12.3 B31.3 Procedure & Performance Qualification Rules and Section IX Exceptions

12.3 B31.3 Procedure & Performance Qualification Rules and Section IX Exceptions

A fundamental objective of the AWS ASME Endorsement Examination is testing a candidate's ability to cross-reference between the general qualification rules of ASME BPVC Section IX and the specific construction code rules of ASME B31.3. While ASME Section IX governs the baseline mechanics of procedure (PQR/WPS) and performance (WPQ) qualifications across all pressure vessel and piping disciplines, it deliberately defers service-specific conditions, toughness requirements, production NDE allowances, and acceptance criteria to the applicable construction code.

Under ASME B31.3 Chapter V (Para 328.2), the code incorporates ASME Section IX by reference but introduces critical additions, modifications, and restrictions that inspectors must enforce on the shop floor and in testing laboratories.

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General Qualification Requirements (Para 328.2.1)

Under Para 328.2.1, the fundamental principle governing welding qualification in B31.3 is Employer Responsibility:

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|                             EMPLOYER QUALIFICATION RESPONSIBILITY                                 |
+---------------------------------------------------------------------------------------------------+
|  1. Each employer (contractor, fabricator, erector) is responsible for all welding performed.     |
|  2. WPSs and welders/operators MUST be qualified per ASME Section IX, except as modified herein.  |
|  3. Welder qualifications are strictly employer-specific (cannot transfer between companies).     |
|  4. Performance testing may be conducted on test coupons OR approved production welds.             |
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Just as mandated in Section IX QW-103 and QW-300, an employer cannot abdicate qualification responsibility. A contractor cannot simply "borrow" a Procedure Qualification Record (PQR) from another engineering firm, nor can a welder qualified by Company A weld for Company B without re-qualification (except under narrow multi-employer operational agreements satisfying Section IX QW-300.2).

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Standard Welding Procedure Specifications (SWPSs) under B31.3

Ordinarily, ASME Section IX requires every fabricator to weld a physical test coupon, record actual parameters on a PQR, and perform destructive tension and bend tests before writing a WPS. However, ASME B31.3 Para 328.2.1(b) provides an important exception by permitting the use of Standard Welding Procedure Specifications (SWPSs):

• Approved SWPS Scope: Only SWPSs published by the American Welding Society (AWS B2.1 series) and formally accepted and listed in ASME Section IX Appendix E may be utilized.
• Mandatory Employer Demonstration (QW-500): An employer cannot simply purchase an AWS SWPS and distribute it to the shop floor. Under Section IX QW-500, the employer must:
  1. Officially sign and adopt the SWPS with proper administrative corporate documentation.
  2. Weld an initial demonstration test coupon in accordance with the SWPS parameters.
  3. Subject the demonstration coupon to visual examination and mandatory mechanical testing (transverse tension and bend tests) or volumetric examination as specified in Section IX.
  4. Record the demonstration coupon results on a certified company document signed by the employer.
• B31.3 Restrictions on SWPSs: Under B31.3 Para 328.2.1(b), SWPSs are strictly prohibited in applications where Charpy V-notch impact testing is required by the engineering design or B31.3, unless the underlying SWPS specifically contains certified, qualified toughness data that satisfies the project's Minimum Design Metal Temperature (MDMT).

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Low-Temperature Toughness & Impact Testing (Para 323.2.2 & Table 323.3.1)

In chemical and cryogenic processing (e.g., ethylene plants, LNG terminals, liquid nitrogen loops), piping operates at temperatures where carbon and low-alloy steels undergo a transition from ductile to brittle fracture behavior. ASME B31.3 governs low-temperature toughness through Para 323.2.2, Fig. 323.2.2A (Impact Test Exemption Curves), and Table 323.3.1.

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|                         B31.3 CHARPY V-NOTCH IMPACT TESTING MANDATES                              |
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|  Trigger Condition     --> Operating temperature colder than Fig. 323.2.2A Exemption Curves      |
|  Required Test Zones   --> Charpy V-notch (CVN) testing of BOTH Weld Metal AND HAZ                |
|  Test Temperature      --> Must be AT or COLDER than the Minimum Design Metal Temperature (MDMT)  |
|  Acceptance (Ferritic) --> Table 323.3.1 absorbed energy based on SMTS (ft-lbs / Joules)          |
|  Acceptance (Austenite)--> Table 323.3.1 lateral expansion >= 0.015 in. (15 mils / 0.38 mm)      |
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Impact Test Acceptance Criteria (Table 323.3.1)

