WPS vs PQR: The Key Differences in Rail Maintenance Projects

WPS vs PQR comes down to order and purpose. A procedure qualification record (PQR) documents one test weld: the actual variables used and the test results. A welding procedure specification (WPS) is then written from it, giving welders permitted ranges. Under AWS D1.1 Clause 5, a prequalified WPS needs no PQR at all.

That sequence matters on a rail project because the job usually mixes three kinds of welding. Steel structures such as platforms, canopies and signal supports are welded to AWS D1.1. Pressure equipment and piping are qualified to ASME Section IX. Rail itself (thermite, flash-butt and arc repair welds) is qualified to railroad practice: the track owner's standards, AWS D15.2 and the AREMA Manual for Railway Engineering. Each has its own PQR rules.

This article covers what each document contains, which comes first, what range a PQR qualifies, who signs it, and how rail welds fit. For how a WPS is written and reviewed, see our companion guide, what is a welding procedure specification.

WPS vs PQR: what is the difference between them?

A PQR is evidence; a WPS is an instruction. The PQR records what was actually done to one test coupon and proves, by testing, that the result met the code. The WPS tells production welders what they may do, within ranges the PQR supports.

ASME Section IX defines both in its Article II: QW-200.1 covers the WPS and QW-200.2 the PQR. ASME publishes suggested formats for each, Form QW-482 for the WPS and Form QW-483 for the PQR. The PQR form ends with the organization certifying that the test welds were "prepared, welded, and tested" to Section IX (ASME Form QW-483). The WPS form has a field for the supporting PQR numbers, which is the link between the two documents.

Key takeaway: the PQR is a fixed historical record, and the WPS is a working document that can be revised as long as it stays inside the PQR.

Which comes first, the PQR or the WPS?

For a qualified procedure, the PQR comes first and the WPS is written from it. In practice the order runs like this:

1. The welding engineer drafts a preliminary procedure (often called a pWPS) for the test.
2. A welder makes a test coupon to that draft, and someone records the actual values used.
3. The coupon is tested: visual, NDT where the code requires it, then mechanical tests.
4. If the results pass, the recorded values and results become the PQR, and the organization certifies it.
5. The WPS is written with ranges that the PQR's essential variables allow, and it cites the PQR number.

The original version of this article said a WPS is always developed after a PQR. That is true for ASME Section IX, which has no prequalified procedures. It is not true for AWS D1.1.

Under AWS D1.1, a prequalified WPS needs no PQR. Older editions put it plainly: prequalification is "exempt from WPS qualification testing", quoted by TWI from D1.1 Section 3.1. In the 2020 and 2025 editions, prequalification moved to Clause 5 and qualification by testing to Clause 6, Part B. A prequalified WPS must still be written down, and it must stay inside every Clause 5 limit: listed base metals, filler metals, joint details, and process limits. Some processes can't be prequalified at all; secondary sources list GMAW short-circuit, GTAW, electroslag and electrogas among them.

Step outside one Clause 5 limit, such as an unlisted steel, a joint detail not in the prequalified figures, or a Charpy toughness requirement, and the procedure needs a PQR under Clause 6. A 2025-edition study guide lists these triggers. Treat the exact clause and table numbers as CONFIRM against the edition named in your contract, because AWS renumbered D1.1 in 2020 and revised it again in 2025 (AWS D1.1:2025 release).

D1.1 also lets the Engineer accept "properly documented evidence of previous WPS qualification" (older-edition wording, quoted by TWI). This is how a contractor reuses a PQR from an earlier job, subject to the Engineer's acceptance.

What range does a PQR qualify?

A PQR qualifies a range, not just the exact values tested. Each code sorts the procedure variables into classes, and only some of them limit what the WPS may say:

AWS D1.1 Clause 6 has its own PQR essential-variable tables, organized by process. AWS D15.2 has separate essential-variable tables for SMAW, GMAW and FCAW arc welds, for thermite welds and for flash welds (Tables 6.1 to 6.3 in the 2022 edition, from the AWS D15.2 preview).

Thickness is the variable most people get wrong. ASME IX Table QW-451.1 sets the base metal thickness range and the deposited weld metal thickness a groove-weld PQR qualifies, plus the tension and bend tests required. AWS D1.1 has its own table. For the same test plate, the two codes give very different ranges, as the next example shows.

Key takeaway: a WPS can only state ranges the PQR's essential variables cover. Anything wider needs another PQR.

Worked example: a 1 in. plate PQR under ASME IX QW-451

Inputs. A contractor qualifies a groove weld for a pressure-equipment repair at a rail maintenance facility:

• base metal: SA-516 Grade 70 plate (P-No. 1), T = 1.00 in. (25 mm)
• process: SMAW with E7018 (F-No. 4), one process filling the whole joint, so deposited weld metal t = 1.00 in.
• no PWHT and no impact testing required by the construction code
• no weld pass thicker than 1/2 in.

