Abstract: A gate valve comprises a valve body, a stem bore which extends through the valve body, a stem which is disposed in the stem bore and which includes a first stem portion that is sealed to the stem bore, a second, smaller diameter stem portion that is sealed to the stem bore, and a gate pocket that is located between the first and second stem portions, and gate which is disposed within the gate pocket between the first and second seats.

Abstract: A gate valve comprises a valve body which includes a stem bore that extends therethrough and a seat bore that extends therethrough and intersects the stem bore generally transversely. A stem is disposed in the stem bore and includes a first stem portion that is sealed to the stem bore, a second stem portion that is sealed to the stem bore, and a gate pocket that is located between the first and second stem portions. First and second seats are each positioned at least partially within the seat bore proximate the gate pocket and each include a flow bore that extends therethrough. The gate valve also includes a gate which is disposed within the gate pocket between the first and second seats, a first actuator for moving the gate from a first position to a second position, and a second actuator for moving the gate from the second position to the first position.

Abstract: In order to provide a metal-to-metal annular seal for use in a high pressure environment typical of a wellhead assembly that is provided on a high pressure, high temperature gas well, especially circumferentially between the outside surface of a tubular part and the inside surface of a relatively massive part, where these parts are to have a fixed longitudinal position relative to one another in use: the available strength for developing the seal are determined; like tapering surfaces are provided on the two parts such as would provide an allowable interference fit when the two parts are brought to the fixed longitudinal position; portions of the outside surface of the tubular part are machined-away to leave tapered land areas, e.g. in two axially closely spaced bands, so that when the two parts are forced to assume the fixed longitudinal position, the seal bands provide an elastic seal that avoids total plastic deformation yet provide the required unit loading.