In this article, I have discussed various aspects related to welding procedure qualification in accordance with ASME BPVC Section IX. These observations are borne out of almost a decade long personal experiences on this subject.
What is a Welding Procedure Specification?
Simply put, a WPS, short for Welding Procedure Specification, is a document (generally not exceeding a couple of pages) that contains instructions for a welder to weld on a job. The job can be a production weld or a test coupon or any other weld.
The instructions are in the form of variables, that are addressed for each process indicated on the WPS. Some examples of these variables are current, voltage, speed, groove design, etc.
The WPS must address all essential and non-essential variables (and supplementary essential variables when applicable). No particular format is insisted upon, as long as all required information is included. A suggested format is given in QW 482 at the end of Section IX.
Why Is a WPS Needed?
Why would a welder need a WPS in the first place?
When I first entered my work shop as a newly minted welding engineer, I noticed that the welders hardly ever touched the WPS. Most welders in my shop are highly experienced fellows with 15-20 years of experience behind them in the field of welding. Most welders are fully familiar with the parameters required to weld with specified electrodes.
My organization manufactures heavy equipment for power industry. It is a huge set up, different shops are assigned to make different components. So, most shops have similar kind of jobs flowing through them, most of the time. Same material, same electrodes, same work, all the time.
The welders in my shops know all parameters by heart, and do not generally feel the need to consult a WPS for performing the welding. [In any case, I have always felt that to produce a good weld, the welder has to have a knack for producing a quality weld. If the welder does not have a feel of the job, the parameters alone, qualified or unqualified ones, cannot guarantee a quality weld.]
So, where does a WPS come into picture? If the welder is highly experienced, and skilled, does he still need a WPS?
The answer to this is that – the WPS does not just serve the purpose of providing instructions to welder, it also is an evidence that the job being welded is Code compliant. The PQR number referred on the WPS is a proof that the welding being done has been simulated in a test coupon and tested through mechanical tests.
The WPS must be readily available at hand, and must be produced whenever asked for by the authorized inspector.
Any job that needs to be Code compliant must be welded only with a qualified WPS. A qualified WPS is called thus only when it is supported by a Procedure Qualification.
What is a Procedure Qualification?
A Procedure Qualification is an exercise that involves preparing a test coupon by welding together two base materials (either same as the ones to be used in production weld, or similar ones; Code lays down stipulations for this) using some parameters.
These parameters are generally derived from judgment, experience, etc. Sometimes, some of the parameters also get dictated by stipulations of the Code.
This test coupon is then subjected to mechanical testing. Specimens for doing mechanical testing (like bend test, impact test etc.) are carved out from the test coupon through machining. These specimens are then subjected to testing in a Laboratory.
If the tests meet the criteria set by Code/Customer Specification, it indicates that the Procedure Qualification has passed. The parameters that were used in the test coupon now become qualified parameters.
In practical terms, this means that if the set of parameters that was used in preparing the test coupon, is used on a production joint – the joint would have the requisite strength, ductility etc.
You go through the exercise of Procedure Qualification because you cannot do destructive testing on the production joint, obviously.
Ultimately, any weld that gets made under the aegis of the Code must have the properties required by the Code. A Procedure Qualification is Code’s way of making sure that that happens.
Welding involves a large number of variables, ranging from current, polarity, voltage, travel speed, electrode type, thickness of job, position of welding, preheat temperature, post-heat, inter-pass temperature, etc. Each variable plays an influencing role in determining the integrity of the weld. Which set of values for these variables would bring about the desired weld?
A Procedure Qualification is Code’s way of establishing that set of variables which when used on the job would surely produce a weld of desired quality for the intended application. By doing destructive testing on a test coupon similar to the production weld, a Procedure Qualification achieves just that.
A WPS that lists these qualified parameters is then called a qualified WPS. A qualified WPS contains reference to the PQR that is used to support that WPS.
The WPS goes around in shop, providing guidance to the welder, as well as ensuring Code compliant welding. The welder must weld within the ranges of variables laid down in the WPS.
Doing so ensures compliance to Code. By consulting a WPS, the authorized inspector too can objectively determine whether the weld is made in compliance with Code or not.
Is it Required to Use Same Variables in Job That Were Used in Procedure Qualification?
No. Section IX lays down rules that define a range of variables within which the production joint can be welded. As long as the welder stays within these ranges, it would not affect the quality of the weld.
