NDT Acronyms and Terms

The inspection methods themselves and the main techniques within them.

NDT Nondestructive testing

Examining a material, part or structure for flaws, or measuring its properties, without damaging it or affecting its future use. The umbrella term for all the methods on this page.

NDE Nondestructive examination or evaluation

Another name for NDT. ASME codes say "examination"; "evaluation" is sometimes used to stress judging what a finding means, not just finding it.

NDI Nondestructive inspection

The usual name for NDT in aircraft maintenance and military work. NAS410 treats NDT, NDI and NDE as equivalent terms.

VT Visual testing

Inspection by eye, aided by lights, mirrors, magnifiers, gauges or cameras. The first and most widely used method, and usually the first step before any other.

RVI Remote visual inspection

Visual testing where the eye cannot reach, using borescopes, video probes, crawlers or drones. Used inside engines, tubes, pipes and vessels.

PT Penetrant testing (liquid penetrant testing)

A liquid dye is drawn into surface-breaking cracks, the excess is removed, and a developer draws it back out so the crack shows. Works on most non-porous materials, metallic or not, but only finds flaws open to the surface.

LPI Liquid penetrant inspection

Another name for penetrant testing (PT).

FPI Fluorescent penetrant inspection

Penetrant testing with a dye that glows under ultraviolet (UV-A) light in a darkened area. Generally more sensitive than visible-dye penetrant and standard for many aerospace parts.

MT Magnetic particle testing

A ferromagnetic part is magnetized and fine iron particles are applied; they gather where a surface or near-surface crack disturbs the magnetic field. Fast and sensitive, but only for magnetic materials such as carbon steel.

MPI Magnetic particle inspection

Another name for magnetic particle testing (MT).

WFMT Wet fluorescent magnetic particle testing

Magnetic particle testing using fluorescent particles suspended in a liquid and viewed under UV-A light. Widely used in refineries and plants to find fine cracking on the inside of vessels and at welds.

UT Ultrasonic testing

High-frequency sound is sent into a material; echoes from flaws or from the far wall reveal internal defects and measure thickness. Needs a couplant (usually a gel or water) between probe and part.

UTT Ultrasonic thickness testing

Using ultrasound to measure remaining wall thickness, usually to track corrosion or erosion over time. The single most common NDT task in many plants.

PAUT Phased array ultrasonic testing

UT with a probe made of many small elements fired in controlled sequence, so the beam can be steered and focused electronically. Produces cross-sectional images and covers a weld or area much faster than a single-element probe.

TOFD Time-of-flight diffraction

A UT technique using a sending and a receiving probe on either side of a weld. It times the weak signals diffracted from the tips of a flaw, which gives an accurate measure of the flaw's through-wall height.

AUT Automated (or mechanized) ultrasonic testing

UT performed with a motorized or encoded scanner that records position and data, so the inspection can be reviewed and repeated. Widely used on pipeline girth welds and for corrosion mapping.

FMC / TFM Full matrix capture / total focusing method

An advanced phased array approach that records every element-to-element signal (FMC) and then focuses on every point in the image by computation (TFM). Gives sharper images of flaws, especially cracks.

GWT / GWUT Guided wave testing (long-range ultrasonic testing; GW in SNT-TC-1A)

Low-frequency ultrasonic waves are sent along a pipe from one probe ring, screening long lengths, including buried, insulated or sleeved sections, for areas of wall loss. A screening tool: findings are followed up with local methods.

EMAT Electromagnetic acoustic transducer

A probe that generates ultrasound inside a conductive material by electromagnetic means, so no couplant is needed. Used for fast boiler-tube thickness scanning, hot surfaces and some in-line pipeline tools.

LUT Laser ultrasonic testing

Ultrasound generated and detected by lasers without touching the part. Used where contact is impractical, for example on complex composite parts or hot surfaces.

IRIS Internal rotary inspection system

An ultrasonic tube technique: a probe inside a water-filled tube fires at a spinning mirror, measuring wall thickness all the way around as it is pulled through. Accurate for wall loss in any tube material, but slow and needs very clean tubes.

