VALVE OPERATION

摘要

An operating mechanism (40) for a valve (11) having a valve body (13) defining a valve seat (19) and a valve member (21) moveable into and out of engagement with the valve seat (19). The valve member (21) comprises a valve disc (25), a valve stem (23), and a bush (29) through which the valve stem (23) extends in threaded engagement therewith whereby relative rotation between the bush (29) and the valve stem (23) causes axial displacement of the valve stem (23) relative to the bush (29). The operating mechanism (40) comprises two operating drive sockets (104, 106) in opposed relation, each of which is drivingly connected to the bush (29). The operating mechanism (40) also comprises two unlocking drive sockets (118, 120) in opposed relation, each of which is drivingly connected to the bush (29). The drive ratio between the operating drive sockets (104, 106) and the bush (29), and the drive ratio between the unlocking drive sockets (118, 120) and the bush (29) are different from each other such that a larger torque is delivered to the bush (29) from operation of either one of the unlocking drive sockets (118, 120) in comparison to the torque delivered to the bush (29) from operation of the either one of the operating drive sockets (104, 106) for the same torque input. With this arrangement, either one of the unlocking drive sockets (118, 120) can be used for unlocking the valve; that is, to move the valve member (21) into a "just open" or throttled position in which the valve disc (25) is out of sealing engagement with the valve seat (19) without rotation of the valve stem (23). Further, either one of the operating drive sockets (104, 106) can be used for opening and closing the valve (11), as well as valve locking. Because there are two operating drive sockets (104, 106) in opposed relation, and also two unlocking drive sockets (118, 120) also in opposed relation, an operator can access the operating mechanism (40) from either side thereof according to what is more convenient.