Abstract
A low emission gate valve comprising a valve body having a flow passage provided with an inlet and outlet for the inflow and outflow of fluids therethrough; a wedge located in the said passage; a stem, the lower portion of which is fixed to the wedge, for raising and lowering the wedge, to control the flow of fluids through the passage; a rotatable shaft, the lower portion of which is hollow to receive the upper portion of the stem; a drive bush, disposed over a bonnet bush, said drive bush also receiving, and threadedly engaging with, the upper portion of the stem, with the lower portion of the shaft fixed to the drive bush; a low emission packing located at a region substantially higher than the region of the bonnet bush, said packing surrounding the shaft in contact therewith; means provided for the upper portion of the shaft for rotating it, whereby, on rotating the shaft, in one direction or the other, with the shaft in rotating contact with the packing, the guide bush is constrained to rotate along with the shaft, in the corresponding direction, to cause the stem to be raised or lowered, in threaded engagement with the guide bush, to raiseor lower the wedge in the passage.
