D1.1 seal welds on painted structures

Date 08-02-2005 20:08

I understand what a seal weld is intended for but I have a problem getting around AWS D1.1:2004 Table 5.8 or Paragraph 5.14. and then in Paragraph 5.24, so I would like to hear any conversation on this as well.
John Wright

By chall

Date 08-02-2005 20:32

I'll bite.

I don't have the code in front of me, but will offer this opinion based on the rationale of ASME Section I.

Section I has various exceptions (notably PWHT) that pertain to non-load bearing/non-pressure boundary, attachment welds. In short, they are treated with a bit less sensitivity than pressure boundary welds.

Using that logic, it seems reasonable to apply less severity (with respect to acceptance criteria) to seal plate welds.

Less severity doesn't mean the craftspeople have a license to run amok. The weld should still pass acceptance criteria, but I think it's reasonable to not treat it the same as a loaded structure.

How's that for weaselary???
Charles.

edit comment: The weld still requires a WPS. Welding through paint is not part of what I would be willing to accept either.

By bamaCWI (**)

Date 08-02-2005 20:59

These seal welds are made prior to coating application.

By swnorris (****)

Date 08-02-2005 22:16

As we all know, seal welding is not considered to add strength to the joint. In most cases, seal welds commonly assume a fillet weld profile and only provide aesthetic requirements. Seal welds are fairly common in building construction and therefore should be specified in the contract documents when required. Simply adding them could create a different problem. In fact, according to AWS D1.1-04, Section 6.5.1 states “The inspector shall make certain... that no unspecified welds have been added without approval.” An alternative may be to investigate the use of silicone caulk to seal exposed joints from the elements after the structural steel is painted. When our work requires seal welding, our shop drawings indicate the calculated weld size and length required. The shop drawings also have a note "In addition to the specified welds, seal weld all joints". Here’s a related link “Use Caution When Specifying Seal Welds”.

http://www.jflf.org/pdfs/papers/design_file6.pdf

John, you do have a point about the minimum size fillets in 5.14, but I think seal welding criteria should be addressed in the contract documents, however, I have never seen it indicated there. Seems that it is a given.

bamaCWI, a seal weld is definitely a permanent weld, but odds are, it has absolutely nothing to do with the strength of the joint. I don't think it would require an additional WPS as long as it falls within the parameters of prequalified criteria. However, you might want to look into 6.5.1 as it relates to your responsibility of whether the fabricator has approval to seal weld.

By HgTX

Date 08-03-2005 18:59

Seal welds are assumed not to contribute to the strength of the joint, but they may still be subject to stress, depending on their location; the seal weld doesn't "know" it's just a seal weld. That means they can break if not done right, just like any other weld.

Hg

By bamaboy Date 08-03-2005 22:09

I think the problem is nomenclature, Seal welds should be treated the same as you would any weld, ie what is the strenght required and what is the purpose of the weld. AWS D1.1 as far as I know does not use the word "seal weld". I had a job a few years back where a fabricator mistook the square butt weld symbol for a "seal" weld , the design engineer of course wanted a full penetration except that he also made a mistake in printing the word "seal" in the arrow tail. So what was the intent of the design. When I looked at the needed strenght of the weld joint, a partial penetration weld would have worked fine and the needed depth of penetration should have been indicated as D 1.1 says. So in a nut shell the "seal" weld is a misleading term and I would say a WPS is needed and the actual weld joint may not fit completely into pre-qualified weld joint configuration.

By bamaCWI (**)

Date 08-04-2005 13:23

My main problem is that some fabricators drop there QC on these welds.
Most of the seal welds I deal with are located between Intermittent welds. The Intermittent welds are made then seal welded between them.
Some of the welds have looked like a rope glued to the joint. My inspection criteria for seal welds are if they do not visually appear to have complete fusion, they are NOT sealed. This brings up some heated discussions with some fabricators. Also I believe cracks could propagate from defects into the other areas.

