Weld Symbol Opinions

Date 07-26-2014 03:59 Edited 07-26-2014 04:14

They look somewhat similar to this with the two uprights, only without the bolts. He wants the full pen where the uprights weld to the cradle.

By Plasma56 (**)

Date 07-26-2014 04:48

I contend your correct.
Single bevel, followed by a fillet weld. Arrow side of joint.

By welderbrent (*****)

Date 07-26-2014 05:02

"The detail shows a symbol like this:"

Really? And the other shoe falls when? 'LIKE' does not inspire confidence that the symbol 'IS' that.

I'd rather see the actual detail or at least it's description. Are there any measurements associated with the 'like this' symbol? 'LIKE' depth of bevel, weld size, etc?

What code are you working too so we can reference the 'ACTUAL' code mandated requirements? What material?

Short version based upon very limited information thus far presented: Yes, it is to be a full penetration weld if that is even close to what the welding symbol looks 'LIKE'.

But, TPI's cannot tell, and should not even suggest, HOW you are to accomplish that. It should be in your shop approved drawings detailed by your people and approved by the engineer of record on the job (the customer's rep). They are responsible to call out the type of joint configuration with depth and angle of bevel, size of weld, backgouge or backing bar, root opening if any, etc.

Short arc!! I'm with you 100% on that one. Not even on the root. At least, if this is to D1.1 which we don't really know yet?? Though you did say 'structural'.

No matter what the process for the root, please tell me he did not direct you to do this without backgouging? If there is no backing and no backgouging then it is not pre-approved and unless you do PQR testing you don't have a proper WPS to complete it with any process. Just because you leave a gap and get burn through does not make it a CJP.

Just my two tin pennies worth based upon limited information.

He Is In Control, Have a Great Day, Brent

By OBEWAN

Date 07-26-2014 16:25

What does the AWS Weld Symbols Standard specify? I do not have my own personal copy handy, but I seem to recall that full penetration is the default for weld symbols when the penetration is not specified. However, I might be confused, because some companies develop their own standards based upon the standards of other authorities.

As for the process, I don't want to enter into that debate at this time. From a practical standpoint, it might be hard to run a root pass in a large gap using the spray arc process if there is no backing bar.

And, then, there is FCAW and Globular Transfer to consider...sorry, it is Saturday....

By OBEWAN

Date 07-26-2014 21:30

Sorry if my first response came off sounding a bit snarky.

But, from a practical standpoint, do the uprights support the cradle? And, if the actual application is in fact similar to the photo, than perhaps the practical world should prevail. Why would full pen be necessary?

Ask the engineer and/or the detailer to be more specific if necessary. Then, if there is still a disagreement, maybe you could pursue a deviation request and note the approval or disapproval in the contract documentation?

I'm done making trouble for now.

Have a good day of rest tomorrow.

By 803056

Date 07-26-2014 13:09 Edited 07-26-2014 15:53

First question: Are these shoes designed by your employer or is your employer a subcontractor?
Second question: What welding standard are you working to? If it is an ASME piping code I would expect AWS D1.1 and AISC are referenced as the appropriate fabrication standards.

Per AWS A2.4, a welding symbol indicating a groove weld is required without dimensions, CJP is required. See AWS A2.4:2012, clause 7.2.2. I'll paraphrase the clause:
Omitting the depth of groove and the groove weld size dimension from the welding symbol requires a groove weld that extends through the thickness of the joint.

I will say the TPI is overstepping his authority as the Owner's representative. The Owner, through the Engineer, is the individual with the authority to make such a request. Even then, the Owner doesn't have the right to dictate the ways and means unless the requirement is included in the project specification or other contract document.

If the design is your employer's or even if it was designed by some other entity, I would submit and RFI as to what the Engineer's requirement is. I would also submit a proposal that a prequalified joint detail per AWS D1.1 be adopted and added to the drawing. Since it is a change as a result of the drawings being incomplete, I would include a PJP detail and a CJP with their associated cost. Let the engineer make the decision and charge accordingly. You might want to add that the issue was raised by the TPI and clarification is needed to mitigate the possibility of unnecessary time, expense, and delays in schedule.

Best regards - Al

By yojimbo (***)

Date 07-26-2014 19:11

803056,

I have a potentially similar issue to resolve so this discussion is of some interest. AWS D1.1 2.3.5.3 states: "The contract documents shall show CJP or PJP groove weld requirements. Contract documents do not need to show groove type or groove dimensions. The welding symbol without dimensions and with 'CJP' in the tail designates a CJP weld as follow- [and the symbol is shown].
The welding symbol without dimension and without CJP in the tail designates a weld that will develop the adjacent base metal strength in tension and sheer".

So my question is: If the OPs CONTRACT DRAWINGS, not shop drawings, do not indicate CJP, then [as in my own situation] I would argue it is NOT by definition a CJP called out and the TPI is interjecting an interpretation that is incorrect. However my argument is based on the assumption that the sentence in the clause referenced above reading "...and without CJP in the tail designates a weld that will develop the adjacent base metal ect", and my understanding of that sentence would be that a PJP or even a fillet weld would develop the required strength criteria listed.