RT Radiographic testing

X-rays or gamma rays are passed through a part onto film or a digital detector; differences in thickness and density show as an image of the inside. Excellent for volumetric flaws such as porosity, and needs radiation safety controls.

CR Computed radiography

Radiography using reusable phosphor imaging plates instead of film; a laser scanner reads the plate to make a digital image. No chemical processing, and images can be enhanced and shared.

DR Digital radiography

Radiography with a digital detector array (flat panel) that produces an image directly, often in seconds. Supports real-time imaging and fast re-shoots.

CT Computed tomography

Many radiographs taken from different angles are combined by computer into a 3D model of the part, inside and out. Used for castings, additive-manufactured parts and assemblies where dimensions and internal flaws both matter.

NR Neutron radiography

Radiography with neutrons instead of X-rays. Neutrons pass through many metals but are stopped by light elements such as hydrogen, so NR shows things like adhesives, seals, water or explosive fill inside metal housings.

ET Eddy current testing (electromagnetic testing)

An alternating magnetic field induces electrical currents in a conductive material; cracks, corrosion and material changes disturb them and the probe senses it. Fast, needs no couplant and works through thin coatings. In SNT-TC-1A, ET is the electromagnetic testing method, which groups eddy current (ECT), remote field (RFT) and ACFM techniques.

ECT Eddy current testing

Another abbreviation for eddy current testing, common in tube inspection, where bobbin, rotating and array probes are pulled through heat exchanger tubes.

ECA Eddy current array

Eddy current testing with many coils in one probe, covering a wider strip in a single pass and producing a C-scan style map. Used on welds, tubes and aircraft structure.

RFT Remote field testing

A low-frequency electromagnetic technique for ferromagnetic tubes and pipes such as carbon steel, where conventional eddy current struggles. Sensitive to wall loss from either side of the tube wall.

NFT Near field testing

An electromagnetic tube technique for carbon steel tubes, especially finned air-cooler tubes. It is good at finding pitting and erosion on the tube's inside surface and quick to run.

PEC Pulsed eddy current

An electromagnetic technique that measures the average remaining wall thickness of steel through insulation, coatings or fireproofing. Used to screen for corrosion under insulation without stripping it.

MFL Magnetic flux leakage

Steel is magnetized close to saturation; where metal has been lost, magnetic flux leaks out and sensors pick it up. Used on tank floors, pipelines (in-line tools), tubes and wire rope.

ACFM Alternating current field measurement

An electromagnetic technique that detects surface-breaking cracks, and estimates their length and depth, often through paint or coatings. Common on offshore structures and welded steelwork.

AE Acoustic emission testing

Sensors listen for the tiny bursts of sound released when a flaw grows, or a material cracks or rubs, while a structure is under load. Monitors a whole vessel or structure at once, and points other methods to where to look.

IR / IRT Infrared and thermal testing (thermography)

Infrared cameras map surface temperature to reveal how heat moves through a part. Finds disbonds and water in composites, and hot spots in electrical and refractory-lined equipment.

LT Leak testing

Methods that prove a system or package is sealed or find where it is not, from bubble tests and pressure-change tests to helium mass spectrometer testing.

GPR Ground penetrating radar

Radar pulses sent into concrete, soil or other non-conductive materials; reflections show rebar, voids, buried pipes and layer changes. Included as a method in SNT-TC-1A.

Shearography (ST) Laser shearography

A laser-based optical method that images tiny changes in surface strain while a part is gently stressed by heat, vacuum or pressure. Finds disbonds and delaminations in composites and honeycomb; NAS410 lists it as a method.

LM Laser methods testing

SNT-TC-1A's method name for laser-based techniques such as shearography, holography and laser profilometry.

VA Vibration analysis

Measuring and interpreting vibration from rotating machinery to detect imbalance, misalignment and bearing or gear wear before failure. A condition-monitoring method recognized in SNT-TC-1A.

MW Microwave testing

Microwaves used to inspect non-conductive materials such as composites, plastics and ceramics for voids, delaminations and moisture. Listed as a method in current SNT-TC-1A.

