Mechanical Properties vs Welder Qualification

By Kix

Date 03-10-2009 13:38 Edited 03-10-2009 13:43

Does your A$$ hurt, because it sounds like you might have just got F'ed. You are correct in thinking that mechanical properties are tested and measured in WPS qualification not welder qualification. The only reason the structural integrity of the weld should be questioned is if the welder in question did not follow the WPS for the seams he welded. If he did follow the WPS and so did all the other welders, then everybodies welds should have to be cut out for what this guy is stating.
Welder qualification is to test a person to see that they can make a sound weld not to check the ductility of the base material or weld after welding. Proper tests are speced out in the code you are working to. The welds should not have to be cut out. RT them and if the WPS being followed was in question do a hardness test, but I wouldn't have them cut out. If you keep welding on the same piece of pipe, the structural integrity of the pipe will be affected. Look through the contract and check all the verbage to see that you aren't missing anything. Sounds like you might have one of those professional bullsh!ters on your hands.

By Nanjing Date 03-10-2009 13:39

Clear up a couple of things. What did the welder fail his test on ? Radiography? You state the owner inspector inspector has maintained continuous inspection verifying the proper use of the WPS by the welder. Why did the owner inspector allow welding to continue before the welder has passed his test? If the welder has worked in accordance with the WPS then thare should be no problems metallurgically, the only problem could be unacceptable welds due to defects that would be discovered when the welds undergo non-destructive testing. I think you took the correct action unless I am missing something here.

By Richard Cook (**)

Date 03-10-2009 14:42

The welder failed the bend test with one of four bends, slag inclusion. I spent the past week addresing issues with welder qualifications mainly data entry errors by the third party. The Inspector kept coming up with a new issue with them each time I addressed his point of concern, showed him several times his error which he reluctantly accepted, but kept digging in the specs to find something he could slap me with. I thought that at the kick off meeting the requirement was waved since it was in excess of the code. The inspector didn't know of the requirement untill he had to find something to hit me with, it was the last of seven issues that I addressed with him and the only one I could not defend. The Inspector has completed several UT exams on the welder with out failure.

It is my fault we got to the point in production, in assuming I had the answer at the kick off, I conceded to that and completed the requalification of the welders. The spec requirement was such, "Certification of welders shall have been within 12 months of starting the project". All welders were current and showed continuity in service in accordance with AWS D1.1 and D1.8 and this project spec is the only thing he could pull out after all his efforts previous to finding it.

By CHGuilford (****)

Date 03-10-2009 16:45

Hmm - point to ponder, is "Certification" the same as "Qualification"? (not that it matters much in your circumstances).

How soon can you "re-train and re-test" your welder?
It might be to your benefit to have the welder do 2 re-tests to make up for the failure. I know that it isn't necessary to do the 2 re-tests if you re-train. But I'm thinking the PR might work to your advantage - you want to show that the welder can pass the tests consistently; that the failure was a fluke. (Hopefully your welder can do it - otherwise you go from bad to worse. Wait a minute -you're already at the worst! They want you to remove the welds.)

If at all possible, and if you can bite your tongue without cutting it off, you could try to get the inspector involved "upstream of the process". By that I mean, get him to "help" you to figure out code provisions as they apply to your work, and ask his suggestions on how to comply. Careful - you don't want him driving your bus, and you don't want him telling the engineer that you don't know anything. But if he feels like "part of the team", maybe that'll help in the long run?

Just be sure your own ego doesn't come into play. When you are the smarter one, you don't have to prove it. "When you argue with an idiot, no one around you can tell the difference" (author unknown).

Unfortunately, I don't follow that advice often enough - but I try.

By js55

Date 03-10-2009 15:37

I think your CWI is inexprerienced (not such an unusual problem if you ask me). This is what happens when CWI's dabble in metallurgical or mechanical issues of which they know little. Unfortunately the whole program of CWI training and indoctrination is interpreted as encouraging it (my CWI seminar actually spent a couple of hours on phase diagrams-interesting, but why?), though I'm sure the intent is a well rounded understanding. IMO
Your welders were qualified to code. So your non compliance is a contract issue. I would suggest a volumetric NDE and move on. From a practical standpoint do you freak out and question every weld when a guy drops an RT?.

