Ultrasonic Testing Services and Conventional NDT Methods

Overview

Standards: ASME BPVC Section V and Section IX (2023 editions). ASTM E94 and E1742 (radiography, film and digital), ASTM E165 and E1417 (liquid penetrant), ASTM E709 and E1444 (magnetic particle), ASTM E164 (contact ultrasonics). ISO 17636 (radiographic testing of welds) and ISO 11666 (ultrasonic acceptance levels).

• Code: ASME BPVC Section V and Section IX, 2023 editions.
• Radiography: ASTM E94 and E1742, film and digital.
• Liquid penetrant: ASTM E165 and E1417.
• Magnetic particle: ASTM E709 and E1444.
• Contact ultrasonics: ASTM E164.

Radiographic testing: film, computed and digital

Film-based and digital radiography using X-ray and gamma-ray sources. RT reveals internal flaws (porosity, inclusions, incomplete fusion) in welds and castings. Permanent, interpretable records with high sensitivity to discontinuities. Computed Radiography capability with Carestream and 3ENDT digital plates and readers brings the workflow up to the modern digital archival standard. Strict radiation safety compliance per AERB directives.

• Sources: X-ray, and gamma from Iridium-192 and Cobalt-60 for dense, thick-wall sections and site work where external power is unavailable.
• Media: film-based and digital radiography.
• Detects: porosity, inclusions and incomplete fusion in welds and castings.
• Automated Radiographic Testing: crawler systems for circumferential butt welds inside cross-country and city gas distribution pipelines.
• Record: permanent and interpretable, at high sensitivity.

Gamma-ray radiography uses Iridium-192 and Cobalt-60 isotope sources for dense and thick-wall sections where external power is unavailable, complementing X-ray radiography for site and pipeline work.

TCR Engineering offers Automated Radiographic Testing (ART) for circumferential butt welds in cross-country and City Gas Distribution (CGD) internal pipelines using advanced crawler systems. This technology enables efficient, high-precision detection of both surface and subsurface defects in welds through external X-ray or Gamma ray radiation. Crawler-based ART supports pipeline integrity and code compliance while minimising downtime.

TCR Engineering also specialises in Gamma Ray Radiographic Testing, which uses gamma radiation to inspect welds and detect internal defects in pipelines. Gamma rays, emitted from a radioactive isotope source such as Iridium-192 or Cobalt-60, have the ability to penetrate thick materials, making them highly effective for inspecting dense pipeline welds. This method is ideal for locations where access to electrical power for X-ray equipment is limited, as gamma ray testing does not require an external power source. Gamma radiography images both surface and subsurface flaws, identifying anomalies that could compromise the integrity of the pipeline. Combining gamma ray technology with our crawler systems allows for comprehensive and efficient inspection of welds in cross-country and CGD station piping works.

What is the difference between film, computed and digital radiography?

The difference is the detector, and the detector decides the time to an image, the archive and what can be done to the image after the exposure. Film records once and cannot be re-processed; computed radiography records on a reusable phosphor plate that is scanned to a digital image; a digital detector array skips the plate and the scanner and puts the image on a screen in seconds.

The physics, the source, the geometry and the sentencing rules are the same across all three. The medium, the time to an image and the archive are not.

ISO 17636-2:2022, "Non-destructive testing of welds. Radiographic testing. Part 2: X- and gamma-ray techniques with digital detectors", covers both CR and DDA in one document, which is the clearest signal in the standards that the two are variants of one route rather than rivals. ISO 17636-1 is the film part.

When is computed radiography the right choice?

Computed radiography is the right choice when the work is in the field, the geometry varies shot to shot, and the plate can be wrapped or clamped to the part the way a film cassette would be. It gives a digital image and a digital archive without asking the site to change how it rigs a shot.

That is why it is the route TCR uses on cross-country pipeline work, where 2,600+ km of pipeline radiography and 14,000+ girth welds have been shot and interpreted. The pipeline application, its client approvals and its procedure references are on Cross-Country and CGD Pipeline Radiography per API 1104; this section covers the method choice, not the pipeline campaign.

When is a digital detector array the right choice?

A digital detector array earns its place when the same geometry is shot repeatedly and the image is needed immediately. Removing the plate and the scanner from the loop removes the two slowest steps, so the technique suits production inspection, in-line work and robotic or crawler-mounted radiography where a human is not handling a cassette between shots.

It is the wrong choice where the geometry changes every shot, where the detector cannot be positioned safely, or where the contract specifies film. A DDA is a fixed panel of a fixed size; film and CR plates bend around a pipe and a DDA does not.

What does TCR need in place before a radiographic shot?

Radiography is the one NDT method with a regulator standing behind it. Source handling, storage and site operation are licensed by the Atomic Energy Regulatory Board, and no shot happens without the licence, the trained radiographer and the controlled area.

