NDT, inspection and repair glossary

NDT inspection

Non-destructive testing (NDT)

Inspection methods that find defects or measure a part without damaging it, so the part can go back into service. NDT inspection

Ultrasonic testing (UT)

High-frequency sound is sent into the material; echoes from flaws or the back wall reveal cracks, laminations and wall thickness. NDT inspection

Phased array ultrasonic testing (PAUT)

UT with a probe made of many small elements fired in sequence, so the beam can be steered and focused to image a weld or part and record the result. NDT inspection

Eddy current testing (ET)

An alternating magnetic field induces currents in a conductive part; cracks and changes in the material disturb those currents and show on the instrument. NDT inspection

Magnetic particle testing (MT, MPI)

A ferrous part is magnetised and coated with fine iron particles, which gather where a surface or near-surface crack leaks the magnetic field. NDT inspection

Liquid penetrant testing (PT)

A dye drawn into surface-breaking defects by capillary action is pulled back out by a developer, showing cracks and porosity as red or fluorescent marks. NDT inspection

Infrared thermography

A thermal camera maps surface temperature to reveal heat loss, hot electrical connections, blockages and some hidden defects without contact. NDT inspection

Visual testing (VT)

Direct or aided visual examination for corrosion, weld defects, damage and dimensional problems. Usually the first inspection done. NDT inspection

Radiographic testing (RT)

X-rays or gamma rays pass through the part onto film or a detector, showing internal defects such as porosity and lack of fusion in welds. NDT training and certification

Third-party inspection

Inspection by an independent company that is neither the buyer nor the maker, to confirm work meets the agreed specification. NDT inspection

Drill pipe and tubulars

EMI (electromagnetic inspection)

Full-length inspection of a pipe body by magnetising it and scanning for flux leakage from transverse flaws, longitudinal flaws and wall loss. Drill pipe inspection

Special end area inspection

Inspection of tool joints and upsets, the parts of drill pipe where fatigue cracks most often start. Drill pipe inspection

Hardbanding

A wear-resistant hard-face layer welded onto tool joints to protect them and the casing. It is inspected for cracking and loss. Drill pipe inspection

DS-1

A widely used industry standard for drill stem design and inspection, covering inspection methods and acceptance criteria for drill pipe and other drill string parts. Drill pipe inspection

API

The American Petroleum Institute, whose specifications and recommended practices cover oilfield equipment, including drill pipe and tubulars. Drill pipe inspection

Calibration and standards

Reference standard

A test piece with known, man-made flaws used to set up and check NDT equipment before inspection. Materials services

EDM notch

A precise slot cut by electrical discharge machining into a reference standard to simulate a crack of known depth and length. Materials services

Side-drilled hole

A hole drilled parallel to the surface of a reference block, used to calibrate ultrasonic sensitivity and distance. Materials services

Certification

ASNT

The American Society for Nondestructive Testing, whose schemes are widely used to qualify and certify NDT personnel. NDT training and certification

SNT-TC-1A

ASNT's recommended practice for employers to qualify and certify their NDT personnel through training, experience and examinations. NDT training and certification

Level I, II and III

NDT certification levels. Level I carries out set tests under supervision, Level II sets up equipment and interprets results, and Level III writes procedures, interprets codes and certifies others. NDT training and certification

Lifting and load testing

Proof load test

A test that loads lifting equipment above its rated load, under control, to show it is fit for use. Load testing

Safe working load (SWL)

The maximum load that lifting equipment is rated to lift in normal service. Load testing

Water-bag load test

A proof load test using bags filled with water to the exact test weight, convenient on site and offshore. Load testing

Pad eye

A lifting point, usually a plate with a hole, welded to a structure or equipment for attaching shackles. Load testing

Load cell

A sensor that measures force. It is calibrated so the applied test load can be read accurately. Load testing

Welding and engineering

WPS and PQR

A welding procedure specification sets out how a weld is made. The procedure qualification record documents the tests that prove the procedure works. Welding and structural engineering

Welder qualification

Testing a welder against a qualified procedure to show they can make sound welds with it. Welding and structural engineering

Post-weld heat treatment (PWHT)

Controlled heating and cooling after welding to relieve residual stress and improve properties. In-situ PWHT is done on site. Welding and structural engineering

Finite element analysis (FEA)

A computer method that divides a structure into small elements to calculate stresses and deflections under load. Welding and structural engineering

Turbine repair and reverse engineering

MRO

Maintenance, repair and overhaul: work on parts that have been in service, as opposed to new OEM manufacture. Aerospace turbine repair

HPT and LPT

The high-pressure and low-pressure turbine stages of a gas turbine engine. HPT blades and vanes run hottest and wear fastest. Aerospace turbine repair

Turbine vane

A static airfoil that directs hot gas onto the rotating turbine blades. Aerospace turbine repair

Cooling holes

Small holes through a turbine airfoil that bleed cooling air over its surface. Repairs must not block them. Aerospace turbine repair

Braze repair

Joining or building up metal with a filler alloy that melts below the part's own melting point, then flows and bonds in a furnace cycle. Aerospace turbine repair

Near-net surface build-up

Metcon's patent-pending process that sprays braze and base-metal powders only where needed, close to the final shape, so little blending is left. Aerospace turbine repair

Blending

Removing excess material by grinding or polishing to restore a part's contour and finish. Reverse engineering and robotic blending

Best-fit form

A target shape computed from the scan of each individual part, so repairs follow that part rather than a generic drawing. Reverse engineering and robotic blending

Blue-light scanning

Structured-light 3D scanning that projects blue light patterns onto a part to measure its surface precisely. Reverse engineering and robotic blending

Point cloud

The set of measured 3D points a scanner produces, before it is turned into a surface or CAD model. Reverse engineering and robotic blending

Scan to CAD

Turning scan data into a CAD model that can be measured, compared with a reference and used to program machines or robots. Reverse engineering and robotic blending

Collaborative robot

A robot designed to work safely near people, used as the central unit of Metcon's blending cells. Reverse engineering and robotic blending