Welder qualification to ASME Section IX

In pressure vessel, piping, and structural fabrication, a weld is only as reliable as the two things behind it: a sound procedure, and the proven skill of the person running it. ASME BPVC Section IX keeps those two legs separate. The WPS and PQR document that the procedure works; the Welder Performance Qualification (WPQ) documents that the welder can execute it. This article walks through the logic of the WPQ — test coupon, positions, essential variables, acceptance criteria, and the continuity rule — with the details that actually matter on site. The goal is simple: when an inspector or welding engineer picks up a WPQ, they should be able to answer "what is this welder authorized to do?" without hesitation.

Edition stamp: The paragraph numbers and ranges in this article follow ASME BPVC Section IX, 2025 Edition (published in July 2025, superseding the 2023 Edition). QW-300.2 (employer responsibility), the QW-452 thickness and diameter ranges — especially the small-diameter fillet rows — and the QW-423 substitution tables can change between editions. In practice, always verify against the edition referenced in your contract.

1. What a WPQ is and what it proves

A WPQ is the record that objectively demonstrates a welder can deposit sound, fused weld metal with a given welding process. The underlying philosophy of Section IX is this: procedure qualification (the PQR) proves the mechanical properties of the weld — tensile strength, toughness, ductility — while performance qualification proves the welder's ability to deposit sound weld metal. That is why a WPQ carries no tensile test. Acceptance turns on the absence of incomplete fusion and incomplete joint penetration — exactly what the bend test or the volumetric examination reveals.

The WPQ test coupon is welded to a qualified WPS (QW-301.2). Using a Standard WPS (SWPS) is not a free option. The employer must first meet the adoption requirements of the QW-500 series — QW-510 in particular: run the demonstration PQR and formally adopt the SWPS. Until it does, it cannot have test coupons welded to that SWPS. One nuance matters here. While welding the test coupon, the welder may change the nonessential variables of the WPS; what binds the welder is not the whole WPS but the performance essential variables listed in the QW-350 series. If the test passes, the welder is authorized to perform production welding within the range recorded on the WPQ.

Whose document is the WPQ? Under Section IX, qualification belongs not to the welder alone but to the welder–employer pair. The employer is responsible for conducting, supervising, and accepting the qualification test and for maintaining the records (QW-300.2). A WPQ earned at one employer is not automatically valid at another. A widespread misattribution surfaces here: Section IX contains no provision allowing one employer to accept another employer's WPQ. That possibility comes only from the construction code referenced in the contract — for example ASME B31.3 para. 328.2.2 and ASME B31.1 para. 127.5 permit such acceptance with the specific approval of the Authorized Inspector, using the same or an equivalent procedure, and limited to piping work. So transfer is possible when those conditions are met and the Authorized Inspector is notified where required; it is not a general right granted by Section IX itself. "He has the paperwork, put him on the joint tomorrow" is the single most common nonconformity in subcontractor and agency-welder workflows.

Take care when comparing with AWS D1.1, too. In D1.1, welder qualification is likewise the contractor's responsibility, so employer-based qualification is a shared feature, not a difference between the two codes. The real differences are that D1.1 is more open to accepting previously issued qualification records with the Engineer's approval, and — more importantly — that the position coverage rules diverge. The next section puts numbers on that divergence.

2. Test coupons and positions (1G–6G)

Qualification begins with a welded test coupon. The coupon may be plate or pipe, and the geometry you choose determines both the product form and the position range the welder will be authorized for.

In the position codes, the number identifies the position and the letter identifies the weld type — G for groove, F for fillet. The position sets differ for plate and pipe:

Plate groove: 1G, 2G, 3G, 4G. Plate fillet: 1F, 2F, 3F, 4F.
Pipe groove: 1G (Rotated), 2G, 5G, 6G. Pipe fillet: 1F (Rot.), 2F, 2FR, 4F, 5F.

There is no 3G, 3F, or 6F on pipe, and the 2F/2FR distinction exists only for pipe (in 2FR the pipe is rotated; in 2F it is fixed). Position by position:

1G / 1F — flat position. On a pipe coupon the pipe is rotated while welding (1G (Rotated) / 1F (Rot.)). On plate there is no rotation: the plate lies flat and you weld from above.
2G / 2F — horizontal position. On plate, the workpiece stands vertical and the weld axis runs horizontal. On pipe, the pipe axis is vertical, the weld lies in a horizontal plane, and the pipe is not rotated. A horizontal fillet welded with the pipe rotated carries the code 2FR.
3G / 3F — vertical position. Plate only. ASME defines neither a 3G pipe groove coupon nor a 3F pipe fillet position. On pipe, vertical progression is covered inside the 5G and 6G coupons.
4G / 4F — overhead position. Again plate only, groove and fillet. For pipe groove welding the equivalent sits inside 5G and 6G; for pipe fillets it sits in 4F and 5F.
5G — pipe horizontal and fixed. The welder has to work flat, vertical, and overhead in one trip around the circumference.
6G — pipe inclined at 45° and fixed. The most comprehensive position, combining every difficulty in one coupon.

