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Up Topic Welding Industry / Technical Discussions / "Appreciable" Weaving
- - By pipelinin.101 Date 04-23-2019 01:16
For context:  ASME defines a stringer bead as "a weld bead formed without appreciable weaving."

Can anyone define what ASME considers "appreciable" weaving when defining a stringer bead?  I am trying to find a credible reference for defining dimensional application of a "stringer" bead.  We have specified a stringer bead for our WPS (SMAW process), but our client is concerned we are outside of the parameters of the definition of a stringer bead due to the width of the bead being used for our fill passes.

What should I recommend as dimensional maximum for our bead width to still be considered a "stringer" bead?  Is there a reference that defines this?

Thanks in advance.
Parent - - By Lawrence (*****) Date 04-23-2019 12:17
I'm not an ASME expert but have at least one idea that might serve at least practically.

I think we can all agree that a stringer bead will get from point A to point B faster than a weave bead.. Yes ?

If the WPS states the weld shall be made with stringer beads, it is likely the PQR also recorded the travel speed.

If the oscillation/manipulation/weave of the weld bead is such that it causes the travel speed to be slower than the WPS value, you have a problem.

This is a lot more difficult to monitor on a 2" pipe than a more straightforward weldment I suppose...

"Appreciable"  is certainly a weasel word...   How does a welder, inspector, engineer, or anybody else quantify that?

"I can't define Pornography, but I know it when I see it"    Same for weaves ?

I do think everybody that is trained and certified to do the work ought to know what a stringer bead should look like when compared to a weave.   One is made with a side to side motion and the other is not.    If the beads are being consistently made with a side to side motion, you most likely need to tighten that up.

But if the welder is moving from point A to point B  slower than the WPS travel speed, and moving from side to side?  That I think is a pretty clear indication of an "appreciable" weave eh?
Parent - - By 803056 (*****) Date 04-23-2019 13:21 Edited 04-23-2019 13:24
I agree with Lawrence that this issue can best be addressed by the travel speed listed by the WPS. That being said, it is incumbent on the individual writing the WPS to do the necessary homework to determine what travel speeds actual produce the desired results.

OK, so some ASME construction codes recognize SWPS. That's a case of buyer beware. They can't be used if PWHT is required and they can't be used if CVN is required. There other issues, but that is a different discussion.

ASME essentially requires the employer to qualify the WPS by testing. During the qualification effort, it is easy enough to determine what the travel speed is. All the more reason to have someone witness the welding of the coupon and to record the nonessential and supplementary variable in addition to the essential variables. One needs data to support the parameters listed by the WPS.

I have taken the position that using the preformatted forms included in most codes simply do not provide sufficient room to record the data that “should” be recorded. I advocate developing a format that can be expanded or contracted as needed. One can use the forms included in the codes as a general format, but don’t feel that the forms have to be used. The age of the dinosaur is long past, there is no reason a computer program such as MS Excel or MS Word cannot be used to develop a format that lists all the information and provides sufficient space to record the data for every weld bead.

I do a reasonable amount of work with aluminum. If GTAW is the process used, it is interesting that none of the preformatted forms included in the codes have an entry for “wave balance”. If the power supply has a control for that function, it is essential the welder “know” what the setting should be. I discovered how important that setting is when I was qualifying several welders in adjacent welding booths. A couple of the welders were really struggling to produce a bead, yet their ammeter and voltmeters were identical to those experiencing little difficulty. Then I noticed the “wave balance” setting. A twist of the knob and the issues disappeared. The control is only active if the welders is welding with AC. The point is, the codes don’t necessarily require all the necessary information be recorded. The person charged with qualifying the WPS and recording the welding parameters needs to understand the process in sufficient detail they know what information needs to be recorded and what parameters need to be monitored.

Parent - - By pipelinin.101 Date 04-23-2019 19:59
Let me provide a little more context here.

We are currently qualifying a procedure to API 1104 and client specifications. We are following a preliminary WPS I have written specifying a stringer bead for the downhill low hydrogen rods that we are using. This was specified as a result of the rods propensity to trap slag with the weave technique. This preliminary WPS was reviewed and approved by the client prior to welding.

During a fill pass, the welder is traveling at a very low speed with very little oscillation. The weld is examined by RT and found to be free of slag. Sadly though, we will not get to destructively test the weld as it has already been rejected. The bead width at 4.5 in/min was roughly 3x the rod diameter.

At this point, it is moot, but is there consensus that 3x rod diameter is not considered “appreciable weaving? I know a stringer bead when I see one, but apparently I do not know the difference between the two.
Parent - - By 803056 (*****) Date 04-23-2019 20:36
While there is no code requirements pertaining to the maximum width of a weave bead, there is likewise no limitation or stipulations regarding what constitutes the maximum width of a stringer bead. A lot of welders will tell me the maximum width of a weave bead with E7018 electrode is anywhere from 2X to 4X the diameter of the electrode. Again, I know of only one instance where a code limits the width of a weave bead. If I recollect, it is found in Section VIII pertaining to an in-process repair after a vessel has been PWHT. 

Parent - - By Shane Feder (****) Date 04-23-2019 22:15
Not a good idea to mix ASME IX and API 1104.
You are qualifying to API 1104 and the comments regarding stringer v weave are not relevant.
The only thing API 1104 is concerned about is travel speed and you have stated that was very low.
If this is a PQR you are performing to qualify your preliminary WPS then you are setting the variables.
If you have a low travel speed but it passes all required destructive and non destructive testing you are fine.

I have said this many, many times previously - politely ask the client why it has been rejected.
They cannot impose ASME IX restrictions on an API 1104 procedure.
Parent - - By 803056 (*****) Date 04-24-2019 00:59
You're right Shane. I only bought ASME into the conversation because it is the only one I know of that requires "stringer" beads for a repair technique. And even that, I wouldn't hang my hat on if the peg it too high.

Best regards - Al
Parent - - By Shane Feder (****) Date 04-24-2019 10:08
OP noted ASME originally, that is why I commented.
Just to expand on Lawrences reply - if the travel speed between A & B is too slow there may be no weaving or oscillation but the stringer bead is deemed too wide (by the client) because molten metal flows outwards in 3 x directions.
How can you deem it too wide if there is no weaving or oscillation ? - you can't !
The only thing to be concerned about with API 1104 is travel speed (unless your client specifications note something you haven't shared with us).
Look at ASME IX as an example - you can have a weave 10, 20, 30 x the electrode diameter and be perfectly code compliant (if impact testing is not required by the construction code).
Parent - By pipelinin.101 Date 04-26-2019 12:21
So we are not "mixing" codes here...  This is being qualified to API 1104.  The issue becomes where the preliminary weld procedure lists a "stringer" technique.  Without API addressing specifically the difference between "stringer" and "weave" I turned to ASME only as reference to have some definition to use as a basis for comparison.

For the sake of the welding procedure, we have multiple coupons with varying travel speeds.  We've made the decision to go ahead and perform our mechanical testing on the coupons with the lower travel speeds (heat input is also essential variable per the client specs in this scenario) to compare the mechanical properties of both welds made with varying technique.

The argument for rejecting the welds was based on the client's concern that there was too much heat input (citing use of a "weave" technique) that would affect the mechanical properties of the weld.  We will perform the additional testing at our cost, not to prove the client wrong, but to ensure we have the best weld procedures in our arsenal for future projects.  I will be happy to share results here once we do.

FYI - filler material is ESAB Pipeweld 90DH (downhill low hydrogen SMAW electrodes.)
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