By CWI555

Date 03-10-2009 16:11 Edited 03-10-2009 16:13

"Welder is qualified and certified for a given process in accordance with AWS by a third party, has welded for many years updating as required. A site specific requirement caused that retesting be conducted on welders, this requirement being in excess of the Industry standards. Testing was completed and one welder failed. The welders had been welding for a couple of weeks and have production welds completed. I wrote an NCR, removed the welder until retrained and qualified, and recommended that all welds completd by the individual go under extensive reinspection and NDT (MT, UT) to asuure quality. "

Question: Why was welding allowed to commence at all; where was the owners inspector; why did he or she not stop the process before production welds were made?

"The Owners Inspector has maintained continuous inspection verifying the proper use of the WPS by the welder, both in production and during the test, and stated on record that all WPS variables were followed. This CWI has convinced the Engineer that the welds have to be cut out because the "mechanical properties" (ductillity, tensile, hardness) of the weld are in question due to the fact the welder has failed the test."

Question: Why did "everyone" on the site allow continued welding with welders not certified to site specific requirements, especially the Owners Inspector who maintained continuous inspection records? Who and when did they actually get around to reading the specs?

Quote: Part C 2008 D1.1
Performance qualification. "This part covers the performance qualification tests required by the code
to determine a welder's, welding operator's, or tack welder's ability to produce sound welds"

4.19.1.1 "Substitution of RT for guided bend test" I think thats pretty damn clear what it's intent is.

paragraph 4.19.1.1 second sub paragraph " In lieu of mechanical testing or RT of the qualification test assemblies, a welding operator may be qualified by RT of the initial 15" of production groove weld. The material thickness range qaulified shall be that shown in table 4.11"

Question: Is their a reason you didn't feel those paragraphs could be invoked? especially the last one?

Moving to the AWS commentary C-4.22 some clarification can be found
C-4.22 Essential Variables

"The ability of a welder to produce a sound weld is considered by the code to be dependent upon certain essential variables, and these azre listed in Table 4.12"
So where did the idea come from to question the weld soundness if all essential variables have been adhered to?

Going to table 4.12 it's title as "Welding personnel performance essential variable changes requiring requalification. (see 4.22)

Para 4.22 Essential variables:
"Changes beyond the limitation of essential variables for welders, welding operators, or tack welders shown in table 4.12 shall require requalification"

Statement
I think both you and the owners inspector have both stepped on your proverbial "censored".
The welder is getting screwed in this mix as well. It may be a real good idea to get together with the owners inspector and
jointly go over the requirements of the code, and the job specs before taking any further action. It may save you both some grief and will likely save some hapless welder before he's fired for BS reasons. My opinion for what it's worth.

Regards,
Gerald

By Richard Cook (**)

Date 03-18-2009 14:12

CW1555
Yes things got turned around, the requirement was questioned and thought waived because it was in excess of the code during the kick off meeting for the project By the Engineer but apparently was not picked up in the changes made before the project started. When the Inspector came on site he came with a personal aggenda. I did screw up on not getting it in writing before the inspector influenced the Owner, everyone remembers the discussion, but no one wants to ruffle feathers but me.

As for the Welder, He has full support from our organization, His Union, the General Contractor and such. We, his employer put him on another of our jobs. I told the inspector I didn't accept his sign off on our welders, his call meant nothing in my program. The welder is a good welder, just had a brain fart that day, tested on equipment he was not used to and didn't question his concerns and kept welding.
Whats really upsetting is four or five production welds were Ultrasonic tested and found acceptable by this Inspector before he found this one requirement he could ding me on. the welders documents have been approved by many other CWIs on different jobs, probably because they thought the errors where insignificant and menial, I don't know.

