Flowserve 1888 Double-Disc Gate Valve - Manual (Page 4)

4
1.0 PHYSICAL DESCRIPTION AND OPERATION OF EQUIPMENT
1.1 Double-Disc Gate Valves
The double-disc design is unique in that there are two independent discs. During each
closing stroke, immediately prior to the disc seating, each disc rotates a few degrees in
the plane of the seats. This rotating feature allows the disc to seat in a different position
on each closing stroke, providing for equal wear and preventing small imperfections from
being agitated into major leakage problems.
The wedge assembly is designed to impart sufficient thrust to each disc to maintain
acceptable low-pressure seat leakage. As the differential pressure across the disc
increases, the seating load also increases, thus maintaining acceptable leakage through
the entire range of operating differential pressures. Since the discs are completely
independent of each other and the design is essentially symmetrical, zero leakage can
be maintained in either direction, depending only on the direction of flow. This feature
eliminates the necessity of installing a check valve to stop reverse flow.
To operate these manual valves, turn the tee handle in a clockwise direction for closure
and counterclockwise for opening.
1888-lb. Double-Disc Gate Valve FCD ADENIM0001-00