High-reliability feedwater heater study: Final report

Closed feedwater heaters are used in both fossil and nuclear power plants to improve thermal performance. Escalating fuel costs are resulting in the justification for greater numbers of feedwater heaters in power plants and for larger feedwater heaters. The increasing fuel costs also make availability of feedwater heaters more critical. The lower heat rates made important by today's high fuel costs justify the need for highly reliable feedwater heating systems. Feedwater heater reliability is influenced by feedwater heater design, associated piping and control systems design, and the manner in which feedwater heaters are operated and maintained. Most feedwater heater problems appear in the form of tube failures. Many forms of tube failures are a result of improper material selection for the service. However, many failures are a result of inadequate protection against impingement at steam inlets and inadequate capacitance to avoid steam blow through the drain cooler. Other tube failures are a result of associated systems design. Insufficient venting will accelerate corrosion and can cause performance losses. Poor lay-up procedures can also accelerate corrosion and lack of maintenance of level controls can result in loss of liquid seal at the drain cooler inlet causing damage to tubes. The purpose ofmore » this report is to provide an assessment of which design features and operations and maintenance practices have the greatest effect on feedwater heater reliability. In addition, existing and new design concepts have been identified which will improve feedwater heater reliability. Further research needs for improving feedwater heater reliability have also been identified. 15 refs., 82 figs., 8 tabs.« less