US Patent 10030784 Ball valve tertiary seal assembly and method

A high pressure ball valve seal assembly utilizes primary, secondary, and tertiary seals to withstand debris, caustic fluids, high pressure, and high temperature. The seal assembly comprises first and second inner seats and first and second outer seats which are retained within the valve body. First inner and outer seats are mounted on a first side of a closure member in the valve cavity and second inner and outer seats mounted on a second side of the closure member opposite the first side. A plurality of sealing rings are provided, whereby the sealing rings may be arranged to provide a tertiary upstream seal physically located on the downstream side of the ball valve.