Prequalified Root Face

Date 07-10-2018 12:28

Hi Scott,
My take is that the prequalified TC-U4a does not list a dimension for "f" and depicts a zero root face, so if you want to use the 1/16" tolerance shown in Fig 5.3 you would want to qualify the procedure to make sure you can successfully burn out that root face and not have an area where you lack fusion in the root.

Personally, I would want to use the zero root face if I was the one who was welding that joint. Curious to hear how the other members here feel about this.

By SWN1158 (***)

Date 07-11-2018 18:59

Agreed. Thank you John!

Scott

By welderbrent (*****)

Date 07-11-2018 22:12

Have to look it over closer but I think I disagree.

Notice that all those items appearing in the Figures with dimensions and tolerances for 'As Detailed' and 'As Fitup' match Figure 5.3.

Figure 5.3 is a 'Workmanship' tolerance table. It shows the tolerances of the Pre-Qualified joints plus some that are not always specified but are part of workmanship. To allow a 1/16" face when a '0' face is shown but not specified should not be cause for a PQR. Just as welding a joint that is approximately 1/8" larger root opening than specified. The Root Opening tolerance is displayed, the root face is not. One is in the Figure 3.2 & 3.3 tolerance table, the other is in the workmanship Figure 5.3 table. Both, are allowable conditions.

BTW, 'Alt 241' = ±.

He Is In Control, Have a Great Day, Brent

By jwright650 (*****)

Date 07-12-2018 11:06

Hi Brent...the "f" dimension is listed in the essential variables(Table 4.5 (33c - any increase in root face)...so I guess if you wrote the WPS with a 1/16" root face, then it would be okay without requalifying?...I'm asking because I have never ran into this particular scenario before and I never gave it any thought until now. Why would you want extra root face when you are using a backing bar? I understand why it is needed in an open root situation as it helps you control burning through and opening up a huge hole when placing the root in an open root.

By Lawrence (*****)

Date 07-12-2018 11:54

I'm not sure it's a matter of "wanting" a 1/16" root face on a CJP with backing, but perhaps rather a reasonable amount of latitude for bevel prep so that work can be fit-up without rejection.

A knife edge bevel requirement with ZERO tolerance as fit-up, might open the door for massive legit rejections or NCR's from preweld inspections eh?

Having had a really tough last couple of weeks dealing with outside inspection "authorities" my imagination runs wild with visions of large weldments being torn apart because somebody noticed a 1/16" root face on a few CJP weldments with backing...

By welderbrent (*****)

Date 07-12-2018 16:09

Hello John,

First, he said this is about Prequalified so Clause 4 does not apply.

On the rest, I agree with Lawrence, not that he needs my confirmation.

The codes allow and ever so small variation in many detail and fabrication conditions because it is generally acknowledged that there is no such thing as perfection in the fabrication process.

When variables are covered in Figures 3.2 & 3.3 then the Clause 5 aligns with those numbers. But, in this particular case we are dealing with an additional portion of the preparation that is not called out specifically. To have a 1/16" root face is not truly a game breaker for the joints involved. If one were to insist that it were, what gauge and how would you suggest measuring 'razor/knife' edges? What thickness is acceptable and what is rejectable? Would you like to put one of my hunting knives up against one of yours for a comparison of what is 'thin' enough on the edge?

The largest part of this whole discussion is to remember that Clause 3 is for WPS development to guide the welders while Clause 5 gives information not available in Clause 3 for further guidance during fabrication. When one clause is silent on an aspect of the weld but the other gives guidance then that guidance is acceptable. If one actually stated that the root face was to be '0' then the context of the other would be taken into account but it is still a 'tolerance' so it would be acceptable unless both stated '0' with a ±0 tolerance which we don't see anywhere because it isn't really possible.

It is not that you want a root face with a backing bar, but why insist on such perfection that it becomes an arguing point on the fabrication floor or in the field. Like Lawrence, and I am one, I can just see some god complex TPI telling you there is too much root face and the whole thing must come back apart to make that a 0 dimension. By whose 'eye'? With what tool? Are you counting the 'roll' left by the grinder?

No, perfection is not our goal. But we do need tolerances with limits.

By SWN1158 (***)

Date 07-12-2018 16:52 Edited 07-12-2018 16:57

I'm talking about the end of a beam being prepped in the shop that has its top and bottom flanges beveled for field welded moments. So there's nothing to take apart. It only takes another minute or two to take the root face down to zero, and if there's no root face tolerance shown in TC-U4a, in my humble opinion, the root face is zero, which matches the prequalified detail. Also, at the bottom of the details, it says (see 3.13) which, 3.13.1 is pretty clear with regard to deviations from the joint detail.

By jwright650 (*****)

Date 07-12-2018 18:43

"First, he said this is about Prequalified so Clause 4 does not apply."-quote

I sort of disagree, as the Essential Variable Table in Clause 4 is for any deviances that would require a WPS(prequalified from Clause 3 or qualified by PQR in Clause 4) to be qualified if the changes deviate in excess of those variables listed in the Table.

