A question came up recently about welding outside of the drawing designated welding zones, such as welding in holes that were misplaced or something similar. We landed on that you need to obtain engineering authority.
Another question came up recently which is similar in nature except it is done with intent. If you utilize bracing to assist in the minimizing of distortions of parts (strong backs, braces, temporary reinforcement, etc.) and they are welded in zones that are not welding zones then do you need to obtain approval for that as well? From a technical standpoint since you are welding in a non-welding zone my initial assessment is that yes you should do that.
In my experience though in different shops and locations that has never really come up so I am wondering if I am missing something.
The bracing would be temporary and removed and the areas cleaned up to look as if it is clean. The parts are cyclically loaded.
Let me know your thoughts.
You did not mention a governing code, so I'm going to assume AWS D1.1
First place to look is Clause 7.17 Tacks and construction aid welds.
There are a couple specific notes in that clause that demand engineer approval for conditions or base metals.
I also think there may be wisdom for the company Weld Manual, Quality Manual or Quality System to take things like strong-backs and temporary construction aid welds into account. This would be best authorized by the responsible engineer, so that if there were areas of exception they can be published.
I do think it's important that the "Engineer" consider things like this. Welders and CWIs certainly are not qualified to say whether welding should or should not be done in a zone that is not specified for welding in the shop drawings. But the engineer may be able to produce some general standards where these things can be applied as a best practice without itemized approval.
Ah you are right, yea D1.1 is the one I am referring to specifically, although that being said we do work per D1.1, D1.2, D1.3, D1.6, D1.8, and D17.1 pretty frequently so I will want to come up with a good general thing for our QMS that sufficiently covers multiple things, D17.1 is the trickiest one, although allot of what we do is class C so it is less stringent.
We dont have an internal engineer and we deal with allot of small projects and jobs so I think something in a best practice/work instruction that details how we handle this may be easier. Itemizing each instance would certainly be tedious.
Thanks for your input Lawrence.
It boils down to the requirements included in the Code of construction and any other contract specifications.
This is where the responsible Design Engineer can and often will define prohibited welds and repairs for critical weldments.
When cyclic loading capacity and high strength steels come together there is in increased ability to develop hydrogen embrittlement and even large variation of hardness in heat affected zones that can shorten weldment fatigue life.
In these cases, the Design Authority often prohibits -
- any weld or tack outside of a designed weld joint
- any temporary fitting aid that involves tacking/welding is to be properly surface finished and inspected with some type of NDT such as Mag Particle and hardness testing
- Base metal repairs, such as welding shut a misplaced bolt hole, may only be done through the use of a qualified repair procedure that has been approved by the Design Authority before use.
The flip side of this coin is all too often, Design Authorities either do not specify restrictions or Production Supervisors / Contractors do not follow specified restrictions. That's when the **** often hits the fan.
Dr. Duane Miller, previously with Lincoln, offered Blodgett Seminars that explained this whole topic very well, offering several case studies of structural failures and collapses that was a real eye opener. He's unfortunately not providing these seminars now that he is retired, but I hope Lincoln will continue. Regardless, there's a lot of papers/articles that Dr. Miller has published that are easily accessible through internet searches. One thing you might try to search for is the many cases of bridge collapse due to fractured welds used to try and fill misplaced bolt holes in Beams.
I will have to see if I can find any records of those seminars, I would like to see some of the information from those. I will look for some of the articles that Dr. Miller published at least.
In Code books the term used for this is "temporary tack welds" to be removed when they have served the purpose.
As already pointed out by Lawrence and Tim it depends on specified Code, base materials, welding procedures, company Quality Manual, etc.
The nature of this is that the tack welds will always leave a spot of diluted weld metal and its HAZ even it is ground flush. Simply based on material and welding consideration, if it is just common carbon steel structures not too thick without specified/planned preheat or PWHT, the management and control effort is not too much and the welders are given enough freedom to tack wherever needed and wanted and people are silent on this.
On the contrary, if it is for some critical materials with specified preheat, PWHT, and NDE, etc., the areas where the tack welds are removed must be carefully/equivalently treated. For example, only qualifed welder following specific WPS with specific brace material can be employed and the areas must be included in the PWHT and NDE(MT/PT) tested both before and after PWHT. In this situation welders can no longer be given such freedom. Just imagine the worst case that unmatching rod for tack weld is used on the base metal and then ground flush so no body can see by eyes and such areas are missed in the PWHT leaving cracks undetected by NDE.....
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