Inspection or testing (of materials and components): verify the structural integrity of material or component without compromising its ability to perform in service

NDT is a Quality Assurance Management tool which can give impressive results when used correctly

NDT plays an important role in everyday life and is necessary to assure safety and reliability

NDT requires understanding of the method available, their capabilities and limitations, knowledge of the relevant standards and specifications for performing the tests

NDT can be applied at any stage of a component manufacture and the components being tested by NDT are either accepted, rejected or repaired

• Most basic and common inspection method
• Tools include fiberscopes, borescopes, magnifying glasses and
  mirror
• Portable video inspection unit with zoom allows inspection of
  large tanks and vessels, railroad tank cars, sewer lines
• Robotic crawlers permit observation in hazardous or tight area such as, air ducts, reactors, pipelines

• A liquid with high surface wetting characteristics is applied to the surface of the part and allowed time to seep into surface breaking defects
• The excess liquid is removed from the surface of the part
• A developer (powder) is applied to pull the trapped penetrant out the defect and spread it on the surface where it can be seen
• Visual inspection is the final step in the process. The penetrant used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity

The part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. These particles are attracted to magnetic flux leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be visually detected under proper lighting conditions

The radiation used in radiography testing is a higher energy (shorter wavelength) version of the electromagnetic waves that we see as visible light. The radiation can come from an X-ray generator or a radioactive source

Particularly well suited for detecting surface cracks but can also be used to make electrical conductivity and coating thickness measurements.

High frequency sound waves are introduced into a material and they are reflected back from surfaces or flaws. Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen showing the depth of features that reflect sound

A method is said to have a good or high sensitivity of flaw detection when it can detect relatively smaller flaws and vice versa

The sensitivity of flaw detection for different NDT methods depends upon a number of variable factors

The objective of most non-destructive testing methods is to detect internal defects with respect their nature, size and location. This is done by different methods depending upon their inherent capability or sensitivity to flaw detection

• Clear Communication
  Written standards make it easy for the customer or user to communicate with the producer

• Economy of Effort
  The purchaser or designer may have a general idea of what is required (and what is available) for a desired level of inspection

• Minimum Performance
  Published codes and standards accepted by industry in general, provide the regulator or the purchaser with confidence that the product or service will at least perform to the level detailed in the standard

• Historical Record
  After the product has gone into service (sometimes years after) a life record of the standard use for production or inspection will likely be sufficient documentation of the process used to produce it

Incorporating the statistical approach in developing acceptance criteria for design stipulated properties