Study on Capacity Check Method of Feed Water Heater Safety Valves in Nuclear Power Plants

The selection of the high pressure feed water heater's safety valve usually follows the principle recommended by HEI standards in thermal power plant. However,the nuclear power plant's heaters generally need to accept a lots of drain from a moisture separator reheater( MSR). When the drain regulating valve was failure in fully open position,a large number of high pressure steam will directly goes into the heater. It make high- pressure heater have a risk of overpressure. Therefore,the safety valve selection of the heaters for nuclear power plants not only need to follow the HEI standards,but also need to check his capacity in certain special conditions. The paper established a calculation method to determine the static running point of the heaters based on characteristic equations of the feed water heater,drain regulating valve and steam extraction pipings,and energy balance principle. The method can be used to calculate the equilibrium pressure of various special running conditions,so further determine whether the capacity of the safety valve meets the requirements of safety and emissions.