Patent ID: 8036837

Claim:
A method of detecting a spring failure in a pneumatic control valve actuator comprising: determining an initial spring constant value (K initial ) of a set of springs of an actuator in a control valve during a first period of operation; receiving from a travel sensor an indication of a travel distance (ΔT) of an actuator rod coupled to the actuator; receiving from a pressure sensor an indication of a change in applied pressure (ΔP) to the actuator, wherein the change in applied pressure corresponds to the travel (ΔT) of the valve; determining in a processor communicatively coupled to the valve actuator a current spring constant value (K current ) of the set of actuator springs during a second period of operation of the control valve based on the sensed travel distance (ΔT) and corresponding sensed pressure difference (ΔP); and generating in the processor an indication of a spring defect if the current spring constant value (K current ) is different from the initial spring constant value (K initial ) by more than a predetermined threshold.