Exactly how far does position authorization reach? This is where the most common field error hides. Per QW-461.9:

On plate, 3G + 4G covers only the flat, vertical, and overhead positions; horizontal (2G) is not covered. All plate groove positions require 2G + 3G + 4G. Because 3G + 4G gives all positions in AWS D1.1, the two codes are constantly confused — do not rule on ASME work out of D1.1 habit.
On pipe, 5G alone does not cover the horizontal (2G) position. The standard field solution is the 2G + 5G combination, which gives the same position range as 6G.
A welder qualified with 6G is authorized for groove welding in all positions, on both plate and pipe. That authorization is not unlimited in diameter, though: the lower diameter limit of QW-452.3 applies independently.
Even a broad position range is bounded by the direction of progression. A 6G or 5G qualification is still limited by vertical progression: qualification earned on a coupon welded uphill does not cover downhill welding, and the reverse is equally true (QW-405.3).
A welder qualified on plate is authorized on pipe only above 610 mm (24 in.) OD; for 24 in. and below, a pipe coupon is required (QW-303.1 and the QW-461.9 notes). The reverse does not hold — there is no provision saying "plate position rules apply to large-diameter pipe." The relationship runs one way: plate qualification extends to pipe over 610 mm OD.
A welder who passes a groove test is authorized for fillet welding in all thicknesses and all diameters (QW-303.1); the reverse is not true — a welder qualified on a fillet coupon may only make fillet welds, and on pipe that authorization applies only to 73 mm (2⅞ in.) OD and above (QW-452.5). On small-bore process piping, this is the limit that generates nonconformities.
Tack welding is a separate item. A welder qualified by a fillet test is authorized to tack weld joints that will be fillet welded (QW-303.2). Tack authorization is not open-ended the way fillet authorization is; read it within the limits of QW-461.9.

This is why pipe shops usually test their welders on 6G, or on the 2G + 5G pair: the widest authorization for the fewest tests.

3. Essential variables (QW-350; process tables QW-352–QW-357)

Performance qualification recognizes essential variables only. The nonessential and supplementary essential categories used on the procedure side do not apply to the welder. Any change beyond the qualified range requires a new qualification test. QW-350 is the general clause; what actually binds the welder are the process-based tables (QW-353 SMAW, QW-355 GMAW, QW-356 GTAW, QW-357 FCAW, and so on). The main items:

Change of welding process (QW-301.2 / QW-303; process tables QW-35x): In Section IX, a process change is not a numbered QW-4xx essential variable. The rule comes from the requirement to qualify separately for each process. SMAW, GTAW, GMAW, FCAW, SAW, and PAW are each a separate authorization; GMAW and FCAW are distinct processes in Section IX and do not count as one item. Using more than one process on a single coupon — GTAW root plus SMAW fill, for example — is governed by QW-306 and produces a separate thickness range for each process. Continuity also runs process by process (QW-322.1).
Removal of backing (QW-402.4): A welder qualified on a backed coupon is not authorized to weld without backing (open root, single-sided access). The reverse holds: qualification obtained without backing covers both cases. A groove weld welded from both sides counts as "with backing."
Change of P-Number (QW-403.18): The essential variable itself is QW-403.18; QW-423 is only the table of permitted substitutions. Do not conflate the two. Note that Group Number plays no role at all in welder performance qualification — group distinctions matter only on the procedure and toughness side.
Pipe diameter (QW-403.16): Read the ranges from QW-452.3.
Change of F-Number (QW-404.15): A change in the classification of the filler metal.
Addition or deletion of filler metal in GTAW/PAW (QW-404.14): A welder qualified autogenously is not authorized to weld with filler metal.
Addition or deletion of a consumable insert (QW-404.22): A routine entry on the WPQ form (QW-484A) for GTAW and PAW root welding.
Change of filler metal product form (QW-404.23): Switching among solid, metal-cored, and flux-cored wire is an essential variable.
Thickness of deposited weld metal (QW-404.30): Exceeding the qualified range.
Change of position (QW-405.1): Adding a new position to the qualified set.
Vertical progression (QW-405.3): Switching between uphill and downhill in vertical welding. Watch for a frequent citation error: this variable is not QW-410.15. QW-410.15 is an entirely different technical item and has nothing to do with the welder's direction of progression.
Deletion of inert backing gas (QW-408.8): The code text runs one way — the variable covers the omission of the gas. Qualification obtained without root gas covers both cases; the reverse does not. This item applies to GTAW and PAW; confirm from the QW-355 list in your edition whether it applies to GMAW. It causes trouble regularly on pipe root welding.
Change of metal transfer mode in GMAW (QW-409.2): Moving between short-circuiting (short-arc) and spray, globular, or pulsed transfer is an essential variable.
Change of current type and polarity (QW-409.4): Recorded as a welder essential variable in the applicable processes — DCEN to AC in GTAW, for instance.

