I am looking for some advice with regard to ASME IX essential variables and tack welding. My client has objected to a qualified GTAW welder tack welding 1/2" pipe welds as his performance qualification range is above 2 1/2" pipe. We accept that the welder concerned is not qualified to weld this size of pipe but is it acceptable to bridge tack or tack the welds ready for a qualified welder to complete the actual joint, after removal of the bridge tacks or tacks.
In my humble experience, the answer is no.
I believe the answer is in the Code of Construction. For example, B31.1, paragraph 127.4.1(C) states: Tack welds permitted to remain in the finished weld shall be made by a qualified welder. Tack welds made by an unqualified welder shall be removed.
I believe the practice is sound, provided the tacks are removed.
Charles.
I agree completely with your response Chall however I would not permit an unqualified welder to perform even tack welds as removal of all tacks is simply to had to verify and prove to others that they have been removed.
Agreed; and neither do we. However, if someone else wanted to, I would be hard pressed to argue the point after the fact.
In my opinion, we engineers should not be dogmatic. Things should be looked at with "horse sense", or if you prefer, good engineering judgment. Codes and standards are not the Sacred Bible in which not a single word may be changed.
Back in my days of erector engineer I was in charge of the erection of a natural gas compressing station located at 80 miles from the nearest civilization. Our client (the gas pipeline owner) required that welders were qualified under API 1104. Why? Because the great majority of the welds to be done at site were for gas pipes that fell under B31.8 (gas transmission and distribution)
However, those weren't the sole field welds. There were also lube oil pipe welds. OK, we can imagine that those pipes could be considered as being B31.4 (petroleum and petroleum products pipelines).
But there were also other welds:
1. A small API D12 lube oil storage tank that arrived to the job site divided into two pieces. What was the correct qualifying Code in that case? ASME IX.
2. Welding prefabricated pipe supports to existing structural steel or to steel plates embedded in concrete foundations.
3. Field made pipe supports. What was the correct qualifying standard for the last two items? AWS D.1
What did the client inspector and me (the contractor) decide? That welders qualified under API 1104 were sufficiently capable of welding the small storage tank and the pipe supports. After all, we (client and contractor) were on the same boat, we were at 80 miles from nearest civilization and could not afford the luxury of bringing in an ASME IX welder and an AWS D.1 welder just to make a few welds.
So, ayresome, my advice is that you sit down at a table with your client before a cup of coffee and discuss the problem from a horse sense (or if you prefer, good engineering judgment) point of view. I myself would accept that a welder qualified for 2 1/2 inches pipe tack welds a 1/2 inches one.
Giovanni S. Crisi
Sao Paulo - Brazil
Excellent post Giovanni. The 'horse sense' idea is one that I hope runs consistent through much of my posts. And you are right, the codes are not Bibles. And too often people read way too much into them. Its interesting that the great bulk of interpretations requested of ASME are responded to with "the code does not address that issue", or some such language. Anybody who has participated in code work understands how truly messy and contentious the whole process is. And whatever comes out of the process is often disagreed with by many who are seated on the committee. Such is committee work.
Codes are absolutely necessary as a minimum safety standard, and as providing industry wide consensus wisdom for viability, but they will never replace "Sound Engineering Judgment. And they readily admit to such, verbatim.
js55, et al; I definately agree with the Code position of Sound Engineering Judgment. No amount of language in code books can replace Sound Engineering Judgment. That said, I maintain my original reply for most "normal" circumstances.
jon,
Sounds like you are practicing sound engineering judgement.
Thanks to all for the advice, the project I am on is to B31.3 and the reference to tack welding is not as clear as B31.1. I totally agree about the horse sense but if my client had any I would not need to post on this subject. My belief is that the reason ASME IX lists diameter as an essential variable is to test the dexterity of the welder. As tack welding is normally at the 12, 3, 6 and 9 oclock positions I believe my welder has demonstrated his ability to deposit sound weld metal by his previous qualification.
Actually B31.3 is very clear:
328.5.1(c)...."tack welds shall be made by a qualified welder..."
Qualification requirements of Section IX apply. The fact that you are only allowing the welder to do tacks is irrelavent with respect to diameter limits. The welder must be qualified for the diameter he is welding on.
In this situation it sounds like the welder is not qualified to do the tacks even if they are to be removed.
Charles
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