Inspection for cracking in black liquor recovery boilers

This paper presents an overview of cracking that has been found in recovery boiler tubes. The inspection techniques used to find cracking are discussed and examples given of typical cracking. Particular attention is given to cracking of composite tubes in recovery boiler Boors, water walls, and smelt spout openings. There are as yet, no established conditions for the occurrence of cracking so all recovery boilers with composite tubes should be considered for inspection regardless of design and operating conditions, including temperature, pressure, and chemistry.