Step 1: find the QW-451.1 row. A 1.00 in. coupon falls in the row for 3/4 in. to less than 1-1/2 in. (19 to under 38 mm).

Step 2: base metal range. That row qualifies a minimum of 3/16 in. (about 5 mm) and a maximum of 2T. So 2 × 1.00 in. = 2.00 in. (about 50 mm). The WPS may cover base metal from 3/16 in. to 2.00 in.

Step 3: deposited weld metal. Because t is 3/4 in. or more in this row, the maximum deposit is 2T = 2.00 in. If t had been under 3/4 in., the cap would have been 2t instead.

Step 4: tests. The row calls for 2 tension specimens (QW-150) and 4 side-bend specimens (QW-160). Side bends replace face and root bends at this thickness.

Step 5: check the modifiers. Two other rules can shrink the range:

Reading the result. A production joint in 1-1/2 in. plate is inside this PQR's range, but one in 2-1/2 in. plate is not. Covering it would take a second PQR, for example on a coupon of 1-1/2 in. or more, which ASME IX qualifies up to 8 in. (200 mm). Under D1.1 the same 1 in. test plate would already cover it, which is why the two codes' PQRs can't be swapped.

The QW-451.1 values come from secondary sources that reproduce the table (a welding-engineering article and textbook excerpts), not from the code itself. They match each other, but they are CONFIRM against the Section IX edition in your contract. The D1.1 row is also secondary (AWS forum and study-guide quotations of the 2015 table).

When does a WPS need requalifying?

A new PQR is needed whenever production would go outside an essential variable the existing PQR qualifies. A change to a nonessential variable only needs a WPS revision.

The original article said a PQR "can be referenced for multiple projects if the same parameters are used". That leaves out the point that matters: a PQR supports any job whose variables fall inside its qualified ranges, on any project, for the organization that qualified it. It doesn't need the same parameters, and it doesn't cover another company.

Common triggers for a new PQR:

• a different welding process, or adding a second process
• a base metal or filler metal outside the qualified groups
• production thickness outside the PQR range, as in the example above
• adding or removing PWHT, or a large preheat reduction
• a new toughness requirement, which brings in the supplementary essential variables
• for rail: a different thermite kit or flash-welding machine setting outside the D15.2 essential-variable tables

Two things don't trigger requalification. One PQR can support several WPSs, and one WPS can cite several PQRs, for example one for the root process and one for the fill. A WPS can also be revised and reissued within its PQR's ranges without new testing.

Who witnesses and signs a PQR?

The organization that will do the production welding qualifies and certifies the PQR; under ASME IX it can't hand that responsibility to someone else. Labs, consultants and inspectors can help, but the signature belongs to the manufacturer or contractor.

ASME Section IX. QW-201 makes the organization responsible for the welding it does and for qualifying its WPSs. A secondary summary of the current rules (QG-106, QW-200.2) says the organization may subcontract the testing if it "accepts full responsibility". It may not subcontract the certification function. The test welder must be under the organization's "full supervision and control", and since the 2019 edition the organization's quality program must name who supervises qualification work. The same source reports that the person who certifies can't also be the supervisor of the test coupon welding (Interpretation IX-20-12). These points come from a welding-engineering article, not the code text, so treat them as CONFIRM (ME Welding). Form QW-483 has fields for "Tests Conducted by" and "Laboratory Test No." beside the organization's certification, which reflects that split.

AWS D1.1. Older editions say "each manufacturer or Contractor shall conduct tests required by this code to qualify the WPS" (quoted by TWI). D1.1 separates the contractor's inspection from verification inspection by or for the owner. The verification inspector audits WPSs, welder records and NDT reports and reports to both parties (AWS Inspection Trends, Feb 2023). The code itself doesn't make a third-party witness mandatory for the PQR test. Contracts often do, naming a CWI, the owner's inspector or the Engineer, so read the project specification.

Rail welds. D15.2 has clauses on inspection responsibility and on designated inspectors' qualifications (8.1 and 8.2 in the 2022 edition; content not verified here). The track owner's welding standard usually names who approves rail weld procedures. Check it before the qualification weld is made.

Key takeaway: get the witness and signature requirements from the contract and the owner's standard before welding the coupon. Re-welding a coupon because the wrong person watched it costs more than asking first.

How are thermite, flash-butt and enclosed-arc rail welds qualified?

Rail welds are not qualified to AWS D1.1. They're qualified to railroad practice: the track owner's welding standard, which typically draws on AWS D15.2 and the AREMA Manual for Railway Engineering (MRE) Chapter 4. Thermite welds also depend on the kit manufacturer's procedure.

