I'm looking at B31.3 - 2004; the maximum joint thickness is the wall thickness of the pipe. No credit is "given" for either face or root reinforcement. What is permitted, in this case, is that provided the face reinforcement is within acceptable limits, root concavity is permitted, provided the thickness through the weld deposit is no less than the wall thickness of the pipe. No limitations for the length of the root concavit, so it would appear that it can be continuous around the entire ID.

Best regards - Al

This is a philosophical question of sorts. Some people will disagree with my methodology, but then it's my name on the certification, not theirs.

Section IX is sparse on acceptance criteria. In my opinion it makes sense to utilize the VT acceptance criteria of the construction code used in production. If my client is working on projects that only involve B31.1 Power Piping, I used the most stringent VT criteria expected, i.e., the face reinforcement is limited by the wall thickness of the pipe and operating temperature.

Likewise, the undercut limits may have to be modified due to the thickness of the tube used. The construction code may permit 1/32 inch deep undercut, but the wall thickness may be only 0.035 inch for the thin wall tubing being used. Clearly allowing undercut that approaches the wall thickness is going to result in some unhappy end users.

If the piping system is installed per B31.3 for high pressure, I apply that acceptance criteria.

Section VIII criteria is applied when the work entails that construction code. The last time I used Section VIII, it didn't include criteria for undercut. However, they did include a paragraph that address base metal thinning due to the manufacturing process (or some such wording). I would categorize undercut as base metal thinning due to the manufacturing process, i.e., welding. I didn't reject the weld for undercut, there's no criteria for it in that version of Section VIII.

In my way of thinking; it does no one any benefit to send a welder out to a site or production floor that can meet Section IX, but not the requirements of the construction code.

Last comment, review the construction code that is applicable to the work being performed to verify additional requirements or restrictions are not imposed by the construction code. Example: If my memory serves me correctly B31.3 for high pressure piping requires the welders to be qualified by bend testing exclusively.

Best regards - Al

If you check Section IX, Article I, paragraph 194-Visual Examination - Performance, it says, "Performance test coupon shall show complete joint penetration with complete fusion of the weld metal and base metal." (copied from the 2001 edition). That is the entire visual criteria contained in Section IX. There is no additional VT acceptance criteria listed to address face reinforcement, melt-thru (root reinforcement or root protrusion), undercut, porosity, etc. Please feel free to point out any additional VT criteria in Section IX if you know where its hidden.

Based on that limited criteria, you can have unlimited reinforcement, root concavity, underfill, unlimited undercut, etc. I've even seen cases where contractors accepted coupons that had both bare GTAW filler metal sticking through the root side of pipe as well as pieces of E7018 protruding into the root (not in the same coupon). There's nothing in Section IX that prohibits those types of discontinuities. The bend specimens passed the guided face and root bends and the welders put to work.

The workmanship and reject rates were as can be imagined, your worst case senario. I was very happy I was not the inspector or involved in the inspection of that project. As a welder at the time, I was only too glad to only be responsible for my welds.

As stated before, I use the visual acceptance criteria listed in the construction code that will be used for production. I list the construction code, and if applicable, the piping category (B31.3 normal, M, high pressure, etc.) on the performance qualifiation test report. I also include a photograph of the welder on the report with my stamp partially over the photograph and the test results. That is to make it more difficult for the "rogue" contractor to conterfeit the test report by placing a different welder's name on the test report.

Best regards - Al

Donnie,
This basically means that the thickness at the point of the concavity must be equal or greater than the adjacent base metal (NWT).
Your situation with 1/16" reinforcement can't really exist if there is concavity because there would be no internal reinforcement. However if you still had 1/16" external (cap), you could have concavity 1/16" in depth. On a radiograph we typically compare the density through the concavity to the density in the base metal.