Bond testing

A family of low-frequency acoustic techniques (for example pitch-catch, resonance and mechanical impedance) that find disbonds and delaminations in composite and bonded structure.

Tap testing

Tapping a composite or bonded surface with a small hammer or coin and listening for a change in sound that suggests a disbond. Simple, but it depends heavily on the inspector.

PMI Positive material identification

Confirming that a component is made of the alloy specified, usually with a handheld X-ray fluorescence (XRF) or optical emission (OES) analyzer. A key control in refineries, where the wrong alloy can fail quickly.

How inspectors are trained, examined and certified, and the documents that govern it.

Qualification

Having the training, experience, vision and examination results required to do NDT at a given level. Qualification comes first; certification documents it.

Certification

Written testimony that a person is qualified. Under employer-based schemes the employer certifies its own people; under central schemes an independent body does.

Level I, II, III (Level 1, 2, 3)

The three certification levels in NDT. Level I performs specific tasks under instruction; Level II sets up equipment, performs and interprets inspections against codes and signs results; Level III is the method expert who writes and approves procedures, examines and certifies others. SNT-TC-1A and CP-189 write them in Roman numerals (I, II, III); NAS410 uses Arabic numerals (1, 2, 3).

Trainee

Someone gaining the training and experience needed for certification, who works under the direct supervision of certified personnel and does not sign for results.

WP Written practice

An employer's own document that sets out how it trains, examines, certifies and recertifies its NDT personnel. Required under SNT-TC-1A, CP-189 and NAS410, and the first thing an auditor asks to see.

RLIII Responsible Level III (Responsible Level 3)

The Level III an employer designates with overall authority for its NDT qualification program and for ensuring the standard's requirements are met. The term comes from NAS410; employers working to other schemes often designate a similar role.

SNT-TC-1A

ASNT's recommended practice for qualifying and certifying NDT personnel. It is a guideline: each employer adapts it into its own written practice and certifies its own people. Levels are written I, II and III.

CP-189 ANSI/ASNT CP-189

ASNT's standard for qualification and certification of NDT personnel. Unlike SNT-TC-1A it is a standard with firm requirements, and it is invoked where codes demand it, notably ASME Section XI for nuclear inservice inspection.

CP-105 ANSI/ASNT CP-105

ASNT's standard topical outlines for NDT training: the subjects a training course should cover for each method and level. Referenced by SNT-TC-1A and CP-189.

NAS410

The aerospace industry's standard for NDT personnel qualification and certification, published by the Aerospace Industries Association. Used across aerospace manufacturing and maintenance; levels are written 1, 2 and 3.

EN 4179

The European aerospace standard for NDT personnel qualification, kept technically aligned with NAS410. Widely required by European aerospace primes and regulators.

ISO 9712

The international standard for central, third-party certification of NDT personnel: an independent certification body examines and certifies the individual, rather than the employer. The basis of many national certification schemes.

ASNT 9712

ASNT's central certification program built to meet ISO 9712. It replaced ACCP for new certifications.

ACCP ASNT Central Certification Program (retired)

ASNT's former central certification program for Level II and III personnel. ASNT stopped taking new applicants in 2023 and is moving holders to its ASNT 9712 program.

ASNT NDT Level III

ASNT's own Level III certificate, earned by passing its basic and method examinations. Employers often use it as evidence of a Level III's knowledge when certifying under SNT-TC-1A or CP-189.

Employer-based certification

A scheme in which the employer qualifies and certifies its own staff under its written practice, as in SNT-TC-1A, CP-189 and NAS410. The certification belongs to that employer and usually ends when the person leaves.

Central certification

A scheme in which an independent body examines and certifies the individual, as in ISO 9712. The certificate travels with the person, though employers still authorize the work they do.

NANDTB National Aerospace NDT Board

A national aerospace body, recognized under NAS410, that can provide or support NDT qualification examinations for that country's industry.

Vision examination

Near-vision acuity (often read on a Jaeger chart) and color-perception checks that NDT personnel must pass, typically every year for near vision. Each standard sets its own requirements.