Lord knows, I understand what Lawrence and you are speaking to regarding the CWI's with the god complex. I totally agree that we need measurable tolerances to work with due to nothing being perfect. No disagreement there.

As for the shop prepping the beam flanges for field welding...I understand part of what the shop is doing here. To maintain the overall length, they leave a small square root face so that they don't loose any length and can keep their bevel prepped straight across the end of the flange......but then are we setting the field up for failure if they don't see the extra root face in time and erect the beam. Then there is nearly no room to get a grinder in there to thin out that root face once the welder finally sits down on the flange and starts fitting up his backing bar. Making adjustments to the root face at the top flange isn't too bad, but that bottom flange is going to be tough if the beam is erected.

By SWN1158 (***)

Date 07-13-2018 11:04

My question now is what circumstances would Figure 5.3 apply to?

By Lawrence (*****)

Date 07-13-2018 12:01

I've asked a couple of folks that same question and am waiting for a response.

But my "read" is this: The title for the figure is "Workmanship Tolerances in Assembly of Groove Welded Joints" Meaning that if you exceed the dimensions set forth in the figure, you would need to qualify via Clause 4.

Too often we try to read more into things than the actual words say. Too often we extrapolate figures beyond what is printed.

Opinion: The code covers unlimited CJP's eh? The best practice is shown in the prequalified joint detail, meaning "AS DETAILED" there is no tolerance for root face on the joints we are discussing. The detailer cannot place a root face on the drawing and remain prequalified.

But on a 4" thick groove weld with backing a root face between 0-1/16" is not a cause for rejection. It is detailed as a knife edge, but Figure 5.3 provides reasonable latitude for workmanship.

Until someone convinces me otherwise, I read Fig 5.3 to apply to prequalified CJP details.

By SWN1158 (***)

Date 07-13-2018 13:16

"If you exceed the dimensions set forth in the figure, you would need to qualify via Clause 4". That was my understanding as well. To validate that understanding, I did a "Figure 5.3" document search, and every hilighted area referred an excessive root opening. Thank you Lawrence. Your knowledge and experience over the years has been a very valuable asset to this great forum.

By Lawrence (*****)

Date 07-13-2018 13:39

One more thing.

Above in the thread it was mentioned that a 1/16" root face might be placed on the WPS. This I think could be argued to be problematic. The "Workmanship" tolerance is my understanding to be an "as fit-up" sort of guidance.

The WPS drawing, is arguably a "detail" and the prequalified details do not speak to/allow for a root face, period.

It's a small thing, but might be picked up in an audit.

I think the better place to make note of the 1/16" root face workmanship tolerance is in your quality manual and in any published work instructions that support the WPS.

That's very knit-picky, but might save a headache later.

Having submitted WPS's for review to places like Caltrans (California DOT) or to the CWB Procedures Group for dual certification, I know the pain of having critical eyes Sherlocking every minute detail.

By SWN1158 (***)

Date 07-13-2018 14:27

Me too..... me too.

By jwright650 (*****)

Date 07-13-2018 16:02

See this is why I like having these forums....the discussion helps all of us come to a consensus regarding interpretation of these codes...even when the code is silent on the subject of discussion.

Thanks to all who chimed in with their view....

By 803056

Date 07-14-2018 13:43

Prequalified groove detail TC-U4a applies to T or corner joints. The note indicates the groove can be prepared by beveling either member or both members provided the required groove angle is maintained. So, with that in mind it would be permitted in the case of a corner joint to prepare the groove as a single V-groove. The bevel angles do not have to be symmetrical provided the groove angle is within acceptable limits.

With regards to the root face; as per the discussion, there is no root face depicted, i.e. the root face is 0-inch (mm). It makes sense that a bevel to a knife edge is desirable to mitigate the possibility of incomplete fusion when the welder deposits the root bead. It is very difficult to “melt” the edge where there is a root face on the beveled member. In the case of a T-joint or inside corner joint it is difficult for the welder to maneuver the electrode to easily fuse melt in the corner between the backing and the root face.
There is little justification for not properly preparing the bevel when fabricating the member. There are excuses, but they hold little validity other than sloppy workmanship. The argument against bringing the bevel to a knife edge is nothing more than an excuse for laziness. Bring the root face to a knife edge is not going to increase the root opening if the individual preparing the bevel takes even minimal care while preparing the bevel.

In reviewing Figure 5.3 (B), one is directed to clause 5.21.4. The clause is addressing issues with the root opening, stating if the root opening exceeds the tolerance indicated, the condition must to be bought to the Engineer’s attention for resolution. The single V-groove depicted does not offer the restricted access, i.e., proper orientation of the electrode such that it bisects the angle formed between the two components being welded. The clause does not address the root face. I would caution the reader that the figure is the same as those found in previous editions of the structural code when tubular connections were not address separately from nontubular connections. I bring this up because the Figures 5.3(A) and (C) indicate the grooves are welded without backing. We should be well aware CJP groove welds without backing are not prequalified. So, should the reader infer these sketches apply to joint details that are qualified by testing?

