3.1 PQR vs. WPS Workflow, Purpose & Content Requirements

3.1 PQR vs. WPS Workflow, Purpose & Content Requirements

Core Principle: In ASME Section IX, procedure qualification establishes the mechanical compatibility and metallurgical integrity of a weldment—not the manual dexterity of the craftsperson. A Welding Procedure Specification (WPS) is an operational recipe defining acceptable parameter ranges for production welders. A Procedure Qualification Record (PQR) is a certified historical audit document recording the actual values monitored during coupon fabrication and the destructive mechanical test results proving the recipe's integrity.

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1. Foundational Philosophy: Recipe vs. Proof

ASME Boiler and Pressure Vessel Code (BPVC) Section IX divides qualification into two distinct domains: Procedure Qualification (Article II) and Performance Qualification (Article III). Understanding this boundary is critical for the AWS CWI ASME Endorsement examination.

Per paragraph QW-100.1:

• Purpose of the WPS: To provide direction to the welder or welding operator in producing production welds that comply with Code requirements.
• Purpose of the PQR: To document the welding data used during the fabrication of a test coupon and the subsequent mechanical test results, proving that the proposed welding procedure will produce joints having suitable mechanical properties (tensile strength, ductility, and notch toughness when specified) for their intended commercial application.

+-----------------------------------------------------------------------------------------+
|                               PROCEDURE QUALIFICATION TRIAD                             |
+-----------------------------------------------------------------------------------------+
|  1. PRE-WELD DESIGN    | Formulate preliminary variables based on engineering criteria  |
|  2. PQR COUPON WELD    | Weld standardized coupon; record actual monitored values       |
|  3. MECHANICAL TESTING | Destructive tests (tensile, bend, Charpy); verify acceptance   |
|  4. PQR CERTIFICATION  | Manufacturer certifies test report accuracy and code compliance|
|  5. FINAL WPS ISSUED   | Synthesize production ranges supported by certified PQR data   |
+-----------------------------------------------------------------------------------------+

An essential takeaway for inspectors: The WPS dictates production boundaries; the PQR validates that those boundaries rest upon verified metallurgical performance.

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2. Welding Procedure Specification (WPS) Architecture (QW-200.1)

Paragraph QW-200.1 governs the preparation, content, and application of the WPS. Every organization fabricating pressure vessels, power piping, or process piping under ASME jurisdiction must maintain written qualified welding procedures.

Mandatory Contents of a WPS (QW-200.1(b))

A WPS must completely address all applicable welding variables—essential, supplementary essential (when required), and nonessential—for each welding process utilized. These variables are tabulated by process in Article IV (QW-252 through QW-267).

1. Essential Variables (QW-401.1): Conditions in which a change is considered to affect the mechanical properties (other than notch toughness) of the weldment. Any change in an essential variable beyond the range qualified on the supporting PQR mandates the qualification of a new WPS or a supplementary PQR coupon.
2. Supplementary Essential Variables (QW-401.3): Conditions in which a change affects the notch-toughness properties of the joint. These variables become active only when notch-toughness (Charpy V-notch impact) testing is invoked by referencing construction codes (such as ASME Section VIII Div 1, ASME B31.1, or ASME B31.3).
3. Nonessential Variables (QW-401.4): Conditions in which a change may be made in the WPS without requalifying the procedure, because the change does not significantly alter mechanical properties (e.g., changing groove bevel angle, root opening, or cleaning method).

CRITICAL EXAM TRAP: Candidates frequently believe that because a variable is labeled nonessential, it does not need to appear on the WPS. This is completely false. Under QW-200.1(b), all nonessential variables applicable to the process must be explicitly addressed on the WPS. They are nonessential only with respect to requalification, not documentation. Leaving a nonessential variable blank or stating "per welder discretion" without defining a range is a nonconformance during code audits.

Parameter Ranges vs. Point Values

A WPS must establish operational ranges rather than isolated point values. For example, while the PQR records that the coupon was welded at exactly 140 Amps, 23 Volts, and 6.2 inches per minute (ipm) travel speed, the production WPS will define a qualified operational envelope: 125–165 Amps, 21–25 Volts, and 5.0–8.0 ipm (provided heat input rules are satisfied).

Standard Form QW-482

ASME Section IX provides Form QW-482 (Recommended Format for Welding Procedure Specifications) in Nonmandatory Appendix B. While organizations may format their WPS to match company preferences, the resulting document must address every required variable listed in the QW-250 table for the relevant process.

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3. Procedure Qualification Record (PQR) Architecture (QW-200.2)

Paragraph QW-200.2 governs the generation, testing, and legal certification of the Procedure Qualification Record.

Mandatory Contents of a PQR (QW-200.2(b))

The PQR is a certified historical record. It must document:

• Actual Monitored Welding Data: The specific base metal specification, P-Number, group number, thickness, joint geometry, filler metal specification (AWS classification, SFA number, F-Number, A-Number), preheat temperature, interpass temperature, electrical characteristics (amperage, voltage, polarity, travel speed), and postweld heat treatment (PWHT) parameters used during coupon fabrication.
• All Essential Variables: Must be documented with the exact values observed during welding.
• Supplementary Essential Variables: Must be documented whenever the WPS requires notch-toughness qualification.
• Nonessential Variables: Per QW-200.2(b), nonessential variables evaluated during coupon welding need not be recorded on the PQR, although documenting them represents standard industry best practice.
• Actual Mechanical Test Results: Tensile specimen dimensions, area, maximum load, ultimate tensile strength, fracture type, and fracture location (weld metal vs. base metal); guided bend specimen type, bend radius, and visual results (e.g., "Pass - no open defects"); and Charpy absorbed energy (ft-lbs or Joules), lateral expansion, and test temperature when impact testing is required.

