PRESSURE DETECTING DEVICE

PURPOSE:To measure pressure accurately even in case of abrupt variation in the pressure of fluid to be detected by arranging a throttle resistor closer to the side of the object of pressure detection than to the axial center of a counter tube which links the object with a manometer. CONSTITUTION:When a nuclear power plant is in normal operation, the main steam pressure in a main steam pipe 44 is detected by a pressure detector 51 to judge whether a rupture accident occurs in the main steam tube or not. If a power transmission system is faulty, a main steam stop valve 43 and a turbine adjusting valve 45 are closed to cut off the supply of main steam to a steam turbine 35, so the steam pressure in the main steam tube 31 varies abruptly and a compressional wave is generated in the main steam pipe owing to the pressure variation and propagates to the pressure detecting device 51 to cause resonance at this time; and the compressional wave has the amplitude reduced by the throttle resistor 55 and is further suppressed with the condensed water in the 3rd counter tube 57, so that the amplitude of a pressure wave detected by the manometer 59 is reduced greatly.