The original article listed SMAW, GMAW, TIG and aluminum for rail maintenance. Running rail is joined by thermite welding in the field and flash-butt welding in plants or mobile units. Arc welding on rail is mostly repair and build-up, with enclosed-arc butt welds as a less common field joint.

AWS D15.2/D15.2M:2022, Specification for Joining Railroad Rail and Related Rail Components, is the AWS document for rail in track. It is the 4th edition. Its foreword says the main change from 2013 was turning it from a recommended practice into a specification with mandatory language. Its scope covers SMAW, GMAW, FCAW, flash welding, thermite welding and rail bonds, and rail classification follows AREMA's rail specifications. Clause 6 covers procedure qualification for thermite welds (6.1), flash welds (6.2), slow bend testing for both (6.3) and arc welding (6.4). Clause 7 covers welder and welding operator qualification, including thermite welders (7.12) and flash welding operators (7.13). These clause titles come from the public preview; the requirements inside them are paywalled.

AREMA MRE Chapter 4 (Rail), Part 3 "Joining of Rail" contains, per the 2025 table of contents, a Specification for the Quality Assurance of Electric-Flash Butt Welding of Rail (3.10), a Specification for Fabrication of Continuous Welded Rail (3.11) and a Specification for the Quality Assurance of Thermite Welding of Rail (3.13) (AREMA MRE Chapter 4 TOC). AREMA publishes recommended practices "as a guide to railways", not regulations. They become binding only when an owner's standard or contract adopts them.

Enclosed-arc welding joins rail ends with coated electrodes, building up the weld inside copper blocks or shoes. Patent literature describes it as slow and operator-dependent compared with thermite (US 5,877,468). That is one reason most US field joints are thermite. Treating it under D15.2's arc welding rules is our reading of the scope; CONFIRM with the owner's standard.

What FRA requires. 49 CFR Part 213 sets no weld procedure or welder qualification rule. A search of the 2024 Part 213 text finds no mention of welding procedures or welders. What it does do is define the defect that a poor procedure produces, in 49 CFR 213.113(d)(6):

"Defective weld means a field or plant weld containing any discontinuities or pockets, exceeding 5 percent of the rail head area individually or 10 percent in the aggregate, oriented in or near the transverse plane…"

Rail weld qualification is how an owner keeps those defects out of track. For inspection of finished rail welds, see aluminothermic weld inspection and flash-butt weld inspection.

Which welding code applies to which part of a rail project?

The code follows the item being welded, not the client. A transit agency's capital project can need three or four sets of WPSs and PQRs at once.

D15.1 covers cars and locomotives, not rail in track. Citing it, or D1.1, for a thermite weld is a common error in procurement documents. For structural weld acceptance after the WPS is in place, see AWS D1.1 weld inspection criteria; for ASME work, see ASME weld ultrasonic inspection.

Side note: welder qualification (WPQ or WPQR)

A PQR qualifies the procedure; a welder performance qualification (WPQ, also written WPQR) qualifies the person. A welder who passes a performance test proves they can follow a qualified WPS. It does not qualify a new procedure.

• ASME IX: performance qualification is in Article III (QW-301 onward). ASME's suggested form QW-484A records the welder's name, the WPS followed, the test coupon, and the range qualified for each welding variable (ASME Form QW-484A).
• AWS D1.1: welder and welding operator qualification for nontubular work is in Clause 6, Part C (2020 layout, secondary). A qualification stays in effect unless the welder hasn't used the process for more than 6 months, or there's a specific reason to question their ability (older-edition wording; CONFIRM).
• Rail: D15.2 Clause 7 covers track welder and welding operator qualification, with separate clauses for thermite welders and flash welding operators. Thermite kit makers and railroads also run their own training and certification. Where the owner's standard sets a requalification interval, follow it.

Under both codes the WPQ form names the WPS used for the test. A welder record with no WPS reference is a common audit finding.

Common WPS and PQR mistakes

These come up repeatedly in qualification packages for structural and rail work:

What a WPS and PQR don't cover

A qualified procedure shows that sound welds are possible. It doesn't prove that any production weld is sound. That is the job of production inspection.

• No acceptance criteria for production welds. ASME Section IX qualifies procedures and people; acceptance comes from the construction code, such as Section VIII or B31.3. D1.1 acceptance is in Clause 8, and rail weld acceptance comes from the owner's standard and D15.2 Clause 8.
• No NDT personnel qualification. The UT or MT technician who inspects the welds is certified by their employer under SNT-TC-1A or a similar program, which is separate from welder qualification.
• No control of workmanship on the day. Fit-up, preheat actually applied, interpass temperature and weather protection still need inspection. For thermite welds, gap, preheat and mold fit decide the result more than paperwork does.
• No coverage outside the ranges. A thicker plate, another steel grade or a new thermite kit falls outside the PQR, as the worked example shows.
• No substitute for rail testing. Thermite welds in service still need internal testing, and vehicle UT covers little of the rail base, so field welds often need hand UT. See weld defect types for what goes wrong in production.

