The basic function of automatic control valves has not changed in the past fifty years. It only improves the fixed basic performance, such as increasing the flow coefficient, reducing noise, reducing cavitation and improving flow characteristics. However, structural design characteristics are changing very slowly. Until the advent of nuclear energy, valve manufacturers had to consider the impact of external forces such as earthquakes in valve design. This paper discusses the improvement of control valves from the perspective of anti-seismic design; such as the selection of materials, the design of drive devices, structural assembly, and assembly of parts.
Control valves for nuclear power plants must be able to withstand the effects of earthquakes. In fact, this is a necessary condition in the United States federal regulations on a wide range of topics regarding the design, construction, and operation of a countrys nuclear power plant. 10CFFR50 is the code name for Federal Equipment Production and Use Permit, and Appendix A lists the General Design Standards for Nuclear Power Plants (GDC). A paragraph in GDC-2 states: Nuclear power plant structures, devices and components must be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, howling winds ... Other GDCs can also be used as a reference for indicating the necessary conditions for the equipment to resist earthquakes and dynamic restrictions. These include GDCs 1, 1, 4, 14, and 30.
Although nominal, such unspecified common standards are practically unenforceable. As the nuclear industry matures, the seismic design and analysis of nuclear power plant equipment will become clearer. These GDCs proposed by all industrial sectors have a place in todays seismic design control valve improvements. The Nuclear Energy Regulatory Commission (NRC) has issued Standard Inspection Schemes and Standard Regulation Guidelines. Industrial organizations have also issued a series of regulations and standards called NRC required standards. Architects and utilities have also begun to publish relevant regulations, which have clear requirements for standard adjustment guidance, standard inspection schemes and permit applications. At last, Control valve manufacturers have improved the product structure design in order to meet the industrial seismic resistance restrictions.