Porosity Acceptance Criteria D1.1

By hogan

Date 02-05-2008 18:58

i think the difference is indications open to the surface. typically

By js55

Date 02-05-2008 19:28

The thing is, I have gotten so in the habit of rejecting porosity of essentially any extent (having essentially written every program I have been involved in that way), the idea that a large cluster of porosity being acceptable is anathema to me.
Is this indeed the case or is there something I am missing?

By jwright650 (*****)

Date 02-05-2008 19:39

Take a look at C-Table 6.1 item 8 - piping porosity....in the Commentary Section of your D1.1(page 457 in 2006).

By jwright650 (*****)

Date 02-05-2008 19:41

I reject all of it also...because it's my shop and it makes people question your quality when they see porosity. As you well know, there are reasons for it and most of it is workmanship related, so I feel it screams bad workmanship very loudly.

By hogan

Date 02-05-2008 19:44

i also reject porosity that is acceptable. i like to think we have a little more pride in our work.

By Kix

Date 02-05-2008 19:45

I look at it as if you see a hole it's piping porosity. If you see cluster porosity then that's just a bunch of piping porosity. If you see linear porosity then that's piping porosity in a line. Or like said above any kind of porosity exposed to the suface is piping porosity. You can't measure the stuff you can't see unless you use RT, and that's a whole new set of criteria. So then you just go by table 6.1 and you know the rest.

By js55

Date 02-05-2008 20:08

This is very interesting indeed. So essentially the answer is yes, technically speaking, and within the letter of the code, if it ain't piping porosity its acceptable.
And consistent with Kix's thinking, generations of welding inspectors have been incorrectly taught to do that very thing, or at least to incorrectly understand what it is they are being asked to do.
I mean, from a practical standpoint you sorta have to treat it all as piping porosity, since by its very 'perpendicular' definition, determining that definition may be impossible without excavation or PT. And if your going ot insist upon grinding or PT you may as well just go ahead and fix the thing.
Doesn't change my perspective on porosity, but it is an interesting revelation upon inspector training.

thanks guys

By CWI555

Date 02-05-2008 21:47

From AWS A3.0:
"piping porosity. A form of porosity having a length
greater than its width that lies approximately perpendicular
to the weld face."

Therefore, I judge it to be any pore for which I cannot see the bottom off no matter what angle of light (will usually try to gauge actual depth as well via thin wire), and if I can see the bottom, it then is porosity or piping porosity based on the definition in A3.0.

If there are no other specific rejection criteria, I let it stand if it does not meet the criteria of the previous sentence. I agree it's usually a sign of poor workmanship, but a porosity, is not specifically rejectable to my knowledge unless call so in contract docs.

Regards,
Gerald

By 803056

Date 02-05-2008 20:11

D1.1 is pretty clear on the type of porosity that is a concern, i.e., elongated porosity, whether the long dimension parallel to the weld axis or normal to the weld surface. As an in-house QC/QA person, you have the latitude to make the acceptance criteria more stringent than that permitted by the code. However, as a third party inspector you are bound by the code requirements unless the fabricator has more stringent criteria listed in their QC manual which was approved by the owner or EOR.

Third party inspectors that apply their own acceptance criteria, you know who I mean, the few that live by the creed, "I don't care what the code says, if I don't like it, I'm not going to buy it!", don't usually last very long as third party inspectors.

Best regards - Al

By js55

Date 02-05-2008 22:21

And what of the new generation of inspectors? Is the current AWS CWI course and testing process considering depth issues of porosity or are the new CWI's being trained in surface diameter only?

By CWI555

Date 02-05-2008 23:40

From the ones I've seen recently, I'd say no.

By 803056

Date 02-06-2008 01:36 Edited 02-06-2008 01:43

I can't speak for all the instructors that teach AWS and other commercial training programs, but to my knowledge the difference between piping porosity and spherical porosity is covered during the discussion of the different types of porosity, i.e., aligned, uniform, elongated, etc.