Each of these is recorded in the "Range Qualified" column of the WPQ. That column is the first place an inspector looks.

4. P-No, F-No, thickness, and diameter range

P-Numbers group base metals by weldability and compositional similarity: carbon steels are P-No 1; low-alloy steels fall in P-No 3, 4, and 5; austenitic stainless steels are P-No 8. P-No substitution is generous for the welder, because the performance test measures manual skill rather than metallurgy. Even so, substitution stays within the limits of the QW-423 table and cannot be stretched blindly.

F-Numbers group filler metals by usability characteristics (QW-432). Coverage does not follow a "hard to easy" intuition — it follows the rows of the QW-433 table together with the backing condition. Two rows, in numbers:

Qualified with F-No 4 (basic, low-hydrogen — E7018): covers F-No 1, 2, 3, and 4. If the coupon was welded with backing, that coverage is limited to backed applications; it grants no authorization for an open root.
Qualified with F-No 3 (cellulosic — E6010): covers F-No 1, 2, and 3. On paper it is the narrower row, but when the test is run without backing (open root), that row covers both backed and unbacked applications. That is where the open-root E6010 test earns its keep in the field: a narrower F-No row in exchange for authorization that carries no backing restriction.

In short, F-No coverage cannot be reduced to a single generalization. Read the table row by row, alongside the backing condition, and verify the QW-433 rows against the edition you are using.

The thickness range is set by "t", the thickness of weld metal deposited on the coupon (QW-452.1(b)). The general framework:

If the deposited thickness is less than 13 mm (½ in.), the upper limit of qualification is 2t. QW-452.1(b) contains only a "Thickness of Weld Metal Qualified, Max." column; for the welder, no lower limit is defined for deposited weld metal. Authorization reaches down to thin sections, and the governing restriction is the thickness range of the WPS being applied. (Lower-limit logic belongs to the QW-451 tables on the procedure side.)
If the deposited thickness is 13 mm or more and was deposited in at least three layers, the upper limit becomes "maximum thickness to be welded" — unlimited in practice. A pass is not a layer; a single layer made of multiple passes does not satisfy this condition.

In every case, that upper limit is also bounded by the thickness range of the WPS being applied.

Pipe diameter (QW-452.3) works the other way around: the restriction sits at the lower end, and the upper end is unlimited. The table has three rows:

Test coupon outside diameter (OD)	Diameter range qualified
Less than 25 mm (1 in.)	The diameter welded and above, unlimited
25 mm (1 in.) to 73 mm (2⅞ in.)	25 mm and above, all diameters
73 mm (2⅞ in.) and over	73 mm and above, all diameters

So a welder qualified in the 25–73 mm OD range is authorized on all diameters of 25 mm and above, while a coupon of 73 mm or larger does not cover diameters below 73 mm. On small-bore process piping, this is the detail most often missed.

5. Acceptance criteria: visual, bend, and volumetric examination

Acceptance of a WPQ test coupon runs in two stages.

Visual examination comes first (QW-302.4, evaluated to QW-194). On plate, examine the full length of the coupon weld excluding the discard end zones; on pipe, examine the full inside and outside circumference of the weld. QW-194 has two elements: complete joint penetration and complete fusion. Freedom from cracking is not among its stated criteria. Section IX gives no numerical visual acceptance criteria for cracks, underfill, undercut, or porosity — a gap well known and often debated in the field. Cracks are rejected at the bend or volumetric stage; if additional visual criteria are needed, take them from the construction code or the contract. No coupon proceeds to further testing until it passes visual.

