Welder Qualification Through Fillet Weld Test Coupon

ASME Section IX permits welding performance qualifications through groove weld coupons as well as fillet weld test coupons. It is for the welding engineer to decide which kind of coupon would be appropriate for his application. In this article we will discuss how to make this choice, and other aspects surrounding welder qualification through fillet weld test coupon.

welding performance qualification though fillet weld coupon
Which one is better for welder qualification – groove weld test coupon, or, fillet weld test coupon?

When Should Fillet Weld Test Coupon Be Chosen?

My Shop Gets Production Jobs That Are A Mix Of Fillet Joints And Groove Joints. I Want To Qualify My Welders With A Minimum Number Of Qualifications. What kind of test coupon is required to qualify my welder?

QW 452.6 permits that all groove joints qualify fillet joints of all thicknesses, fillet sizes and diameters. So, it would seem that as far as possible, you should qualify only groove joints so that fillet joints are automatically taken care of.

However, sometimes the choice can be sometimes restricted by welding positions. A fillet weld that needs to be welded in 5F or 6F cannot be welded by a welder qualified in groove in 1G, or 2G or even 3G position.

Of course, a 13 mm thick groove joint in 6G position gives enormous flexibility to the qualified limits of the welder’s performance qualification. Such a welder can weld ALL fillet joints of ALL sizes in ANY position. But it is a slightly difficult coupon weld, and therefore slightly hard to qualify.

So, if the production welding involves fillet joints in 5F or 6F positions, qualifying the welder on a fillet weld test coupon, to be welded in 5F (or 6F, as required), would be the way to go, instead of aiming for groove weld coupons in 6G position.

Does A Groove Weld Qualify All Fillet Joints?

QW 452.6 loudly declares that a qualification done on any groove (of any thickness) qualifies the welder to do fillet joints of all thicknesses, any diameters, and all base material thicknesses.

This seems a little disproportionate. The Section IX specifies elaborate tests, acceptance criteria, qualifying ranges etc. if you are qualifying your welder with a fillet weld test. But if the welder has done a groove joint, any groove joint, well he is a superman. He can now weld on ALL fillet joints, restricted only by the positions specified in QW 461.9.

Say, you have a welder qualified on a groove joint of 5 mm thickness. In accordance with rules of Section IX – this welder is well qualified to make a 50 mm thick fillet joint between two 100 mm thick pipes of 500 mm OD. Sounds too liberal?

The interpretation IX-86-74 contained a fascinating query in this context. The query indicated that a welder qualified on a groove weld is making acceptable groove welds. However, while making fillet welds – he produces areas of melt-through, sagging of metal and dripping of the molten metal.

In essence, the inquirer wanted to know whether the Section IX really intends that a welder qualified on a groove weld can make fillets of all sizes, on all pipe diameters, and all base metal thicknesses. Second, if the aforementioned quality problems occur, does Section IX require re-qualification of the welder?

The reply given by ASME to this interpretation establishes that the liberty is unambiguous, and very much intended. Further, it is for the fabricator to establish the criteria for doing re-qualification. Section IX has not addressed those.

Talking about liberties, this brings to mind another similar liberty given by Section IX. This one is applicable when you are trying to renew the expired validity of a welder’s qualification, as per QW 322.2. Say, your original qualification is in 6G position on a pipe of OD 50 mm, thickness 15 mm. If this qualification has expired, all you need to do is take a carbon steel plate of 5 mm thickness, and perform a groove weld on it in 1G position, and do its’ RT.

If RT of this 5 mm thick groove is alright, your the validity of welder’s qualification in 6G gets reactivated!

Now, all this flexibility feels good when you are the welding engineer, and you want to prove the compliance of your welders’ qualifications in front of the authorized inspector. But you wonder at these rules.

So, yes, answering the question in the title, qualification on a groove weld does qualify the welder for all fillet joints, restricted only by QW 461.9.

Visual Testing For Fillet Weld Test Coupons

Is Visual Testing Required For Fillet Weld Performance Qualification Coupons?

When you are qualifying your welder through the mechanical testing option, QW 452.1, which is for groove weld tests, clearly tells that visual testing is required. QW 452.5, which is for fillet weld tests,  on the other hand, does not specify visual testing. So, is visual testing as per QW 302.4 not required for fillet welds?

From above, it appears that Code does not require visual testing for fillet welds. Now, visual testing takes hardly a couple of seconds. Why would Code knowingly and conspicuously omit VT for fillet weld test coupons?

The answer to this is that – in fact, visual testing is required for fillet weld Performance Qualification coupon. This was made clear by ASME in an Interpretation issued back in 1995, Interpretation number IX-95-17.

