Fitness for Service Assessment and Repair of the Liner of a High Pressure Heat Exchanger

A high pressure carbamate condenser (HPCC) is a shell and tube heat exchanger with low pressure steam/condensate on the shell side and high pressure carbamate solution on the tube side. The inlet channel of the exchanger is protected from the internal corrosive environment by means of an austenitic stainless steel liner. During the first internal inspection after commissioning, a bulge was observed in the liner where a pass partition plate is joined to the liner. Surface-breaking cracks were observed at the partition plate to liner welds in the bulged region. The cracks were removed by shallow grinding, but a fitness-for-service assessment was required to evaluate the suitability of the bulged liner for continued service. Due to the complexity of the geometry, a handheld 3D geometry scanner was used to accurately measure the deformed shape of the bulge. Using the measured geometry, a finite element model was developed and used to perform a level 3 fitness for service assessment. This paper will describe the assessment procedure in detail as well as the complex internal repairs that were ultimately implemented in order to restore the integrity of the equipment.