Research on Improvement of Pilot Solenoid Valve for Emergency Diesel Generator in Nuclear Power Plant

The pilot solenoid valve used in the compressed air start-up system of emergency diesel generator in nuclear power plant fails frequently, and the failure modes are mainly manifested as inability to switch normally and jamming and air leakage. This failure will affect the reliability and availability of the compressed air start-up system of diesel generator and directly lead to the failure of diesel generator to start. In order to solve this problem, the defects in the structural design of the pilot solenoid valve were found through functional testing and disassembly, and it was clear that the root cause of the failure was the unreasonable reset structure of the pilot solenoid valve. The improvement measures mainly include the improvements of the main valve body structure, spool assembly interference structure, main spool guide structure, main spool return spring, diameter of the moving iron core crimping nozzle and the coil power of the pilot solenoid valve. The improved solenoid valve successfully completed all qualification tests. The test results show that the improved solenoid valve solves the failure of normal switching and jamming and air leakage, and improves the reliability of the air starting circuit of the emergency diesel generator.