intermittent chain weld issues

Date 06-23-2020 14:22

It is not up to the welder to make changes on the fly. The drawing is the working document he has to follow unless the designer/engineer approves any changes before the welder welds the component.

Years ago, in a land far far away, it was a requirement that the ends of the joint be welded with a full length increment. Where necessary, the welder was to increase the length of the last increment to facilitate the full increment length at either end of the joint.

In 1976, with the publication of the new edition of A2.4, the note that required the full increment at the ends of the joint was eliminated. I, being of sound mind and eagle eyed, made note of the omission and promptly send a letter to the committee chair informing him of the oversight.

His response, Professor Green of Ohio State fame; the omission of the note was no oversight. If the designer/engineer wanted a weld at the ends of the joint, there were ways to indicate that, but it wasn't the intermittent fillet weld symbol. Further, he noted there were no implied tolerances, those, if needed were left to the discretion company or fabrication document. In addition, the minimums of the intermittent fillet weld symbol were:

Size - minimum acceptable size (no maximum)
Increment length - minimum length of each increment (no maximum)
Unwelded space between each increment and maximum unwelded space at the end of the joint: Pitch distance minus increment length. (no minimum)

Again, tolerances are not part of the welding symbol per A2.4

I hope that bit of history provides you with the information you need.

Al

By WeldinFool (**)

Date 06-23-2020 18:18

Damn, you're good! Keep up the good work Al!

By 803056

Date 06-23-2020 19:05

I keep trying my best.

Al

By cbutts

Date 06-24-2020 10:32

Thanks Al, so in the code when it refers to spacing is that the spacing from the end of one weld to the start of the next weld or is the spacing on center of each weld, i did see the in 2.12.2.2.1 it refers to intermittent welding, on built up members, would this be for example, setting an angle on a plate or would that be misinterpreting the code?

By 803056

Date 06-24-2020 13:43 Edited 06-24-2020 13:49

The unwelded space is the distance from the end of one weld to the beginning of the next weld, disregarding unfilled craters, cold starts that may exhibit a bit of incomplete fusion (think FCAW and GMAW).

As an inspector, I use a pair of dividers to check intermittent fillet weld that are relatively short or a tape when inspecting weld too long or spaced too far apart to use the dividers. I check the weld sizes with the fillet gage, then the length of each increment, then the unwelded spaces between the increments. I don't bother with the center to center distance because it isn't a critical dimension. The center to center can be short or too far apart and still be acceptable provided the weld lengths are sufficient and the unwelded space between the increments isn't too great.

The attached sketch is pretty much the same as I used back in 2018 to respond to a similar question regarding intermittent fillet weld lengths. I added the ideal center to center distances (pitch) in red, the actual center to center distances in green, and of course, that means the weld lengths are the blue line segments. By the way, the weld spacing and lengths, as shown, are acceptable provided the size is correct.

I hope this clarifies what I am trying to convey. The sketch is often more useful than my words.

Al

IntermittentWeldSymbol24-Jun-2020Model1.rsz.jpg (28k)

By welderbrent (*****)

Date 06-23-2020 20:24

Good day,

I agree with Al as to how things are currently written in A2.4 and D1.1 for application of intermittent fillet welds.

It is not the welder's prerogative to alter measurements to get equal spacing of the welds including a weld at each end. It also is not the fabricator's option to do so.

If a 3 - 12 (3" on 12") is called out, then you start at one end and weld 3", skip 9" and weld 3" more. Thus achieving the 3" C-C all the way down the line. At the far end, as long as the space does not exceed 9" you need no more weld. Obviously, if the welder deposits a weld slightly over 3" in length the space will be less than 9". All conditions are acceptable as the 3" C-C is still maintained and you have met minimum length of weld and maximum length of unwelded space requirements.

In the past few years I have seen many drawings note a 6" weld on both sides at both ends and intermittent fillet welds in either chain or staggered along the internal balance of the span. Sometimes this is a 'typ' note to be followed at all such connections.

But, the bottomline is that your welder is incorrect in the altering they did and some of your reasoning is incorrect as well though closer to acceptable.

We are not in a position to make any changes. Operate per plans and/or report our observations. Up to the eningeer.

An additional comment: observe the spacing is the length of the weld minus the C-C distance and cannot exceed that amount. In my example above that is a 9" space.

Have a Great Day, Brent

By 803056

Date 06-24-2020 12:58

The welding symbol provides the "minimum" welding requirements to meet the need to transfer the applied load from one member to the connecting member. The intermittent fillet weld is often used where the loads are not high and minimal weld is needed. The designer has to size the weld based on the load, but also based on the minimum weld size dictated by the thickness of the base metal. The welds are preferably spaced "uniformly" along the length of the joint to minimize distortion, i.e., buckling, etc. So, one can think of the intermittent fillet weld as being the minimum amount of weld needed to get the job done.
If the welder lays out the welds as suggested by Brent, he hooks the tape on the end of the member and marks out the weld length, followed by the unwelded space, weld length, unwelded space, .... the required weld will be sufficient to meet the needs of the design.

If the welder makes the weld slightly longer, no harm, no fowl other than lost profit for the employer. Some welders are fastidious about the weld size and the weld length, others, let's say they are not as careful. If the welds are too big, the lengths too long, the strength requirement is met, but from a management perspective, it is a profit eating problem. In the case of architecturally exposed steel, it can be a workmanship and appearance issue.

The intermittent fillet weld symbol shouldn’t be used if the weld must be located precisely, it was never intended for that purpose.
I once encountered an inspector that insisted the welds be located within 1/16-inch of the ideal location and the weld lengths couldn’t be more that 1/16-inch longer than specified. The welders would spend hours with their end grinders and carbide burr removing the excess weld. If the welds were too small or too short, the sky would come crashing down. That inspector was a fool and he cost his employer many thousands of dollars because the application didn’t warrant the degree of precision he demanded. I challenged him and asked what was the basis of his unreasonable demands. His response was “That’s what I want.” He and his ego were sent packing when upper management got wind of what was going on.

The inspector should understand the impact of being overzealous. If the welds are too short, too small, there is an impact on the safety of the structure. If the welds are too big or too long, there is an impact on the profit margin. Shop supervision has a responsibility to ensure the employer makes a profit. The inspector has a responsibility to ensure a product is shipped that meets the requirements of the drawings. Under ideal circumstances, there is communication between the different parties and problems and short-comings can be identified and solved. Under unfavorable conditions, the different parties are in conflict, each “protecting” their own self-interest. The employer usually is the loser in the latter case.

That's my story and I'm sticking to it.

Al

By Jim Hughes (***)

Date 06-24-2020 14:10

What Al said was very true in the new construction Nuke industry of the 80's. It was a note on the drawing or detail to indicate how you finish a "stich weld". That is what us welders called it.

By swnorris (****)

Date 06-27-2020 16:05

For intermittent welds, unless welds are required at the ends, I like to mark the first weld location in the center of the joint, and space the welds accordingly towards each end, so that the weld pattern ends up being centered across the length of the joint on each side.

By Mwccwi

Date 07-09-2020 11:12 Edited 07-09-2020 11:18

Scott,
in June 2015 while collecting PDHs, I took the AWS on-line Welding symbols class and starting the increament at the center of the joint was a recommendation in the training. Since then when I do shop training I teach the methodology of if the weld symbol leader is pointing directly at the end of the joint then this is where to start the increatments, if the symbol leader is pointing any other location along the joint, then it is time to use the method of starting the increament at the center of the joint. This training keeps my welders making weldments that look consitant between welders and shifts.
When I inspect I verify meeting minimum specifed weld length and that the maximum unwelded spacings are not longer than the welding symbols length-pitch requrement. Long welds and short space usualy aren't a rejecting but a training issue.

Attachment: intermittentweldspacing.pdf (23k)

By swnorris (****)

Date 06-27-2022 17:44

Martin

You said “if the weld symbol leader is pointing directly at the end of the joint then this is where to start the increatments

If the intermittent welds are say, 2@12, each intermittent weld will not only be 12” center to center, each weld will also be 12” at the left end of each intermittent weld, and 12” at the right end of each intermittent weld.

I don’t start at one end of a joint with a 2” intermittent weld at the very end, I start marking welds at the center of the joint and work my way towards each end with the 12”. And if there is not 12” left at each end to make the 2@12, the ends are not welded, unless the drawing requires a weld at each end, which they sometimes do.

I’ve just always measured from the center and taught from the center because the example in A2.4 is from the center.

By Mwccwi

Date 06-27-2022 19:24

Scott,
What figures and what paragraphs have the example from the center? I have 2004. 2012. and 2020 editions and all of the examples have break lines at both ends of the figures, except the figures showing additional segments.

By SWN1158 (***)

Date 06-27-2022 21:27

A2.4 98 Figure 33 Application of Intermittent Fillet Weld Symbols shows three examples (2 @ 4 one side, 2 @ 4 chain, and 32 @ 10 staggered) with welds measured center to center.

A2.4 07 Figure 33 shows the same.

A2.4 2012 Figure 33 shows the same.

A2.4 2020 Figure 8.2 shows the same.

And all three show details with additional segments show 9" center to center, and 11" center to center.

Am I missing something?

By Mwccwi

Date 06-27-2022 22:00

Scott, I understand the center to center dimensions, I thought our discussion was where begin the 1st increment on the joint. 2-4 start 2" weld segment then measure center to center of the segments. Start 2" at the end of the or at the center of the joint.

By swnorris (****)

Date 06-28-2022 13:23

Ok. I think we’re on the same page. I just start in the middle and work towards each end with the center to center spacings. This way, the intermittent weld pattern is centered up on the joint, because more often than not, the welder will start with a 2” weld at the very end, and move towards the opposite end with 2” stitches. When the welder reaches the other end, they will typically add another 2” weld, because it “looks better”, regardless if there is less than 12” left at that end. And we know that the only time welds are needed at each end is if the design documents require them.