Limited certification

Certification restricted to a specific technique, product or task within a method, for example ultrasonic thickness measurement only.

API ICP API Individual Certification Programs

The American Petroleum Institute's certification programs for inspection and technical personnel, such as API 510, 570 and 653 inspectors, and hands-on ultrasonic examiner qualifications. Covered in our article on API inspector certifications.

CWI Certified Welding Inspector

The American Welding Society's certification for welding inspectors, covering the inspection of welding before, during and after the weld is made. Senior grade: SCWI.

Who writes the codes, who enforces the rules and who runs the programs. Named for identification only; NDT LLC is not affiliated with any of them.

ASNT American Society for Nondestructive Testing

The US professional society for NDT. Publishes SNT-TC-1A, CP-189 and CP-105 and runs its own certification programs.

ASME American Society of Mechanical Engineers

Publisher of the Boiler and Pressure Vessel Code (BPVC) and the B31 piping codes. Section V of the BPVC covers NDE methods; Section XI covers nuclear inservice inspection.

BPVC ASME Boiler and Pressure Vessel Code

The ASME code for design, fabrication, inspection and testing of boilers, pressure vessels and nuclear components, adopted into law by many US states and cities.

API American Petroleum Institute

The US oil and natural gas industry association. Publishes many of the codes and recommended practices for inspecting refineries, pipelines, tanks and oilfield equipment, and runs the API ICP certifications.

AWS American Welding Society

Publisher of welding codes such as AWS D1.1 for structural steel, and of the Certified Welding Inspector (CWI) program.

ASTM ASTM International

A standards organization whose committee E07 writes most of the test-method standards for individual NDT techniques.

ABS American Bureau of Shipping

A classification society that sets rules for ships and offshore units and surveys them through construction and service, including their weld inspection.

NAVSEA Naval Sea Systems Command

The US Navy command responsible for ships and submarines. Its technical publications set NDT and personnel requirements for naval shipbuilding and repair.

AIA Aerospace Industries Association

The US aerospace and defense trade association. Publishes the National Aerospace Standards (NAS), including NAS410.

PRI Performance Review Institute

The not-for-profit organization that administers the Nadcap accreditation program on behalf of the aerospace industry.

Nadcap

An industry-managed program that accredits special processes in aerospace, including NDT, through audits against common checklists. Administered by PRI; many aerospace primes require it of their suppliers.

FAA Federal Aviation Administration

The US civil aviation regulator. Its rules in Title 14 of the Code of Federal Regulations govern aircraft maintenance, mechanics, repair stations and airworthiness directives.

EASA European Union Aviation Safety Agency

The European Union's aviation safety regulator, covering airworthiness and maintenance organizations.

NRC Nuclear Regulatory Commission

The US regulator for civilian nuclear power plants and radioactive materials, including the licenses used for industrial gamma radiography.

OSHA Occupational Safety and Health Administration

The US workplace safety regulator. Its Process Safety Management standard sets mechanical integrity requirements, including inspection and testing, for plants handling highly hazardous chemicals.

IAEA International Atomic Energy Agency

The United Nations-affiliated agency that promotes safe and peaceful use of nuclear technology, including safety standards and training material that touch NDT.

PHMSA Pipeline and Hazardous Materials Safety Administration

The US Department of Transportation agency that regulates pipeline safety, including 49 CFR Part 192 for gas and Part 195 for hazardous liquids.

CSB U.S. Chemical Safety and Hazard Investigation Board

An independent federal agency that investigates major chemical accidents and publishes findings and recommendations. It does not issue fines or regulations.

NTSB National Transportation Safety Board

The independent US agency that investigates transportation accidents, including aviation and pipeline accidents, and determines their probable cause.

BSEE Bureau of Safety and Environmental Enforcement

The US regulator for safety on offshore oil and gas facilities on the Outer Continental Shelf, including platform inspection requirements in 30 CFR Part 250.

EPA Environmental Protection Agency

The US environmental regulator. Its Risk Management Program rule (40 CFR Part 68) includes mechanical integrity requirements parallel to OSHA's PSM standard.

