Yoshihisa Kiyotoki

HHC (Hitachi Hyper Valve): Corrosion Resistant, Withstands Erosion and Low CO Release

In order to prevent valve performance deterioration by corrosion and wear against the seat (following, the valve-seat) of the valve-disc and the valve-body at fossil and nuclear power plants, a Co-base alloy is hard-faced onto the valve-seat. However, valve-seats deteriorate, for example, by corrosion, cracking and erosion. Moreover, the drift of the set point of the safety valves also occurs, by the phenomenon of Corrosion-Bonding. A valve-seat with excellent corrosion resistance, erosion toughness and mechanical toughness is sought. And, if possible, a low Co release rate material is preferred in nuclear power plants. Therefore, to improve valve performance, we manufactured a new valve named HHV with a valve seat, whose metal microstructure is different from that of conventional valve seats, within the range of chemical compositions of RCoCr-A (AWS). We also, evaluated the performance of the HHV Valve. We verified that HHV has improved valve performance. Moreover, we applied HHV under actual operating power plant conditions. The results show that HHV is superior to conventional valves in corrosion resistance, etc.© 2004 ASME