Design CAV4
13
For TSO (tight shutoff) trim, perform the following
steps (refer to figures 7 and 8).
Thread the outer plug onto the inner plug until the
parts seat metal to metal, using a strap wrench or simi-
lar tool that will not damage the outer plug guide sur-
faces.
Mark the top of the inner plug and outer plug with
alignment marks in the assembled position.
Disassemble the outer plug from the inner plug
and install the seal over the inner plug, so that the seal
rests below the threaded area.
Thread the outer plug onto the inner plug and
tighten with a strap wrench or similar tool until the
alignment marks line up. This will ensure that the plug
parts are metal to metal and the seal is compressed
properly. Do not damage the outer plug guide sur-
faces.
Install set screws centering the inner plug in the
outer plug and torque to 11 N
m (8 lbf
ft).
Assemble the piston ring, anti-extrusion rings,
backup ring, and retainer.
6. Slide the valve plug and stem assembly (key 4) into
the cages.
7. Place a new upper bonnet gasket (key 6) onto the
upper cage (key 3) as shown in figure 10.
8. Install the bonnet (key 12) over the valve stem and
onto the valve body (key 1).
9. Lubricate the threads of the studs (key 28) and the
faces of the hex nuts (key 27) with lubricant (key 18 or
equivalent)(not necessary if new factory prelubricated
hex nuts are used). Replace the washers and hex nuts
but do not tighten them. Torque the nuts in a criss-
cross pattern to no more than 1/4 of the nominal
torque value specified in table 6. When all nuts are
tightened to that torque value, increase the torque by
1/4 of the specified nominal torque and repeat the
crisscross pattern. Repeat this procedure until all nuts
are tightened to the specified nominal value. Apply the
final torque value again and, if any nut still turns, tight-
en every nut again.
10. Install new packing and packing box parts per
steps 12 and 13 of the
Packing Replacement section.
11. Mount the actuator by following the procedures in
the appropriate actuator instruction manual. Check for
packing leakage as the valve is being put into service.
Retighten packing flange nuts as required. After the
valve is returned to service, retighten the hex nuts (key
27) to the torque listed in table 6.
CAUTION
The soft metal seat life can be seriously
shortened if the following step is not
carefully completed.
12. Isolate the valve from the process and stroke the
plug at least three times with maximum actuator force
to seat the plug surface against the soft metal seat.
Use of Flushing Trim
Install the flushing trim (figure 11) prior to system
flushing in order to protect the Cavitrol IV trim and the
valve body gasket surfaces.
Gaskets (keys 6 and 7) that have not been in service
(i.e., original gaskets in a Design CAV4 valve being
installed or new gaskets for a valve already installed)
may be used with the flushing trim.
Key numbers referenced in this section are shown in
figure 11, unless otherwise indicated.
1. Remove the actuator, and disassemble the valve
body by completing steps 1 and 2, and 4 through 7 of
the
Trim Removal procedure.
2. Install the lower flushing plate (key 31).
3. Thread the cage retainer (key 5) into the valve body
hand-tight.
4. Install the lower bonnet gasket (key 6), the upper
flushing plate (key 30), and the upper bonnet gasket
(key 6).
5. Place the bonnet (key 12, figure 10) on the valve
body. Lubricate the threads of the studs (key 28) and
the faces of the hex nuts (key 27) with lubricant (key
18 or equivalent) (not necessary if new factory prelu-
bricated hex nuts are used). Replace the washers and
hex nuts but do not tighten them. Torque the nuts in a
crisscross pattern to no more than 1/4 of the nominal
torque value specified in table 6. When all nuts are
tightened to that torque value, increase the torque by
1/4 of the specified nominal torque and repeat the
crisscross pattern. Repeat this procedure until all nuts
are tightened to the specified nominal value. Apply the
final torque value again and, if any nut still turns, tight-
en every nut again.
6. After system flushing is completed, remove the
bonnet (key 12) and bonnet gaskets (key 6), upper
flushing plate (key 30), cage retainer (key 5), lower
flushing plate (key 31), and cage gasket (key 7).
7. Assemble the valve as described in the
Trim Re-
placement procedure.