ISO International Organization for Standardization

The global federation of national standards bodies. Publishes ISO 9712 and many NDT method standards.

CEN European Committee for Standardization

The body that publishes European Norms (EN standards), including many NDT standards used in Europe.

ANSI American National Standards Institute

Coordinates the US voluntary standards system and accredits standards developers and certification programs. "ANSI/ASNT" in a title means the document is an American National Standard.

EPRI Electric Power Research Institute

A not-for-profit research organization for the electric power industry. Among other work it administers the nuclear industry's Performance Demonstration Initiative for ultrasonic examination.

NBBI / NBIC National Board of Boiler and Pressure Vessel Inspectors / National Board Inspection Code

The National Board is an organization of US and Canadian jurisdictional boiler and pressure vessel officials. Its NBIC covers inspection, repair and alteration of boilers and pressure vessels in service.

AMPP Association for Materials Protection and Performance

The corrosion and coatings association formed in 2021 by the combination of NACE International and SSPC. Publishes corrosion-control and coating standards.

SAE SAE International

A standards body for aerospace and automotive engineering. Publishes Aerospace Material Specifications (AMS), several of which cover NDT processes.

TAPPI Technical Association of the Pulp and Paper Industry

The pulp and paper industry's technical association. Publishes Technical Information Papers (TIPs), including guidance on inspecting recovery boilers, digesters and dryers.

BLRBAC Black Liquor Recovery Boiler Advisory Committee

A North American industry committee that develops safety practices for kraft recovery boilers, including emergency procedures for tube leaks.

ICNDT International Committee for Non-Destructive Testing

The worldwide federation of national NDT societies, which promotes cooperation and harmonized personnel certification.

Terms from refineries, chemical plants, pipelines and the programs that keep them safe.

MI Mechanical integrity

The program that keeps process equipment fit to contain what it holds: written procedures, training, inspection and testing, and fixing deficiencies. A required element of OSHA's PSM standard.

PSM Process Safety Management

OSHA's standard (29 CFR 1910.119) for facilities handling highly hazardous chemicals above threshold quantities. Its mechanical integrity element requires documented inspection and testing of process equipment.

RAGAGEP Recognized and generally accepted good engineering practice

The yardstick OSHA's PSM standard uses for inspection and testing procedures. In practice, industry codes such as API 510, 570 and 653 are commonly treated as RAGAGEP.

MOC Management of change

A formal review of any change to a process, equipment or procedure before it is made, so that new hazards, including new damage mechanisms, are caught.

API 510 / 570 / 653

API's in-service inspection codes and standard for pressure vessels (510), piping (570) and aboveground storage tanks (653). Each covers inspection, repair and alteration, and each has a matching API ICP inspector certification.

RBI Risk-based inspection

Planning inspection by risk, the likelihood of failure times its consequence, rather than by fixed intervals, so effort goes where it matters most. Described in API RP 580 and 581.

FFS Fitness-for-service

An engineering assessment of whether equipment with a known flaw or damage can keep operating safely, and for how long. The main US method is API 579-1/ASME FFS-1.

IOW Integrity operating window

Set limits on process conditions such as temperature, pressure or chemistry; staying inside them keeps damage mechanisms predictable. Described in API RP 584.

Damage mechanism

The specific way a material degrades in service, such as corrosion, cracking, creep or embrittlement. Knowing the mechanism is what tells you which NDT method and where to look; API RP 571 describes those common in refining and petrochemicals.

CUI Corrosion under insulation

Corrosion of piping and vessels hidden beneath thermal insulation, where water gets in and stays. Among the most common causes of leaks in plants because it cannot be seen.

HTHA High-temperature hydrogen attack

Damage to carbon and low-alloy steels in hot, high-pressure hydrogen service, where hydrogen reacts with carbon in the steel to form methane, causing fissures and loss of strength. Hard to detect; API RP 941 addresses it.

SCC Stress corrosion cracking

Cracking caused by the combination of tensile stress and a corrosive environment, such as chlorides with stainless steel or caustic with carbon steel. The cracks can be fine and branched, and hard to find.

