When the production welding involves a lot of welding of pipes, it is best to qualify your welder on a pipe test coupon. Although, welder qualification for pipe welding need not be necessarily be done on a pipe; a welder qualified on a plate is qualified to weld on pipes too, with some restrictions, as described later in this article.
In this article, we will discuss the pipe diameter – which is an essential variable for welder performance qualification. In the latter half of the article, some interesting questions surrounding the issue of welder qualification for pipe welding have been discussed.
If you have a lot of pipe welding going on in my shop, what diameter should you choose for the test coupon for qualifying your welder in accordance with Section IX? What is the range of qualified pipe diameters once a welder has been qualified on a pipe of certain OD?
The following paragraphs will answer these questions.
When it is required to qualify a welder for pipe welding, the outer diameter of the pipe is an essential variable that needs to be taken care of. Pipe diameter appears as an essential variable for most of the processes under QW 350, and it has been defined in QW 403.16.
QW 403.16 points us to QW 452.3, which lists the qualified range of pipe diameters on which he is qualified to weld on in production welding.
Per QW 452.3, a welder qualified with any pipe of OD 73 or above, is qualified for welding on ALL pipes of OD 73 and above. Besides, a welder qualified with any pipe of OD between 25 mm to 73 mm, is qualified for welding on ALL pipes of OD 25 and above.
Also, a welder qualified with any pipe of OD less than 25 mm, is qualified for welding on ALL pipes of OD equalling the OD of the test coupon, and above.
The range of qualified diameters for welding performance qualification is summarised below:
|OD of the test coupon||Minimum OD qualified|
|Less than 1 in. (25 mm)||Size welded to unlimited|
|1 in. (25 mm) to 2-7/8 in. (73 mm)||1 in. (25 mm) to unlimited|
|Over 2-7/8 in. (73 mm)||2-7/8 in. (73 mm) to unlimited.|
So, if your shop gets a large number of pipes for welding, with varied diameters, it would be a good idea to qualify your welder with a pipe of lowest OD that you might come across in the production welding.
Important point: When the production welding involves groove weld attaching a set-on nozzle or branch on a pipe/shell, such that the weld preparation is on the nozzle (or branch), the pipe diameter of nozzle has to be reckoned for determining welder’s eligibility vis-à-vis QW 452.3.
When the production welding involves groove weld attaching a set-in nozzle or branch on a pipe/shell/head, such that the weld preparation is on the pipe/shell/head, the pipe diameter of pipe/shell/head has to be reckoned for determining welder’s eligibility vis-à-vis QW 452.3.
This clarification has only been introduced in the recent years, and did not exist before 2015 edition of Section IX.
Exceptions to QW 452.3
QW 403.16 lists the exceptions when the restrictions given in QW 452.3 are not applicable. These exceptions are as follows:
- Fillet welds: A welder qualified through a groove weld is qualified to make fillet joints of all diameters, as given in QW 452.6. So, a welder qualified on a groove weld on a pipe is not restricted by QW 452.3 when he is welding on fillet welds. QW 403.16 establishes this exception by pointing us to QW 303.1, which includes the mention of QW 452.6.
- Overlays in longitudinal direction: When it is required/permitted to deposit a corrosion-resistant overlay in longitudinal direction (as opposed to circumferential direction), the welder is in effect not welding over a curvature. In such cases too, restrictions of QW 452.3 are not applicable. This is also applicable to hard-facing overlays. This stipulation has been given in QW 381 and QW 382. QW 403.16 establishes this exception by pointing us to QW 381 and QW 382.
Maximum Qualified Outer Diameter
Is there a limit on the maximum qualified OD for welder qualifications, as per Section IX?
No, there is not a limit on maximum qualified OD for welder qualifications. A welder qualified with a pipe of a certain OD is permitted to weld on all pipes of OD higher than the one used in qualification. This has also been made clear in Interpretations IX-89-106 (qs 2) and IX-89-104.
In the context of above discussion, keep in mind that all the restrictions just discussed only pertain to outer diameter of the pipe. What about the inner diameter? This is addressed later in this article.
Can A Welder Qualified On A Plate Weld On A Pipe?
