Advances in the Design and Qualification of Main Steam and Main Feedwater Isolation Valves (MSIV and MFIV) With Type A, Gas Hydraulic Actuators

Flowserve and its heritage companies have supplied valves for many of the critical applications within commercial nuclear power generation plants since the beginning of commercial nuclear power generation. Two of these highly critical applications are the Main Steam Isolation Valves (MSIVs) and the Main Feedwater Isolation Valves (MFIVs). As the requirements of these two applications have evolved, so have the applicable valve and actuator designs and their qualifications. Although functional qualification standards (ASME QME-1) for power operated valve applications have been developed within the US nuclear industry, their use is relatively new within the US. In order to globally supply these valves, Flowserve has functionally qualified its MSIVs and MFIVs to this standard. In addition to the valves, the actuators have also evolved. Flowserve’s type A, gas / hydraulic actuator has been updated to improve its reliability and provide better performance for the power plants. The updated Flowserve type A, type A, gas / hydraulic actuator has completed the Environmental Qualification testing in accordance with the requirements of IEEE 323, 344 and 382. The Flowserve MSIV and MFIV designs have been selected for installation in many of the new Generation 3 and Generation 3+ nuclear power generation plants. This paper briefly discusses: • The history of the MSIV and MFIV valve applications within the nuclear power generation plants and • The Flowserve MSIV and MFIV, ASME QME-1 functional qualifications. Major paper emphasis is placed on: • The latest updates to the Flowserve type A, type A, gas / hydraulic actuator design, and • The latest results of the Flowserve type A, gas hydraulic actuator environmental qualification to IEEE 323, 344 and 382.