George Maksin, Chairman of American Society of Non-Destructive Testing (ASNT) Pittsburgh Chapter enlisted the help of Dr. Zee to kick-off the 2010/2011 season by presenting  a power point presentation titled “Failure Analysis and Case Histories" at Dynasty International in Cranberry, Pennsylvania.  Case histories that involved the use of various NDT ultrasonic testing, magetical partical testing and a variety of other NDT test methods were woven into the presentation geared towards identifying materials suspected of failure due to corrosion, corrosion, fatigue, or metal loss.  Although commonly accepted as part of the testing performed on-site to identify structures at risk due to a variety of concerns, NDT is also commonly used in a laboratory setting as well. Below several of the more commonly NDT methods are listed.  If you would like additional information regarding NDT please feel free to contact Jose Borge, Matco's ASNT NDT Level III Technician at  This e-mail address is being protected from spambots. You need JavaScript enabled to view it .    

Ultrasonic Testing (UT)

In ultrasonic testing, high frequency sound waves are introduced into a material via a transducer coupling medium to detect imperfections. The most widely used technique is pulse echo, whereby sound is introduced into a test specimen and reflections (echoes) from the internal imperfection or the part’s geometrical surfaces are returned to a receiver.

Magnetic Particle Testing (MT)

This Non-Destructive method is accomplished by inducing a magnetic field in a ferromagnetic material and then applying either dry or wet iron particles to the surface of the test piece. When a surface or subsurface discontinuity interrupts the magnetic field induced in the part, part of the field is forced out in the air above the discontinuity, forming a leakage field. Iron particles will form an outline of the leakage field revealing its location, size and shape.

Eddy Current Testing (ET)

Electrical currents (Eddy Currents) are generated in a conductive material by a changing magnetic field. There are factors which contribute to the strength of eddy currents such as; frequency, applied voltage, permeability and lift-off. Relevant indications are noted by the inspector when the flow of eddy currents is interrupted by a defect. These electrical currents are also affected by the electrical and magnetic permeability of a material, which allows this method to be used to sort some materials based on these properties.

Penetrant Testing (PT)

The process of this widely used test method involves coating the test specimen with a visible or fluorescent dye. The dye penetrant is allowed to dwell in the part for a specific amount of time, as to ensure that it seeps down into any surface crevice. After the dwell time, the excess penetrant solution is removed from the surface, and a developer is applied to draw out the penetrant left behind in surface defects. With fluorescent dyes, ultraviolet lights are used to make the bleedout fluoresce brightly, allowing the inspector to easily see the surface imperfections.

Radiography (RT)

This involves the use of high energy Gamma or X-Ray radiation to produce a latent image on a piece of photographic film. The materials thickness and density changes are indicated as lighter or darker areas on the film. This allows for the interpretation of the materials internal features and soundness. X-ray machines or radioactive isotopes are used as a source of radiation. Cracks on a weld sample are noted on a radiograph as a thin dark irregular line along the length of the weld bead.

Case Histories:  A recent example of MATCO’s ability to solve particularly difficult NDT questions concerned a major site cooling system which evidently was undergoing serious corrosion problems, placing the entire system in jeopardy. Small leaks had already been detected, several pipe joints had been removed, and significant metal loss was seen. The entire system needed to be checked. Ultrasonic examination seemed the obvious choice… but it didn’t work at all. The problem was that the system, composed of carbon steel pipes from 24 to 10 inches in radius, had been constructed with Victaulic couplings. These consist of heavy steel bolted clamps tied into rolled-in grooves at the end of each piece of pipe, over a rubber gasket. The clamps prevented the ultra sonic probe from transmitting or receiving properly so that the sites of most serious damage could not be examined.

A new high-tech alternative was computed radiography, a process which can take place in the field. The pipes have to be emptied of water, but the detector plates are placed entirely on the opposite side of the pipe from the x-ray source which exposes the plate through the two layers of clamp and the two layers of steel in the pipe. Digital processing allows the extraction of the relevant information from the signal and presentation of that information as an image.