Performance and Service Life Considerations—Closed Feedwater Heaters

Because of the potential restriction of plant capacity and increases in fuel consumption cost that result from the removal of closed feedwater heaters from service, there is a need for the application of new design and operation concepts that enhance both the thermal performance and the availability of heaters and their associated systems. Practical operating practices, which take into consideration the highly localized environments in closed feedwater heaters and the individual susceptibilities to failure of the various tube materials in common use, have evolved from direct experience with closed feedwater heater problems. Many electric utilities have adapted these operating concepts in their standard operating procedure. Life extension programs for feedwater heaters that are repaired or to be replaced must include the provision for new operating concepts. Heaters that are subjected to the same operation conditions that led to the original failures may be expected to fail for the same reasons, often in a much shorter time. The acquisition of accurate data on operating performance, the location of tube distress, combined with the application of new, successful practices in feedwater heater design, operation, and maintenance, have provided the best assurance of a satisfactory service life of closed feedwater heaters.