I would assume (very dangerous) that like any training program, the basics are covered during the fundamentals portion of the seminars and code specific requirements would be addresses in that portion of the program. I've sat through several CWI seminars over the years and I seem to remember the instructors differentiating between the various types of porosity. The fundamentals portion of the seminars is general and not code specific.

I just checked three different recent welding codes, D1.1, D1.5, D1.6 and each addresses piping porosity and provides limitations for acceptance. I even went back in time and checked D1.1-83. Even then the three categories of welds, static, cyclic, and tubular, addressed the issue of how much piping porosity was permitted. There is no mention or limitations imposed on spherical porosity under visual examination . As I looked through the book I noticed there were a lot of notes and highlighted passages. The section on piping porosity is highlighted. I bet someone pointed it out to me and told me it was important or I used it in one of the courses I taught for the local AWS section and I thought it was important enough to note.

Evidently, it has been some time that the criteria for porosity has been limited to piping porosity in the structural welding codes.

Just a quick question, have you rejected structural welds that have to meet D1.1 because of spherical porosity? And if you have, what was your criteria based on? :( Once again, the in-house QC/QA program can be as stringent as you want to the point that none of the welds pass visual examination, but the third party inspector has to stick to the criteria that was agreed to by the owner, EOR, and fabricator.

Best regards - Al

By CWI555

Date 02-06-2008 02:32

In answer to your question, no I have not ever rejected due to spherical pores when it was straight up straight down D1.1. However; there have been contract docs I've had to work to for which the EOR did specify it. For D1.1 it is my understanding piping porosity is required, if it doesn't meet that definition it passes. I don't make a habit of rejecting for ugly, regardless of my personal opinion.

Regards,
Gerald

By 803056

Date 02-06-2008 05:23

Good response.

I've worn my fingers to the bone looking for "ugly" in the AWS welding codes and haven't found it yet, but that doesn't stop me from looking.

Had an interesting job this morning. A two man shop had to fabricate about 20 pieces of steel framing for an exposed fire escape. I asked for copies of their welding documents a couple of weeks ago and told him it was in his best interest to send them so I could review them before he started fabrication.

You know the story, I sent them already, you should have them. I e-mailed them, you should have them. The truth of the matter is you know he didn't have them to begin with and he fabricated all the steel.

I arrived at his shop and looked the welds over and said, "I see you used solid wire on these."

"Yup." was the response.

"What were your welding parameters?" I asked.

"The machine is still set up just as it was when we welded them." was the answer.

"Do you have your welder certs?" I asked him.

"I only have the stick certs, I didn't get the ones for mig from the guy that takes care of my paperwork."

"No problem, I have some plates in the van. I can test you right now so there won't be any delays." And I pulled the plates out of my van for the fillet break test.

I told him to check his settings and run a quick practice plate to make sure everything was to his liking. Which he did.

We ran the test and cut the ends off and proceeded to break the fillet. As he broke the fillet weld with a four foot pipe wrench, I told him, "It shouldn't break that easy."

I then took the pieces and showed him how there was no fusion in the root. There was about an 1/8 inch of IF to either side of the root. I then explained how AWS doesn't permit short circuiting transfer unless he qualifies the welding procedure.

"What do you mean when you say short circuiting transfer?" was his next question, and this is from a self professed expert welder with 25 plus years of fabrication experience.

We had a little discussion about GMAW, the influence of the shielding gas and welding parameters on the mode of transfer and the benefits of using spray mode transfer on heavy structural material.

As we left the shop the two engineers turned to me and said, "You knew the welds were bad by looking at them didn't you? Why did you have him run the test plate if you knew it wouldn't pass?"