Now, not all variables are equally important. Some are more important than others. The important ones must be necessarily followed within the range defined by the qualification. That is, whatever was followed in qualification must be followed in the production weld too.
Any change beyond this range would affect mechanical properties, in the eyes of the Code. Therefore, any change in these variables would require re-qualification of the Procedure. Such variables are called essential variables.
There are other variables which aren’t so important, such as groove design, root spacing etc. Following a different value in the production weld (as compared to the one followed in qualification) would not affect the mechanical properties of the weld.
Therefore, these variables can be changed as desired by the welding engineer, and doing so would not require a re-qualification of the procedure. Such variables are called non-essential variables.
Now, although a change in non-essential variables does not require requalification, revision of the WPS is surely required. The welding engineer must amend the WPS, showing the changed values of the non-essential variables. It is the welder’s job to follow the WPS in total. If he is unable, he must inform the welding engineer appropriately.
There is a third kind of variables too – supplementary essential variables. These variables become additional essential variables in those cases where the construction code requires impact toughness properties from the joint.
Groove Dimensions of a Procedure Qualification Coupon
What groove dimensions, such as groove angle, root gap, root face, etc. should be adopted when doing a procedure qualification?
For most processes, the joint design details such as root gap, backing, groove-type etc. are non-essential variables. This means that regardless of what was followed for these variables in the procedure qualification, a WPS can be written for any root gap, with or without backing, any groove design, etc. in the production welding.
However, when you are first qualifying a procedure, you must adopt a groove design, root gap, etc. So what groove design and root gap must you adopt?
Well, if you know about the jobs you are going to support with your PQR, you may adopt these details of the most commonly occurring joint in the production.
NDE of the Test Coupon
Is It Required to Do RT/UT for Procedure Qualification Test Coupon?
Section IX does not require any non-destructive testing for procedure qualification test coupons. Only the mechanical tests are required to qualify a procedure.
This has been made clear by Section IX in an Interpretation as well. The question one in the interpretation IX-78-64 asks precisely the question asked above. The reply given by the Committee makes it amply clear that Section IX per se does not require any NDE of the procedure qualification test coupon.
However, having said this – there is something more that needs to be taken note of. Sometimes, the construction code may specify NDE for the test coupon. And we know that the requirements specified by the construction code take precedence over those of Section IX. This has been loudly communicated in QG-100.
So, if the construction code specifies any NDE – that needs to be compulsorily complied with while making the procedure qualification test coupon. The acceptance criteria will be as per whatever construction code specifies.
Another situation where NDE needs to be done for the test coupon is when the contract specifies it.
In any case, the Section IX does not prohibit us from doing NDE. The requirements given in the Section IX are only the minimum requirements that need to be met. The welding engineer can choose to include NDE during procedure qualification if he/she feels that the needs to the end application would be better served by doing NDE.
In other words, it is at the discretion of the welding engineer. The evaluation criteria can be taken same as those for the production welds.
However, the results of the NDE examination cannot serve as grounds for rejection of coupon, if the results are not perfect.
If imperfections are revealed during NDE, the further course of action should be decided based on judgment. If the indications have not appeared in a pattern, the defective portion can be excluded from the coupon. In other words, if the imperfections have occurred as isolated incidents, then the same does not indicate a deficiency in the welding procedure.
In such cases, the coupon can be taken up for mechanical testing, provided enough length is available for drawing the required specimens. The judgment in such cases has to be based on mutual agreement between the fabricator and the inspector.
The Business of P-Numbers
Can a PQR be used to support welding of ANY two base metals having same P numbers as the ones used for qualifying the PQR?
P-number is an essential variable as per QW 403.11. So, any change in base metal having a different P number vis-à-vis the one used in Procedure Qualification will require re-qualification.
However, if you are using a base metal having same P number in production as the one used in Procedure Qualification, then as per Section IX rules it does not require requalification of Procedure. Does this mean one can use ANY base material as long as it falls in the same P number?
No. Section IX only specifies minimum requirements. Using Section IX does not free you from applying engineering judgment regarding the compatibility of the base materials, metallurgical properties etc. Just because a base metal has the same P number as per QW 422 does not mean you can indiscriminately substitute the base metal used in PQR.
Section IX says as much in QW 200.3.
So, the answer is – a judgment must be made regarding applicability of P-numbers. A similar judgment is required for filler metal on the WPS as well.
Is Position an Essential Variable for Procedure Qualifications?
No, welding position is not an essential variable for procedure qualifications.
