Intermittent Fillet Weld Standard of Practice 1

[NS4U]

Say I have 10 in. long joint that I need to weld and I call for a 2 in. long fillet welds at every 5 in.

How would the welder make this weld?

Would they lay down a 2 in. bead at each end of the joint? If this is the case how much weld metal (in terms of length) would be placed in the joint?

or..

would they lay down a 2 in. bead at one end of the joint then work their way down at 5 in. on-center? Would this result in the bottom of the joint not being welded? If this is the this case how much weld metal (lengthwise) would be laid down in the joint?

I'm asking how much weld metal will be put down becuase I'm trying to visualize what the joint would look like after it's welded.

Thanks.

 

[NS4U]

Also, if this is discussed in any welding codes that would be helpful to know as well.

Thanks!

 

[MintJulep]

If it matters to you then specify on the drawing exactly what you want.

Otherwise what you get will be at the whim of the welder, regardless of what standards may or may not exist.

 

[NS4U]

obviously that's an option.

but I also don't want to go note crazy for something that is commong practice.

 

[gtaw]

Assuming the correct welding symbol is used, the weld size is the minimum, the length of the weld is a minimum, and the maximum unwelded space between weld increments is simple the pitch minus the length.

In the example you offered, the minimum length of each increment is 2 inches. The maximum unwelded space between increments is 5-2 or 3 inches. The welder can start the first weld three inches (or less) from either end of the joint.

If the designer requires the weld to start at the end of the joint, a separate welding symbol must be used indicating the specific location of the initial weld. Likewise if the last weld increment must terminate at the end of the joint. This is nothing new; it has been in AWS A2.4 since 1976.

A little history; prior to the 1976 edition of AWS A2.4, a note was included in the standard that stated the intermittent fillet weld had start at one end of the joint and terminate at the opposite end of the joint. Where necessary the first and last increment lengths had to be lengthened. However, the requirement was dropped from the standard in 1976. As the committee stated, whether the initial and last weld increments occur at the ends of the joint is a workmanship issue and that is separate from a standard on welding symbols.


Best regards - Al

 

[wannabeSE]

If you are not certain about a weld call-out that you are specifying, there is no guarantee the welder will interpret it correctly. AWS A2.4 Standard Symbols for Welding, Brazing, and Non Destructive Examination covers AWS weld symbols. A helpful online reference is on the AWS website:

http://www.aws.org/technical/errata/A2.4errata.pdf

.

If 2-5 is used on the weld call out for the length and spacing of the fillet welds, I would expect the welder to place 2" long welds spaced at 5" on center. I am assuming that you are preparing structural drawings rather than shop drawings. If the piece is 10" long and needs 2" long welds at each end, I would have the arrow point toward one end, specify a 2" long weld and add the annotation "TYP EA END" at the tail of the weld symbol. Or, I might specify 2" welds at 8" and ad the annotation "2 WELDS MIN" or "ONE WELD EA END" at the tail. Then, I would check the shop drawings to see if the detailer correctly interpreted my intent.

 

[NS4U]

thanks gtaw that backgroud info was wht i was looking for. i will add a note in the tail to weld at each end

 

[dhengr]

NS4U:
Most engineers would want the ends of the joint welded/protected, so you end up with three bits of weld, one each end and one in the middle. Thus, Gtaw’s last para. on AWS history. The expensive part of your detail is the layout, and this exact kind of uncertainty. No welder wants to be called back due to a weld less than 2" long, so they will all be 2.5"+, nor does he want to be called back because his spacing is too long, so again he over welds. The starting and stopping of intermittent welds slows the process and leaves potential stress raisers at each start and stop point, without a little dwell time and extra effort on the part of the welder. You didn’t spec. the weld size, but why not use a 10" long weld a 16th or two smaller, to achieve the same shear strength. You’ll make life easier for the welder, layout man, and inspector, and end up with a better looking welded joint, without appreciably more weld metal and much less total fab. time.

 

[Tmoose]

If the joint is subjected to dynamic loading some references would advocate the end welds wrap around the gussset, plate, etc. Some would not recommend intermittent welds in a dynamically loaded joint at all.

 

[gtaw]

I lean toward the position taken by dhengr with regards to a smaller continuous fillet weld versus an intermittent weld having a larger size. The exception to the "rule" is when the continuous weld does not meet the minimum size requirement of the structural welding code.

Assuming both the intermittent fillet weld and the continuous fillet weld do meet the minimum size requirement, the continuous weld is more cost effective. As an example consider the following: You have a choice of a 1/2 inch intermittent fillet weld 4 inches long on 8 inch centers or a continuous 1/4 inch fillet weld. Both are capable of transmitting the same static load. The difference is that the 1/2 inch intermittent weld requires twice the volume of weld metal and most likely requires multiple passes. The multiple pass fillet welds will produce more angular distortion because the total angular distortion increases with every weld pass. While it is not directly proportional, the greater number of thermal cycles usually results in more distortion. The labor cost is also increased when the number of weld passes increases.


Best regards - Al