My reply was, "The welder didn't know he was doing anything wrong. He didn't know the code requirements or the different modes of GMAW transfer. If I simply rejected the work without the test, he would never believe that there was a problem with short circuiting GMAW or understand the nature of the problem. In his mind I would simply be another hardaXX inspector. Now he saw the problem first hand, he knows how to make a sample weld to verify the machine is getting the required fusion, and he can make the necessary corrections if the machine isn't set properly. The lesson still stings, but he's happy that he's learned something he didn't know before."

It was a good day.

Best regards - Al

By ssbn727 (*****)

Date 02-06-2008 08:47

Way to go Al :) :) :)

Respectfully,
Henry

By js55

Date 02-06-2008 14:40

Al,
As a matter of course I write all my QC programs to reject porosity of any kind and of any extent. In my opinion there just isn't any justification for its existence. Besides the fact that it eliminates the necessity of welders and inspectors having to retain the criteria in their heads. No porosity is easy to achieve, its easy to remember. I would however applaud D1.1's engineering approach(necessary to say since I do criticize without hesitation) to acceptance criteria in this case and would not argue that the code become more stringent. However, were I to be inspecting to the code I would do so based upon the Table 6.1 criteria.

By CWI555

Date 02-07-2008 01:17

Jeff,

I agree with the idea there is no real justification, but I still hold to the theory that it's better to default to the code than make it more or less stringent. For programs I've written, they will be no more, no less, than D1.1 or whichever other code I may be working to. As your probably well aware, once you have a shop set up, your onto the next one, that shop you've just finished with has to live with that program once it's done. Those inspectors for that shop may not be there 1 day or 5 years from the time you left. In another day and time, that inspector gets themselves in a ringer because they are going by what they have been taught in the past which was more stringent than the code. As for memorizing the criteria, that's about the worst thing any inspector can do. To this day I will look it up every time for each specific incidence. My memory is not that bad, but it's a good work habit to be in.

IMHO, inspectors as a whole need to be in the habit of looking it up every time. Procedures, standards, and codes, change from time to time, and bottom line is, the inspector needs to be in the habit of recognizing and adapting to that fact.

Regards,
Gerald

By js55

Date 02-07-2008 14:46

Gerald,
I think your approach is as ligit as any. And perhaps even more justifiable than my own considering that I've argued the very same approach in other contexts. Its engineeringly sound, and cost effective.
My approach, in this case, is my own preference and the arguments I use to justify it actually fly in the face of my own usually minimalist approach, sorta. In this case I do come down on the side of more stringency in order to simplify (restoring some semblance of my minimalism) the information the shop has to deal with, and it seems to me it just isn't that hard to achieve. And it can be taken advantage of as a marketing tool, especially when you are dealing with unsophisticated customers where appearance may be everything and the subtleties of engineering soundeness may be lost on them.
I suspect that the percentage of sophisticated customers that you deal with is higher than mine. Most of the sophisticated customers I deal with are ASME not AWS.

By 803056

Date 02-07-2008 04:21 Edited 02-07-2008 04:33

Most welding standards recognize the relative innocuous nature of porosity and allow for some porosity unless there is a cause for concern with fluid leakage.

Your argument could be used for every weld discontinuity seen by the visual inspector. Yet welding standards accept some undercut (ASME Section VIII doesn't even include undercut as a visual attribute to be evaluated), undersized welds, spatter, and yes, even some cracks (per API 1104 and AWS D1.2).

I agree with you that it would make our job as an inspector easier if we arbitrarily set the acceptance limits for weld discontinuities at zero. No gray areas, just a thumbs up or thumbs down. At least that's how I used to approach welding as a welder before becoming an inspector and working with engineers and a couple of fabricators.