Before proceeding further, a bit of historical perspective here. Before 1974, welding positions were very much an essential variable for PQRs. That is, a separate procedure qualification was required for every position that would occur in the production welding. This was highly restrictive. In 1974, this restriction was lifted.
Position is no longer an essential variable. This means that a procedure qualified in any position can be used to support production welding in any other position.
The Section IX thinks that the weld metal deposited in the overhead or vertical position does not know that it has been deposited in the vertical or overhead position. So it will have same mechanical properties as the weld metal sitting in the flat position.
Depositing metal in the out of position joints is a skill. It has therefore been taken as an essential variable for welder qualifications. The mechanical properties of the weld metal do not get affected by whether it has been deposited in the flat or vertical or overhead or horizontal position. It has therefore not been taken as an essential variable for procedure qualifications.
An interesting thing to note here is that welding position was a supplementary essential variable (that is, only for welds requiring toughness property). This was addressed in QW-405.2, which specified that a “change from any position to the vertical position uphill progression. Vertical‐uphill progression (e.g., 3G, 5G, or 6G position) qualifies for all positions.”
This variable has been deleted from the 2019 edition onwards. That is, now, a procedure qualified in the plain old flat position can be used to support production welding in any other position regardless of whether toughness is a consideration or not. Isn’t that wonderful?
Qualifying Multiple Processes in a Single Qualification
Can multiple processes be qualified through a single Procedure Qualification coupon?
Yes, this is permitted (addressed in QW 200.2). In such case, thickness deposited by each process shall be measured and recorded. And weld metal of each process shall be included in the requisite mechanical tests. This is as good as qualifying each process individually. The only liberty is that the welding work alone can be done on a single coupon.
In fact, if the production work requires multiple processes in a single joint (for example, GTAW + SMAW), WPS for such production work can be supported by a single PQR (which was qualified by using multiple processes in a single coupon), or multiple PQRs (which were qualified individually for each process).
However, in cases where toughness testing is a consideration, qualifying multiple processes (for multiple sets of variables) in a single coupon may pose a small problem.
The Section IX requires that a portion of each process be included in the mechanical test specimens. On the other hand, some construction codes (ASME Section III Part NB being a prominent example) require that the impact specimen be located such that its longitudinal axis is at least 0.25t from a surface, where ‘t’ is the thickness of the test weld.
It may not be possible to satisfy both these requirements at the same time. Therefore, in such cases – multiple coupons should be prepared so that both – Section IX and construction code – requirements can be satisfied.
In addition to above, one PQR can be used to support multiple number of WPSs as well.
In essence, one PQR can support multiple WPSs, multiple PQRs can be used to one WPS too.
Is Sub-contracting the Qualification Work Allowed?
Can an organization sub-contract the Procedure Qualification work?
This is a logical question that bothered me for quite some time in my initial days as a welding engineer. A Procedure Qualification is after all just verified data arising out of doing testing on a coupon. All the variables (as intended by Section IX) are objectively measured and recorded in a scientific manner. How does it matter where the qualification was done?
The work in my organization moves at a snail pace. Everything proceeds extremely slowly. Ideally I would want to qualify my Procedure Qualifications at a sub-contractor’s works where the work happens without any undue delay. The sub-contractor gets paid commensurately to the amount of work done, so he obviously has enough incentive to work fast. However, the Authorized Inspector does not permit this.
The inspector desires that the procedure qualification be done within the organization where I work, under our full supervision and control.
There is another situation. Sometimes, a couple of sub-assemblies are off loaded to a sub-contractor by my organization. The sub-contractor is a different organization. The job is a Code –related work. Although my company assumes full responsibility for the work done by the sub-contractor, we do not have a direct day-to-day control over the functioning of the subcontractor.
Now, I want that the sub-contractor should able to use my Procedure Qualifications. However, authorized inspector does not permit this. He insists that the sub-contractor re-qualify the Procedures that are going to be used to support his portion of the joints. This causes me a bit of dismay. Why can’t the sub-contractor use my PQRs?
After all, the technical data remains same. Eventually, the Procedure Qualifications done by the sub-contractor are also going to throw up same WPS as my company uses.
The authorized inspector is right in this case because his stance is backed up by the Code.
Section IX intends that the organization that does the manufacturing work must qualify, certify, and own the complete responsibility of all the qualifications (be it Performance Qualifications or the Procedure Qualifications) that are going to be used in the manufacture of Code related components.
