A bidirectional pressure self-balancing stop valve includes a valve body (1), a valve disc(4), a press ring(16), a valve bonnet(17), a valve rod(19) and a balance hole(21).The valve disc (4) is located inside a chamber of the valve body(1), the press ring (16) is disposed on the upper side of the chamber of the valve body(1). The excircle of the valve disc(4), the press ring(16) and the valve body(1) form an annular groove, inside which is disposed with a composite seal ring that is high temperature resistant or corrosion resistant. The composite seal ring includes an upper washer(14), an upper seal ring(13), an upper distance ring(12), a blocking ring(11), a lower distance ring(10), a lower seal ring(8) and a lower washer(7) from top to bottom. A lower end surface (22) of the upper washer (14) and an upper end surface (25) of the upper distance ring (12) are in the shapes of a conical surface, an inclined plane or a spherical surface, formed by squeezing the upper seal ring (13) towards the internal direction of the valve disc. A lower end surface (26) of the upper distance ring (12) and an upper end surface (28) of the lower distance ring (10) are in the shapes of a cylindrical surface, a conical surface, an inclined plane or a spherical surface, formed by squeezing the blocking ring (11) towards the external direction of the valve body; and a lower end surface (29) of the lower distance ring (10) and an upper end surface (32) of the lower washer (7) are in the shapes of a conical surface, an inclined plane or a spherical surface, formed by squeezing the lower seal ring (8) towards the internal direction of the valve disc. The stop valve have pressure self sealing characteristic and long reliable sealing quality.
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