Non-Destructive Testing Services: Choosing and Applying the Right Method

Non-destructive testing finds flaws in materials, welds and components while leaving the item fit for service. No single method finds everything: each responds to particular flaw types, orientations and depths, and choosing the wrong one produces a clean report on a defective component. itmad provides NDT inspection by ISO 9712 and ASNT Level II qualified technicians, covering ultrasonic, phased array, TOFD, magnetic particle, penetrant, eddy current and visual methods and a range of supporting tests. itmad operates across the Middle East, Asia and Europe. Last reviewed: October 2026.

Choosing the method

Method selection follows from four questions: what material, what flaw type is of concern, where it is likely to be, and what access is available. Surface-breaking cracks in ferrous material call for magnetic particle testing, which finds tight cracks that penetrant cannot enter, and in non-magnetic material for dye penetrant. Surface cracks under paint or coating call for eddy current, without stripping the finish. Internal or subsurface flaws call for ultrasonic, phased array or radiography, because no surface method will detect them.

Flaw height and crack growth monitoring call for time of flight diffraction, and wall thickness and corrosion mapping for ultrasonic thickness measurement. A loss of pressure boundary integrity calls for leak testing, with the technique matched to the acceptable leak rate, and doubt about the material grade for positive material identification. Where a specification names the method, itmad applies it. Where it states only an acceptance criterion, itmad selects a technique capable of detecting flaws at that threshold and records the justification, and it will say when the requested method cannot answer the question being asked.

The methods

Ultrasonic testing (UT) finds internal flaws and measures wall thickness with high-frequency sound, detecting subsurface defects that no surface method can reach, from one side of the material. Phased array ultrasonics (PAUT) uses multi-element probes that steer and focus the beam electronically to produce imaged weld volume data, and is frequently accepted in place of radiography. Time of flight diffraction (TOFD) sizes flaws from the signals diffracted at their tips and is the most accurate method for measuring through-wall flaw height and monitoring crack growth.

Magnetic particle testing finds surface and near-surface cracks in ferrous materials, including tight fatigue and creep cracks that penetrant would miss, while dye penetrant testing finds surface-breaking defects in any non-porous material, including stainless steel, aluminium and other non-magnetic alloys. Eddy current testing detects surface cracks through paint and coatings and also measures conductivity and sorts alloys. Visual testing is the foundation of every inspection programme and finds most defects when applied properly to a written procedure.

Supporting methods include hardness testing, which verifies post-weld heat treatment and sour service compliance and is portable on installed plant; positive material identification by XRF and optical emission spectrometry, including carbon for L-grade verification; ferrite measurement of phase balance in duplex and austenitic welds on the production component; leak testing by bubble, pressure decay, vacuum decay and tracer gas methods spanning six orders of magnitude in sensitivity; helium leak testing with mass spectrometer detection to 1×10⁻¹² mbar·l·s⁻¹; vacuum box testing for weld seams and tank floors accessible from one side only; heat exchanger tube testing to locate individual leaking tubes in a bundle; thermographic inspection of electrical and mechanical plant under load; and contamination testing for free iron, halide and low-melting-point metal contamination on stainless and duplex surfaces.

Personnel qualification

NDT results depend more on the technician than on the equipment. An instrument reports a signal, and deciding whether that signal is a flaw, a geometric echo or a surface condition is interpretation, which is where inspections succeed or fail. itmad's technicians are qualified to ISO 9712 and ASNT SNT-TC-1A Level II, with PCN and NAS 410 qualification where the work requires it, and Level III oversight of procedure approval and technique validation.

When NDT is applied

NDT is applied during fabrication, at the stages defined in the inspection and test plan; at pre-service acceptance, before equipment is handed over or commissioned; through in-service inspection programmes at a defined interval; during shutdowns and turnarounds, where access is available and time is short; after repair, weld repair or replacement of a pressure-retaining component; following an overload, impact or process upset; and as part of failure investigation, to establish extent and mechanism. Work is carried out at the client's site, in fabrication yards, at refineries and offshore, and itmad can supply qualified NDT technicians for project-based and resident inspection assignments.

What the client receives

Reports identify each item examined, referenced to weld number, drawing or line number, and state the method, technique, equipment and procedure applied, with calibration records and reference block traceability. Indications are recorded with location, dimension and character, and each item has an accept or reject status against the governing code or specification, together with the technician's qualification level and certification reference. Where several methods are applied to the same scope, the reporting is consolidated.

Frequently asked questions

Which NDT methods does itmad offer?

Ultrasonic, phased array, TOFD, magnetic particle, dye penetrant, eddy current and visual testing, plus hardness testing, positive material identification, ferrite measurement, leak and helium leak testing, vacuum box testing, heat exchanger tube testing, thermographic inspection and contamination testing. Each method is matched to the material, the flaw type and the access available.

How is the right NDT method chosen?

By four questions: what material, what flaw type is of concern, where it is likely to be, and what access is available. Magnetic particle suits surface cracks in ferrous material, penetrant suits non-magnetic material, eddy current suits cracks under coatings, and ultrasonic or phased array suits internal flaws.

What happens if the specified method cannot answer the question?

itmad says so. Where a specification names the method it is applied, and where it states only an acceptance criterion itmad selects a capable technique and records the justification.

What qualifications do the technicians hold?

ISO 9712 and ASNT SNT-TC-1A Level II, with PCN and NAS 410 qualification where the work requires it, and Level III oversight of procedure approval and technique validation. Results depend more on the technician than on the equipment.

When is NDT required?

During fabrication, at pre-service acceptance, through in-service programmes, during shutdowns, after repair of a pressure-retaining component, after an overload or process upset, and in failure investigation. The work is carried out on site, in fabrication yards, at refineries and offshore.

Can itmad supply NDT technicians to projects?

Yes, for project-based and resident inspection assignments. The technicians hold ISO 9712 and ASNT Level II qualifications in the methods required.