How EMA Industries applies this

EMA Industries provides WPS/PQR support alongside AWS D1.1 structural weld UT, MT and PT, rail weld inspection, and NDT Level III services. It works from Southern California and mobilizes nationwide. On a mixed rail project, the first step is sorting which items fall under D1.1, ASME IX or the track owner's rail welding standard. Then each WPS can be checked against the PQR ranges before welding starts. See our weld inspection and ultrasonic examination services or contact EMA Industries to discuss a qualification package.

Frequently asked questions

How often should a WPS be updated?

A WPS needs revising when production changes a nonessential variable, and a new PQR when it changes an essential one. No code sets a calendar interval for WPS review. Many organizations review their WPSs when a code edition named in a new contract changes, or when a new material, consumable or thermite kit is introduced.

Can one PQR support more than one WPS?

One PQR can support any number of WPSs, as long as each WPS stays inside the PQR's qualified ranges. A single WPS can also cite more than one PQR, for example separate PQRs for the root and fill processes. What a PQR can't do is support a WPS for another organization, or one written to a different code.

What happens if a PQR test fails?

A failed coupon can't support a WPS. The organization finds the cause, adjusts the procedure and welds a new coupon. Some codes allow a limited retest of the failed test type from the same coupon. D15.2 has a retest clause (6.7), and D1.1 has its own retest rules. Check the clause in your edition before deciding whether to retest or start over.

Can a contractor use another company's PQR?

Under ASME Section IX, generally not. Each organization must qualify its own procedures, with narrow exceptions such as a change of company ownership (QW-201.1) and AWS standard welding procedure specifications adopted under Section IX's own rules. Under D1.1, the Engineer may accept documented previous qualification. Get that acceptance in writing.

Does a thermite rail weld need a PQR?

A thermite weld is qualified differently from a structural weld. The track owner's standard sets the procedure, usually based on the kit maker's instructions, AWS D15.2 Clause 6.1 and AREMA MRE Chapter 4, Part 3.13. Qualification tests include slow bend testing and weld metal checks. An AWS D1.1 or ASME IX PQR doesn't qualify a thermite weld.

Sources

• AWS D15.2/D15.2M:2022, Specification for Joining Railroad Rail and Related Rail Components, 4th ed., public preview (abstract, foreword, scope, table of contents): https://pubs.aws.org/Download_PDFS/D15.2-D15.2M-2022_PV.pdf
• AWS D15.1/D15.1M:2025, Railroad Welding Specification for Cars and Locomotives: https://pubs.aws.org/p/2260/d151d151m2025-railroad-welding-specification-for-cars-and-locomotives
• AWS, D1.1/D1.1M:2025 release announcement: https://www.aws.org/about/news/d11-release/
• AWS Inspection Trends, D. Peterson, Feb 2023 (contractor's inspection vs verification inspection): https://www.aws.org/magazines-and-media/inspection-trends/it-feb-23-feat-02-peterson/
• ASME, Form QW-482 suggested format for WPS: https://www.asme.org/wwwasmeorg/media/resourcefiles/aboutasme/standards_certification/bpvc%20data%20forms/bpvc_ix_qw-482.pdf
• ASME, Form QW-483 suggested format for PQR: https://www.asme.org/wwwasmeorg/media/resourcefiles/aboutasme/standards_certification/bpvc%20data%20forms/bpvc_ix_qw-483.pdf
• ASME, Form QW-484A suggested format for WPQ: https://www.asme.org/wwwasmeorg/media/resourcefiles/aboutasme/standards_certification/bpvc%20data%20forms/bpvc_ix_qw-484a.pdf
• AREMA, Manual for Railway Engineering (2025), Chapter 4 table of contents: https://publications.arema.org/publications_toc/MRE_006/Chapter%2004%20TOC.pdf
• 49 CFR 213.113 on eCFR: https://www.ecfr.gov/current/title-49/subtitle-B/chapter-II/part-213/subpart-D/section-213.113 (text read on Cornell LII: https://www.law.cornell.edu/cfr/text/49/213.113)
• TWI, "Can one company use welding procedures qualified by another company?": https://www.twi-global.com/technical-knowledge/faqs/faq-can-one-company-use-welding-procedures-qualified-by-another-company
• ME Welding, "Administrative requirements of welding qualifications to Section IX" (secondary): https://mewelding.com/administrative-requirements-of-welding-qualifications-to-section-ix/
• US Patent 5,877,468, Method and system for welding railroad rails (background on enclosed-arc and thermite welding): https://patents.google.com/patent/US5877468A