maximum coverpass width 1

[Downhand]

I am working to the B31.3 code and API and ASME codes. Where can I find the maximum width of weave for a coverpass? I am often told that it is 3 times the diameter of the rod, however, I would like to confirm this.

 

[stanweld]

It is not defined in the referenced Codes. This is generally understood as good practice regarding SMAW welding with low hydrogen electrodes; the "3 x electrode core wire diameter" applies to manipulative weaving - the width of the deposited weld bead is larger.

 

[Downhand]

Thanks stanweld. If none of the codes referenced contain this information, do you know any North American codes that do references this. If no North American codes reference this then where does this standard come from? In all reality, if the heat input values do not exceed the limits of the procedure does it really matter if the welder chooses to weave more than 3 times electrode diameter?

 

[DVWE]

In all reality, if the heat input values do not exceed the limits of the procedure does it really matter if the welder chooses to weave more than 3 times electrode diameter?

It doesn't, as long as heat input (when required) is not exceeded.

But it sounds like you might have some concern here? I see the "3X electrode diameter" restriction often. Probably because someone, sometime, somewhere has seen a 5" wide weld cover pass and it didn't look right, and I would agree.

 

[metengr]

The limitation to weave is considered a practice. In addition, most weld procedures I have reviewed normally state this practice as a requirement.

 

[HgTX]

There are a lot of strongly held conventions that are not in codes. A similar one is the relationship between weave width and electrode diameter.

(And, really, a big chunk of any code is someone sat down and wrote down some of those strongly held conventions.)

Hg

Eng-Tips policies: faq731-376

 

[gtaw]

3 times the electrode diameter, 4 times the electrode diameter; there are at least a thousand rules of thumb and wives tales floating around in the industry that has no basis on facts. It is usually "I heard that you ..... (fill in the blank)."

I have worked with many different welding codes and standards and do not recollect one instance where the width of the SMAW weld pass is limited to a multiple of the electrode diameter.

Consider the following:

AWS D1.1 permits a single pass fillet weld in the vertical position to have a 1/2 inch leg size. The structural welding code/steel limits the maximum low hydrogen electrode diameter to 5/32 inch. Based on the leg dimension, the width of the fillet face should be on the order of 0.7 inches. Remember, this is a single pass weld. The width of the weave would be on the order of 4-1/2 times the diameter of the 5/32 inch electrode or nearly 6 times the diameter of a 1/8 inch electrode.

The width of the layer of any weld made with SMAW is "not applicable" per table 3.7 which addresses prequalified WPS requirements.

Many of the "rules" we hear are institutionalized by the same people that believe preheat is intended to drive moisture out of the base metal, once dried, preheat serves no additional purpose. Aluminum should be blackened with soot and preheated until the soot burns off, and a million other useless "rules" with no basis on fact or code based requirements.

If you are required to meet notch toughness requirements, travel speed is perhaps the most influential single variable controlled by the welder, but it is the heat input and cooling rate that influences the notch toughness of the weld, not the width of the weave.

Best regards - Al

 

[racookpe1978]

OK. Let me (try to) apply your princples to fillet weld "number of passes/weld size."

I need to use GTAW (because of other restrictions irrelevent to the question) to complete various size fillet welds: 1/4, 5/16, 3/8, 1/2, 5/8, 3/4 are usually what's called out. Carbon steel most of the time, sometimes stainless, sometimes CS to stainless.

Length of the weld joint will vary, let's assume 12 inches total. Field welding - The guy is doing it on his hands and knees, all positions, usually in tight quarters.

Fine. I've seen the welders get it done all the time.

My question: How much longer time (ohow many more number of passes) "should be" required to complete those larger welds? Is there any way I can justify the joint re-design by establishing " A 1/4 single pass fillet takes 20 minutes per foot, but a 1/2" fillet the same length takes 8 passes" ??

Can I estimate one GTAW pass can "fill" +3/32" in greater thickness and be 1/4" to 5/16 wide?

 

[metengr]

Well, as usual, I needed to go back and jog my memory. There is one instance where the bead width is indeed limited to 4X the electrode diameter. This is referenced in the half bead temper bead weld repair requirements in ASME Section I, PW-40.3.2 (d) as an alternative to PWHT, and I quote

(d) The maximum deposited weld bead width for any
electrode shall be four times the electrode core diameter.

 

[SJones]

thread286-272239

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04

 

[gtaw]

You caught me with my pants down. I forgot that specific situation. So, in the case of a welded repair on a vessel that has already been PWHT, a repair can be facilitated without additional PWHT if the certain conditions are meet.

The limitation on the width of the individual weld pass is applicable only to this situation. It isn't a requirement that is applicable to all welding.



Best regards - Al

 

[metengr]

gtaw;
We all get caught with our pants down at various points in time otherwise, one would never learn. It is my opinion, that the limitation for the bead width as a "practice" was prior to development of the half bead temper bead weld method, and was around to avoid excessive heat input into the weld joint. Since someone asked where in the US codes this is stated, this limitation on weld bead width only applies to the half bead temper bead repair method.