Procedure Qualification by Demonstration (PQD): ASME Section V Article 14

What is Procedure Qualification by Demonstration?

Procedure Qualification by Demonstration (PQD) is the process of proving that an NDT procedure can reliably detect and characterise the defects it is intended to find — not just on paper, but through physical examination of a representative mockup containing known defects. It is distinct from procedure compliance (meeting the written requirements of a code) and procedure validation (statistical confidence in detection rates).

PQD is mandatory under ASME Section V Article 14 for certain advanced examination techniques, particularly when used as an alternative to other methods or when applied to complex geometries. Failure to include the required PQD documentation in your procedure — or failure to perform the demonstration before the examination — is a non-compliance that will result in the procedure being rejected by the Authorised Inspector.

When is PQD Required?

ASME Section V Article 14 (T-1410) mandates PQD in the following cases:

• TOFD as an alternative to RT (Code Case 2235 or equivalent) — demonstration on a mockup containing intentional defects is required before any production examination
• PAUT on complex or non-standard geometries — nozzle-to-shell welds, dissimilar metal welds, clad materials, austenitic welds
• Any examination technique on material/geometry for which the technique has not been previously qualified
• When specified by the referencing Code section (e.g., ASME Section VIII Code Case 2235 explicitly requires PQD for the TOFD application)
• Client or owner specifications — Major oil and gas operators (ExxonMobil, Saudi Aramco, BP, Shell) typically require PQD for all advanced UT applications regardless of code requirements

Article 14 Requirements — What Your Procedure Must Include

T-1410 General Requirements

Your procedure must acknowledge the PQD requirement and state:

• The applicable code/case that triggers the PQD requirement
• Whether PQD has been completed or is required before examination
• Reference to the Procedure Qualification Record (PQR) — the document that records the PQD results
• The essential variables that, if changed, would require the demonstration to be repeated

T-1420 Mockup (Qualification Block) Requirements

The mockup is the physical specimen used for the demonstration. It must:

• Represent the examination geometry: Same weld configuration (groove angle, root geometry), same nominal material thickness range, same surface condition (as-welded or dressed)
• Represent the material: Same P-number grouping, similar acoustic velocity (for UT-based methods), same metallurgical condition (as-welded, PWHT'd)
• Contain representative defects: The nature, depth, orientation, and size range of defects expected in production welds. For weld inspection, this typically means crack-like defects at various through-thickness positions (surface-breaking, mid-wall, root)
• Have a blind set: For formal qualifications, the mockup should contain a set of known defects (open set — used for procedure development) and a blind set (defects unknown to the examiner during demonstration)
• Full documentation: mockup drawing, material certification, defect characterisation records (UT or RT of the defects prior to PQD, or TOFD/PAUT characterisation validated by destructive sectioning)

T-1430 Demonstration Requirements

The demonstration itself must be conducted as follows:

• Performed by the personnel who will perform or supervise the production examination (or representative personnel)
• Using the same equipment, probes, software settings, and technique parameters as the production procedure
• Witnessed by the Authorised Inspector (AI) or Owner/User representative, or documented such that results are verifiable
• Detection performance criteria must be pre-defined: what constitutes a successful demonstration (e.g., detection of all defects ≥ a specified size with acceptable false call rate)

T-1440 Procedure Qualification Record (PQR)

The PQR is the traceability document that links the demonstrated procedure to the production examination. It must include:

• Date and location of the demonstration
• Mockup identification and defect inventory (known defects and their dimensions)
• Equipment used (instrument serial numbers, probe identification, software version)
• Personnel identification and certification records
• Examination data (typically data files referenced by filename)
• Results: defects detected vs. total defects, sizing accuracy (if applicable)
• Witnessed by statement with AI/Owner-User signature
• Conclusion: procedure is qualified for the specified application range

T-1450 Re-qualification Triggers

Your procedure must list the essential variables that require re-qualification when changed. For TOFD/PAUT, these typically include:

• Change in examination material (P-number group change)
• Change in examination thickness range (outside qualified range)
• Change in weld joint configuration or geometry
• Change in technique (e.g., from A-scan to TOFD, from single angle to sector scan)
• Change in instrument or probe model (different manufacturer or type)

Common PQD-Related Non-Compliances

1. PQD requirement not acknowledged — Procedure uses TOFD or advanced PAUT on a complex geometry but makes no mention of Article 14 or the requirement for demonstration
2. No PQR referenced — Procedure notes PQD is required but does not reference an existing PQR, implying the demonstration has not been done
3. Mockup not representative — PQD performed on a simple plate mockup but the production application is a nozzle-to-shell weld with complex geometry access
4. Re-qualification variables not listed — Essential variables are stated for the technique but not for the PQD — examiner changes instrument without re-qualifying
5. PQR not signed by AI — PQD was performed but the AI witness requirement under ASME was not met; PQR is unsigned
6. Defect characterisation in mockup absent — Mockup contains intentional defects but their dimensions were never independently verified (by destructive sectioning or another method)

How PQD Integrates with Your Written Procedure

The written procedure and the PQR work together:

• The written procedure states the technique parameters and references the applicable PQR by document number
• The PQR demonstrates that those parameters work for the specific geometry and material
• The Authorised Inspector reviews both before authorising the examination to proceed
• Any change to an essential variable in the procedure triggers a review of whether re-qualification is required

If you are using TOFD or advanced PAUT and your procedure does not have a PQR attached or referenced, the examination results may not be accepted — even if the examination was technically flawless. Getting PQD right upfront prevents costly re-examination.