The owning organization must directly control and supervise the personnel involved in the conduct of a Procedure Qualification. Such persons must be either direct employees of the organization or be contract employees performing work under direct control of the organization.
However, Section IX does permit subcontracting some or all work necessary in qualifying a Procedure if the work is done under the direct supervision and control of the main organization, and the main organization accepts full responsibility for such work.
All this has been made amply clear by Section IX in QG-106 and QW-200.2.
What is a Procedure Qualification Record (PQR)?
In simple terms, a PQR is a record of the events that happened during the Procedure Qualification episode. It contains the parameters that were followed in the preparation of the test coupon, and the results of the testing that the coupon was subjected to.
It is a permanent record, and is an asset of the organization.
The PQR must be certified by the organization that does the manufacturing work. Any change to the PQR (or a WPS supported by a PQR) can be made only by re-qualifying the Procedure, unless the changes are editorial in nature, or unless the changes are in the non-essential variables.
What information Should be Contained On a PQR?
Section IX’s directions regarding the contents of a PQR can be found in QG-102 and QW-202.2(b).
Section IX requires that as a minimum, the actual values used in the qualification of all essential variables (and supplementary essential variables, if applicable), and test results shall be recorded on a PQR. Including non-essential variables is at the option of the organization.
Any additional helpful in making a good weld may also be included.
Some organizations prefer to annex the report containing the test results along with the PQR, instead of transferring the results on to the PQR format. This is a perfectly acceptable practice. This also finds the committee’s nod, as can be seen in their reply to Interpretation IX-15-16.
A PQR is different from the WPS in that the WPS is a working document, while PQR is like a certificate – a record.
Although Section IX does not compulsorily require recording non-essential variables, (it has been left to the option of the organization, per QW-200.2(b)), it is a good practice to record all non-essential variables too.
Another thing to be noted here is that the values reflecting on the PQR must be an actual record of the values (be it an essential variable or a non-essential variable) followed in procedure qualification. If a variable was not recorded during the procedure qualification, it shall not be addressed on the PQR. This has been stated in QW-200.2(b).
Any Format for PQR?
Does Section IX require any particular format for documenting a PQR?
No. A PQR can be documented in any suitable format as long as all essential, non-essential (and where applicable, supplementary) variables are addressed. A suggested format for documenting a Procedure Qualification is given in QW 483 of Section IX.
Validity of a Procedure Qualification Record
A procedure qualification record has lifetime validity. In other words, it never expires. The qualification done in accordance with any edition of Section IX (going back to as far as the 1962 edition) can be used to support production activity for which the current edition has been specified.
However, new procedure and performance qualifications must be made in accordance with the current edition only.
This understanding has been established in the QG-108, and finds reaffirmation in the interpretation IX-04-10.
Read more: Validity Of Welder Qualification
How To Write A PQR
A PQR is a record of actual variables that were adopted in making the procedure qualification test coupon. All essential variables (and when applicable – supplementary essential variables) must be recorded.
The ‘R’ in ‘PQR’ is short for ‘record’, and stands to convey that all information therein is a record of what happened.
QW 200.2 (b) firmly says that if any variable(s) is not monitored during the qualification, it shall not be recorded.
It is worth noting here how the Section IX uses the wording “…shall document all essential variables…” for PQRs; and uses “…shall describe all essential variables…” for WPSs.
It is important to understand that in case of PQR, each piece of information is a record of what occurred. In other words, all information on the PQR must be as per the actual values recorded during the procedure qualification.
Besides recording of variables, another important feature of a PQR is its certification. A completed PQR must be certified by the qualifying organization. The certifying statement must include sentences to the effect that the variables recorded on the PQR are a true record of actual variables used on the test coupon, and that the coupon was welded and tested in accordance with requirements of Section IX of ASME BPVC.
It should be noted that this certification is necessary. A PQR without such a certification is useless.
Are Non-essential Variables Required To Be Documented On A PQR?
A change in non-essential variables does not require re-qualification of the procedure specification. So one tends to think that these (non-essential variables) are trivial and need not be recorded on a PQR.
The Section IX says in QW 200.2 (b) that recording non-essential variables is optional. [Recall from the above discussion that in case of a WPS, it is mandatory to address all non-essential variables.]
So, while it is not mandatory to record non-essential variables on a PQR, my experience shows that it is best to record them. It helps the welding engineer get a complete and clear picture of what occurred during the procedure qualification.
