What Are The NDT Techniques Commonly Used?

non destructive weld testing, ndt companies uk, examples of non destructive testing, non destructive testing technician, ndt midlands

What Are The NDT Techniques Commonly Used?

An Introduction To Non Destructive Testing

Non Destructive Testing is an umbrella term for a whole range of techniques and approaches that can be used to test materials to make sure they pass the correct specifications for their intended use. Non Destructive Testing is an integral part of many industries such as aerospace, power generation, manufacturing, fabrications, transport, medical & pharmaceutical, and much more, as it is vital that all component parts that are being put to use are correctly made, functional, and not damaged or fallen into disrepair. In many cases, non destructive testing can literally be the difference between life and death for the people working in these industries or using products. In this blog, we will go through what are the NDT techniques commonly used in these industries, as well as giving a brief description of how each one works and some of their applications.

One of the most widely used and often overlooked areas of non destructive testing is Visual Examinations. Often used for visual welding inspections, visual examinations are where a product or material is inspected visually for any imperfections or defects, usually by a trained engineer. While there are some flaws and faults that are too small to be seen, often a qualified technician is able to spot surface discontinuities such as surface cracking, undersized welds, overlap, undercut, either incomplete or excessive root penetration, excessive reinforcement and burn through.

Magnetic Particle Testing, often known as an MPI test, is often used to detect surface flaws in welds that are too small to be picked up on during a visual examination. In magnetic particle inspection, a test specimen is magnetised, and very fine iron particles are applied. If the structural integrity of the test piece is sound, the magnetic field will stay within the material, however, if there are flaws, it will create a leakage flux, which will attract the iron particles to the discontinuity, making it visible to the inspector. This is very effective at finding small surface cracks on welds, however, if the flaws are beneath the surface of the material being tested, they may not show up during Magnetic Particle Inspection.

Radiography is often used during non destructive testing as it is able to internally map out the structure of welds, rather than just detecting flaws on the surface. X-Ray weld inspection involves the use of X-Rays produced by an X-Ray tube that penetrate the material and help us gain a clearer idea of any imperfections that are present within the weld. These pass through the material onto a film, resulting in the internal structure of the material being displayed on the film, working similar to how X-Ray non destructive testing works in the medical industry. Radiography is used in many industries and is one of the most widely used forms of testing.

Dye Pen Testing is sometimes used on welds in addition to visual examinations. During these inspections, a brightly coloured liquid penetrant is applied to the test piece, which is left to soak before being cleaned away. After this a developer is applied (usually a white powder), which will then show cracks and discontinuities where the dye penetrant has managed to seep into. There are high margins for error here, so this must be carried out by trained non destructive testing technicians to yield the best results.

Ultrasonic Testing is primarily concerned with testing the thickness of a material, and as such is a very widely used form of inspection to test for corrosion and damage within welds and materials. It works by firing soundwaves at the test piece, which are then picked up by a transducer and used to determine how thick the material is. Ultrasonic NDT can sometimes be specified to ensure no laminations are present in materials that are to be subsequently welded in highly stressed joint configurations or, even after welding has taken place, to ensure imperfections such as lamellar tearing have not occurred during the welding operation.

Positive Material Identification, or PMI testing, is a very fast and easily accessible form of non destructive testing. It is used to determine the chemical composition of a test piece, and is important both for assessing the quality of said test piece alongside determining what other materials are best used alongside it. X-Ray Fluorescence is the most common form of PMI Test, which normally is used in the form of a handheld gun. Results from this are normally rapid and accurate, making it an incredibly important practise in many industries.

Ferrite Inspection is a non destructive weld testing method used to detect the amount of ferritic content in austenitic and duplex stainless steels. It is important to make sure these metals have the correct ferritic content for their use, as errors here could have a detrimental effect on a metals service life and usefulness. A Ferritscope is usually used to measure the percentage of ferrite content, which gives fast and accurate results. 

For more information on these types of Non Destructive Testing and their uses and applications, visit our services page, and contact SureCheck for all of your non destructive testing needs, both onsite and offsite.

non destructive weld testing, ndt companies uk, examples of non destructive testing, non destructive testing technician, ndt midlands

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top