| 摘要 |
A valve with redundancy on closing comprises a single valve body, first and second substantially hemispherical hollow valve members disposed inside said valve body, each including an orifice allowing fluid to pass therethrough, independent first and second rotary drive means for the first and second hemispherical valve members, and first and second sealing devices each comprising at least one annular gasket and each associated with a respective one of the first and second valve members, the first and second valve members being of different diameters and one being nestable inside the other. It is preferable for at least one of the sealing devices to be retractable so as to avoid confining fluid inside the valve.
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