| 摘要 |
<p>A valve body includes a chamber for the flow of fluid between an inlet and an outlet thereto. The chamber includes an upper portion with an opening therethrough and a lower portion including a valve seat between the inlet and outlet openings. A valve seat insert is positioned in the valve seat and includes a pair of oppositely positioned ports communicating with the inlet and outlet openings. The valve seat insert is compressed to prevent leak paths between the valve body and the valve seat. A bonnet is positioned in the chamber upper portion and is connected to the valve body and extends upwardly therefrom. A stem is positioned for longitudinal movement in the bonnet and includes a lower portion for sealingly engaging the valve seat insert. An upper portion of the stem is connected to an actuator which extends upwardly and out of the bonnet. The stem upper portion is threadedly connected to the actuator, and the actuator is threadedly connected to the bonnet. The lead of the threaded connection between the stem and the actuator is in a direction opposite to the lead of the threaded connection between the actuator and the stem such that rotation of the actuator generates rapid nonrotational, longitudinal movement of the stem between the open and closed positions of the valve. A bellows surrounds the stem below the actuator to provide a seal around the stem between the valve body and the actuator. A stem restraining washer is clamped on the valve body in surrounding relation with the stem. Flats on the stem engage flats of the washer to prevent rotation of the stem upon rotation of the actuator to open and close the valve.</p> |
