Flowserve Double-Disc Gate Valve Sizes 2.5 - Manual (Page 26)

Anchor/Darling Double Disc Type Gate Valves FCD ADENIM0003-01 - 07/14
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8.1.2 The lower wedge and wedge spring can now be positioned
on the upper wedge. Assemble the discs, disc retainers and
fasteners onto the wedge assembly.
8.1.3 Slide the stem T-head into the corresponding T-slot of the upper
wedge.
8.1.4 Retain the discs on the disc stem assembly with a C-clamp and
lower the assembly into the body. Once the discs are secured
by the guides in the body, the C-clamps may be removed and
the assembly lowered the rest of the way in place.
8.1.5 Check the location of the discs relative to the seat rings to
determine if they are properly positioned to cover the seats. It
may be necessary to remove material or add material to the
lower wedge feet to properly position the discs.
8.1.6 Caution: Proper fit-up (clearance confirmation) of the disc
retainers must be confirmed, especially if any new valve internal
parts are used or if seating surface lapping has been performed.
With the disc pack in the valve body and fully seated a 1/8”
clearance (minimum) shall be confirmed between the wedge
side of the disc retainer and the mating surface of the disc
retainer groove of each disc. If this clearance is less than
1/8”, the disc engaging end of the corresponding disc retainer
shall be machined to establish the required clearance. After
modification the clearances shall be rechecked to confirm.
NOTE: Disc retainers supplied as spare parts are furnished
without disc retainer holes. Prior to drilling, the disc retainers
must be properly located by placing the disc on the upper
wedge and positioning the disc retainer on the wedge, in
the disc groove against the disc. Slide the disc up as far as
possible as limited by the disc trunnion hole in the upper
wedge. Raise the retainer another 1/16” to properly locate
it. Drill the disc retainer fastener hole (1/16” dia. larger than
fastener nominal diameter) in the retainer. Repeat the above to
locate the other disc retainer on the opposite side and drill the
fastener hole.
8.2 Bonnet – flanged joint
8.2.1 Prior to lowering the bonnet (002) into position, a new gasket
should be placed in the gasket groove on the body flange.
Carefully insert the stem into the backseat bushing in the bonnet
and lower it into position on the body. In lowering the bonnet
be careful that neither the backseat nor the stem are scratched
or gouged. Damage to either of these surfaces can impair their
sealing ability. If orientation of the actuator is important, the
bonnet should be rotated to its proper position prior to lowering
it onto the gasket. With the bonnet in place, the studs (200)
and nuts (230) can be installed. Prior to installation the studs
and nuts should be cleaned and thoroughly lubricated with a
high quality lubricant. Any nuts or studs with damaged threads
should be replaced (refer to figure 13).
8.2.2 It is very important that the body-bonnet bolting be torqued to
specific values in accordance with a specific procedure. The
torque values are shown in Table 2 for various diameter studs.
8.2.3 The nuts should be tightened evenly using a crisscross pattern
similar to the one shown in Fig. 21. Tighten all of the nuts
to 1/3 of the recommended value initially. Then repeat the
sequence raising the torque to 2/3 of full torque. Finally, torque
all the nuts to the recommended value following the crisscross
pattern. It is essential that the flange faces remain parallel and
all the bolting has uniform tension. Failure to achieve this may
cause gasket weepage when the joint is subjected to operating
pressures and temperatures.
8.2.4 Lower the yoke over the stem. And install and tighten the yoke
capscrews.
8.3 Bonnet – pressure seal joint
8.3.1 Lower the bonnet over the stem and into the neck of the body.
Care must be taken in lowering the bonnet on the stem, so that
neither the backseat nor any surface of the stem is damaged.
It is also very important to keep the bonnet from cocking as it
is lowered into the body. If it does bind, the bonnet must be
straightened before insertion can continue.
Measuring from the bonnet bolting surface to the top of the
body is the simplest way to detect cocking.
8.3.2 With the bonnet resting on the counterbore in the neck, a new
gasket (030) and the spacer ring (032) can be inserted. The
gasket must also be inserted with care. Once these are in
place, the four-piece gasket retainer can be put into place. It
is important to remember that the piece with the drilled hole
must be positioned last. If the valve is installed in other than
a stem vertical position, it may be necessary to orient or hold
the retainer such that the pieces stay in place until the bonnet is
moved into its raised position (refer to figure 16).
8.3.3 With the gasket retainer in its proper position, the bonnet
retainer (034) can be lowered over the stem and placed in
its position on top of the body neck. The bonnet capscrews
(216) should then be inserted through the bonnet retainer and
threaded into their holes in the bonnet (refer to figure 16).