Parallel Slide Isolating Gate Valves are offered in two types - full bore and reduced bore pattern. The reduced bore pattern is particularly suitable for high pressure, high temperature steam. High-pressure valves, with bypass arrangement, have an equalising pipe as part of the bypass design to eliminate pressure build up in the intergate chamber of the valve.
Protection Of Seat Faces
When a reduced bore valve is in the fully open position, the cylindrical follower (eye piece) connects the inlet and outlet nozzles thereby providing a continuous Venturi profile through the valve bore. This gives a smooth unobstructed flow, eliminating eddies and reducing pressure drop through the valve to an absolute minimum. A further advantage of this feature is that it also gives protection to the working face of the valve seats when the valve is in the open position.
Additional Features for the Reduced Bore Valves
The area under load is less than on corresponding sizes of full bore gate valves, thereby, imposing a smaller load on the operating mechanism.
There are further advantages of using a reduced bore valve. A significant reduction in disc travel is achieved due to proportionately smaller components being used. This makes the valve more compact, a considerable advantage when space is restricted. The smaller seats and discs also reduce the load area compared to that of a full bore Parallel Slide Valve, this makes operation far easier and the overall weight much less.