Eddy Current Testing
Eddy Current Testing is a method that utilises single and dual-element ECT probes — a coil of conductive wire is excited with an alternating electrical current. This wire coil produces an alternating magnetic field around itself. The magnetic field oscillates at the same frequency as the current running through the coil. When the coil approaches a conductive material, currents opposed to the ones in the coil are induced in the material — eddy currents. The two major applications of eddy current testing are surface inspection and tube inspections. Surface inspection is used extensively in the oil & gas sector, but also in the petrochemical industry. The technique is very sensitive and can detect tight cracks. Surface inspection can be performed both on ferromagnetic and non-ferromagnetic materials.
Magnetic Particle Testing
Magnetic Particle Inspection is a method of detecting surface breaking discontinuities and some sub-surface flaws in ferromagnetic materials. The item that is being tested, is magnetised using various types of magnetisation and with an inspection medium applied to the test surface, this will aid with locating the flaws, such as ink containing ferromagnetic particles that are attracted to the flaw during the magnetisation phase. Inspections can be carried out on Castings, General Forgings, Wrought Products and Welds either onsite or in house.
Dye Penetrant Inspection
Also known as Liquid Penetrant Inspection (LPI) or Penetrant Testing (PT), it is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). The penetrant may be applied to all non-ferrous materials and ferrous materials, and through capillary action, the penetrant enters the discontinuity. To visually see the defect the area tested is thoroughly cleaned and a developer applied which draws the penetrant out to become visible either with natural light or Ultraviolet light (UV). PT is used to detect casting, forging and welding surface defects such as hairline cracks, surface porosity, leaks in new products, and fatigue cracks on in-service components.
Ultrasonic inspection is a method which utilises high frequency soundwaves to perform volumetric examinations of materials. Ultrasonic testing is used most commonly to detect internal flaws but in some instances, can be used to detect surface flaws as well. Ultrasonic testing works by introducing soundwaves in to the material under test, these waves then propagate through the material. Any discontinuity in the beam path will cause part of the sound wave to be reflected back to the probe, which is then detected and displayed on the ultrasonic flaw detector.
Ultrasonic Testing can be applied to a wide and varied range of product sectors but most commonly are Castings, General Forgings, Wrought Products and Welds as to locate and identify pre-and in-service defects.
Visual Inspection can be conducted with or without optical aids and is the original method of NDT. Many defects are surface-breaking and can be detected by careful direct visual inspection.
Optical aids include low-power magnifiers, microscopes, telescopes and also specialised devices such as boroscopes, endoscopes and other fibre-optic devices for the inspection of restricted access areas. These devices can also be used with LED camera systems. Much of the success of visual inspection depends on the surface condition and the lighting arrangements. Surface preparation such as cleaning and etching is often used and also surface replicas can be taken for both macro- and microscopic examination. High-speed visual inspection with automated output is used for the inspection of the surface of sheet material and television techniques may use enhanced image and pattern recognition methods. Remote photography of inaccessible surfaces, such as inside a vessel, is also possible.
Visual Testing is used to detect casting, forging and welding surface defects such as cracks, surface porosity, surface bursts and fatigue cracks on pre and in-service components.