Vice versa, can a welder qualified on a pipe weld on a plate?
For someone not well versed with Section IX, this question can be fascinating.
Clearly, welding on a pipe requires a different skill than welding on a plate. Welding on a pipe is tougher than welding on a plate. Further, welding on a pipe of lower OD is more difficult than welding on a higher OD pipe.
As the OD increases, welding on a pipe keeps getting easier, and after a certain point, welding on a pipe is no different than welding on a plate. Locally, during welding, a very high OD pipe feels just like a plate.
So logically, a welder qualified on a plate should be good enough to weld on pipes of high OD too. That is what Code thinks too.
So, at what point can we say that a pipe exceeding a certain OD can be welded by a welder qualified on plate. What is that cut off OD? The answer to this is found in QW 303/QW 461.9.
If you go through QW 431.9, you would find that this cut off OD is 610 mm. A welder qualified on a plate can weld with equal freedom on all plate thicknesses and on all pipes of OD more than 610 mm.
The position restrictions for the plates, and pipes of OD more than 610 mm, are the same. In other words, he is qualified to weld on all those positions on a pipe for which he is qualified to weld on a plate.
Now, Section IX permits a welder qualified on a plate to weld on pipes of outer diameter LESS than 610 mm too. A welder qualified through a groove weld on a plate can also weld on pipes with OD 73 mm and over, but with some extra restrictions on positions.
For example, a welder qualified through a groove weld on a plate in 3G position, can weld on all plates, and all pipes of OD over 610 mm, in Flat and Vertical position. He can weld on pipes of OD less than 610 mm too, as long as they are more than 73 mm OD, but only in Flat position.
Likewise, a welder qualified through a groove weld on a plate in 4G position, can weld on all plates, and all pipes of OD over 610 mm, in Flat and Overhead position. He can weld on pipes of OD less than 610 mm too, as long as they are more than 73 mm OD, but only in Flat position.
There are similar restrictions for qualifications done in special positions, and qualifications done in a combination of positions like 2G and 3G, etc. For 1G and 2G, however, there are no such restrictions.
So, to summarise, a welder qualified on a groove on a plate can weld on pipes of OD more than 610 mm, no problem at all. He can also weld on pipes of OD less than 610 mm, and more than 73 mm, but with some additional restrictions on position.
Look up QW 461.9 for getting the whole picture.
It is worth noting that these restrictions do not apply in case of Procedure Qualifications. If a WPS has been qualified on a plate, it can be used for welding on all pipes too. This is because pipe diameter is not an essential variable in QW 250. Likewise, a WPS qualified on a pipe can be used for welding on a plate as well.
This small matter found a mention in Interpretation IX-89-82.
Can a welder qualified with pipe weld on plate? Oh yes, he can, Section IX permits it. No problem. But with the usual position restrictions of course, as given in QW 461.9.
Interesting Questions Involving Welder Qualification For Pipe Welding
These questions occurred in my mind, or formed part of discussions with the authorized inspector, over the course of my official work. I hope it helps in enriching the understanding of reader too.
Inner Diameter of Pipe For Welding Qualification
- My Welder Was Qualified With A 10 mm Thick Pipe Of OD 70 mm. Now, I Have Received A Job Wherein I Need To Weld A 10 mm Thick Pipe Of OD 40 mm. Is My Welder Qualified To Make This Weld, As Per Section IX?
As per QW 452.3, a welder qualified with any pipe of OD between 25 mm to 73 mm is qualified for welding on all pipes of OD 25 mm and above. So, it would seem that the welder having a qualification described in the question is qualified to make the required weld.
The production pipe described in the question has inner diameter of 20 mm. So when the welder starts making the weld, he is in effect welding over a curvature of 20 mm (and not 25 mm).
To cite another example, in my work place, I have a welder qualification on a pipe of OD 100 mm. With this qualification, my welder is qualified to weld on all pipes of OD more than 73 mm.
However, I sometimes get a job in my shops that is 100 mm in OD, but 20 mm thick. This means that the diameter of the pipe over which the welder begins the root pass is only 60 mm.
