2.4 Acceptance Criteria for Procedure Qualification

2.4 Acceptance Criteria for Procedure Qualification

A candidate WPS is qualified only when every destructive specimen satisfies the acceptance requirements of API 1104:2021 Section 5.6 (butt welds) or 5.8 (branch and fillet welds). This section gives the exact thresholds and the worked calculations the endorsement exam favors.

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1. Tensile Test Acceptance (5.6.2.3)

The specimen is pulled to failure and tensile strength S = maximum load ÷ smallest original cross-sectional area. Acceptance compares strength to the pipe's Specified Minimum TENSILE Strength (SMTS) — a critical 22nd-edition detail:

1. Break in the weld or fusion zone: acceptable if the observed strength is ≥ the SMTS of the pipe material AND the fracture meets the nick-break soundness requirements of 5.6.3.3.
2. Break in the parent metal (outside weld and HAZ): acceptable if strength is ≥ 95% of SMTS.
3. Break in the weld below SMTS: the weld is set aside and a new test weld is made.
4. Different grades in one joint: the lower grade's SMTS governs.

Critical exam distinction: the comparison value is the pipe specification's minimum TENSILE strength (e.g., API 5L X65 → SMTS 77,600 psi), never the yield strength (SMYS) and never the material's actual measured tensile strength. A weld break between SMYS and SMTS FAILS.

Worked Example (X65, SMTS = 77,600 psi)

Reduced-section straps 1.000 in. wide × 0.375 in. thick → area A = 0.375 in.².

• Specimen A (weld-metal fracture), P = 29,250 lbf: S = 29,250 / 0.375 = 78,000 psi ≥ 77,600 psi → PASSES.
• Specimen B (parent-metal fracture), P = 28,125 lbf: S = 75,000 psi; threshold = 0.95 × 77,600 = 73,720 psi → 75,000 ≥ 73,720 → PASSES (weld shows no internal defects).
• Specimen C (weld-metal fracture), P = 27,000 lbf: S = 72,000 psi < 77,600 psi → FAILS; a new test weld is required.

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2. Nick-Break Acceptance (5.6.3.3)

The exposed fracture surfaces of each nick-break specimen are examined for soundness:

• Complete penetration and fusion across the root and between passes — zero tolerance for lack of penetration or lack of fusion.
• Gas pockets: greatest dimension of any single pocket ≤ 1/16 in. (1.6 mm); combined area of all gas pockets ≤ 2% of the exposed surface area.
• Slag inclusions: depth ≤ 1/32 in. (0.8 mm); length ≤ 1/8 in. (3 mm) or one-half the specified wall thickness, whichever is smaller; adjacent inclusions separated by at least 1/2 in. (13 mm) of sound metal.
• Fisheyes (per AWS A3.0) are not cause for rejection.

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3. Guided-Bend Acceptance (5.6.4.3 / 5.6.5.3)

Root, face, and side bends are bent in the Figure 8 jig (plunger radius 1-3/4 in., die radius 2-5/16 in.):

• No crack or other imperfection exceeding 1/8 in. (3 mm) or one-half the specified wall thickness, whichever is smaller, in any direction, in the weld or at the fusion zone after bending.
• Corner-crack exception: cracks originating on the outer bend radius along the specimen edges, measuring less than 1/4 in. (6 mm) in any direction, are disregarded unless obvious imperfections are observed in them.

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4. Branch and Fillet Welds (5.7-5.8)

Branch and fillet procedure test joints are not tensile or bend tested. Section 5.8 requires at least four nick-break specimens cut from the joint at the Figure 10/11 locations (approximately 90° apart, covering crotch and saddle areas), each broken in the weld and evaluated to the same soundness limits as 5.6.3.3: complete penetration and fusion, gas pockets ≤ 1/16 in. with combined area ≤ 2%, slag ≤ 1/32 in. deep and ≤ 1/8 in. or t/2 long, and ≥ 1/2 in. separation. For pipe under 2.375 in. OD, two test welds may be needed (two specimens from each).

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5. Single-Specimen Failure and Replacement Rules

The 22nd edition handles isolated specimen failures narrowly:

• Improper preparation or testing: a specimen that fails due to improper specimen preparation or testing may be replaced and retested (any test type).
• Nick-break, root/face bend, or side bend on test welds over 12-3/4 in. (323.9 mm) OD: if only ONE specimen fails, the company may either reject the weld or replace it with two additional specimens cut as close as possible to (adjacent to) the failed location. Both replacements must pass; if either fails, the weld is unacceptable.
• Tensile break in the weld below SMTS: no specimen replacement — a new test weld is required.