Limitations of 439 SS in HP Feedwater Heater Application

This paper presents a case history of problems experienced with a replacement HP feedwater heater that was manufactured with Type 439 stainless steel tubing. The subject heater was installed after numerous problems during manufacturing and was commissioned for service in February 2007. The first failures were experienced after only 2 years of operation. Reports indicate that after the discovery of the first leaks, maintenance groups servicing the heater were never able to get the heater completely leak-tight. Ultimately, the frequency and magnitude of subsequent leak incidents that followed caused the power generating company to fully bypass the heater in September 2009. The paper offers a full chronology of events that ultimately led to the demise of subject heater. The primary objective of the paper is to share the lessons learned during the root cause analysis of the problem, including the inherent limitations related to subject tube material. Specific steps identified herein were taken by the power generating company to ensure that the technical specification for the next replacement heater would preclude any similar problems from occurring.