The Paradise Generation Station Unit 3 is a supercritical fossil plant with a 1,078 MW rated capacity. The #3B feedwater heater (FWH) is a two-zone (condensing and subcooling) horizontal FWH and is the second of four high pressure (HP) FWHs after the boiler feed pump in the “B” string, one of two HP FWH strings (See Figure A2 at the end of this paper for an outline drawing of the heater. The heater has 1447 SA-556-C2 Carbon Steel tubes, 3/4” OD × 0.085 min wall. The heater was built in late 2006/early 2007 and was installed in summer 2007.
After just a few years of operation, the #3B FWH experienced several failures at the entrance to the drain cooler (DC) zone. The #3A FWH, of identical construction and built and installed at the same time, did not show the same level of damage.
In order to determine the failure mechanisms involved, a post-mortem of the heater was performed. This paper shall discuss the post-mortem inspection conducted as well as the suspected and confirmed causes of failure in the heater.