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.

To confirm and size carburization, a TOFD probe, held within a special holder, is scanned around the tube, across the Top (hot-side) of the tubes.

Data is gathered and saved for each scan and analysed immediately.

The photo at right shows the ultrasonic TOFD image from a carburized area

Background on carburization:

As the material carburizes, it loses ductility and can eventually fail.

The carburized material represents virtually no actual wall loss, therefore A-Scan ultrasonics is ineffective at determining caburized thickness.

The only effective ultrasonic method to determine case depth is TOFD.

The image at right shows a sample of carburized pipe, showing the case depth of the carburization.

The tubes are first scanned with a rapid, electromagnetic technique known as RFT.

At right: an E-PIT probe, used to gather the data to create the overview image of the furnace floor tubes (below).

The colours represent Undamaged material (green), Medium Damage (yellow) and Severe damage (red>>black)

Once the worst damage areas are defined, TOFD is applied to determine depth of damage.

For more information: info@russelltech.com, or call (780) 468-6800 (sales)