By jon20013 (*****)

Date 08-04-2005 14:06

I'll toss in my two cents: Personally, I think Scott said it best; "Seal welds are fairly common in building construction and therefore should be specified in the contract documents when required. Simply adding them could create a different problem. In fact, according to AWS D1.1-04, Section 6.5.1 states “The inspector shall make certain... that no unspecified welds have been added without approval.”

bamaCWI, you mention you have criteria for inspecting the seal welds; is this in a job specification, procedure, or where is your criteria coming from?

Like most people in here, I would agree seal welds probably don't need to meet minimum size requirements, having no design strength for consideration however, I personally believe the profiles and undercut criteria should meet D1.1 unless otherwise specified.

By bamaCWI (**)

Date 08-04-2005 18:19

My criteria comes from the general notes of the prints which states:
"Welding is to comply with American Welding Society D1.1"
In another note it states that: "Minimum weld does not apply to seal welds" , but it states nothing about discontinuities.
I may be wrong ( I am still a green ) but I am interpreting this as saying minimum weld size doesn't apply but other criteria does apply.

Thanks for the reply

By jon20013 (*****)

Date 08-04-2005 19:37

Is it indicated anywhere (either specs or drawings) of where the seal welds should be made? For example on some of our drawings we state "Seal weld for all areas where weld symbols are not shown."

By swnorris (****)

Date 08-04-2005 20:12

I agree with jon20013 that seal welds should be held to the same visual acceptance criteria as any other welds.

By bamaCWI (**)

Date 08-04-2005 21:36

They are not noted in specs. The only reference I have in drawings is the general notes and connection details.They show locations of all seal welds in the details.

By jwright650 (*****)

Date 08-04-2005 20:11

They use seal welds so that the structural steel doesn't collect water and weep rusty stains down onto their pretty painted surfaces that might be exposed to view and then also you seal weld before galvanizing too for the same reasons. I'm still riding the fence on this guys, but I lean towards rejecting them on not meeting the min fillets table.
John Wright

By jon20013 (*****)

Date 08-05-2005 09:40

I agree with you John as to their purpose, but to me, personally, I don't care about size as long as the profile conditions are met.

By CHGuilford (****)

Date 08-06-2005 15:37

To me, seal welds are the red-headed step child that everyone knows about but don't want to admit to. (I hope I am not offending anyone who actually is a red-headed step child).

Failed seal welds certainly can contribute to failure of a structure by propagation of cracking to the base metal. Naturally it depends on where and how the seal welds are made. By way of illustration, how many people have ripped into a hotel room coffee maker filter when tearing open the outer wrapper? (You can tell where I spent last week)
It has never made sense to me to require fillets welds to have the proper terminations and then run a skinny little fillet weld right into it.

Unfortunately, seal welds are often an afterthought. I think it is important for the designers to understand that seal welds are often left to the welder to determine size and quality. Generally, if the seal welds actually seal and do not have overlap, porosity, or excessive undercut, they are considered to be good. It also needs to be understood that the seal weld will be made at a higher travel speed than most welding will, and that despite the lower heat input, seal welds will significantly contribute to distortion.

In many cases, it may be wiser to skip the seal welding and use a joint sealing compound as was already mentioned. We have had good success on painted steel in using a polyurethane joint compound on top of the primer or mid-coat, before spraying the top coat.
Galvanized weldments are also routinely seal welded. That sometimes causes cracking when hot dipped. Also, I have personally worked on galvanized walkway trusses that had been exposed to a month of rain in a coastal environment. The weld joints had not been seal welded and the only rust was noted where the diagonals had not been fitted tightly or where the zinc was damaged.

The bottom line is, whether right or wrong, seal welds are not controlled as well as the "structural" welds are. If they need to be, then the designer ought to put a note on the drawings, or in the specs, that requires a WPS to cover the seal welds. Without that communication, it will be assumed that seal welding is not a major concern.

Chet Guilford

By bamaCWI (**)

Date 08-08-2005 22:08

Thanks for the discussions guys. I am sticking to 5.24 until drawings or specs are revised.