SEBIM relief valve is mainly used in safety important system of the nuclear power plant to provide the overpressure protection for the pressure vessel and pressure pipeline which related to the nuclear safety. It is probable that the system will lose the overpressure protection function and lead to a major security hidden danger in the nuclear power plant if the relief valve setting value happens drift. So the problem of the SEBIM relief valve setting value drift has becoming the focus of attention of the whole nuclear industry.
It is of great significance to study the setting value drift condition of SEBIM relief valve in the practical application. This paper analyzes the structure and operating principle of the SEBIM valve, and studies the main failure mode of the setting value drift of SEBIM relief valve combining with the operating environment of the equipment. And this paper collects the setting value check data of the SEBIM valve used in two domestic nuclear power plants (These two power plants are named NPP A and NPP B in this paper) during its operation period, and carries on the analysis and evaluation.