MIC Microbiologically influenced corrosion

Corrosion accelerated by bacteria and other microorganisms, often in stagnant water, tank bottoms and firewater systems. Tends to produce deep, localized pits.

FAC Flow-accelerated corrosion

Wall thinning of carbon steel in flowing water or wet steam, where the protective oxide layer dissolves faster than it forms. Tracked by thickness measurement in power plants and steam systems.

Wet H2S damage (HIC, SOHIC, SSC)

A family of cracking and blistering in carbon steel exposed to water containing hydrogen sulfide: hydrogen-induced cracking, stress-oriented HIC and sulfide stress cracking. Found in sour-service oil and gas equipment.

Sulfidation

High-temperature corrosion of steel by sulfur compounds in crude oil. Low-silicon carbon steel can corrode much faster than the rest of a pipe run, which is why component-by-component inspection matters.

Creep

Slow, permanent deformation of metal under stress at high temperature, which can lead to rupture. Tracked in furnace tubes, boiler tubes and hot piping.

TML / CML Thickness measurement location / condition monitoring location

Marked points on equipment where thickness or condition is measured at every inspection, so corrosion rates can be calculated. API 570 now uses CML, the broader term.

Corrosion rate and remaining life

The rate at which wall thickness is being lost, from repeat measurements, and the time left before the wall reaches its minimum required thickness. The basis of most inspection intervals.

MAWP Maximum allowable working pressure

The highest pressure a pressure vessel is permitted to operate at, as calculated under its design code for its actual condition.

MAOP Maximum allowable operating pressure

The highest pressure a gas pipeline may be operated at under federal pipeline rules. The hazardous-liquid equivalent is MOP.

SMYS Specified minimum yield strength

The minimum yield strength required by a pipe's material specification. Pipeline rules often express operating stress as a percentage of SMYS.

HCA High consequence area

Under federal pipeline rules, an area where a pipeline failure would have serious consequences, such as populated or environmentally sensitive areas. Pipelines that could affect an HCA must be under an integrity management program.

ILI In-line inspection

Inspecting a pipeline from the inside with a tool (a "smart pig") carried along by the product flow. Tools use MFL, ultrasonic, EMAT or caliper sensors to find metal loss, cracks and dents.

Pig

A device sent through a pipeline to clean it, separate products or, as an intelligent pig, to inspect it.

DA / ECDA Direct assessment / external corrosion direct assessment

A pipeline integrity method that uses above-ground surveys and records to pick dig sites, then examines the pipe directly in the dig. Used where in-line inspection is not practical.

Hydrotest Hydrostatic pressure test

Filling a pipeline, vessel or system with water and pressurizing it above its operating pressure to prove strength and tightness. Removes defects that would fail at the test pressure.

TAR Turnaround

A planned shutdown of a plant or unit for maintenance and inspection. Most internal vessel inspection happens here, so NDT demand peaks.

OCTG Oil country tubular goods

Casing, tubing and drill pipe used in oil and gas wells. Inspected at the mill and again in the field before use.

AST Aboveground storage tank

A large atmospheric or low-pressure tank storing crude, products or chemicals, usually inspected under API 653 in the oil industry.

The vocabulary of detection: how well a technique finds flaws and how results are judged.

Indication

Any response or evidence from an NDT method, such as an echo, a bleed-out or a shadow, that needs interpreting. Not every indication is a flaw.

Discontinuity vs defect

A discontinuity is any interruption in the normal structure of a material. It becomes a defect only when it fails the acceptance criteria of the applicable code or specification.

Relevant and non-relevant indications

A relevant indication comes from a real discontinuity; a non-relevant one comes from geometry or the test itself (a sharp corner, a change in section); a false indication comes from poor processing.

Acceptance criteria

The limits in a code, standard or specification that decide whether an indication is acceptable or rejectable. The inspector applies them; the engineer or code sets them.

