Furnace tubes that are made of a high-chrome material can carburize when in hydrocarbon service.

Coker furnaces, found in oil refineries,are particularly susceptible to carburization.

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

followed by a TOFD (Time of Flight Diffraction) technique to accurately measure case depth.

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

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)