Non-Destructive Testing (NDT) is a term typically used for any testing program that does not harm or degrade a product or a part of a product. The requirements for Non-Destructive Testing usually emerge during the development and prototype stage of a product design program.
Many kinds of Non-Destructive Testing are utilized depending upon the product. Ultrasonic Testing (UT) is used to determine the material thickness of an item or for the detection of internal flaws that could weaken a component. Liquid Penetrant Inspection (LPI) is used to detect surface flaws in metal and other types of materials. This method requires the items inspection; solvent cleaned, apply penetrating dye to its surface and subsequently tested. After a period, it is to be solvent cleaned again and, after which, there is an application of a white colored developer. Any defects or discontinuities will then be evident both visually and by Black Light Inspection (in a dark room). If no flaws are found the part will be cleaned and released for use. A written Certification will be created to give provenance for the Inspection acceptance. An additional method for flaw detection utilizes magnetized steel parts. The term for this process is Magnetic Particle Inspection and is performed in a similar manner as the Liquid Penetrant Inspection, except the liquid for this process has concentrated iron particles in the solution. The part is placed in a magnetic conducting device and magnetized while the solution being sprayed onto the areas of interest. Upon the accomplishment of this process, the part is inspected under a black light in a dark room. Any defects will be quite evident. After the parts are deemed acceptable, they will be demagnetized and released for use, and the process will be documented and certified.
Another typical Non-Destructive Testing process is X-Ray Inspection. Parts that have critical welds are set up in an X-Ray chamber in a manner that will show the area of interest on X-Ray film after exposure to radiation. This process requires much skill and experience. Once the X-Ray process is complete, the Technician will develop the film in a processing machine and then in a dark room place the film on a backlit screen and read the film for defects. Any deficiencies found become marked on the parts and the film made available for review and if possible reworked after which the parts are again X-Rayed. Acceptable parts become documented on a reader sheet, then Certified and released for use.
All of the NDT processes defined above require the parts bear Part Numbers and Serial Number Identification. Each customer must supply a Purchase Order precisely specifying the process performed and the Inspection Acceptance criteria; this is for traceability documentation.
Other Non-Destructive Inspection techniques are product specific, such as rigorous functional testing developed by the manufacturer for their OEM products. Other tests structure are for pressurized products, as an example; Compressed Gas Cylinders undergo Pressure Proof Testing prior to acceptance for sale to the public.
Whichever Non-Destructive Testing that is applicable to a given product or industry it is the Reliability and Safety of products at stake. Testing not only saves lives but also is cost effective, both directly and indirectly. Bottom line, it speaks to a company’s reputation in the marketplace.