US Patent 10100607 High temperature, bi-directional shear seal and related methods

A valve includes an outer piston, an inner piston telescopically disposed in the outer piston. A cavity separates at least a portion of the inner piston and the outer piston. The valve also includes a seal disposed in the cavity and that forms an upper pressure chamber and a lower pressure chamber. A first flow space connects the lower pressure chamber with a first flow path and a second flow space connects the upper pressure chamber with a second flow path. A biasing member engages the inner and outer piston.