NDT (Non Destructive Testing) is a testing and analysis methodology used in evaluation of a material or a component of a structure for deviation in acceptance or discontinuities in the asset without causing damage to the part itself.
NDT has a wide variety of methods that are used to determine the integrity of the part.
There are many types of NDT techniques used but the following are most commonly used in various manufacturing and service applications.
What is Dye Penetrant Testing?
Dye Penetrant Testing (DPT) involves application of a coloured low viscous fluid on the part. The fluid seeps into the cracks or any other kind of defect that is open to the surface. Once this penetrant is in the defects a developer is applied which helps the penetrant to come out of the defect and becomes visible hence creating an indication of the flaw. A visual inspection is then performed under ultraviolet or white light, depending on the type of penetrant used.
What is Magnetic Particle Testing?
This method works by inducing the magnetic flux in the part to be tested. If any discontinuities or detect is present on the surface or near the surface the magnetic field distorts and leaks around the defect. By application of magnetic medium on the surface, the particles attract to the area where flux leakage has occurred producing a visible indication of the defect. This indication can be evaluated by the operator any the necessary measures are taken, if any.
What is Ultrasonic Testing?
The technique uses a pluser unit to power an ultrasonic transducer. The transducer is placed into contact with the tested object with a thin layer of couplant and sound waves are generated into the object. The reflected waves are assessed and the signals from the echo are shown on the display unit. Skilled interpretation of the signals indicates if there are any defects or discontinuities.
What is Radiographic Testing?
It is one of the most versatile method that can be used performed on site of offsite and on part having varying dimensions. The radiography technique used X-ray or Gamma ray as a source to penetrate materials to be tested. The radiation is passed through the component and captured on the radiographic film, and the difference in density is analyzed.
The main advantage of radiography is that is required minimum surface preparation and provides permanent and multiple records of the tested part.
What is Eddy Current Testing?
ECT equipment is highly portable as it consist of a display, and can detect discontinuities it is highly reliable and ideal for onsite inspection. Flaws displayed are in real time allowing inspectors and managers to make quick decisions. These are also very much useful in inspection of complex shapes and geometries.
ECT uses electromagnetic induction to detect defects in conductive materials by inducing an eddy current field in the specimen under test. Various kind of inspection can be performed using ECT like surface or near surface defects, coating thickness measurements it can be also used for metal sorting according to conductivity and hardness.
What is Phased Array Ultrasonic Testing?
A PAUT probe is made up of multiple small ultrasonic probes which can be fired individually. By varying the time of the pulse of each probe ultrasonic rays can be steered into various angles and focal distances. Therefore wave can be swept across the material and thereby covering the object.
What is Infrared Thermography Testing?
Objects release infrared radiation (Thermal waves) which is invisible to naked eyes. An infrared camera measures thermal energy and map temperature difference of the object. This image captures the heat flow to, through and from the object. The analysis of this image can highlight problems such as corrosion, erosion as well as flaws in the materials such as air gaps or inclusions.
As nearly everything becomes hot before failing, thermography is an important diagnostic tool to find deterioration of the equipment. Many times object that show low thermal energy indicates loss of power and energy faults.
What is Magnetic Flux Testing?
(MFL) Magnetic flux leakage is a NDT method that is used to detect corrosion, pitting or erosion in steel structures like pipes, floors, storage tanks. These can lead to loss of product and damage equipment hence it becomes necessary to inspect such parts to prevent occurrence of such problems.
MFL provides high-speed and reliable inspection of steel structures. Our highly qualified inspectors have gained years of experience in inspection and mapping structures. We use highly advanced MFL instruments to carry out inspection.
This method uses permanent magnets or electromagnets to magnetize the part upto the saturation point and changes in the magnetic field is recorded. If there are any discontinuities the magnetic field leaks and then this leakage is analyzed to determine location and nature of the defect both near the surface and far away.
What is Time of Flight Diffraction?
Time of flight diffraction (TOFD) is one of the most reliable NDT method for pre service and in service inspection of welds. An accurate assessment of welded joints is necessary for stability, safety, integrity for maintaining the reliability of parts.
Two probes are placed on the opposite side of the test piece, one probe acts as a transmitter while the other probe acts as a receiver. When there is no flaw is detected the receiver picks up two waves – one wave travels along the surface and other reflects from the backwall. If there is any defect there is a diffraction from the tip of the discontinuities. By calculating the time of flight of the pulse, the depth of the discontinuities can be calculated by trigonometry.
What is Leak Testing?
Leak Testing is a form of Non-destructive Testing (NDT) method that uses either a pressurized or evacuated system to detect the location of leak and possibly measure the leakage through the leak. LT when compared to other methods, either surface (MT, PT) or Volumetric (UT, RT), has a higher degree of sensitivity to locate the leak or measure leakage and advanced LT is Divided into three main categories by American Society of Non-Destructive Testing. Leak Detection, Leak Location, Leak Measurement.