We use Union hands and we do not know exactly who will be sent to our field site and only get their documents as they arrive. The site Superintendent brought the crew in and sent the documents straight to the Inspector without processing them through me, of which I have never been a part of that process in the field anyway. The Inspector comminced to chew them up, some issues rightly so, but out of seven issues on these documents, four I showed him he was wrong, two were data entry or ommision errors by the testing group and finally the last issue at the last minute, the project requirement. He spread the situation across the first two weeks, I only got involved after the fact when no one on site could address the issues, towards the last of the first week. So that's why it got that far, things happen sometimes, and our industry works on schedules, the welder was qualified and certified, in ours, the general contractors and Unions eyes, which included three other CWIs. The problem was we could not get the ear of the Owner.

I quoted all you referenced, whats sad the Owner sat in the "bring it to a head" meeting and said it "all sounds reasonable" but then came down on the side of the Inspector, and all he provided is his statement on the "intent" of the code. Each time the owner looked at him and asked if what I was quoting was correct, he said yes, but came back and convinced the Owner on the "intent". I do not blame the owner, he needs to trust the "professional" he hires for his expertise, and they don't want to think they hired an idiot.

oh well, on we go, I've implemented for our field projects a QA review, by me, to avoid this in the future. It adds to my work load I'm the shop QA Manager, but at least the Hall is a good bunch and jumped through hoops for me on this issue.

By Kix

Date 03-18-2009 20:27

The fact that your inspector said bend tests are to check the ductility of the weld says it all. So did you end up having to cut out all thos welds or what?

By kipman

Date 03-19-2009 00:25

Woody,
Is the inspector in question a member of the AWS D1 code committee? If not, how does he know what is the "intent" of the code writers? The only thing available to go on are the words in the code - I'm always wary when someone states that they know more than what is written.
Mankenberg

By 3.2 Inspector (***)

Date 03-10-2009 16:24

X-ray the welds and move on....

3.2

By defaced (**)

Date 03-18-2009 15:52

"He states that AWS does bend test on welder qualifications to check ducttillity and we should always perform bends. I argue, why does AWS allow substitution of Radiography and in AWS D1.8 UT also, in lieu of bends, if the test is for mechanical properties. I know for WPS qualification you can not substitute RT or Ut for mechanical testing, a matter of fact you must do RT to support the qualification."

Not that this is going to help much since is sounds like the issue has been resolved but I think it might be a nice back pocket item. I had a similar conversation with a gent at the Naval Surface Warfare Center, Carderock Division last week because I had some procedure qualification welds fail root bends. He said that bends are intended to open up pre-existing defects, not to check the ductility of the weld and that tensiles are meant to check ductility. Also as an aside, NAVSEA Tech Pub 248 (Navy welding qual doc) offers a similar provision for welder quals where radiography or bends can be used for qualification.

By Shane Feder (****)

Date 03-23-2009 03:09

Hello guys,
Just to add my 2 cents worth, not sure if it will help or confuse.
ASTM E290-97a Standard Test Methods for Bend Testing of Material for Ductility
ASTME190-92 Standard Test Method for Guided Bend Test for Ductility of Welds

Now we have the arguement that Welder Qualification Bend Testing is only used to determine whether the welder can produce "sound" welds. What is a "sound" weld ?
I have searched google, I have searched this forum, I have searched everywhere and I cannot find a definitive explanation of what is a sound weld. The closest I can find is the dictionary which gives me defect - free.
I agree totally that the WPS qualification is for testing the metallurgical and mechanical properties of a weld and the WQT is for the welders ability but if bend testing is used for WQT then the materials ductility is relevant to the end result.

This excerpt is from a paper by Omer.W.Blodgett - Understanding Bend Tests
"Bend specimens have been called "a poor mans tensile test". Although it will not show the quantitative values associated with a tensile test, a bend test will demonstrate both the quality of the weld and its overall ductility. Usually, bend tests are designed so that the outer surface of the specimen is stretched to a ductility level that approximates the minimum percent elongation required in a tensile test. When defects exist in materials strained to these limits, the material tears locally. When tearing exceeds a specific limit, the specimen fails."