Retests in Procedure Qualification
If a mechanical test does not meet the acceptance criteria, can an immediate retest be done with twice the number of specimens?
For Performance Qualifications, if one or more tests (be it visual test or non-destructive examination or mechanical tests) do not pass the acceptance criteria, Section IX permits an immediate retest by doubling the number of samples required to be tested.
However, such stipulation has not been permitted/demanded for Procedure Qualifications.
If one or more tests do not pass the acceptance criteria, one should find out the cause behind it. If it is established that the cause is not related to welding variables, a retest can be done from the original test coupon (if there is balance material available) or a freshly prepared one.
When the cause is determined to be one of the welding variables, a new test coupon has to be welded by making the necessary changes to the variable that caused the failure. Such changed variable should be recorded on the PQR.
If the cause is determined to be some other factor other than welding variables, a fresh coupon can be prepared by taking care of the ‘factor’ that caused the failure. If the new coupon passes, the factor should be documented properly, and addressed such that it does not reoccur in production welding.
This has been detailed in QW-202.1.
Read more: Retests In Welding Performance Qualification
Indeed, yes. A procedure qualified on a groove weld can be used to support fillet welds in “all thicknesses of base metal for all sizes of fillet welds, and all diameters of pipe”. So if I have to qualify a procedure for supporting fillet weld(s), a groove weld would be the preferred option.
Procedure qualification for a fillet weld can be made on a fillet weld coupon also. The required tests and limits qualified would be as per QW-451.3.
However, there is something to be noted here. The Section IX intends that the procedure qualification for only the non-pressure retaining fillets can be done through a fillet weld test coupon. That is, if the production fillet is a pressure-retaining joint, the PQR for it must have been done on a groove weld coupon only.
This understanding, while not so clear in the earlier editions, has been made crystal clear in the 2021 edition.
Tests Required for Procedure Qualification
What are the Tests Required for Procedure Qualification as per ASME Section IX?
Typically, tension tests and bend tests are required to qualify a procedure. When toughness is a consideration, impact tests and drop weight tests also need to be included. The number of specimens differs depending on the base metal thickness in the test coupon.
When the procedure is to be qualified through a fillet weld test coupon, macro-examination of a number of cross sections of the coupon is the required test.
The type and number of specimens required for various BM thicknesses are given in table QW-451. These tables also contain the range-qualified for the base metal thickness and the deposited weld metal thickness as well. The orientation of specimens and the acceptance criteria are defined in QW-150, QW-160, QW-170 and QW-180.
The manner of removal of samples is addressed in figures under QW-462.
Tests Required for Fillet Weld Test Coupons
Which test is required for fillet weld procedure qualification as per ASME Sec IX?
The required tests have been stated in QW-452.3. Five specimens for macro-examination are required when the fillet is between two plates.
When the fillet is between a pipe and plate, or, between a pipe and pipe, four specimens are required for macro-examination.
The method of testing and acceptance criteria is enshrined in QW-183.
Procedure Qualification for Pipe Welds
Can a Procedure Qualification Done on a Plate be Used for Pipe Welding? Or Vice Versa?
Yes, it can. Section IX places no such restrictions on procedure qualifications. A PQR qualified on a plate can be very much used for welding a pipe, and vice-versa. Not just this, a procedure qualified on a plate can be used to support welding on a pipe of any diameter (provided you have a qualified welder for that diameter, of course).
Note that this liberty is not thus for performance qualifications. A welder qualified on a plate can weld on pipes, but with some restrictions (defined in QW-461.9). And vice-versa.
In simple words, pipe diameter is not an essential variable for procedure qualifications. The weld metal sitting in a pipe joint does not know that it is sitting between two pipes. So it will have the same mechanical properties as the weld metal sitting between two plates.
Depositing sound weld metal in pipe joints is a skill. It has therefore been taken as an essential variable for welder qualifications. The mechanical properties of the weld metal do not get affected by whether it is sitting in a plate joint or a pipe joint. It has therefore not been taken as an essential variable for procedure qualifications.
Is Pipe Diameter an Essential Variable for Procedure Qualifications?
As explained in the above paragraph, pipe diameter is not an essential variable for procedure qualifications.
So, this is all I have to offer right now on this subject. Procedure Qualifications is a vast subject and therefore not possible to cover in the scope of one article. Many other articles appear on this website addressing various aspects of PQRs and their qualification. It is a work in progress.
Thanks for reading. Please do share your thoughts in the comments section below.