Non-destructive testing (NDT) comprises a group of component testing methods for assessing the serviceability of a part without compromising its integrity. NDT is used frequently in safety-critical industries such as oil and gas, offshore and marine, petrochemicals, aerospace, power generation and medical instruments and prostheses. Due to non destructive inspection’s (NDI) ability to ensure exceptionally high levels of safety and quality, NDT plays a crucial role in both original equipment manufacturer and in-service maintenance. Do you want to learn more? Visit contact Salem Design & Manufacturing.
Virtually all materials contain microscopic pores, vacancies and contaminants, which can be cast or extruded into a material during primary manufacture or subsequent fabrication. These defects can extend when stressed, eventually leading to part failure. Because the cost of part failure is extraordinarily high in safety critical industries, it is of paramount importance to detect flaws that effectively predict part failure before it actually happens. In principle, NDT attempts to locate flaws in a part’s surface that predict future failure before the part fails in service and without compromising the part’s utility.
The most widely used NDT methods are: liquid fluorescent penetrant (LP), magnetic particle (MP), ultrasound (UT), x-ray and eddy current testing (ECT). Liquid penetrant fluorescent testing employs a fluid dye that makes the cracks visible under white or black light. Similar to fluorescent dyes, magnetic particle testing employs a layer of fine iron particles applied to a temporarily magnetized part. Because flaws alter the magnetic field, the iron particles conform to the shape of the flaw. Although both liquid penetrant and mag particle testing offer a fast, inexpensive means of nondestructive flaw detection, they are both limited to detecting the length and width of a flaw. Neither LP nor MP is capable of measuring a crack’s depth.
Ultrasound and x-ray testing are capable of detecting defects both on the surface and throughout the body of a part. While both UT and X-ray are capable of detecting flaws in non-metallic parts, they both necessitate the use of cumbersome procedures and materials as well as hazardous waste disposal.
Eddy current testing circumvents the problem of detecting the depth of surface flaws at the same time it eliminates waste disposal problems. Eddy current testing uses the physical characteristics of electrical currents induced by an electrical coil into the metal part itself. Discontinuities in the metal disturb the eddy current which feeds back to the coil, then to signal processor, where it is interpreted as a flaw.
In summation, there are a variety of NDT methods that allow for comprehensive inspections of metal components. These testing solutions help maintain manufacturing quality standards of newer products as well as safety standards for older operating equipment and machinery. Efficient NDT testing of equipment allows thousands of industries to maintain confidence in the quality of their products and services.