Improving Boiler Reliability Through NDT

TesTex, Inc. has worked with numerous utilities that experienced Boiler Tube Failures in areas such as water walls, superheaters, reheaters, etc. In this presentation we will discuss specific areas of a given boiler describing what problems (failures) the units were experiencing and what solutions were implemented. We will also discuss various failure mechanisms for boiler tubing, the causes, and various Non-Destructive Testing (NDT) methods used to locate and identify these flaws. Some specific case studies of boiler tube failures are listed below. Xcel Energy-Valmont Station, Boulder, CO Boiler: This 166mw Coal Fired Boiler was experiencing water wall tube failures due to corrosion cells and hydrogen damage. This unit has been inspected with Low Frequency Electromagnetic Technique (LFET) four times over the last seven years. This unit has gone from experiencing tube failures every two weeks to only having 1–2 failures per year. Western, PA Power Plant: This 835 MW Coal Fired Boiler was experiencing reheater tube failures due to oxidation pitting in their horizontal sections. Sections of this reheater were inspected with the Low Frequency Electromagnetic Technique using Low Profile scanners to access the bottom half of the tubes in the horizontal sections. Several flaws were found and repairs were made. Similar inspections were also performed in the plant’s other two boilers where no defects were found. These inspections helped the plant locate and make repairs to flawed regions in the boilers. Their run-time between boilers tube failures has risen significantly.