Intermittent/Stitch Weld Spacing Tolerance

Date 11-16-2011 12:19

I agree that the spacing dictated by the welding symbol is a min dimension for lengths and max for spacing...now about the end where the spacing leaves it flapping in the breeze.....here at work we usually split up that last spacing or two.........so that even though the spacing would work out to leave the end unwelded, we weld it anyway by adjusting the spacing of the last couple of welds(even if they are closer together) to make it work out. Hope that makes sense.

By welderbrent (*****)

Date 11-16-2011 12:20

Ryan,

WELCOME TO THE AWS WELDING FORUM!!

Now, yes, it is a minimum. But I would not recommend adding to the length to make the pattern come out exactly right to have weld at the end of the members. The economics and structural strength and stresses all come into consideration.

Some things should be considered:
1) It may not be necessary to have weld AT THE END of the run;
2) The economics of changing the length and doing all the math to make sure you have the right amount of weld;
3) Changing the amount of weld does not change the center to center spacing- 2 in 12 or 2.3 in 12, you still have 12 inches from center to center so you haven't changed anything by changing the length of the weld. Per A2.4 you are not considering the distance between the welds, only center to center;
4) All you have to do if it is really desirable to have weld at the end is to add another weld that is closer to the last one than what the print called out, or running the last weld an inch or two longer than called out would also be acceptable in most situations.

To me, point #3 is of most importance in line with your question. You must consider the code and print intent. You can't add to the length of the weld and thus change where the weld pattern ends.

Have a Great Day, Brent

By RyanMz Date 11-16-2011 14:08

Thanks for all the great advice but I need some documentation to back this up. If I send product to a customer and it gets rejected, I need to be able to show them where it says that weld length is a minimum.

Ryan

By jwright650 (*****)

Date 11-16-2011 14:28

Hi Ryan,
I'm not certain where you can find that exact wording, other than maybe in the design clauses of the welding codes.

ie D1.1:2010 Clause 2.3.4 says the contract dwgs state what the effective lengths shall be. Throughout Clause 2.4 in D1.1 it shows how to figure the effective lengths and then those would be regarded as minimum lengths.

AWS 2.4:2007 5.17 gives you wording for weld tolerances and how to relay those tolerances to the welder.

By jwright650 (*****)

Date 11-16-2011 16:09

Is it possible before shipping the product to the customer, to check with them about the lengths and spacings along with your concerns?

They may appreciate your efforts to make sure that you will furnish a part that will be acceptable to them ahead of receipt of the part.

Who was responsible for producing your shop drawings? If in-house, then have your detailer send a (RFI)request for info to clarify. Or if they sent you the drawings to build from, pose the questions and concerns to their drawing/engineering department.

By Lawrence (*****)

Date 11-16-2011 15:50

Ryan,

Welcome to the forum!

In addition to the excellent posts you have been given I can add a couple of thoughts.

#1.. Mil-STD-2219 has been superseeded by AWS D17.1. This may or may not have an effect on the contract you are preparing to weld to, but it would be wise to double check to make sure you are working to the latest most applicable standard.

#2 Assuming you are doing DOD/NASA aerospace contracting, you should have access to your major vendors Standard Practice Manuals. Pratt, GE, Allison, Boeing, All have standard practice manuals, for fabrication and repair where you might find the answer for your intermittant weld layout issues. Also, the original class 1 repair/fabrication doccuments for the specific part you are fabricating/repairing may have information on your part that includes weld mapping.

By waccobird (****)

Date 11-16-2011 16:27

RyanMz

I do my layout from both ends having no welds farther apart or shorter in length than detailed.

Just my ¢¢'s

And Welcome to the Forum

Marshall

By 803056

Date 11-17-2011 17:26

I agree with most of what has already been said.

The welding symbols as per AWS A2.4 have no tolerances stated or implied. Tolerances are a workmanship issue, not a welding symbol issue.

The interpretation I received many years ago from the AWS A2.4 committee went something like this:

The size is a minimum.
The length is a minimum.
The unwelds spaces between adjacent weld increments are considered to be maximums. the unwelded space is calculated as Pitch minus Increment Length.

If the detailer wishes the weld to be carried (started or terminated) to the ends of the joint, it shall be detailed separately from the intermittent fillet weld symbol.

When I check intermittent fillet welds, I check the length of each increment to verify it meets the minimum length, then I check the unwelded spaces to verify they do not exceed the maximum (P-L). Of course one must not forget to check the size. If there is an unfilled crater or if the start of the intermittent fillet appears to have incomplete fusion, it is not included in the length of the weld increment.

Best regards - Al

By welderbrent (*****)

Date 11-17-2011 22:58

Your last comment about craters and start ups is why I personally like to make my intermittents about 1/2" in total length longer than what is called out.

But, question, doesn't D1.1 Clause 2 have something about effective length not having to take starts and end craters into account? That doesn't mean a person should let major overlap, lack of fusion at the start and/or major craters at the end go without repair.

Have a Great Day, Brent

PS: I never did find you around FABTECH for that cup of tea. Still here in Chicago. I leave early in the morning. Been one full and good week.

By 803056

Date 11-18-2011 05:41

I never made it to Chicago. I had to cancel on Saturday afternoon. I have a wicked case of bronchitis, verging on pneumonia, so I had to opt out this year. I finally have it under control. It always seems to take two trips to the doctor to get the right stuff to knock it out. I cannot figure out why they cannot give me the right combination of stuff on the first visit. It isn’t like this is the first time I’ve had this problem.

Anyway, back to your question. You are quoting from Clause 2, Design. The clause states that the designer doesn’t have to figure in an allowance for cold starts and unfilled craters. That doesn’t relieve the fabricator from the responsibility of providing full size and full length welds as indicated by the drawings. After all, I believe we’re in agreement that the weld lengths and sizes specified by the drawings are minimum values.

Since the inspector’s responsibility includes ensuring the minimum weld sizes and lengths are met, we have an obligation to include only those portions of the weld that meet the drawing in all respects. Cold starts, unfilled craters, undersized welds, unacceptable profile, i.e., overlap, inclusions, etc., are simply not acceptable if they don’t meet the minimum requirements of the drawing and the applicable welding standard.

See you next year. I hope you enjoyed the show and got to meet a lot of new friends while you are there.

Best regards – Al

By welderbrent (*****)

Date 11-19-2011 21:13

It was a very rewarding week in all regards Al. Except that I didn't get to meet you. I was really looking forward to that possibility.

Yes, I did meet many and hopefully made some long lasting friendships. Lots of good people showed up. Seminar instructors, AWS staff, AWS Officers, other attendees, etc. And the show floor was an indescribable success. I have been to trade shows in Port, OR and Phoenix, AZ and this was very impressive and much larger than any of those.

Hope to see you next year.

Have a Great Day, Brent