Non-Destructive Testing (NDT)
In the field, NDT is often used as an umbrella term to refer to non-destructive inspection methods, inspection tools, or even the entire field of non-destructive inspections. For commercial application, the goal of NDT is to ensure that critical infrastructure is properly maintained in order to avoid catastrophic accidents.
MAGNETIC PARTICLE INSPECTION
This method is used for the detection of surface and near-surface flaws in ferromagnetic materials and is primarily used for crack detection. The specimen is magnetised either locally or overall, and if the material is sound the magnetic flux is predominantly inside the material. If, however, there is a surface-breaking flaw, the magnetic field is distorted, causing local magnetic flux leakage around the flaw. This leakage flux is displayed by covering the surface with very fine iron particles applied either dry or suspended in a liquid. The particles accumulate at the regions of flux leakage, producing a build-up which can be seen visually even when the crack opening is very narrow. Thus, a crack is indicated as a line of iron powder particles on the surface.
DYE PENETRANT INSPECTION
This non-destructive testing technique, also known as liquid penetrant inspection (LPI), is a cost-effective method used to locate surface breaking flaws such as cracks, porosity, laps, seams and other surface discontinuities. Dye penetrant inspection can be applied to both ferrous and non-ferrous materials and all non-porous materials (metals, plastics or ceramics).
ULTRASONIC THICKNESS MEASUREMENT
Ultrasonic nondestructive testing, also known as ultrasonic NDT or simply UT, is a method of characterizing the thickness or internal structure of a test piece through the use of high frequency sound waves. The frequencies, or pitch, used for ultrasonic testing are many times higher than the limit of human hearing, most commonly in the range from 500 KHz to 20 MHz.
HARDNESS TESTING
Hardness testing is a relatively simple and inexpensive nondestructive test that can be performed on the exterior surface of materials or welds. Although hardness testing cannot usually find defects, it can show that material or welds have not become overly brittle during welding or heat treatment.
PHASED ARRAY ULTRASONIC TESTING
Phased Array Ultrasonic Testing (PAUT) is an advanced nondestructive examination technique that utilizes a set of ultrasonic testing (UT) probes made up of numerous small elements, each of which is pulsed individually with computer-calculated timing (“phasing”). Phased array probes can be used manually in a free running mode scrubbing the surface of a component, attached to an encoder to record position, or mounted on a semi-automated or motorized scanner for optimum productivity. PAUT can be used to inspect almost any material where traditional UT methods have been utilized and is often used for weld inspections and crack detection.
RADIOGRAPHIC TESTING
RT is used to detect discontinuities such as porosity, cracks and inclusions in materials or welds. It is performed by placing film or a digital detector on one side of a weld and introducing a radiographic source (X-ray tube or a radioactive isotope) on the other side. Radiation from the source that is not absorbed by the weld passes through and exposes the film, leaving an image of the internal structure of the weld and any flaws once the film is developed. Cracks, porosity, and lack of fusion appear as dark indications on the film. Low density inclusions will also appear as dark areas, while high density inclusions will appear as light areas.
SURFACE PREPARATION
Prior to coating, a suitable surface preparation must be performed according to the coating system manufacturer and the coating contract specification. To ensure that the applied coating system performs as designed, during the surface preparation stage several tests and the corresponding services that can be provided such as:
- Visual inspection for the determination of rust grade
- Measurement of dust on the surface
- Surface chemical cleanliness
- Blast cleaning media cleanliness
- Surface roughness/profile (
- Water pH measurement