Advanced ultrasonic and eddy current inspection of recovery boiler floor tubes

Inspection of recovery boiler floor compound tubes for surface cracking is usually done with penetrant testing. This method requires thorough cleaning of the floor. The tubes must be free from all dirt, oil and grease in order to be able to perform a reliable penetrant test. When using eddy current testing the surface only needs to be free of dirt and other obstacles: removal of grease and oil is not necessary. Eddy current testing equipment for boiler floor tubes has been developed and includes an eddy current device, computer and a carriage for the probes. These probes are designed to detect cracks initiating from the side fillet welds to the tubes and cracks initiating on top of the tube. The resolution is highest near the welds and on top of the tube. Results show improved crack detectability compared with penetrant testing. Local corrosion in compound tubes also can be detected and distinguished, and the testing of carbon steel tubes for surface cracking has been researched. The results of the eddy current test are recorded with the help of a probe locator and custom software. Computerized ultrasonic testing has been used for thickness measurement of carbon steel tubes. Thickness measurements are made over the whole length of the tubes and minimum thicknesses are recorded within a chosen interval. The equipment makes possible quick thickness measurements of whole floor areas.

Keywords:

• Recovery Boiler
• Non-destructive Testing
• Eddy Current
• Ultrasonic