• AERB licences: 23-IRLOP-893925 for radiography operation; 22-ASSF-793303 and 23-ASSF-927086 for source storage.
• Personnel: ASNT Level II for acquisition and Level III for procedure approval and interpretation.
• Reporting: under NABL ISO/IEC 17025:2017 certificate NABLT0726MH18640.
• Acceptance: the fabrication code that governs the joint, with the radiographic technique to ISO 17636-1 or ISO 17636-2 as specified.

What happens to a plant's legacy radiographic film?

Film does not last as long as the asset it documents, and a film library that cannot be searched is a record nobody reads. TCR has digitised 250,000+ radiographic films to ASME Section V Article 2 and ASTM E1936 for Indian oil and gas operators, which turns a physical archive into images that can be re-examined, compared shot to shot and attached to a weld record.

Worth being plain about what that is and is not. Digitisation is a housekeeping step. The value is in what follows it: a qualified interpreter reading the image against the code, which is the same skill that sentences a live shot. Digitisation itself is offered as a service to IOCL and GAIL requirements, described on pipeline radiography; here the figure stands for the scale of the interpretation base.

Magnetic Particle Testing (MT)

Detection of surface and slightly subsurface discontinuities in ferromagnetic materials. Dry or wet fluorescent particles under visible or UV light. Yokes, coils, and bench units for various part sizes. ASTM E709 and ASTM E1444.

• Materials: ferromagnetic only.
• Detects: surface and slightly subsurface discontinuities, through the leakage field they interrupt.
• Particles: dry, or wet fluorescent under visible or ultraviolet light.
• Equipment: yokes, coils and bench units for varying part sizes.
• Internal access: wet fluorescent techniques under black light through borescopes.

The Magnetic Particle Inspection method of non-destructive testing is used by TCR for locating surface and subsurface discontinuities in ferromagnetic material.

When the material or part under test is magnetised, discontinuities lying generally transverse to the direction of the magnetic field interrupt it. This causes a leakage field, and therefore, the presence of the discontinuity is detected by using finely divided ferromagnetic particles applied over the surface, some of these particles being gathered and held by the leakage field. This magnetically held collection of particles forms an outline of the discontinuity and indicates its location, size, shape and extent.

At TCR, dry magnetic particle examinations and wet fluorescent magnetic particle examinations are performed on ferromagnetic materials to detect surface and slightly subsurface discontinuities.

Specialised wet fluorescent magnetic particle techniques are available for black light internal examinations of equipment through borescopes.

Visual Testing (VT)

Direct and remote visual inspection per ASME Section V and API standards. Borescope and videoscope fleet (18 high-resolution units in continuous rotation across the group).

• Modes: direct and remote visual inspection.
• Standards: ASME Section V and the API standards.
• Fleet: 18 high-resolution borescope and videoscope units in continuous rotation across the group.

Paint and Coating Thickness

TCR undertakes inspection of paint and/or coating, applied to metal surfaces. The paint and coating inspection team at TCR is equipped with wet film thickness gauges, dry film thickness gauges, holiday detectors, a hygrometer with dew point calculator and a metal surface thermometer.

TCR's paint and coating inspectors verify that all work inspected conforms with the requirements of the relevant code, specification and/or standard with respect to the paint/coating procedure, the physical application as well as the physical examination, including testing.

Senior TCR paint inspectors are qualified BGas (British Gas Corporation) and are NACE certified. The inspectors are responsible for verifying the following requirements:

• The Blasting and Coating Materials
• The Blasting and Coating Equipment
• The Temperature and Humidity
• The Surface Condition
• The Application Procedure

The inspectors prepare records covering:

• Materials Control and Identification
• Climatic Conditions and Surface Condition
• Details Of Abrasive(S) and Application Procedure
• Abrasive/Wire Brush Standard
• Details Of Coating and Application Procedure
• Equipment Calibration
• Inspection Results

Is radiography or ultrasonic testing better for weld inspection?

Neither is better for every weld. Radiography records a permanent image and shows volumetric flaws such as porosity and slag clearly; ultrasonic testing finds planar flaws such as cracks and lack of fusion, gives their depth, and needs no radiation controlled area. TCR Engineering applies both to ASME Section V and chooses by joint, thickness, flaw type and governing code.

• Cracks and lack of fusion: ultrasonic testing angled to the flaw, which a radiograph can miss when the flaw is not aligned with the beam.
• Porosity and slag inclusions: radiography, which images their shape and spread along the weld.
• Thick sections and flaw height: phased array and TOFD, which size through-wall extent for fitness-for-service work.
• Thin wall and small bore: film or computed radiography, where an ultrasonic beam has too little wall to work in.
• Live plant and shared work areas: ultrasonic testing, because a radiographic shot clears the area under the AERB licence.
• The deciding document: the fabrication code or client specification, which often names the method; welding inspection witnesses the result against it.