This invention relates to an acoustic method for testing the spring in a spring-loaded mechanical device, and more particularly to an acoustic non-intrusive method for checking the set point of the spring-loaded device by monitoring the resonant frequencies of various vibration modes of the spring.
The steam pressure safety/relief valves of boiling water nuclear reactors have been identified as a major problem. One common failure mode is shifting of the pressure set point at which the valve opens outside of the allowable specifications as the result of aging of the spring and valve parts under high temperature conditions. According to applicable licensing regulations, safety/relief valves must be checked periodically for pressure set point. The existing procedure for testing the pressure set point is very costly and time-consuming. The valve, which is several feet high, must be removed from the reactor and checked with high pressure steam supply in the factory. Besides the expense and lost down time, this procedure provides little information about incipient failure. Moreover, removing the valve from the reactor and testing it with high pressure steam also increases greatly the possibility of the valve not reseating well due to the intrusion of foreign material.
The present invention is directed to an acoustic method for determining non-intrusively the set point of a spring-loaded mechanical device, in particular the set pressure of a pressure relief valve.