ASNT NDT Level III Basic cheat sheet

Penetrant testing detects surface-breaking discontinuities only; it is ineffective on porous or rough surfaces that trap penetrant and cause false indications.

Radiography detects volumetric discontinuities and changes in density or thickness; it is insensitive to tight planar defects oriented parallel to the beam.

Ultrasonic testing detects internal planar defects well when the beam is oriented perpendicular to the defect; it requires a coupling medium and good surface finish.

Magnetic particle testing applies only to ferromagnetic materials and detects surface and near-surface flaws; it cannot inspect austenitic stainless steel or aluminum.

Eddy current testing detects surface and near-surface flaws in electrically conductive materials and is sensitive to conductivity, permeability, and lift-off changes.

Acoustic emission detects growing defects under load by sensing transient elastic waves; it is a passive, monitoring technique requiring stress on the part.

Visual testing is the most common first-line method; direct visual is limited by illumination, resolution, and access, while remote visual uses borescopes and cameras.

Leak testing methods include bubble emission, pressure change, helium mass spectrometry, and halogen detection, each with different sensitivity ranges.

Radiographic film density is typically held between 2.0 and 4.0 for X-ray inspection depending on the applicable code and film class.

Select the method by defect type and location first: surface-breaking flaws favor PT, MT, ET, or VT; internal volumetric flaws favor RT or UT.

Material governs feasibility: MT requires ferromagnetic material; ET requires conductive material; PT requires a nonporous, clean surface.

Geometry governs access: RT needs access to both sides; UT needs contact or immersion access; PT needs surface exposure to penetrant and developer.

UT is generally superior to RT for tight planar defects and thick sections; RT is superior for complex geometries and for documenting a permanent record.

PT and MT are typically less expensive and faster than RT or UT but detect only surface or near-surface flaws.

Eddy current is well suited to tubing and thin-wall heat exchanger inspection from the inside surface.

Acoustic emission is suited to continuous monitoring and locating active defects in large structures under load.

Method sensitivity is not absolute: each method's probability of detection depends on flaw orientation, size, geometry, and inspector technique.

When methods are compared, consider cost, speed, coverage, sensitivity, and the ability to produce a permanent record.

Level I performs specific calibrations and tests under supervision and reports results; Level II performs and interprets tests and directs Level I work.

Level III is responsible for method selection, procedure development, interpretation of codes and standards, and certification of personnel.

Qualification is the demonstrated ability to perform a method; certification is the written attestation of that qualification by a certifying authority.

Certification schemes commonly include training hours, experience hours, and a written and practical examination for each level and method.

Certification is method-specific and level-specific; a Level II in UT is not certified in RT unless separately qualified.

Recertification is typically required periodically, often every three to five years, and may require re-examination or documented continuing experience.

Vision requirements apply: near vision acuity and color perception must be verified and periodically rechecked.

The employer or certifying agency is responsible for certification; the individual is responsible for performing only within the scope of certification.

Written procedures must be approved by a Level III and must be available to the inspector performing the test.

A specification states the requirements a product or service must meet; a code is a collection of mandatory rules referenced by law or contract.

A standard is a consensus document that may be referenced by a specification or code; a recommended practice is advisory, not mandatory.

A procedure is the detailed written instruction for performing a specific test; it must be qualified and approved before use.

The hierarchy of documents is typically: contract, code, specification, standard, procedure, and work instruction.

Acceptance criteria define the maximum allowable discontinuity size or indication level; rejection criteria define what must be rejected.

Calibration and reference standards must be traceable to a recognized national standard and must be checked at defined intervals.

A procedure qualification demonstrates that the procedure can achieve the required sensitivity on a known reference standard.

When documents conflict, the contract or purchase order normally governs the order of precedence unless otherwise specified.

Ferromagnetic materials include iron, carbon steel, and many alloy steels; austenitic stainless steel and aluminum are nonmagnetic.

Castings can contain shrinkage, porosity, and hot tears; forgings can contain laps, seams, and forging bursts.

Weld discontinuities include porosity, slag inclusions, lack of fusion, lack of penetration, undercut, and cracks.

Heat treatment can change conductivity and permeability, which affects eddy current and magnetic particle test results.

Grain size and structure affect ultrasonic attenuation; coarse-grain austenitic welds scatter ultrasound and reduce detectability.

Surface finish affects penetrant, magnetic particle, and ultrasonic coupling; rough surfaces increase noise and false indications.

Corrosion and fatigue cracks typically initiate at surfaces and stress concentrations, favoring surface-sensitive methods for detection.

Material thickness and density affect radiographic exposure and ultrasonic inspection technique selection.