From a practical standpoint, it is my experience that CJP corner joints welded with backing with a root face rarely passes ultrasonic testing. The reoccurring defect is incomplete fusion between the backing and the root face. The welder simply has limited access to maneuver the electrode to ensure proper fusing in the corner. Granted, I only have 33 years of experience testing welds with ultrasonics, so what do I know about the subject? Am I saying it is impossible to produce an acceptable weld if there is a root face present? No, but the reject rate does cause one to wonder how one can justify leaving a root face when the prequalified groove details for CJP single V-groove and bevel grooves with backing depicted by the figures in 3.3 do not include a root face in the figures. Evidently, some though has been given to the subject.

I tend to agree with the poster’s position with regards to the presence of a root face at the base of the bevel groove. It shouldn’t be there.

Al

By Lawrence (*****)

Date 07-14-2018 14:24 Edited 07-14-2018 14:27

So let’s go to your last sentence... It should have been the first one.

“I tend to agree with the poster’s position with regards to the presence of a root face at the base of the bevel groove. It shouldn’t be there.’

D1 is not a best practices manual eh?

So Al, did you mean:

1). The root face should not be there.

2.). The root face shall not be there.

The original question (I think) wanted to understand the code demand or tolerance.

An answer including “should” does not speak to compliance.

We are all in agreement that the best practice is a knife edge.

Are you ready to say that the 1/16” root face in the figure does not apply to prequalified CJP details? Meaning that any root face other than a knife edge SHALL be cause for rejection if the detail is a prequalified CJP groove?

All that talk about laziness and sloppy workmanship is just distracting from the code question.

By 803056

Date 07-14-2018 15:13 Edited 07-14-2018 15:16

OK, back me into the corner.

I do not accept or reject the work I inspect. I report the work as "complying with the requirements" or “not in compliance”. The report goes to the Engineer who per the code has the authority to accept the condition “as built” or require the contractor to take “corrective action”.

As the verification inspector, I have no authority to require the contractor to scrap, replace, or repair work that does not comply with the contact or the code. I’m the eyes and the ears of the Engineer. As the verification inspector I cannot tell the contractor “how” to repair work that is nonconforming. To do so makes me part of the problem.

At the time of the inspection I alert the contractor to the nonconforming condition. He has an opportunity to take corrective action, in which case it is noted the work was corrected. If not, the Engineer has to make a decision on the disposition of the nonconformance.

In the situation being discussed, I have bought the condition to the contractor’s attention and in most situations, it has been rectified by the contractor with a few passes of the grinding disk. If the condition is not corrected and it is accepted by the Engineer, it usually results in a rejected weld in the field. The incomplete fusion is then repair at considerable more expense. I find that the contractor pays more attention to details when there is a cost associated with the nonconforming conditions. It is not difficult to correlate the nonconforming condition reported in the shop to the rejected weld in the field.

I don’t argue the point with the contractor or the Engineer. I simply report what I see.

As for the code, the prequalified groove details and fillet details depicted in Clause 3 stand on their own. If the code committee feels a root face is permitted, it should be addressed in the columns listing the “as detailed” and/or “as fit up” tolerances. The root face dimensions and tolerances are addressed in other groove details where a root face is permitted and there are tolerances provided. That isn’t the case in the situation described in this post.

I admit I use the word “should” rather frequently in conversations with both the contractor and the Engineer. Both are free to disagree with my understanding of the code. The Engineer is the arbitrator when there is a disagreement regarding what is or isn’t specified by the Farm Code or any AWS structural code.

With regards to stating my conclusion, I figured it would make sense to develop the facts before forming a conclusion rather than stating a conclusion and then try to support it with references that may not be all inclusive. As an inspector I have a bias toward the Owner (who pays me) whose interest is obtaining a product that meets the contract and meets his needs. At times the fabricator's interest to maximize profit conflicts with the interests of the inspector and the Owner. When there is a conflict, each party will attempt to apply the code provisions in their favor. The Engineer is the arbitrator. However, if the contractor feels aggrieved there are other remedies.

Al

By Lawrence (*****)

Date 07-14-2018 19:16 Edited 07-14-2018 19:18

Thanks for expanding Al.

It pleases me to still be able to provoke you from time to time :)

I appreciate they way you explore the question from the viewpoint/bias of different roles.... Something I have been more and more exposed to over the last few years with MBMA and AWS Committies and task groups. But something I often forget When questions arise and opinions come flying out of my mouth.

Great insight Al.

By SWN1158 (***)

Date 07-16-2018 11:53

Thank you all so much for your thoughts and references. It sounds like I'm on the right track. Just because I'm not a card carrying CWI doesn't mean that I can't carry on a valid conversation with one who is, although I was told "until you go to school and become a CWI, we don't need to have these conversations", as I was attempting to explain my points and provide references to back them up. Part of my frustration was that I could barely get in a word edgewise. He simply would not even consider a single thing I said. I've been in the structural steel business for 41 years. I was taught by some of the best and I continue to be taught by some of the best in the business on this great forum. Ok. Enough of my whining. Much thanks and gratitude you all :)