Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / Inspection & Qualification / Inspection myths and facts?
- - By Lawrence (*****) Date 06-25-2016 17:01
I was taught decades ago that when measuring porosity that:

"If the distance between two pores was less than the diameter of the larger pore, that both pores shall be measured as a single indication regardless of the pore diameter."

An example of this would be a string of porosity along the axis of a fillet weld.  Many of the pores measure less than 1/32" but are very close together. 

I see nothing in the D1.1 inspection criteria (Table 6.1 or anyplace else) that puts text support to what I have believed to be an inspection fact for a long time.

According to Table 6.1  I could have a line of porosity with a pore measurement of less than 1/32" that extended the length of the entire weld and it would be acceptable.

It's something I've been thinking about for a while and the other day somebody else asked me how to deal with type of situation... Looking for code text to back a rejection of porosity in a line.

What say you ? 

What can we hang our hat on here that I'm missing?
Parent - - By welderbrent (*****) Date 06-25-2016 17:38
I never heard that that I recall and I sure don't know how you could stand your ground from the codes. 

Now, having said that, if I saw porosity like that and the shop was not fixing it without me saying a word, it would be in my report and I would seriously question their desire for quality.

Parent - - By Lawrence (*****) Date 06-25-2016 17:53
See that's the thing..

We all know that it's bad.

Everybody but the code?

Really...   We are pretty full of ourselves if we expect a producer to fix something that is code compliant eh?
Parent - By welderbrent (*****) Date 06-26-2016 04:43
Yep, undercut, porosity, and other 'borderline' situations.  When handled correctly and a good working relationship with a decent QC program is in place they often repair items that would be code acceptable without me even pointing them out.  And, if I do say something about an area, they will often fix it especially if there are other repairs they have to do in the area anyway.

And I don't have to be full of myself at all to get results as long as I am reasonable and back any actual repairs marked with my marker up with code if challenged.  They know I don't make pure personal opinion calls and work with me, both the QC dept and the floor leadmen and welders.

Spent years establishing a good rep as reasonable and not over the top with personal opinion.  Things like undercut just because your fingernail hangs up on it.  Now that's stupid.  It will set you at odds pretty fast with everyone.  Use the correct tools and back it up with the codes.

Parent - By pipewelder_1999 (****) Date 06-25-2016 21:01
It is defined in 3.0 but I have never found it in D1.1 for Visual . Here is a commentary with it referred to but no information.

Aligned rounded indications are addressed for NDE methods .

Parent - By ctacker (****) Date 06-26-2016 05:25
I've also had a hard time believing you can have one porosity hole up to 3/8" in diameter in a linear inch of a fillet weld, or even two in 12 inches of weld.
Parent - By thirdeye (***) Date 06-27-2016 19:19
I don't recall ever hearing about that formula for calculating allowable sizes of porosity.  I do go along with welderbrent with the idea that a responsible QC/QA department will generally repair items that may be within code, but could telegraph an image that would make a customer loose that ol' warm and fuzzy feeling when it comes to first impressions... and when a customer sees sloppy workmanship on the surface, it's easy for them to think there could be subsurface flaws as well. Most of the porosity I see on the job are single pores or smaller clusters, and when excavated they often size-up on excavation and can go quite deep, which can be another reason a responsible inspector will remind a responsible QC/QA guy that this scenario might exist.  I carry a couple of the smaller wires from a torch cleaning set and can sometimes wiggle that wire a good 3/16" into a surface pore.

I cut my teeth in RT in the 70's and there were plenty of times I'd see an acceptable diameter pore, but it would be so dark it was obvious it had some significant height to it, and I would recommend a repair. Here is a section view and etching showing a really nice elongated pore just under the surface, and below that is some surface worm tracking.

Parent - - By CWI555 (*****) Date 06-27-2016 21:34
By decades, does that go back into D1.0 into first edition D1.1 prior to the release of D1.5 (71-74)?
Parent - By Lawrence (*****) Date 06-27-2016 21:39
I have a PDF of the "First Edition" of D1.1   But I was not worried about  porosity at that time.... More like how to perfect a Fake ID
- - By 803056 (*****) Date 06-26-2016 02:08
Let's differentiate between spherical porosity and piping porosity. AWS D1.1 only includes criteria for piping porosity.