I worked with a manufacturer that fabricated pressure vessels for over 50 years. The QC inspector and the AI were constantly banging down welds that met the acceptance criteria because they "knew the welders could do better". I told them that the only thing they were accomplishing was increasing the cost of the vessel without any increase in value or longevity for the customer. Sooner or later upper management would go to a lower cost sources. And that is exactly what happened. The vessels were subcontracted to every Tom, Dick and Harry that had an ASME U stamp and guess what, the undercut, spatter, and the ugly welds were perfectly acceptable because they met code. All the fabrication was outsourced and we no longer needed the welders, QC inspector, or the AI. Me, I got the job of finding subcontractors that could build the vessels we used to build in-house.

I was told a story by Bob McMaster many years ago about "fitness for service". He told me that during WWII he went to England at the time when the English were battling the Germans for air superiority. The purpose of the visit was to see how the Brits handled quality control and NDT. They handed him a radiograph of a propeller shaft with an crack running nearly the length of the shaft.

Bob said, "Clearly this shaft would be rejected because there is a longitudinal crack running the length of it."

The Brit replied, "I can guarantee that shaft was install and the airplane is most likely flying as we speak."

"Why would you install a shaft that is defective?" Bob asked.

"My dear friend, the life expectancy of the aircraft is less than 40 hours, surely the shaft will outlast the aircraft!" was the reply.

Food for thought.

Best regards - Al

By js55

Date 02-07-2008 14:55

Like the terrorist worrying about the quality of the duct tape used to strap the TNT to his chest.

By CWI555

Date 02-07-2008 01:03

Thats a good approach. Good job. Though, I do think based on what you've stated in regards to "You know the story" the guy did at least have some idea he was doing something he was not susposed to.

Regards,
Gerald

By 803056

Date 02-07-2008 04:31

I tend to agree with you Gerald. I still don't have the paperwork, but it really doesn't matter at this point. Bad mouthing the welder to the engineers wouldn't have impressed them. They saw first hand what was the consequence of using short circuiting GMAW.

It was the welder's first fillet break test (according to him). He said he had always taken the 3/8 inch or 1 inch grooved plate test. But of course, not with short circuiting GMAW.

God bless him and all the other fabricators. If they did everything right the first time I would have to find a real job.

I have to visit the shop tomorrow to verify all the existing welds were removed and he'll have a second chance to do it right.

My concern is that it gets welded properly this next time.

Best regards - Al

By js55

Date 02-07-2008 14:52

Now isn't this interesting. Perhaps I'll just shut up for a moment (nah). I'm not too sure though, that I want to pursue this discussion any deeper since Gerald and Al, with great articulateness, are starting to corner me into a place I dont want to go. In other words, the breakdown of my oft supported minimalism.

By 803056

Date 02-07-2008 15:17

Don't get bashful on us now!

You know the reason we always come back to the forum is to kick up some dust and have some good discussions. You, Gerald, John, and Henry are among my favorite people to discuss these matters. You always back up your opinions with some valid ideas and principles. That's why we're here and of course toss a barb or two on occation. :)

What have you to add Henry?

Best regards - Al

By js55

Date 02-07-2008 15:45

Al,
Bashful?? LMAO!!
I've been called a lot of things. But thats a first.
I just wanted to clarify the point that I think you and Gerald are essentially correct. I have no beef with it. And I think the record is clear that were I to have a beef I would not hesitate to toss myself upon the gauntlet. Even at the risk of taking a disputatious azz whoopin.
That my exception to the porosity issue is exactly that. An exception. As a matter of choice. And when I write a program I make the options clear to all involved.

By 803056

Date 02-07-2008 16:40

As an in-house QC/QA person, that is your prerogative. In some cases it is prudent to do exactly as you have done. A typical situation would involve customer expectations and the need to have a product that conveys the impression of high quality and a visually pleasing appearance.

Who among us don't look at welds in airports and other public buildings as we stroll through and say, "That is one ugly weld, who inspected that!" While it may meet the code requirements, an ugly weld doesn't give the desired impression that the contractor had his processes under control or that QC was doing a good job of ferreting out unacceptable welds.

There are instances where "tightened acceptance criteria" is truly justified.