One of two alternatives follows:

Guided bend test: Test specimens cut from the groove-welded coupon undergo face/root or side bending. Specimen count and type come from QW-452.1(a) and QW-462: a typical plate or pipe groove coupon needs 2 specimens, while 5G and 6G pipe coupons need 4. Specimen type depends on thickness — side bends at roughly 10 mm (⅜ in.) and above, face plus root bends below that. The acceptance limit is numerical: after bending, the convex surface must show no open discontinuity exceeding 3 mm (⅛ in.) measured in any direction (QW-163). Disregard open discontinuities at the corners of a specimen unless there is definite evidence that they result from incomplete fusion, slag inclusion, or another internal discontinuity. Note carefully: ASME sets no numerical corner tolerance. The 6 mm (¼ in.) corner-tear allowance so often attributed to ASME is specific to AWS D1.1. The warning at the top of this article — do not rule by D1.1 reflex — applies here too.
Volumetric examination (RT; UT under conditions): Section IX accepts volumetric examination as an alternative to bending for groove-welded performance coupons (QW-304 for welders, QW-305 for welding operators; QW-191 for UT). Volumetric examination reveals discontinuities in the deposited metal — porosity, slag, incomplete fusion — without destroying the coupon. The process restriction is critical: the volumetric route is open only for groove welds made with SMAW, SAW, GTAW, PAW, and GMAW, or combinations of these. FCAW is not on that list — you cannot qualify volumetrically with FCAW; the bend test is mandatory. Because FCAW is one of the most common field processes, this omission produces noncompliant WPQs in practice. The minimum length to be evaluated (QW-302.2) is 150 mm (6 in.) of weld on a plate coupon and the full circumference on a pipe coupon. If you intend to use the UT alternative, verify the applicability conditions of QW-191 in the edition you are working from.

Initial production welding in place of a test coupon: This option is not reserved for operators. Under QW-304, welders too may qualify through volumetric examination of the initial production weld rather than by welding a separate coupon. The dimensions come from QW-302.2: at least 150 mm (6 in.) on plate; the full circumference of the weld on pipe; and, in 5G, 6G, or special positions, the full circumference of the production weld.

The volumetric alternative carries two critical restrictions:

Radiography cannot qualify short-circuiting transfer (QW-304). The restriction covers the short-circuiting mode of GMAW and FCAW, and the code text ties it explicitly to radiography. Cold lap and incomplete fusion — the characteristic discontinuities of this mode — cannot be seen reliably on a radiograph. So in this mode, qualify by bend test or by UT under QW-191; the UT route stays open. This is one of the most common nonconformities on site.
For aluminum (P-No 21–26), titanium (P-No 51–53), and zirconium (P-No 61–62), the volumetric alternative is generally closed. The defined exception for GTAW-welded coupons applies only to P-No 21–26 and P-No 51–53. There is no GTAW exception for P-No 61–62 (zirconium); for that group the volumetric route is closed entirely. If you plan to rely on the exception, verify the QW-304/QW-305 text word for word in your edition.

Volumetric examination applies to groove-welded coupons only. Fillet weld qualification tests use the fillet-weld break test and macro etch instead: the break test per QW-181.2, macro etch acceptance per QW-184, and removal of the test specimens per QW-462.4 (QW-180 series).

6. How the WPQ relates to the WPS

A WPQ never stands on its own. The coupon is welded to a WPS, and production welding runs under a WPS:

The PQR proves the welding procedure is mechanically valid — a record supported by testing.
The WPS defines the parameter window to be used in production; the PQR supports it.
The WPQ proves a given welder can execute that WPS soundly in practice.

For a production weld to be documentarily valid, all three must line up: a valid WPS, the PQR that supports it, and the WPQ of a welder authorized within the scope of that WPS. QW-300.2 adds a fourth link: the WPQ must bind this employer. That is the chain the inspector looks for during field checks. If any link is broken, the weld cannot be accepted on paper — an NCR is raised and the situation is reassessed.

7. Validity and continuity: the 6-month rule

Section IX sets no fixed expiry date for a welder's qualification. It applies the principle of continuity instead. Per QW-322.1, if a welder does not use the relevant welding process for a period of 6 months or more, qualification for that process expires. The code says "expire," not "suspend" — use the correct term so the obligation is not softened. The practical formula is simple: weld with that process at least once every 6 months, and be able to prove it. Continuity is process-specific and employer-based, and the record of which process the welder used on which date must be traceable.

