Furnace tubes that are made of high-chrome material often will carburize when in hydrocarbon service.
Coker furnaces, found in oil refineries,are particularly susceptible to carburization which starts on the inside of the tube.
As carburization is difficult or impossible to detect with standard A-Scan ultrasonics, Russell NDE has developed an electromagnetic technique to detect the worst areas. The technique is known as E-PIT (External Pipe Inspection Tool).
The E-PIT Tool can be scanned down the length of the tubes (see photo to right), and will detect variations in the amount of carburization present. In order to quantify the amount of carburization, the tube can then be scanned with CIRC E-PIT, a new Tool from Russell, that can detect and quantify carburization, so long as adequate calibration standards are available (photo lower right)
Confirmation and sizing of carburization can also be accomplished by the TOFD (Time of Flight Diffraction) technique for internal carburization to accurately measure case depth.