Best regards - Al

By Lawrence (*****)

Date 02-07-2008 22:25

Darned Right!

Nothing at all wrong with in house QA exceeding the code on visual criteria... If management is willing to back the possible expense of compliance that is :)

By CWI555

Date 02-08-2008 00:34

That is one ugly weld, who inspected that!" So true, but the ones that really disturb me are the ones that you know within a 90 Percent probability what the code was, and in knowing that, know there is no way it could have passed legitemately. That is unless it was the FC 2002.

Regards,
Gerald

By ssbn727 (*****)

Date 02-08-2008 05:41

Ischcabibble!!! :) :) :)

No seriously Al, Gerald, and Jeff... Why would I want to spoil a perfectly good discussion when you guys are handling it so well??? Btw Al, I'm going to PM you tomorrow because right now I need some shut eye :) ( Just got back from teaching tonight ;) )

Anywho, Thanks for even considering my own participation in this discussion... I consider it an honor to even be included in the same sentence with you gents!!! :) :) :)
I'm fresh out of "barbs" to throw out so, I'm going to shut my brain off now ;)

Respectfully,
Henry

By js55

Date 02-08-2008 14:59

Sometimes I like when Henry shuts his brain off. Often his posts make me feel like I should be working harder. :>)
Your a tough fellow to keep up with Henry. I still haven't digested the stuff you posted in the Metallurgy forum. And it may be awhile before I do.

And thanks. Bhadesia's Bainite book is awesome. But the thing in print form is 3" thick!!! Way way more about bainite than I wanna know.

By ssbn727 (*****)

Date 02-08-2008 16:07

You're "weldcome" Jeff!!!

I know what you mean about the Bhadesia's Bainite book... Some of the math in there is keeping me in stitches :) :) :)

Respectfully,
Henry

By missouridave Date 02-08-2008 16:45

Great topic guys! When I train my inspectors in regards to D1.1 porosity, I tell remind them that the code only addresses "piping" porosity. Typical, runof the mill cluster porosity is acceptabel per the code. The problem with Porosity is it's easy to see. Anybody and everybody can identify a clusters of pores. The fact that it is normally not detrimental to a weld is irrelelavent. Oh and for what it's worth, when I was just starting out as an inspector about 15 years ago, I called the AWS tech dept about this very questions. the short, terse response I got....AWS is not concerned with porosity.

By James Corbin (**)

Date 02-09-2008 01:21 Edited 02-09-2008 01:30

I know its opening a can of worms but ---- While doing some checking on porosity I found yes there is not much said beyond piping porosity in the D1.1 BUT the D1.5 does talk about this issue. (I could not find my 2002 so here it is from the 96 version) Annex B Nonmandatory Lists common Weld discontinuities with graphics and so does the B1.10 and B1.11. The explanation of each type of porosity is long so I will just list them:
1) Uniformly Scattered Porosity
2) Cluster Porosity
3) Linear Porosity
4) Piping porosity
If you read between the lines you will find each type can be related to not controlling some part of the welding process. If you think the porosity is Very bad:
Check the as welded parameters they may not match the WPS i.e. cfh flow, volts too high (causes worm tracks),
Check the cleanliness of the base material; primer, cutting fluid or oils may exist on the base material.
Check the technique the weldor is using i.e. angle of the gun/nozzle or nozzle size, ESO or wet or was wet electrodes.
Check the airflow around the weld area; wind is limited to 5 mph,
Check weldors termination of the arc,
I have even seen a cylinder the was contaminated (left open) and when filled had moisture trapped in it causing hydrogen to be induce into the weld pool (porosity occurred)
There is more---- I will agree if it happens only once in a while I will blow it off but I may note which weldor did it and watch his/her welding technique. The end result is YOU Don't have to accept porosity if it can be traced to some of the above (or more).
No matter what if porosity is continuous and traceable to its cause, it can and should be stopped. Use other parts of the code if you want to make it an issue.