16.3 Acceptance Criteria and Quality Control

ASNT NDT Level III Basic Examination Exam

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1 Introduction & Exam Overview

1.1 Current Exam Facts 1.2 Level III Role and Certification Path 1.3 Eligibility, Fees, Scheduling, and Retakes 1.4 Study Strategy and Exam-Day Approach

2 Chapter 2: Materials Fundamentals for NDT

2.1 Ferrous Metals and Iron-Carbon Phases 2.2 Non-Ferrous Metals and Alloys 2.3 Mechanical Properties and Crystal Structure

3 Chapter 3: Manufacturing Processes

3.1 Casting Processes and Cast Discontinuities 3.2 Forging, Rolling, and Forming 3.3 Extrusion, Drawing, and Machining 3.4 Heat Treatment Effects

4 Chapter 4: Welding and Joining Processes

4.1 Fusion Welding Processes 4.2 Weld Metal and HAZ Discontinuities 4.3 Brazing, Soldering, and Mechanical Joining

5 Chapter 5: Discontinuity Classification

5.1 Inherent Discontinuities 5.2 Processing Discontinuities 5.3 Service Discontinuities

6 Chapter 6: Specific Discontinuity Types

6.1 Cracks and Fracture Modes 6.2 Porosity, Inclusions, and Lack of Fusion 6.3 Laminations, Seams, Laps, and Undercut 6.4 Relevant vs Non-Relevant Indications

7 Chapter 7: NDT Method Selection and Inspection Planning

7.1 Method Selection Principles 7.2 Surface vs Volumetric Methods 7.3 Inspection Planning and Flaw Expectations

8 Chapter 8: Ultrasonic and Radiographic Testing

8.1 Ultrasonic Testing Principles and Applications 8.2 UT Limitations, Calibration, and Evaluation 8.3 Radiographic Testing Principles and Applications 8.4 RT Limitations, Image Quality, and Safety Basics

9 Chapter 9: Magnetic Particle, Liquid Penetrant, and Visual Testing

9.1 Magnetic Particle Testing 9.2 Liquid Penetrant Testing 9.3 Visual Testing

10 Chapter 10: Electromagnetic, Leak, Acoustic Emission, and Infrared Testing

10.1 Electromagnetic / Eddy Current Testing 10.2 Leak Testing 10.3 Acoustic Emission Testing 10.4 Thermal / Infrared Testing

11 Chapter 11: Specialty Methods and Method Comparison

11.1 Neutron Radiography 11.2 Magnetic Flux Leakage 11.3 Method Comparison and Supplemental Examinations

12 Chapter 12: SNT-TC-1A Recommended Practice

12.1 SNT-TC-1A Overview and Written Practice 12.2 SNT-TC-1A Training and Experience 12.3 SNT-TC-1A Examinations and Recertification

13 Chapter 13: CP-189 Standard Practice

13.1 CP-189 Overview and Scope 13.2 CP-189 Mandatory Requirements 13.3 SNT-TC-1A vs CP-189 Comparison

14 Chapter 14: CP-105 and NDT Training Programs

14.1 CP-105 Purpose and Topical Outlines 14.2 Developing and Approving NDT Training 14.3 OJT, Mentoring, and Instructor Oversight

15 Chapter 15: Building and Managing Certification Programs

15.1 Building Qualification and Certification Programs 15.2 Administering Examinations and Evaluating Competency 15.3 Program Audits and Managing Certifications

16 Chapter 16: Codes, Standards, Procedures, and Quality

16.1 Interpreting Codes, Standards, and Specifications 16.2 Developing and Approving NDT Procedures 16.3 Acceptance Criteria and Quality Control 16.4 External Audits and Inspection Documentation

16.3 Acceptance Criteria and Quality Control

Key Takeaways Explain This Topic AI

Domain 5.5–5.6 covers assisting with acceptance criteria when none exist and applying quality-control protocols to NDT operations.

Relevant indications are those that must be evaluated against acceptance criteria; rejectable indications fail those criteria—relevance and rejectability are related but not identical concepts.

When acceptance criteria are missing, the Level III interfaces with engineering/owner/design authority rather than inventing unofficial pass/fail rules alone.

QC protocols include procedure compliance checks, calibration currency, personnel currency, process audits, and control of nonconforming product.

Evaluation documentation must support independent review: what was found, how it was measured, which criterion applied, and the disposition path.

Last updated: July 2026

16.3 Acceptance Criteria and Quality Control

Quick Answer: Domain 5.5–5.6 expects Level IIIs to help develop acceptance criteria when none exist (with proper engineering/owner interface) and to apply quality-control protocols to NDT work. On the exam and on the floor, separate relevant indications (must be evaluated) from rejectable indications (fail the acceptance criteria). Document evaluations so a second qualified person can reconstruct the decision.

Sections 16.1–16.2 got the requirements and procedures right. This section is the decision and control layer: what “pass” means, how quality systems keep NDT honest, and how the Level III interfaces with design when the package is incomplete.

