per B31.3 have been supported with qualifications ranges of T/2 to T+1/4" for thickness below 5/8" Whether it was correct or not becomes immaterial at this time since many of those welds have been in service for decades. It is noted that qualification on material less than 1/4" the 2T thickness of ASME Section IX applied.

The T/2 to T+1/4" applies to thick materials as well; e.g., Impact test qualification on 1.5" thick material is supports welding of pipe from .75" to 1.75" not the 5/8" to 8" permitted by ASME IX.

 

[metengr]

Just a short follow-up, if you review the 2006 Edition of B31.3, there is Note (2) this note states,

Impact tests that meet the requirements of Table 323.3.1 which are performed as part of the weld procedure qualification, will satisfy all requirements of Para 323.2.2 and need not be repeated for production welds.

The above does not mean that one can pick and choose between Section IX or B31.3 for WPS qualification with impact testing.

 

[FluidicTech]

Metengr- You have helped answer a few of my questions before, and I generally believe the advice you gave was correct and helpful. But, I have to respectfully disagree with you on this one.

When writing a WPS in accordance with Section IX the user is only required to follow the supplementary essential variables when impact testing is required by a construction code or other Sections. ASME B31.3 requires impact testing in various instances, but as you noted, Note 2 of Table 323.2.2 states that the user may substitute impact testing on welds and HAZ in the weld procedure qualification in lieu of performing impact tests on production material.

I had a similar question that arose not to long ago, and someone directed me to Interpretation 4-17 of ASME B31.3. This shows the following:

Date Issued: January 29, 1986
File: B31-85-031

Question: When qualifying welding procedures which require impact testing, is the basic qualified thickness range 1/2t to t+1/4 in. rather than the range given in Section IX of the ASME Boiler and Pressure Vessel Code of the lesser of 5/8in., and t to 2t as in QW-403.6 (where t is the thickness of the test coupon)?

Reply: Yes

Therefore, I would agree with the vendor that the qualified range of the WPS, when used on ASME B31.3 applications, is 0.25" to 0.75".

 

[metengr]

FluidicTech;
Thanks for the update and the reference to the interpretation. Yes, I agree, the code of construction requirements should prevail over general requirements in other code book sections. I kind of stated that in fisrt response to the OP and somehow,I must have mis-read Note 2, which is the reason for interpretations.