The present application provides for apparatuses and methods for monitoring steam turbine valve assemblies. In one embodiment of the present application a method for monitoring valve assemblies is provided. First, the vibration characteristics of at least one valve assembly prior to operation may be measured. Next, the behavior of that valve assembly may be monitored during operation of the valve assembly, then compared to the vibration characteristics determined prior to operation. Comparing the valve assembly behavior monitored during operation to the valve assembly characteristics measured prior to operation may allow for estimating the stress levels experienced by the valve assembly during operation.