When you are qualifying a welding procedure under ASME Section IX, the test coupon has to demonstrate that the process produces sound weld metal — not just that the welder can lay a bead. Before the coupon goes to the lab for tensile bars and bend specimens, QW-195 establishes whether NDE applies and what it requires. Getting this right keeps your qualification package defensible when an Authorized Inspector or third-party auditor looks it over.
What QW-195 actually covers
QW-195 is a short article in ASME Section IX that establishes examination requirements for test coupons produced during procedure qualification. It references three other QW articles:
- QW-191 — the acceptance criteria for radiographic and ultrasonic examination of test welds
- QW-142 — the examination requirements specific to fillet weld test coupons
- QW-171 — the impact testing article, which is the primary trigger for volumetric examination under QW-195
The core rule: volumetric examination (RT or UT) of the groove-weld test coupon is required when the qualification includes Charpy V-Notch (CVN) impact testing. For standard qualifications without impact testing, visual examination of the coupon before sectioning is typically sufficient to satisfy QW-195.
Why impact testing triggers volumetric examination
Impact test specimens must be taken from defined locations in the weld cross-section per QW-171.1. If the coupon contains a buried porosity cluster, a lack-of-fusion void, or an incomplete-penetration discontinuity in the impact specimen zone, the test result will reflect the flaw rather than the inherent material toughness. The procedure would then be qualified on degraded data.
Volumetric examination before sectioning confirms the weld is sound throughout, ensuring that impact results represent the process at its actual performance level, not a region contaminated by a defect. This is the same logic that drives RT acceptance of pressure-vessel shell courses before hydrostatic testing — confirm the baseline is clean before relying on the test result.
Visual examination: the baseline requirement
Whether or not volumetric NDE is required, ASME Section IX expects visual examination of the test coupon before destructive testing. The inspector looks for:
- Cracks in the weld and the heat-affected zone
- Incomplete fusion at weld toes and at the root
- Underfill or concavity that exceeds acceptable limits
- Surface irregularities indicating a fundamental process problem
A coupon that fails visual examination signals something went wrong during the qualification weld: wrong preheat, wrong technique, contaminated base metal, or a parameter that drifted outside the intended range. The responsible path is to document the failure, investigate, and re-weld a new coupon — not proceed to destructive testing on a visually defective sample that will produce unrepresentative results.
For an overview of how NDE fits into structural production weld acceptance, see NDE method selection for structural welds.
RT acceptance under QW-191
When radiographic examination is performed on a PQR test coupon, QW-191.1 specifies the acceptance criteria. Unacceptable conditions include:
- Cracks — any length, any orientation
- Incomplete fusion or penetration — any evidence of lack of bond to the base metal or at the root
- Elongated slag inclusions — length exceeding limits in QW-191.1.1 (governed by ratio of length to thickness)
- Porosity clusters — area fraction exceeding the limits in QW-191.1.2
These are conceptually equivalent to RT acceptance criteria from AWS D1.1 structural or API 1104 pipeline work, though the ASME formatting differs. The underlying philosophy is consistent: the weld must show no planar or extensive volumetric discontinuities before its mechanical properties are used to support a qualified procedure.
If the coupon fails RT, the qualification is not valid. The coupon is rejected, root cause is investigated, and a new coupon is welded and examined before destructive testing proceeds.
UT as an alternative to RT
QW-191.2 allows UT as an alternative to RT for volumetric examination of test coupons. The UT must meet the acceptance requirements of the applicable construction code's UT procedures.
In practice, RT is more common for coupon examination because it provides a permanent film record that the AI and owner can independently review. UT reports are acceptable but require an examiner trained in the specific technique, calibrated to applicable reference blocks. For a one-off PQR coupon, the marginal cost of RT film is often lower than configuring UT calibration for a single piece.
Where digital RT (computed radiography or digital detector arrays) is available, the digital image file serves as the permanent record in place of film. The acceptance criteria under QW-191 apply equally to film and digital RT.