Flowserve Double-Disc Gate Valve Sizes 2.5 - Manual (Page 5)

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Anchor/Darling Double Disc Type Gate Valves FCD ADENIM0003-01 - 07/14
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and high sealing pressure. The greater the valve pressure the
tighter the seal. No bolting force is required to maintain the
seal although the bonnet is initially drawn into contact with the
pressure seal by cap screws.
1.3.2 Disc Assembly: The Anchor/Darling Double Disc assembly
(Fig. 5) consists of dual floating discs with a two piece wedging
mechanism between them. Trunnion on the back of each disc
fit into holes in the upper wedge. The upper wedge in turn is
connected to the stem, which allows it to serve as a carrier
for the discs. A lower wedge is loosely hung on a land on the
upper wedge between the discs.
As the disc assembly is lowered into the seat (Fig. 6), the lower
wedge contacts a bridge in the bottom of the body between the
seats. Further travel of the upper wedge (Fig. 7) causes it to
contact the lower wedge on the beveled interface and spread
both the wedges and the discs out against the seats.
When the stem is raised, the upper wedge immediately pulls
away from the lower wedge, eliminating the force of the discs
on the seat.
Body seat rings are set into machined recesses in the body
which support and retain the rings (Fig. 8). A seal weld is
provided between the body and the rings. This weld is for
sealing only and is not structural. The seat rings are replace-
able.
1.3.3 Valve Actuation (Topworks)
A gate valve is actuated by moving the disc assembly in and out of
the seats with the stem. The necessary thrust for opening or closing
is imparted to the stem by the valve actuator which is supported
and restrained by the yoke structure. Five (5) types of actuators are
normally supplied; handwheel, manual gear, electric motor, pneumatic
cylinder and hydraulic cylinder. The first three impart rotary motion to a
stem nut which converts the rotary motion to linear stem movement via
Figure 4
Figure 3
Figure 2