What I am confused about and hope someone can clarify is this;
ISO 5173 Bend Testing states "....in order to assess ductility and / or absence of imperfections on or near the surface of the test specimen."
What happens if imperfections are not near the surface ?
If you have lack of fusion between the root and hotpass will that show on the bent Face Bend Specimen ?
I realise it would probably show on the Root Bend Specimen but what if the only areas of LOF were in the 3" of Face Bend Specimen area ?
Would a 6 mm (1/4") gas pore in the same position on the plate cause the bend specimen to tear on the Face Bend surface or would it be classed as acceptable?

I have never thought about it before as I always perform RT for welder qualification but it seems there is a possibility that you could quite easily have unacceptable internal defects that would not become evident because the surface didn't tear.
Any thoughts ?,
Regards,
Shane

By defaced (**)

Date 03-23-2009 14:11

"a bend test will demonstrate both the quality of the weld and its overall ductility."

I don't agree with this. If you look at a typical transverse bend, depending on the material - this isn't all inclusive, the area around the weld will not conform to the mandrel diameter, is will actually be flatter. This is an indication that the area in question has not been subjected to the same level of strain as the surrounding base metal.

When you cut a sample out, you can usually tell if you have LOF in the root. If I were the tester and the code did not provide a strict order of removal, I'd take the suspect specimen and subject it to a root bend.

As for the gas pore, it would depend on how close it is to the surface. If you've got a 3/8" thick bend and the 1/4" pore is close to the surface, I'd expect it to tear open or at least provide some indication that there is an issue (local depression).

By Shane Feder (****)

Date 03-23-2009 19:30

defaced,
The statement you quoted was not made by me, the gentleman who made it is Senior Design Consultant for Lincoln Electric so I think there is a strong possibility he knows what he is talking about.

I take it by your last statement that if the pore was not close to the surface then there is a possibility that there would be no indication on the surface after bending. That reinforces the concern I was trying to make - does bend testing allow unacceptable internal defects to be missed if they are not close to the surface under tension?
RT is looking at 100% of the weld whereas it appears bend testing is only looking at a percentage of the weld.
Regards,
Shane

By defaced (**)

Date 03-24-2009 12:36

Sorry Shane, I wasn't trying to imply those were your words. I agree with him in theory, a bend that perfectly conforms to the mandrel surface will be proof of elongation, but in practice it's a different story which is what I'm getting at.

I've seen stuff pass X-ray that failed bends. On a cladding project I just finished, tiny LOF at the toe lines went undetected through RT and UT but failed macros and bends. This was 3/8" clad on 2" plate, which is probably the reason why it passed RT - the RT process simply wasn't sensitive enough to pick up that size of defect, and it was in a bad orientation for RT. And as we've agreed, if there's internal porosity, a bend won't likely show anything unless it's enough to tear open or split the sample in half. If you really want to CYA, you kinda have to do both bends and RT.

By James Corbin (**)

Date 03-24-2009 03:44 Edited 03-24-2009 04:00

Woody Just a thought out of the B4.0-07:
1) 6.8.1 ......the specimen shall be tested at ambient temperature and deformation shall occur in a time period no shorter than 15 seconds and no longer than 2 minutes..............
2) Figure 6.2 Fixture Dimensions for 20% Elongation of Weld and then read Note 5
3) 6.10.2 ......bend testing at 20% elongation is normally considered sufficient........
I will attach a pic of what happens when elongation is less than 20%, I will assume yours was not if the only thing said about the bend face was a slag inclusion. Evidence of slag is not evidence of elongation failure. The bend test will only test to 20% - the PQR tensile pull test data will let you know the exact elongation % only from the original test.
You can make your own conclusions

Attachment: P1010065fcs.jpg (358k)

By arrowside (**)

Date 03-24-2009 13:55

While the other guy's discussion on ductility and elongation is interesting, I feel that it was simply a last ditch effort by the owner's inspector to make himself look like king shizit on turd island. If the owner had any sense, he would realize how much extra money his inspector is about to cost him. The welder had an issue, and it was dealt with. UT his previous welds and move on. Why take them out if the WPS was followed? UT will show if they are good or bad. Sounds to me like the owner's inspector has an inferiority complex. I hate working with inspectors that feel as though they have to overthink everything. They're usually the ones that have 0 hrs. under the lid, in my opinion.