As given in QW 304, there are only two ways for qualifying a welder – either through the combination of mechanical and visual testing of QW 302.1 and QW 302.4 respectively, or volumetric testing of QW 302.2. Considering that fillet welds are qualified through the first option, visual testing is required.

Food for thought: Do other Codes like KTA etc. require visual testing?

Tests Required For Fillet Weld Test Coupon

The tests required for welding performance qualification through a fillet weld test coupon are as follows:

  1. Visual testing per QW 302.4
  2. Fracture examination per QW 452.5
  3. Macro-etch examination per QW 452.5

Acceptance Criteria For Testing Of Fillet Weld Test Coupon

The method of testing and acceptance criteria for the tests indicated in the above paragraph are enshrined in QW 182 and QW 184 for fracture tests and macro examination. The criteria for visual testing is defined in QW 194.

Acceptance Criteria For Visual Testing

The coupon shall “show no cracks and complete joint penetration with complete fusion of weld metal and base metal.”

Acceptance Criteria For Fracture Testing

The acceptance criteria for fracture tests is given in QW 182, and goes like this: the fractured surface shall show no evidence of cracks or incomplete root fusion, and the sum of the lengths of inclusions and porosity visible on the fractured surface shall not exceed 10 mm for plate-to-plate fillet weld coupon, and 10% of the length of specimen (quarter taken for fracture testing) for pipe-to-plate fillet weld coupon.

Acceptance Criteria For Macro-examination

The acceptance criteria for macro-examination is given in QW 184, and goes like this:

  1. The weld shall have a concavity/convexity no greater than 1/16 in. (1.5 mm).
  2. The difference between the leg lengths of the fillet shall not be greater than 1/8 in. (3 mm).
  3. Visual examination of the cross section of weld and HAZ shall show complete fusion and freedom from cracks, except that linear indications not exceeding 1/32 in. (0.8 mm) are acceptable.

Note: The 2021 edition of Section IX has brought some changes to QW 184. As per the 2021 edition, NO cracks are allowed, and NO incomplete fusion is allowed. Other linear indications with a length no greater than 1/32 in. (0.8 mm) are still allowed though. I wonder what those other indication are.

Miscellaneous Thoughts On Fillet Weld Performance Qualification

Consider the following question.

A Welder Was Qualified On A Fillet Weld Performance Qualification Test Coupon. The Coupon Passed All Criteria Laid In Section IX. Must He Produce Fillets Meeting QW 184 In Production Welds Too?

The acceptance criteria laid for performance qualifications are generally stricter than those for production joints.

A good welder continues to produce the same quality that he achieved in the Performance Qualification. However, a welder’s skill may not remain same over a period of time, depending upon the kind of challenges he faces in his work, his motivation levels, discipline enforced in his organization etc.

The macro examination of a welder’s Performance Qualification coupon needs to meet the criteria laid out in QW 184, which requires that, the difference between the lengths in the legs of a fillet shall not exceed 3 mm.

Does Section IX require that this stipulation be continue to be observed in production joints too? Is it alright if the welder produces skewed, disproportionate welds in the production joints? Is it enough ground to question his ability as per QW 322.1 (b), and revoke his qualification?

The answer to the above questions is – No.

Firstly, QW 184 is only applicable for Welder Performance Qualifications, not for production joints. The quality expected from production joints would be specified in construction code. Section IX does not require stipulations of QW 184 to be observed in job.

Secondly, Section IX does not establish conditions under which a welder’s capabilities to make sound welds can be questioned. Such decisions have been left to the judgement of authorised inspector. This was clarified by ASME in Interpretation IX-04-21.

Likewise, the criteria laid for radiography examination of a groove weld Performance Qualification is enshrined in QW 191. Does Section IX require that the same RT quality be observed in job too? Does it affect a welder’s qualification if the RT of his production joint does not meet the criteria specified by the construction code?

The answer to these questions is ‘No’ too. The reason is same as explained in the forgoing example of fillet welds.

Passing a Welder Performance Qualification test is akin to getting a degree from a college. It certifies that you have passed all examinations required to get qualified as a computer engineer etc.

But it is not a guarantee that you would do well in the organization that you join after passing out of college. Your performance at your work place should be judged from the requirements of your organization, not from the curriculum followed in your college.

Does a welder, who prepares fillet weld procedure qualification test coupon, also gets qualified?

Yes, indeed he does. QW 301.2 expressly permits this. Albeit, such welders are qualified only to weld on non-pressure retaining fillet welds. This stipulation has been introduced only in 2021 edition of Section IX.

So, these were some of the insights I have to offer on the subject of welder qualification through fillet weld test coupon. Would you like to add something? Please do let know your thoughts in the comments section below.

The Interpretations referred in this article can be found here on ASME’s official website.

See More:

WPS Qualification For Pressure Retaining Fillet Welds

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