Pressurizer Manway Closure Re-Engineering

Abstract

The primary heat transport system pressurizer vessels at Darlington NGS have required a substantial maintenance of the gasketed joints. Two of these joints are the upper inspection port and the lowery manway. In at least one instance there has been erosion damage to the carbon steel sealing faces from leakage of the high energy primary fluid. In the work described in the paper, each of the two closures was re-engineered to incorporate a seal welded diaphragm in place of the gasket. This approach for which patent protection is sought, required machining and weld build up of the nozzle gasket area to facilitate seal welding of a custom diaphragm plate. The closure covers were modified to support the diaphragm and were reinstalled using the original bolting arrangement. The paper describes the re-engineering of these closures as well as the retrofit of the seal welded diaphragms in the field.