TSC designs and builds electromagnetic sensor probes for the industrial NDT market. These probes are used for the detection and sizing of surface-breaking cracks in metals and for the determination of stresses in steel. The company expends a great deal of effort in research and development; this R&D typically consists of numerical simulations and the creation of prototype probes. This paper details the research and development of some of the more complex probes TSC has recently created.

ACFM is an electromagnetic NDT technique used to inspect metal structures for surface-breaking cracks, through a variety of non-conductive coatings. However, if the coating is conductive, such as flame-sprayed aluminium or zinc galvanising, the electromagnetic surface properties of the structure are altered. These metallic coatings were modelled using Comsol multiphysics, and the model verified by experiments with metal-coated samples. The results show that accuracy of sizing is decreased, depending on coating thickness and whether the crack penetrates through the conductive coating or not. If the metal coating thickness is too thick, then defects may be completely masked.

The performance of existing ultrasonic and magnetic flux leakage techniques in detecting rail surface-breaking defects such as head checks and gauge corner cracking is inadequate during high-speed inspection, while eddy current sensors suffer from lift-off effects. Early detection of such rail defects is of paramount importance since a single crack can potentially lead to fatigue failure. The results obtained through rail inspection experiments under simulated conditions using an alternating current field measurement (ACFM) micro-pencil probe suggest that this technique can be applied for the accurate and reliable detection of surface-breaking defects at high inspection speeds.

The continuous increase in train traffic, axle load s and operating speeds means that the catastrophic failure of a rail section may resu lt in very serious derailments, such as the one that took place in Hatfield, UK, in 2000, c ausing loss of life, injuries, severe disruption in the operation of the network, unneces sary costs, and loss of confidence in rail transport by the general public. Reliable a nd cost-effective inspection of rail tracks is therefore of paramount importance to ensu re the safe travel of passenger and freight rolling stock. Tests carried out using Alte rnating Current Field Measurement (ACFM) sensors proved their capability in detecting Rolling Contact Fatigue (RCF) damage at high speeds even when measurable lift-off is involved. This paper summarises the results related to the implementatio of the ACFM technology as part of the INTERAIL inspection platform.

Digital radiography offers several advantages over conventional film-based radiography for NDT applications; the digital detectors typically require much less radiation to create an image. The disadvantage ofusing digital detectors is the relatively poor resolution in comparison to fine-grain film. The manufacturers of such detectors counter this objection by pointing out that projection magnification can be used to increase the image size, thereby increasing the effective resolution of the final image. This is correct, if a suitable mini- or micro-focus generator is used. Unfortunately, these generators tend to be significantly lower in power, so it is essential that the detector be extremely sensitive. Many manufacturers of digital radiographic inspection units claim that their systems can use projection magnification up to a factor of 100 or more. This may be the case, but the geometric unsharpness (calculated from their own published specifications) would be many times larger than the pixel-pitch, making such high values of projection magnification redundant. TWI has been working with a consortium of digital radiographic users from across Europe. Our intention is to develop an inspection unit that uses a highly sensitive digital detector that is capable of rivalling fine-grain film in sensitivity, contrast and resolution. The samples used range from 1 mm-thick magnesium castings to 10 mm-thick steel welds.

Flexible risers are flexible pipes used to bring oil from oil wells deep underwater to the surface, where it can be processed by Floating Production, Storage and Offloading (FPSO) installations. Flexible risers consist of a number of layers of steel and polymer that have a complex structure and some layers are shielded by others, making non-destructive testing particularly difficult. This paper presents some experimental radiography of a sample flexible riser. Both single-wall and double-wall techniques were used with X-rays and gamma rays with both computed radiography imaging plates and an amorphous silicon flat-panel detector. The layer of the riser that is of particular interest is the pressure armour, which is the layer designed to withstand the internal pressure. It is a layer that is particularly difficult to inspect, as it is shielded by a metallic layer on both sides.The resulting images were used to develop an image processing technique designed to detect separations in the pressure armour, which is also presented here. The technique is based on the use of the Hough transform to detect nonstructural lines in the image. This technique has been tested on a defect simulated by image processing and an artificial defect introduced to the flexible riser sample. The technique was found to be successful in detecting the artificial defect in a set of images, with only 4% of misclassification, which were all false positive results.

Above-ground storage tanks are used to store bulk fluids, such as oil, foodstuffs, pesticides and fertilisers. If one of these tanks were to leak, the potential damage to the environment would be catastrophic. To prevent such a disaster, the tanks are regularly inspected to ensure that the steel plates have not corroded, which could cause a failure of the tank. Robot Inspector is a semi-autonomous robotic inspection system, for the inspection of above-ground storage tank floors. It is the product of the Robot Inspector Consortium, a group of European companies and research organisations, part funded under the CRAFT co-operative research program.

Digital radiography is becoming more commonplace within the industrial NDT field. It offers several advantages such as defect recognition software, advanced analysis tools,.shorter exposure times, and lower energies - and yet many companies are still sceptical about its use. These companies are questioning whether they should wait for the new, technology to improve before buying, or invest in the new technology now before being left behind. This paper attempts to answer some of the common objections raised against digital, and to compare the relative merits of analogue (film) radiography against the various types of digital. It also examines some of the new terminology surrounding computed radiography and highlights some of the differences in technical skills required from radiographers and analysts.Much of the resistance to computed radiography is from radiographers themselves, who are used to using film and developers. Many are not comfortable with the new digital technologies, and are suspicious of the advantages offered by digital image processing. This paper attempts to dispel some of the myths regarding digital radiography, and takes an objective look at the various technologies on the market today.