POD Probability of detection

The chance that a given inspection, done by a given procedure and people, will find a flaw of a given size. Always less than 100 percent, and a function of flaw size.

a90/95

The flaw size that a technique detects with 90 percent probability, demonstrated with 95 percent statistical confidence. A standard way to state the reliable detection capability of a procedure, especially in aerospace.

Sensitivity

The smallest flaw or change a technique can reliably detect. Set during calibration and checked during the inspection.

SNR Signal-to-noise ratio

How strongly a flaw signal stands out from background noise. A low SNR, common in coarse-grained materials, makes small flaws hard to find.

DAC Distance-amplitude correction (curve)

A UT reference curve that shows how the echo from a standard reflector falls off with distance, so indications at any depth can be compared fairly.

TCG Time-corrected gain

The electronic alternative to a DAC curve: the instrument raises the gain with depth so the same reflector gives the same screen height at any distance.

IQI Image quality indicator (penetrameter)

A small wire or hole-type gauge placed on the part during radiography; seeing the required wire or hole on the image proves the technique had enough sensitivity.

Reference standard (calibration block)

A block or tube with known, artificial reflectors or flaws, used to set up and check an instrument before and during inspection.

Couplant

The gel, water or oil between an ultrasonic probe and the part, which lets sound pass across the gap.

A-scan, B-scan, C-scan, S-scan

Ways of displaying ultrasonic data: A-scan is signal amplitude against time; B-scan is a cross-section; C-scan is a plan-view map; S-scan is a phased-array fan-shaped sector image.

Encoded scan

An inspection in which probe position is recorded by an encoder along with the data, so the results can be mapped, reviewed by others and compared next time.

Procedure and technique sheet

The procedure is the approved written instruction for applying a method to a class of work; a technique sheet gives the exact settings for a specific part or weld.

Terms you meet when NDT supports aircraft maintenance.

A&P Airframe and Powerplant mechanic certificate

The FAA mechanic certificate, with airframe and powerplant ratings, issued under 14 CFR Part 65. It authorizes maintenance and return to service within its privileges, but it is not an NDT certification.

IA Inspection Authorization

An FAA authorization held by experienced A&P mechanics that allows them to perform annual inspections and approve major repairs and alterations for return to service. Renewed every two years.

AD Airworthiness directive

A legally enforceable rule the FAA (or another authority) issues to correct an unsafe condition in a product. Many ADs require a specific NDT inspection at set intervals.

SB Service bulletin

A manufacturer's notice recommending an inspection, modification or procedure. Not mandatory by itself unless an AD or the operator's program makes it so.

AC Advisory circular

FAA guidance explaining acceptable ways to meet its rules. AC 43.13-1B, on acceptable methods for aircraft inspection and repair, includes a chapter on NDI.

OEM Original equipment manufacturer

The company that designed and built the aircraft, engine or component. The OEM's manuals define the approved NDT procedures for its products.

MRO Maintenance, repair and overhaul

Organizations and work that keep aircraft and components airworthy, from line maintenance to heavy checks and shop overhaul.

NDI / NDT manual

The manufacturer's manual of approved NDT procedures for an aircraft or engine type, down to probe, frequency and reference standard. Inspectors must work to its current revision.

SRM Structural repair manual

The manufacturer's manual giving allowable damage limits and approved repairs for aircraft structure. Findings from NDT are dispositioned against it.

Part 145 repair station

A maintenance organization certificated by the FAA under 14 CFR Part 145. Many NDT shops that inspect aircraft parts hold this certificate.

ATA Spec 105

An airline industry specification (published by Airlines for America) giving guidelines for training and qualifying NDT personnel in aviation maintenance.

Damage tolerance

A design and maintenance approach that assumes cracks may exist and sets inspections so a crack is found before it grows to a dangerous size. It is why inspection intervals and NDT reliability are linked.

BVID Barely visible impact damage

Impact damage to composite structure that leaves little or no visible mark on the surface but may hide delamination underneath, which is why composites need instrumented NDT.

Terms from inspection of nuclear power plants.

ISI Inservice inspection

The periodic examination of a nuclear plant's pressure-retaining components during its operating life, under ASME Section XI, organized into ten-year inspection intervals.