Acceptance Criteria: What They Are For

Acceptance criteria are the rules that convert examination results into accept, reject, or repair dispositions. They may be expressed as:

Maximum discontinuity length, height, or area
Amplitude relative to a reference (DAC, DGS, notch, side-drilled hole)
Film density / image quality thresholds plus discontinuity charts
“No cracks” or “no incomplete fusion” absolute rules
Statistical or lot-based rules for some product forms
Hybrid rules combining size and location (for example toe cracks vs buried porosity)

Acceptance criteria are product quality decisions , not pure physics. A detectable indication can be relevant and still acceptable if it is within limits. A non-relevant geometric indication should not be treated as a rejectable defect merely because it produces a signal.

Relevant vs rejectable (and non-relevant)

Use precise language—Basic loves these distinctions:

Term Meaning
Indication Response or visual evidence that requires interpretation

Non-relevant indication Caused by geometry, part design, or benign conditions; not a discontinuity of concern under the procedure

Relevant indication Associated with a discontinuity (or potential discontinuity) that must be evaluated against acceptance criteria

Rejectable (unacceptable) indication A relevant indication that fails the acceptance criteria
Acceptable relevant indication A real discontinuity (or allowed condition) that is within limits

Exam trap: Equating “I saw an indication” with “the part fails.” Evaluation is a two-step process: characterize relevance, then apply criteria.

Assisting When Acceptance Criteria Do Not Exist

Domain 5.5 specifically includes helping develop acceptance criteria when none are provided. This is not a license for the Level III to invent secret shop limits for pressure equipment or safety-critical parts without design authority.

Proper interface model

Confirm silence — verify the code/spec/drawing truly lacks applicable criteria for this product form and examination.

Escalate — notify engineering, design authority, owner, or customer quality as required by the contract and quality manual.

Propose technical input — the Level III contributes method capability, typical discontinuity morphology, sizing uncertainty, and industry-precedent options.

Document the decision — formal criteria (drawing note, ECR, specification revision, approved deviation) before production acceptance.

Freeze uncontrolled acceptance — do not ship “best judgment” accepts on critical product while waiting for criteria unless a documented engineering disposition explicitly authorizes interim controls.

What good Level III input looks like

When assisting criteria development, contribute:

Detection capability and limitations of the selected method/technique
Expected discontinuity types from the process (welding, casting, forging, service)
Measurement uncertainty (sizing accuracy, orientation effects)
Consistency with related code families if the product is analogous and the design authority chooses that path
Repair/re-exam practicality

What not to do:

Copy unrelated product criteria blindly without design review
Set criteria only to maximize shop throughput
Use “we always accepted that” tribal memory as the sole basis for safety-critical parts

Confuse reporting thresholds (record everything above X) with acceptance limits (reject above Y) without clarifying both

Applying Quality Control Protocols to NDT

Domain 5.6—apply QC protocols—means NDT is run as a controlled process , not as artisanal craft. QC elements Level IIIs own or strongly influence:

Process control
Only approved procedures/work instructions in use (current revision)
Personnel certified and current (vision, method, technique limits)
Equipment calibrated or performance-checked within intervals
Materials (penetrants, particles, film, couplant) within shelf life and system family
Environmental conditions within procedure limits (temperature, lighting, ambient UV, humidity as applicable)
In-process checks
System performance checks at required frequency (sensitivity, field strength, densitometer, UV intensity)
Coverage verification (scan plans, overlap, exposure calculator records)
Independent review or dual interpretation when specified (common in RT programs)
Hold points observed; customer witness arranged when the ITP requires it
Nonconformance and product control
Rejected items identified and segregated
Nonconformance reports routed to material review/engineering
Repair procedures approved before blend/weld repair
Re-examination after repair using the governing method/extent

Trend analysis: recurring reject causes may trigger process corrective action upstream (welding, machining, heat treat)

Audit and surveillance
Internal process audits of NDT (not only personnel-file audits—see 15.3)
Surveillance of technicians for procedure compliance
Corrective actions with effectiveness checks

QC is how you keep Domain 2 “application of methods” from drifting into uncontrolled practice.

Engineering Interface and Evaluation Documentation
Engineering interface

NDT does not replace design. The Level III’s interface responsibilities include:

Clarifying whether an indication is in a critical location relative to design stress or fatigue concern (often requires engineering input beyond NDT sizing alone)

Supporting fitness-for-service discussions with measured data, not vague “looks bad” language
Explaining method limitations so engineering does not assume NDT found “everything”

Aligning repair acceptance with the same or more stringent criteria as original fabrication when codes require it

Documentation of evaluations

Evaluation records should allow a qualified reviewer to answer:

What was examined (part ID, heat/serial, weld ID, location map)?

Which procedure/revision and acceptance document/revision applied?

Who performed the exam (certification evidence available)?

What equipment/calibration state was used?

What indications were recorded, with measurements and sketches/images as required?

What was the disposition (accept/reject/repair) and who authorized it?

Incomplete reports are a classic audit failure mode: the part may be fine, but the quality system cannot prove it.

High-Yield Exam Traps for This Section

Treating all relevant indications as automatically rejectable.

Treating all non-relevant indications as optional to document when the procedure requires recording.

Inventing acceptance criteria for code-stamped or customer-critical work without design/owner authority.

Confusing sensitivity settings with acceptance levels.

Skipping re-examination after repair.

QC that checks only certificates and never watches actual technique compliance.

If you can explain relevant vs rejectable, describe how you would develop missing criteria through engineering, list core QC controls for an NDT process, and specify what belongs in an evaluation record, you are aligned with Domain 5.5–5.6.