Abstract: A valve, such as a butterfly valve, having an offset closure vane supported on stub shafts for operating the vane in the flow passage of the body, has all exposed and/or potentially vulnerable metal surfaces encapsulated in a corrosion resistant polymeric plastic coating. Annular seals of resilient composition bonded to a steel insert are formed with an annular radial recess at an axially intermediate location and are positioned on the vane shafts axially squeezed between vane and body bosses thereat. In this arrangement, controlled deflection is provided by the seals in effecting a positive sealing pressure whereby the shafts are protected against exposure to line content. At the same time, the seals are rendered self-packing in response to pressure of line content while also functioning to assure concentric centering of the vane in the body passage.