The authorised inspector permits my welder to make the weld, no issues there, since QW 452.3 clearly specifies ‘outer’ diameter of the pipe.
But the question troubled me for a long time. In the eyes of the Code, does my welder have the requisite skill to weld over a diameter of 60 mm?
Because, it seems that in the eyes of the Code, a welder qualified on a 100 mm diameter is only skilled enough to weld over diameters of 73 mm and above. However, in my case, he is welding over a 60 mm diameter. Not 73 mm.
Should inner diameter not be an essential variable as well?
Eventually, I found the answer to this question in an Interpretation. The Interpretation number is IX-95-04 (qs 1). The Committee’s reply to the question in this Interpretation firmly establishes the answer to the problem described above.
It makes it absolutely clear – that inner diameter is NOT to be considered as an essential variable for performance qualifications.
When Welding Is Followed By Drilling
Are Small Diameter Restrictions Applicable When The Deposited Weld Metal Is going To Be Drilled Out?
In my shop, there is a joint in which a nozzle needs to be welded onto a shell. The nozzle has a OD of 70 mm, and is a solid piece at the time of welding but undergoes drilling to make a 15 mm hole later on.
One of the welders in my shop has a Performance Qualification to weld on pipes of OD 73 mm onwards. Another welder has a qualification to weld pipes of 25 mm OD, so I am not short on resources. As per Section IX, the welder’s qualification must have been welded on a pipe of OD less than 70 mm for him to be permitted on this joint.
But for some reason one day, I wanted to use the first welder on this joint for a few passes at the root. The inspector objected. I argued that the deposited weld metal is going to be drilled out. The weld deposited by the welder is only a temporary occupant.
The inspector did not budge, saying something like temporary joints require qualified welders and qualified procedures too.
I was wrong. I came across an Interpretation which proved the inspector right. IX-81-10 address precisely the question asked above. Should the small diameter restrictions of QW 452.3 still apply when the weld metal is going to be drilled out? The answer given in Interpretation was a ‘Yes’.
Pipe Diameter Restrictions For Procedure Qualification
Are Small Diameter Restrictions Of QW 452.3 Applicable For Procedure Qualifications Too?
Asked simply, assume that a procedure qualification has been done on a pipe of certain OD, say 50 mm. Can this procedure be used to support welding of other diameters too, say 15 mm, or 500 mm?
The answer is that small diameter restrictions of QW 452.3 are applicable only for welder qualifications. They do not apply to procedure qualifications.
This means that a procedure qualified on a pipe of any OD can be used for welding on pipe of any other OD, provided you have a qualified welder to weld on that OD, and all other essential variables of QW 250 are satisfied.
This is clear enough in Section IX. Someone still asked a similar question to ASME in an Interpretation, and ASME made it clearer, in Interpretation IX-82-07.
Pipe Diameter Restrictions On Longitudinal Welds
When a welder needs to make fillet welds on production pipes of OD less than 73 mm, he needs to make small diameter fillet weld test coupons in accordance with QW 452.4 for his performance qualification (alternatively, he may also qualify through a groove weld test coupon as specified in QW 304). This has been outlined in QW 303.2.
Now, assume that the welder needs to make a fillet weld on a plate to pipe joint. The pipe OD is less than 73 mm. However, the fillet weld is required to be deposited in the longitudinal direction (not circumferential direction), that is – in a direction parallel to the axis of the pipe.
Is this welder required to have qualified on the small diameter fillet weld test coupons of QW 452.4?
The answer is no. Although this is not explicitly mentioned in the Section IX, it is the Code’s intent that the small diameter restrictions are applicable only for the welds made in circumferential direction.
This intent becomes visible through various Interpretations issued by ASME. One such Interpretation is IX-92-45.
A similar direction appears in QW 381 for corrosion resistant weld metal overlays too, wherein it has been expressly stated that “…the limitations of position and diameter qualified for groove welds shall apply to overlay welds, except the limitations on diameter qualified shall apply only to welds deposited in the circumferential direction…”.
So this was all about welder qualification for pipe welding, in accordance with Section IX. Would you like to add something? Do leave your thoughts in the comments section below.