In the late 1990’s, two of the high-pressure feedwater heaters at PSEG Power LLC’s Mercer Generating Station began to experience tube leaks after almost 40 years of operation. Prior to the repair, these leaks were occurring at least once per month. Based on eddy current and video probe inspections, the area of tube degradation appeared to be isolated to the desuperheater region of the bundle. PSEG Power LLC performed a life assessment of the feedwater heaters and, based on the good condition of the remainder of the heaters, determined that repair of the desuperheater region could improve the reliability and significantly extend the operating life of the heat exchangers. The heater condition, coupled with a repair vs. replace economic model, led to the decision to sleeve the feedwater heaters. During the April 1999 maintenance outage, Framatome ANP performed repair work on the two high pressure feedwater heaters. This repair consisted of installing an 11 foot-2 inch (3404 mm) sleeve in all outlet tube ends, spanning the desuperheating region. The sleeving method used consisted of a three step process. After the sleeve was installed, its lower end was roll expanded within the tubesheet. Next, the entire length of the sleeve in the desuperheater section was expanded into close contact with the parent tube. The final installation step was upper hydraulic expansions, above the desuperheating zone end plate, in nondefective portions of the tube. This installed sleeve became the pressure boundary in the desuperheater section of the feedwater heater. After more than 4 years of operation, no tube leaks have been noted and the need to replace the components has been eliminated for the foreseeable future.

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