Wedge gate valves differ from parallel gate valves in that the closure member is wedge-shaped instead of parallel, as shown in Figure. The purpose of the wedge shape is to introduce a high supplementary seating load that enables metal-seated wedge gate valves to seal not only against high, but also low, fluid pressures. The degree of seat tightness that can be achieved with metal-seated wedge gate valves is therefore potentially higher than with conventional metal-seated parallel gate valves.
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