In addition to BTF’s, erosion damage to non-pressure part components can result in costly maintenance and repair to ductwork, structural members, heat exchangers and ash separation equipment.

Solutions to these chronic erosion problems involve flow modification for redistributing of fly ash and reduction of flow in regions with serious erosion problems. Flow modification devices include vanes, baffles and expanded metal screens. The underlying assumption for the use of flow modification, as an erosion control strategy, is that erosion is localized and not occurring widely across any given region of the boiler. If widespread erosion exists, other means would be required to correct the problems; such as: derating, fuel change or redesign of pressure parts or other effected components.

Selection and placement of particular flow control devices is based upon a knowledge of the unit’s erosion history (Boiler Assessment) and some type of testing for measuring gas flow (see flow chart at left). Testing most often means a cold air velocity test (CAVT) in the unit at ambient conditions. In lieu of a CAVT, a physical or computer model can be used when unit testing is not possible.

Check the Erosion Control Program section to learn about options for running a program at your site.