When impact testing is mandated, three specimens from the Weld Metal and three specimens from the Heat-Affected Zone (HAZ) must be tested at a temperature no warmer than the design MDMT:

1. Carbon and Low-Alloy Steels (Absorbed Energy Criteria):
   • Specified Minimum Tensile Strength (SMTS) <= 65 ksi (450 MPa): Average of 3 specimens >= 13 ft-lb (18 J); minimum individual specimen >= 10 ft-lb (14 J).
   • 65 ksi < SMTS <= 75 ksi (517 MPa): Average >= 15 ft-lb (20 J); minimum individual specimen >= 12 ft-lb (16 J).
   • 75 ksi < SMTS < 95 ksi (655 MPa): Average >= 20 ft-lb (27 J); minimum individual specimen >= 15 ft-lb (20 J).
2. Austenitic Stainless Steels (Lateral Expansion Criteria):
   • Rather than absorbed energy, austenitic grades (e.g., 304L, 316L) are evaluated by transverse lateral expansion measured opposite the notch. All specimens must achieve a lateral expansion of at least 0.015 in. (15 mils / 0.38 mm).

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The Conversion of Section IX Supplemental Essential Variables

A critical concept on the AWS endorsement examination is how B31.3 toughness requirements transform ASME Section IX variables:

[!IMPORTANT] Supplemental Variables Become Mandatory Essential Variables: Under ASME Section IX (QW-401.3 and QW-250), notch toughness variables are designated as Supplemental Essential Variables. For ordinary ambient-temperature piping, these variables do NOT apply. However, the instant ASME B31.3 mandates impact testing under Para 323.2.2, EVERY supplemental essential variable in Section IX automatically converts into a full, mandatory ESSENTIAL VARIABLE for the WPS and PQR.

Key Section IX Supplemental Variables Triggered by B31.3:

• QW-403.5 (Base Metal Group Number): A change from one Group Number to another within the same P-Number (e.g., welding P-No. 1 Group 1 to P-No. 1 Group 2) requires procedure requalification.
• QW-405.2 (Progression): A change from upward to downward progression in vertical position welding is an essential variable.
• QW-406.1 (Preheat Decrease): A decrease of more than 100°F (55°C) from the preheat temperature recorded on the PQR requires requalification.
• QW-407.2 (PWHT Temperature and Time): A change in postweld heat treatment temperature range or an increase in total soaking time beyond that qualified requires requalification.
• QW-409.1 (Heat Input Limitation): An increase in heat input (J/in) beyond the maximum qualified on the PQR, or a change in arc current mode (pulsed vs. spray) is strictly prohibited without requalification. Heat input is calculated as:

$\text{Heat Input } (\text{J/in}) = \frac{\text{Voltage } (\text{V}) \times \text{Amperage } (\text{A}) \times 60}{\text{Travel Speed } (\text{in/min})}$

Excessive heat input creates slow cooling rates, leading to coarse grain growth in the HAZ and disastrous loss of Charpy impact toughness.

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Welder Performance Qualification by Volumetric NDE (Section IX QW-304)

Under ASME Section IX QW-304, a welder may be qualified either by destructive mechanical bend testing or by volumetric nondestructive examination (radiographic or ultrasonic examination performed in accordance with QW-191). Two details of QW-304 are examinable:

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|              WELDER QUALIFICATION BY VOLUMETRIC NDE (SECTION IX QW-304 / QW-305)                 |
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|  1. Minimum examined length --> 6 in. (150 mm) of weld, and for pipe the ENTIRE circumference.    |
|  2. Small-diameter pipe     --> Multiple coupons of the same diameter may be required, but the    |
|                                 number need not exceed FOUR consecutively made test coupons.      |
|  3. Initial production weld --> A minimum 6 in. (150 mm) length of the first production weld(s)   |
|                                 made by the welder may be examined instead of a separate coupon.  |
|  4. GMAW short-circuiting   --> MAY NOT be qualified by volumetric NDE. Bend tests only.          |
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What ASME B31.3 Actually Adds in Para 328.2

B31.3 Para 328.2 requires WPSs and welders to be qualified as required by ASME BPVC Section IX except as modified by Para 333 for brazing of Category D piping and by the following subparagraphs. Those subparagraphs are administrative, not additional NDE:

[!WARNING] Para 328.2.4 is a records clause, not an NDE clause. There is no B31.3 rule requiring 100% examination of a welder's entire initial production weld, and no B31.3 "disqualification cascade" requiring every earlier weld by that welder to be re-examined. The volumetric qualification rules are Section IX's (QW-304), and the consequences of failing a performance qualification are Section IX's retest provisions (QW-320). What B31.3 adds is the owner-approval gate on accepting qualifications performed by others, the pipe-or-tube-coupon restriction on accepting a previous employer's WPQ, and the records availability requirement at the welding location.

