Letter from the Level III
|Posted on November 9, 2014 at 3:50 PM|
Did you know?
Non-Destructive Testing (NDT) is nearly 200 years old.
The earliest recorded Non-Destructive Testing was way back in 1820………One of the earliest surface inspection techniques involved rubbing carbon black on glazed pottery. The carbon black would settle in surface cracks rendering them visible.
Soon after, it became the practice in railway workshops to examine iron and steel components by the "Oil and Whiting" method. In this method, a heavy oil common to railway workshops was diluted with kerosene in large tanks so that locomotive parts such as wheels could be submerged. After removal and careful cleaning, the surface was then coated with a fine suspension of chalk in alcohol so that a white surface layer was formed after the alcohol evaporated. The test object was then struck with a hammer, causing the residual oil solution in any surface discontinuities to seep out and stain the white coating (a crude PT examination had been performed).
The “Oil and Whiting” method was in use from the latter part of the 19th century to approximately 1940, when the magnetic particle method (MT) was introduced and found to be more sensitive for ferromagnetic iron and steels.