Butterfly valve method and apparatus

摘要

A method for exploiting the net torque exerted by a conveyed fluid on the valve plate of a butterfly valve to facilitate control of the valve, and a butterfly valve (40) adapted for use with the method are disclosed. The method employs translational movement of the valve plate to facilitate rotational movement of the same and to effect dynamic torque balancing. The butterfly valve (40) employs a differential gear (50) as a mechanical resolver to produce either rotational or translational components of movement depending on whether the net torque exerted by the fluid is sufficiently high to overcome impedance to translational movement.