Certification Responsibilities (QW-200.2(c))

A PQR is not valid until certified by the fabricator. The manufacturer or contractor must include a signed certification statement asserting that the statements in the record are correct and that the test coupons were prepared, welded, and tested in accordance with the requirements of ASME Section IX.

+-----------------------------------------------------------------------------------------+
|                          PQR LEGAL CERTIFICATION BOUNDARIES                             |
+-----------------------------------------------------------------------------------------+
| WHO CAN CERTIFY?         | ONLY the Manufacturer or Contractor having operational        |
|                          | control of the coupon welding (QW-201 / QW-200.2(c)).         |
|--------------------------+---------------------------------------------------------------|
| CAN AN AI CERTIFY?       | NO. The Authorized Inspector (AI) verifies compliance and     |
|                          | reviews records, but does NOT legally certify the PQR.        |
|--------------------------+---------------------------------------------------------------|
| CAN A TESTING LAB SIGN?  | The testing lab certifies only the test results it performed. |
|                          | The manufacturer must sign the overarching PQR certification. |
|--------------------------+---------------------------------------------------------------|
| SUBCONTRACTING LIMITS    | Coupon machining, NDE, and mechanical testing may be sub-     |
|                          | contracted; coupon welding MUST remain under the fabricator's |
|                          | full operational control (QW-201).                            |
+-----------------------------------------------------------------------------------------+

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4. Revising WPS vs. PQR: Living Document vs. Frozen History

One of the most heavily tested areas on the AWS CWI ASME Endorsement exam is the divergence in revision rules between a WPS and a PQR.

The Immutable PQR Rule (QW-200.2(c))

Once mechanical testing is completed and the PQR is certified, the recorded data cannot be altered to qualify different parameters.

• What if a clerical error occurred? If a typographical error was made (e.g., typing "ASTM A106 Grade B" when the certified mill test report proves the coupon was "ASTM A333 Grade 6"), an editorial correction is permitted provided verifiable documentation exists.
• What if unrecorded parameters were monitored? An addendum may be added to an existing PQR if the data was actually recorded during the original test coupon welding (such as unrecorded interpass temperatures that were documented on shop travelers) and verifiable records exist.
• What is strictly prohibited? Changing test results, fabricating data, or "revising" recorded amperage or base metal thickness to match a desired production range. Any change in an essential variable necessitates welding an entirely new test coupon.

Revising a WPS (QW-200.1(e))

A WPS may be amended, revised, or completely rewritten at any time without requalification, provided the changes involve only nonessential variables or stay within the boundaries established by the supporting PQR(s). If an essential variable or supplementary essential variable is modified beyond the qualified range, the fabricator must either:

1. Reference an existing certified PQR whose ranges cover the new parameters, or
2. Weld and test a new qualification coupon under the new variable conditions.

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5. Practical Inspection Scenarios & Common Exam Traps

Scenario 1: Missing Nonessential Variable on WPS

During an audit of a piping fabrication shop, an AWS CWI examines a Gas Metal Arc Welding (GMAW) WPS. Under joint design, the WPS specifies "Single-V Groove, 60-degree included angle, 1/8-inch root face." However, the root opening space is left blank. The quality manager argues: "Root opening is a nonessential variable under QW-402.1 for GMAW, so leaving it blank allows our welders to fit up however they want."

• Audit Finding: Nonconformance. Per QW-200.1(b), all nonessential variables must be explicitly addressed. The WPS must state an acceptable range (e.g., "Root Opening: 1/16 in. to 1/8 in."). A blank variable provides no direction to the welder.

Scenario 2: Contractor Revising a PQR Amperage

A contractor qualifies a Submerged Arc Welding (SAW) PQR on 1.0-inch plate. The PQR documents that the coupon was welded at 450 Amps and 32 Volts. Two months later, the contractor needs to weld a heavy vessel shell at 650 Amps. To avoid coupon welding, the welding engineer crosses out "450 Amps" on the PQR, writes "650 Amps", initials the change, and reissues the WPS for 550–700 Amps.

• Audit Finding: Critical Violation of QW-200.2(c). The PQR is an immutable historical record of what actually happened during the coupon test. Re-writing actual data is illegal. Because amperage and electrical parameters affect heat input (and deposition rates), increasing amperage to 650 Amps requires welding a new PQR coupon if heat input is an essential or supplementary essential variable, or if process limits dictate.

6. Summary Checklist for WPS/PQR Compliance Audits

When reviewing welding documentation prior to production welding under ASME Section IX, verify the following six-point checklist:

1. WPS Variable Completeness: Does the WPS address every essential variable, supplementary essential variable (if impact testing applies), and nonessential variable listed in the QW-250 table for each process used?
2. Definite Ranges: Are all variables stated as defined ranges or specific conditions rather than open-ended statements (e.g., "as required")?
3. PQR Recorded Actuals: Does the PQR list the actual single values or tight observed ranges recorded during welding, rather than copying the broad ranges found on the WPS?
4. PQR Certification: Is the PQR signed and dated by an authorized representative of the manufacturer or contractor, with the exact wording certifying compliance with Section IX?
5. PQR-to-WPS Alignment: Are all operational ranges on the WPS fully supported by the base metal thickness, weld deposit thickness, filler metal classification, and preheat/PWHT data recorded on the supporting PQR(s)?
6. Specimen Count & Results: Does the PQR document the mandatory minimum number of tension and bend specimens required by Table QW-451.1, with quantitative ultimate tensile values and qualitative bend results recorded?