Renewal (QW-322.2) is far more flexible than most people assume. An expired qualification is renewed by welding a single test coupon in that process — plate or pipe, any base metal, any thickness, any diameter, in any position — and testing it per QW-301 and QW-302. A successful test restores all the base metal, thickness, diameter, and position ranges the welder previously held for that process. In other words, you do not need to repeat a 6G coupon to get 6G authorization back. Repeating one is common practice, and it only adds cost.

Alongside continuity there is a second mechanism. If the employer has specific reason to question a welder's ability — recurring rejects in production, for instance — the qualification may be revoked for that process and requalification required. Continuity is about time; revocation is about performance.

Do not confuse this with ISO: ASME puts no expiry date on the document, whereas ISO 9606-1 defines a set validity period and a regime of periodic confirmation. The two systems do not share the same validity logic. If you work on the ISO side, verify the period and confirmation requirements from the edition in force. The rules in this article are ASME rules.

8. Welder or welding operator?

Section IX qualifies two distinct roles under two distinct sets of rules:

Welder: the person who directs the welding equipment manually or semiautomatically. Because manual skill is decisive, variables such as position, vertical progression, and F-No are essential variables (QW-350 series; process tables QW-352–QW-357).
Welding operator: the person who sets up and operates automatic or machine welding — orbital GTAW, mechanized SAW, and the like. The essential variables are defined separately in the QW-360 series and split between machine welding (QW-361.1) and automatic welding (QW-361.2). Typical items include a change of welding process, switching between automatic and machine welding, going from direct to remote visual control, adding or removing automatic arc voltage control in GTAW, adding or removing an automatic joint tracking system, adding or deleting a consumable insert, and going from single pass per side to multiple passes per side. There is a widespread misconception about position: the addition or deletion of position(s) is an essential variable for machine welding (QW-361.1); it is absent from the list only for automatic welding (QW-361.2).

For operators, QW-305 allows qualification through volumetric examination of the first 1 m (3 ft) of production welding instead of a test coupon. This is not an operator privilege. As noted in section 5, QW-304 opens the same route for welders; only the dimensions differ — 150 mm on plate, full circumference on pipe.

The practical consequence: someone qualified as a manual GTAW welder must qualify separately as a welding operator to run the orbital or mechanized version of the same process. Substituting one document for the other is an error, and an inspector should reject it.

From the field

Four WPQ errors come up more than any others:

Overstating position authorization. Treating a welder qualified on plate 3G + 4G as qualified for "all positions" — that is the AWS D1.1 reflex. In ASME, horizontal (2G) is not covered. Likewise, 5G alone does not give horizontal; you need 2G + 5G. Watch the other direction too: 6G pipe qualification covers plate, but plate qualification covers pipe only above 610 mm (24 in.) OD. And even the widest position range is bounded by vertical progression (QW-405.3).
The backing question. A welder qualified on a backed coupon is not authorized for unbacked, single-sided root welding (QW-402.4), and welding from both sides also counts as "with backing." This has to be visible in the "Range Qualified" column of the WPQ.
No continuity record. Having the certificate in hand means nothing if the welder cannot show that they welded with that process within the last 6 months — the qualification has expired. Ask for provable continuity records, not just the date on the certificate. A signed, dated, process-specific tracking sheet is the gold standard.
Welding on another employer's WPQ. Qualification is employer-specific (QW-300.2). Section IX contains no provision governing transfer; that possibility arises only from the referenced construction code (ASME B31.3 para. 328.2.2 / ASME B31.1 para. 127.5), with the specific approval of the Authorized Inspector, using the same or an equivalent procedure, and limited to piping work.

As an inspector, work the order this way: first the employer who owns the document, then the continuity record, then the Range Qualified column, and only at the end the position and thickness arithmetic.

Related standards

ASME BPVC Section IX (2025) — Welding, Brazing, and Fusing Qualifications (performance qualification in the QW-300 series).
ASME B31.3 / ASME B31.1 — Process and power piping codes (paras. 328.2.2 and 127.5 on acceptance of WPQs).
ISO 9606-1 — Qualification testing of welders for steels (the European counterpart of the ASME WPQ; validity and confirmation regime differ from ASME).
ISO 14732 — Qualification of welding operators and weld setters.
ISO 15614-1 / ISO 15609-1 — Welding procedure qualification and the WPS.
ISO 5817 — Quality levels for imperfections in fusion-welded joints.
ISO 6520-1 — Classification and terminology of weld imperfections.
ISO 2553 / AWS A2.4 — Welding symbols.
AWS D1.1 — Structural welding code for steel (with its own welder qualification rules; position coverage and the bend corner tolerance differ from ASME).

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