Flowserve 1888 Parallel Slide Gate Valve User Manual
Page 4
1.0
PHYSICAL DESCRIPTION AND OPERATION OF EQUIPMENT
1.1
Parallel Slide Gate Valves
The Flowserve Corporation Parallel slide gate valve design is unique in that
there are two independent discs. During each closing stroke, the two free
floating parallel discs are allowed to rotate 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 disc 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. Furthermore, the differential pressure on the disc surfaces is all
that is required to maintain leak tightness, and sealing is not dependent
upon stem force. 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.
2.0
DESIGN CONDITIONS
2.1
N/A
3.0
OPERATING CONDITIONS
3.1
N/A
4.0
TEST CONDITIONS
4.1
Each valve covered by this manual has received the following hydrostatic
tests with no measurable leakage:
4.1.1 A shell hydrostatic test at 1.5 times the 100
°
F pressure rating.
4.1.2 A seat leakage and disc closure test at 110% of the 100
°
F pressure
rating.