I hope I have made myself clear. Contract docs. dont call out a CJP, so there is no CJP required, and a PJP is all that is called for. My questions then are, would a fillet weld meet the required strength criteria? Or is there a specific PJP prequalified weld configuration figure that you consider most appropriate to suggest to the EOR for approval?

For additional clarity: Would a fillet weld develop the strength requirements defined in the clause referenced above?

As ever,

Thanks.

By 803056

Date 07-27-2014 11:51 Edited 07-27-2014 12:28

The key is "...will develop the adjacent base metal strength in tension and shear."

The next step is deciding what is the most economical means of developing the required strength. The designer can use a CJP, a PJP, fillet welds, or a combination of CJP or PJP and fillet welds.

Consider the allowable stresses assigned to the weld types per Table 2.3. Simplifying the requirements: the CJP weld can be assigned the same allowable stresses as the base metal when loaded in tension or shear. However, the PJP is only permitted a fraction of the stress, so the weld size is roughly three times larder. Likewise for the fillet weld. Both the PJP and the fillet welds have built in "cracks" in the weld root where there is incomplete penetration in the case of the groove weld or incomplete fusion in the case of the fillet weld. Both conditions represent notch-like stress risers that concentrate the stress in the weld root and enhances the probability of initiating a crack.

Back to the economics of the situation: assuming you have a 1 inch thick plate of ASTM A36 used to fabricate a T-joint. The required fillet size needed to develop the tensile strength and shear strength of the butting member, double fillet welds measuring 3/4 times the thickness of the plate is required. the area of the double fillet weld is about 1 square inch. Compare that to a CJP groove weld using a 45 degree groove angle of 1/2 square inch. Which requires less weld? Which is the most economical? It is simple economics. The volume of the CJP is reduced even further if double groove welds are used.

So, you are correct, the choice is up to the designer. CJP, PJP, or fillets, as long as the loads are transferred from one member to the next, all is good when the Engineer is not specific as to the weld type required. The sketch compares the relative volume of weld metal for a CJP single bevel, CJP double bevel, and double fillet welds. What I didn't get into is the relative volume required for PJP double bevel grooves. I suspect the relative volume would be the same as the double fillet welds.

Best regards - Al

VolumeversusStrength27-July-2014Model1.jpg (96k)

By yojimbo (***)

Date 07-29-2014 14:33

Al,

Very helpful explanation, thanks. To make sure I'm understanding correctly: any of the possible weldments are able to achieve the required strength in your 1" plate T configuration and the volume of the deposits would be a determining factor in the economics of its production.

If so, then in the case where a CPJ is not specifically called out, the fabricator would need to decide whether a CPJ requiring more joint preparation and possibly more skill to produce was more economical than a larger sized fillet or PJP.

Inspection criteria and potential repair rates/difficulties would need to factor in as well I would think. Given the OPs configuration I wouldn't want to have to consider any repairs to the inner side of either of the welds, would be a bear to get at them. I am not clear if there are different inspection criteria for fillets vs. CJPs or PJPs. The overwhelming majority of my CJP welding has always been on pipe to either ASME or API but as a welder I've always just treated them the same, ie. make sure they're 100% clean and don't look back. My impression has always been that a CPJ was inspected to a more stringent criteria, which if true [and I have no substantiated reason or code reference to hold this opinion] that a fillet or PJP might not be the way I would want to go.

Could you respond to the relative stringency of the inspection criteria?

By 803056

Date 07-29-2014 18:24 Edited 07-29-2014 20:37

I didn't say the welding symbol has to call for a CJP in the tail. The applicable code may take a stance on the subject as does AWS D1.1. AWS A2.4 basically takes the position that a welding symbol that doesn't list a depth of bevel and a weld size is by default a CJP.

AWS D1.1 differentiates between a contract drawing and a shop drawing. The shop drawing must show the required details. The contract drawing leaves the contractor latitude to select a specific groove detail.

Again, the code must be consulted regarding the need for different acceptance criteria or the extent of inspection for CJP, PJP, or fillet welds. AWS D1.1 makes not distinction between the weld type except in the case of certain connections subject to specific fatigue loads.

Best regards - Al

By ZCat

Date 07-26-2014 19:26

Per AWS A2.4, a welding symbol indicating a groove weld is required without dimensions, CJP is required. See AWS A2.4:2012, clause 7.2.2. I'll paraphrase the clause:
Omitting the depth of groove and the groove weld size dimension from the welding symbol requires a groove weld that extends through the thickness of the joint.

Thanks, Al. I guess I was wrong.

I, as a lowly welder, don't have knowledge of all the backstory on these shoes and the job specs and the controversy over the root gap and all. Just seems like overkill to me. I'm thinking maybe the designer put the wrong symbol where a fillet weld would suffice. Or, maybe could have specified partial joint penetration. But, I'm no engineer, either.