The GMAW-S Volumetric Examination Prohibition

Section IX QW-304 excludes the Short-Circuiting Transfer Mode (GMAW-S) from qualification by volumetric NDE:

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|                         THE GMAW-S PERFORMANCE QUALIFICATION BAN                                  |
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|  Rule: Welder qualification for GMAW-S CANNOT be accomplished by Radiographic or Ultrasonic NDE.  |
|  Governing Clause: ASME Section IX QW-304 (applied through B31.3 Para 328.2)                      |
|  Mandatory Qualification Method: Mechanical Bend Testing ONLY (Root/Face or Side Bends)           |
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Physical and Metallurgical Rationale

Physical and Metallurgical Rationale

GMAW-S operates at very low arc voltages (14 to 22 V) and low amperages, with the wire repeatedly dipping into the weld pool and short-circuiting 50 to 200 times per second. Because the heat input is extremely low, GMAW-S is notoriously prone to cold lap (lack of sidewall and interpass fusion).

• These planar fusion defects have zero opening width and are often oriented at an angle along the bevel sidewall, perfectly parallel to the radiographic beam.
• Consequently, radiography cannot reliably detect cold lap in GMAW-S. A coupon riddled with severe lack of fusion can appear completely clean on an X-ray film.
• Therefore, both ASME Section IX (QW-304) and B31.3 mandate that welders using GMAW-S must be qualified strictly by mechanical bend tests (side bends per QW-452.1 or transverse face/root bends), which physically tear open unfused sidewalls under severe plastic strain.

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ASME Section IX vs. ASME B31.3 Qualification Comparison Matrix

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Real-World Inspection Scenarios & High-Frequency Exam Traps

Scenario: The Illegal GMAW-S Production Qualification

A mechanical contractor on a refinery flare line project attempts to qualify a new welder on a 6-inch carbon steel spool (Schedule 40) using the GMAW process. The welding foreman utilizes a short-circuiting arc (18 V, 130 A, 75% Ar / 25% CO2) for the open-root pass. Upon completion, the contractor submits the spool for 100% radiographic examination. The RT film shows no porosity or slag, and the RT level II technician signs off the welder qualification report (WPQ).

The CWI Audit Finding: The Certified Welding Inspector reviews the WPQ package and immediately rejects the certification. Under ASME Section IX QW-304, applied to this work through B31.3 Para 328.2, volumetric examination may not be used to qualify welders in the short-circuiting transfer mode. Because GMAW-S is highly prone to cold lap that escapes radiographic detection, the welder can only be qualified by destructive mechanical bend testing (two root bends and two face bends per QW-452). The qualification is void, and the welder cannot touch production piping.

Common Exam Traps to Avoid

• The "Plug-and-Play" SWPS Trap: An exam question asks if a contractor can use an AWS Standard Welding Procedure Specification (SWPS) immediately upon purchase. No. Under Section IX QW-500 and B31.3 Para 328.2.1(b), the employer must weld and mechanically test an official demonstration test coupon before applying the SWPS to production.
• The Para 328.2.4 Misattribution Trap: Para 328.2.4 is the qualification records clause — copies of PQRs and WPQs kept available to the Inspector where welding is being done. If an option attaches an NDE extent or a disqualification penalty to 328.2.4, it is wrong. The extent of volumetric qualification is Section IX QW-304's 6 in. (150 mm) minimum, entire circumference for pipe, and not more than four consecutive coupons for small-diameter pipe.
• The Performance Qualification Transfer Trap: Para 328.2.3 permits accepting a previous employer's WPQ, but only subject to owner approval, only for qualifications made on pipe or tube coupons, and only with QW-322 continuity evidence obtained and the record signed by the new employer.
• The Heat Input Oversight Trap: Assuming that heat input calculations are only necessary for high-strength military alloys. When B31.3 Table 323.3.1 triggers impact testing on ordinary carbon steel (P-No. 1) operating at low temperatures, heat input (J/in) becomes a mandatory essential variable under QW-409.1. An inspector who fails to verify amperage, voltage, and travel speed violates code mandates.
• The Austenitic Impact Metric Trap: Looking for foot-pound (Joules) absorbed energy values on Charpy reports for 300-series stainless steels. Under B31.3 Table 323.3.1, austenitic stainless steels are evaluated based on transverse lateral expansion (>= 0.015 in. [0.38 mm]), NOT absorbed energy.