Parent - By Superflux (****) Date 06-26-2016 02:55
Creative QC'ing comes into play.
With a measurement of depth that would indicate less than the desired throat dimension, then add the major axis of the opening, it is possible that you might come up with an "Under run" situation if it were the worst case scenario with <1/32" porosity yet with multiple occurrence. So in other words, after an intense amount of measurement you might could show that the sponge looking weld was not meeting the volume of desired weld material
If all else fails, it definitely would fall under the QC's judgement of Poor Workmanship Practice.
Parent - - By js55 (*****) Date 06-28-2016 10:59
We have two conversations running side by side. The definitive points are Al's and third eye. Al clarifies the point that in D1.1 what we normally think of as porosity is not addressed AT ALL. Third eye makes the point that customer expectations are ALWAYS in excess of code mins.
The seeming negligence of the porosity determination in D1.1 is not a negligence at all. It is based on sound engineering assessment of the structural deleteriousness of porosity which is generally negligible.
Appearance is another issue altogether.
Parent - - By 803056 (*****) Date 06-28-2016 22:00
At issue is whether the porosity substantially reduces the cross section of the weld. Spherical porosity generally has little impact on the load carrying capacity of the weld.

Parent - - By js55 (*****) Date 06-29-2016 15:43
This is true. And not only that I read some papers some years ago where they did mechanical testing experiments with Swiss cheese welds. Porosity will create triaxial stress fields that can actually increase yield strength. Though it reduces ductility.
If memory serves, and its been along time, the detrimental cross sectional reduction was around 50% or so.
Parent - - By js55 (*****) Date 06-30-2016 13:23
It might be interesting to read the article and determine how they translate what appears to be a consideration of microvoid coalescence to results of macro mechanical testing, i.e. tensiles, bends, elongation, ROA. That is, is if I could understand what the F they are saying. :lol:
Parent - - By CWI555 (*****) Date 06-30-2016 20:12
Boiled down, compression not so much a problem. Shear and or tensile, is another story.
Parent - - By Bill M (***) Date 09-27-2016 14:16
Hi Mr. Third Eye,

I am very curious about your porosity pictures I also took the attached photos in Wyoming back in 2006!

Parent - By 803056 (*****) Date 09-28-2016 12:41
Nice macroetch specimen and educational.

With regards to the criteria of two indications, side by side, separated by a small distance counted as one large indication, I believe you are thinking of the criteria as it applies to radiography.

When performing RT, D1.1 requires side by side indications to be separated by a certain distance and they must be located a specific distance from the ends of the joint. The larger the indication, they must be further apart. To complicate matters, the nature of the load also comes into play. In the current edition of the New Farm Code, as well as in previous editions, the tables addressing the matter are found in Clause 6. 

As long as we are on the subject, I am always looking for good photographs of discontinuities and defects. If you are willing to share you photographs with me, I will appreciate your contribution. We will be revising the "Guide for Visual Examination of Welds" and good photographs are always welcome.

Best regards - Al
Parent - - By thirdeye (***) Date 10-07-2016 13:47
Bill M, sorry for the delayed answer I've been spending more time on the new AWS member network.  I do third party inspections for your company's repair facility in Wyoming, so we wound up photographing the same coupon. We have met a few times over the years. I wish I could remember more of the details of why the coupon was cut right at that pore but it's possible the indication showed on the x-ray and we decided to investigate further.
Parent - By Bill M (***) Date 10-07-2016 19:51
Well...I had to dig deep to find my copy and thought it was more than coincidence that we took the same picture 11 years ago! 

You are probably on the right track... we x-ray welder qual. coupons, no other reason to slide and dice.

You take care sir,

Feel free to use my photo as you like
Up Topic Welding Industry / Inspection & Qualification / Inspection myths and facts?

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill