Question AWS14.1 Pattern Weld

By TimGary (****)

Date 10-29-2015 18:29

Stitch welds are detailed with min and max dimensions.
In this case, the 3" length is the minimum weld length, and the 6" pitch is the maximum pitch distance between stitch weld centers.

It is acceptable to exceed the min length and decrease the max pitch, within reason.
It is not acceptable to place a weld less than the min length or further apart than the max pitch.

You should have placed a 3" min length weld on the end of the joint.

Tim

By 803056

Date 10-29-2015 20:53 Edited 10-29-2015 21:59

What the hell is a stitch weld?

I know what an intermittent weld is, but I'm clueless about a stitch weld.

Al

By TimGary (****)

Date 10-30-2015 18:32

Stitch Weld -
AKA - skip weld, chain tack, etc.
Rarely known as - Intermittent weld...

:evil:

Just pulling your chain Al :grin:

By 803056

Date 10-30-2015 19:13

I get so confused!

I look at it this way; The weld size is a minimum, the length is a minimum, the maximum space between the end of the joint and the first increment or between weld increments is no more than the pitch minus the length. Actually, this isn't my interpretation, it is based on a response I received from the committee many years ago. Sorry, I cannot locate the written response I received some 40 years ago.

Back in "76" when A2.4 underwent a number of changes, I noticed the figures for intermittent fillet welds omitted the note that all intermittent fillet welds shall start and terminate at the ends of the joint, and where necessary, the length increased .....

So, being a good little fella, I wrote to the committee and told them of the error. Their response was that it was not an omission. If the designer wants the welds to start at the ends of the joint, a different symbol is required. The initial weld can be placed away from the end of the joint as long as the unwelded space does not exceed pitch minus length. They also said that there is no tolerance implied by the welding symbol. Tolerances, such as undersized welds, welds that are too short, etc., is the providence of the welding code or standard, not AWS A2.4.

Best regards - Al

By welderbrent (*****)

Date 10-31-2015 00:22

Now I'm confused...SSSOOOO, does that mean that the weld in question here would be acceptable? After all, they had the spacing/pitch right...they just ran out of material. All except the last intermittent fillet were of the correct length. If only that plate had been a little bit longer all would be well in the welding world.

Brent

By In Tension (**)

Date 10-29-2015 22:35

Some sound advice from TimGary, Al, and your welding inspector. Call it an intermittent weld and extend the last one to 3". This satisfies the minimum length requirement without violating the max pitch requirement and also Al's penchant for standard terminology, all by simply adding 1/2" of weld. There are other solutions as well, depending on how the symbol is specified (or not) but in no case should any of the welds be less then the specified length. They may be longer, but never shorter.

By welderbrent (*****)

Date 10-30-2015 00:05

Helzin,

WELCOME TO THE AWS WELDING FORUM!!

Remember, most everything in D1.1 and 14.1 as well as other codes is based upon a minimum. There are many ways that your situation could have been altered and still meet the code criteria per the detailed weld. The best in my personal opinion, as has already been stated, is to just increase the length of the last weld by 1/2" into the 'space' between the 2 intermittent welds.

I have seen lots of variations which normally do nothing more than take up time. For example, calculating the length and spaces to figure out how much space would be at BOTH ends and start the welds with a longer fillet at both ends making all others perfectly spaced (don't know if I made sense with that and I don't have time/skills to draw and example). First and last welds would be longer than 3" but everything else would be equally spaced per the drawing specs.

Just my two tin pennies worth.

He Is In Control, Have a Great Day, Brent

By 803056

Date 11-01-2015 16:06 Edited 11-01-2015 16:13

The ends of the joint do not need a full increment of weld, as long as the first full increment (length) is no more than the maximum unwelded space (pitch minus increment length) from the end of the joint. The partial increment (at the ends of the joint) can be considered a tack weld and ignored.

That is a change between A2.4 prior to 1976 and post 1976. The note requiring a full length increment of weld at the ends of the joint was eliminated from the 1976 edition and those that followed. The response I received stated that if the engineer required a weld at the end of the joint, it had to be specified by a separate welding symbol.

In another response regarding the interpretation of the intermittent weld symbol, there are no implied tolerances. Tolerances are workmanship issues and are the purvey of the applicable welding standard or the contractor's quality standards.

That being the case, I apply the following:

Weld size - minimum (discounting cold unfused starts or unfilled craters)
Weld length - minimum (disregard unfilled craters or cold unfused starts, such as those associated with GMAW on aluminum or steel)
Unwelded length - maximum (pitch minus length)

As long as the three criteria are met, all is good. Over welding (length or size) is no justification to reject welds unless restrictions have been imposed by the engineer, code, or in-house quality standards.

I use my fillet gages and my dividers to check intermittent fillet welds. It is a three step operation where: (1) I use the fillet gage to check size, (2) then I set the dividers for the maximum unwelded spacing. If all is good, (3) I reset the dividers for the minimum weld length. Done deal and there is no need to use a tape measure for anything other than setting the dividers.

If the weld size is too small: fail. If the increment is too short: fail. If the unwelded space it too great: fail. If the weld size is too large: accept. If the length is too long: accept. If the unwelded space is too great: fail.

I do not play the game of the symbols calls for 50% of the joint length to be welded, now measure the acceptable weld to see if it represents 50% of the joint length. The criteria is liberal enough to meet without playing games. If the welder can't meet the criteria, it time for him to go home a play with his Lego blocks.

Best regards - Al

By welderbrent (*****)

Date 11-02-2015 14:13

And just for the record, I was not saying I approved of some of the things I have seen, only that shops come up with a wide variety of personal interpretations on how to weld the last odd length segment of the joint.

Brent

By 803056

Date 11-03-2015 01:34

Understood.

Al

By flamin

Date 11-04-2015 20:36

Interesting topic,
I don't have D14.1, however per D1.1 (2010), in a case where the last weld segment doesn't meet the minimum length requirement noted in the welding symbol, would 2.4.2.3 rather than 2.4.2.4 then be the minimum requirement (unless otherwise called out) since it wouldn't technically be part of the length/pitch pattern as indicated by A2.4 : 7.4.5?

Thanks

By 803056

Date 11-05-2015 01:18

Clause 2 addresses issues related to design, so the designer must work within the constraints when specifying the production welds. I would consider the weld near the end of the joint nothing more than a tack weld. Best practice would be to remove it altogether if anyone had heartburn.

Best regards - Al