The following explains the theory behind some of the conventional nondestructive testing (NDT) services provided by Quality Control Services. Despite the fact that some of these techniques have been available for a relatively long time, we are constantly striving to keep abreast of all the latest developments in hardware and equipment in order that our clients may receive the best service possible. Our commitment to fulfill all our clients' inspection requirements by providing an "all-round" service also means that additional conventional techniques are being introduced and provided as required.
Dye Penetrant Examination (PT) also known as Liquefied Penetrant Examination is a Non-Destructive Testing method. The method is used for crack detection in new and in-service installations to verify compliance and ensure safe operation.Dye Penetrant Examination involves applying a liquid to the surface of a material and leaving it to rest for a pre-determined period of time. The liquid, the so called penetrant can be either a color that is easily visible under normal lighting conditions or a yellow/green fluorescent color that requires special lighting conditions to be effective.
Magnetic Particle Testing is a Non-Destructive Testing method for detection of cracks on or just below the surface of ferrous metals. It is a quick and reliable technique for detection and location of example surface cracks. A magnetic flux is sent through the material. At the location of the imperfection a leakage field is created. This attracts metal iron dust, which is sprayed onto the surface. The length of the imperfection can be determined very reliable. Magnetic Particle Testing does not indicate the depth of the imperfection. Acceptance criteria define whether or not the indication is non-acceptable (a defect) or not. It can be applied to relatively rough and dirty surfaces but flaw sensitivity is decreased for this. Fluorescent particles can be used when maximum sensitivity is required.
UT utilizes mechanical waves (vibrations) that travel well through many materials, especially metals. The technique has proven to be extremely useful in finding structure-critical material irregularities. Sound waves travel at rates that are determined by the material's physical characteristics of elasticity, density, and homogeneity. UT is used in the testing of materials such as fine-grained metals (aluminum), and for the detection of inter-laminar separations and regions that have been improperly processed or damaged in layered composite structures. Some advantages of UT include its high sensitivity to defects that are most critical to structural integrity (e.g. cracks). It is characterized by its ease of use, portability of the testing equipment, and applicability to the testing of a wide range of materials.
A major advantage of the penetrating radiation method of NDT is its inherent display of results in single or multi-dimensional graphical images. RT is most sensitive to material changes along the projection of the beam allowing thin cross-sectional discontinuities (such as cracks) to be detected if their major surfaces are aligned parallel to the beam path. RT can be used to detect internal discontinuities in almost any material that is not too thick. RT is based on the detection of differences in the transmission or absorption of penetrating radiation by different parts of the object being radiographed. Aries offers RT inspection services using both X-ray and gamma-ray sources, depending on client or specific job requirements.
This test method covers procedures for detecting or locating leaks, where quantitative measure is not practical. The technique is applicable to any test specimen on which a pressure differential can be created across the area to be examined. An example of this technique is the application of leak-test solutions to pressurized gas-line joints. It is most useful on piping systems, pressure vessels, and storage tanks.
Visual Inspection (VI) is one of the most widely used Non-Destructive Testing (NDT) methods for the detection of discontinuities before they cause major problems, e.g. poor welding, surface defects, corrosion pits, general condition, degradation, blockages and foreign materials.
Visual Inspection means the inspection of equipment and structures using a combination of human senses such as vision, hearing, touch and smell. Visual Inspection is sometimes carried out in conjunction with devices such as a low power magnifying glass, boroscopes, fiberscopes, digital video borescopes, camera systems and robotic crawler systems.
With Positive Material Identification (PMI) the alloy composition, and thus, the identity of materials can be determined. If a material certificate is missing or/and you need to be certain about the type of material used, PMI as an NDT method is the best solution. Positive Material Identification is particularly used for high quality metals like stainless steel and high alloy metals.