AVARIS: An Innovative Process to Repair Seal Seat Surfaces in Gate and Check Valves

Abstract

AREVA Valve Repair in situ – AVARIS in short – is an innovative process for repairing valves in situ, i.e. in the assembled state. This novel technology allows the body of seal seats of gate and check valves to be worked on and reconditioned in the power plant, in their position without extracting them. An application for a patent has already been filed for AVARIS on a global scale. Until now, damaged seal seat surfaces were grinded off to recondition them and to restore their planity. However, each grinding process also reduces the thickness of the residual hardfacing layer. Finally, the residual hardfacing layer disappears completely and parts of the base material are worn. As the valve’s base material is much softer than the hardfacing material, the valve’s sealing function is no longer guaranteed. Instead of replacing the valve body and cutting it out of the piping system, AREVA has developed the AVARIS valve repair process and filed an application for patent. This new process is used to recondition the bodies of gate and check valves while they are in place, and it is even applicable in places that are difficult to access. The essential steps of the refurbishment include turning down of the worn seal seats, overlay welding of the new hardfacings and finish turning. A grinding process is used to finish the surface quality. AVARIS offers great advantages for the global maintenance market because time, effort and costs are saved. This new technology has been successfully applied in various valve reconditioning projects in German and French nuclear power plants since 2010. Further follow-up orders in German and international plants such as in France and Sweden show that valve refurbishment with AVARIS heads to establish itself as a reliable and flexible process in power plants worldwide.