Gate valves, also referred to as sluice valves, have a barrier, the 'gate', that lifts out the path of flow. Gate valves were once the most widely used valves in industrial piping systems, however their popularity has now been replaced by ball valves.
A gate valve is operated by turning a handwheel, key cap or other mechanism which acts on a long screw thread to raise and lower the gate. Although a gate valve requires many turns to open and close it fully, the handle takes up a small amount of space compared with a ball valve which requires space for the handle to be turned.
Gate valves are not suitable for variable flow control or throttling as the seating is perpendicular or at right angles to the direction of flow. Repeated movement of the wedge (gate) near the point of closure under high velocity flow, may create a drag on the seating surfaces and causing galling or scoring on the down stream side. A slightly opened edge may cause turbulent flow with vibration and chattering of the wedge.
Gate valves are ideal for maintaining complete shutdown of a line with infrequent opening operations as the handwheel may take some time and effort to completely open the valve. Knife gate valves (with a thin rigid gate) can be used with slurries, fibres and powders that might otherwise accumulate inside a ball valve.