PSI Preservice inspection

The baseline examination of components before a nuclear plant, or a replaced component, enters service, so later inservice results can be compared against it.

ASME Section XI

The part of the ASME Boiler and Pressure Vessel Code that sets rules for inservice inspection of nuclear power plant components, incorporated into US regulations by 10 CFR 50.55a.

ASME Section III

The part of the ASME Boiler and Pressure Vessel Code covering the construction of nuclear facility components, including the examinations required during fabrication.

10 CFR 50.55a

The NRC regulation that incorporates the ASME Code, including Section XI, into law for US nuclear power plants, with conditions of its own.

Appendix B 10 CFR Part 50, Appendix B

The NRC's quality assurance criteria for nuclear power plants and fuel reprocessing plants. Its criteria cover control of special processes such as NDT, and the records that prove it.

NQA-1

The ASME quality assurance standard for nuclear facilities, widely used to put Appendix B requirements into practice.

Part 21 10 CFR Part 21

The NRC rule requiring suppliers and licensees to evaluate and report defects and noncompliances in safety-related items and services, which can include NDT services.

Appendix VIII

The part of ASME Section XI that requires ultrasonic procedures, equipment and personnel to prove, by performance demonstration on flawed specimens, that they can find and size real flaws.

PDI Performance Demonstration Initiative

The US nuclear industry's program, administered by EPRI, for carrying out Appendix VIII performance demonstrations of ultrasonic procedures and examiners.

SG Steam generator

In a pressurized water reactor, the heat exchanger where hot reactor coolant in thousands of tubes boils water on the other side. Its tubes are inspected by eddy current at refueling outages.

RPV Reactor pressure vessel

The thick steel vessel that holds a reactor's core and coolant. Its welds, nozzles and head penetrations are examined under ASME Section XI.

PWSCC / IGSCC Primary water SCC / intergranular SCC

Forms of stress corrosion cracking important in nuclear plants: PWSCC affects nickel alloys such as Alloy 600 in pressurized water reactors; IGSCC affected sensitized stainless steel piping in boiling water reactors.

Refueling outage

The planned shutdown, typically every 18 to 24 months, when a reactor is refueled and most inservice inspection is done under tight schedule and radiation-exposure limits.

Weld procedures, inspectors and the flaws they look for.

SCWI Senior Certified Welding Inspector

The American Welding Society's senior welding inspector certification, for inspectors who manage inspection programs and staff.

WPS Welding procedure specification

The written, qualified instructions for making a weld: process, materials, positions, preheat, heat input and other variables. Welders must follow it.

PQR Procedure qualification record

The record of the test weld and the mechanical and other tests that prove a WPS produces sound welds with the required properties.

WPQ Welder performance qualification

The record showing an individual welder has passed the test to make welds to a qualified procedure within stated limits.

HAZ Heat-affected zone

The band of base metal next to a weld that did not melt but was changed by the heat. Often harder, more brittle or more crack-prone than the rest of the metal, so inspectors pay close attention to it.

PWHT Post-weld heat treatment

Controlled heating of a completed weld to relieve residual stresses and temper hard zones, often required by code for thick sections and certain services.

Girth weld

A circumferential weld joining two lengths of pipe. Pipeline construction rules set how many girth welds must be examined by NDT.

CJP Complete joint penetration

A groove weld in which weld metal extends through the full thickness of the joint. Usually requires volumetric NDT, UT or RT, when the code calls for it.

LOF Lack of fusion (incomplete fusion)

A weld flaw where weld metal did not fuse with the base metal or with a previous weld pass. Planar and potentially serious; best found by UT.

IP Incomplete penetration

A weld flaw where the weld metal does not reach through the root of the joint as intended.

Porosity

Gas pores trapped in solidified weld metal. Rounded and usually less critical than cracks, and shows clearly in radiography.

Slag inclusion

Non-metallic solid (flux residue) trapped in the weld, often between passes. Found by RT and UT.

Undercut

A groove melted into the base metal at the toe of a weld and left unfilled. Found by visual inspection and limited by code.