Trim Removal - Fisher Design CAV4 Instruction Manual

Design CAV4
Table 6. Valve Body-to-Bonnet Bolting Torque
VALVE SIZE, VALVE SIZE,
INCHES
2
3
4
6
12. Install new packing and the metal packing box
parts according to the appropriate arrangement in fig-
ure 5. Slip a smooth-edged pipe over the valve stem,
and gently tamp each soft packing part into the pack-
ing box.
13. Slide the packing follower (key 22), wiper (key 21,
not used with graphite ribbon/filament packing), and
packing flange (key 16) into position. Lubricate the
packing flange studs (key 14) and the faces of the
packing flange nuts (key 15). Replace the packing
flange nuts.
For spring-loaded PTFE V-ring packing, tighten
packing flange nuts (key 15) until the shoulder on the
packing follower (key 22) contacts the bonnet (key 12).
For other packing types, tighten the packing flange
nuts (key 15) to the maximum recommended torque
shown in table 5. Then loosen the packing flange nuts,
and retighten them to the recommended minimum
torque in the table.
14. Mount the actuator on the valve body assembly,
and reconnect the actuator and valve stem according
to the procedures in the appropriate actuator instruc-
tion manual. After the valve is returned to service, re-
tighten the hex nuts (key 27) to the torques listed in
table 6.

Trim Removal

The 3-inch CAV4 valve is a clamped-in
trim design. No cage retainer is used.
See figure 10. Therefore, if you are using
these instructions for a 3-inch valve, dis-
regard references to a cage retainer.
The valve trim consists of the valve plug and stem as-
sembly (key 4), the valve plug rings, if used, (keys 8,
9, 10, 11, and 37), the upper cage (key 3), the cage
retainer (key 5), the lower cage assembly (key 2), the
separable seat ring (key 35, seal ring construction
only), the upper and lower bonnet gaskets (key 6), and
the cage gasket (key 7).
During trim removal, inspect the seating surface of the
plug and lower cage or seat ring. Also inspect the in-
side diameter of the lower cage. If the seating surfaces
8
TORQUE
NSm LbfSft
974 717
1058 780
1776 1310
2712 2000
Note
need to be refinished, or if the inside diameter of the
lower cage has plugged holes, deep scratches, or oth-
er signs of wear, the cage retainer and lower cage as-
sembly must be removed. A seat ring or lower cage
assembly and cage retainer in good condition may
both remain in the valve body.
A cage retainer tool is required to remove the cage
retainer and lower cage assembly. If specifically or-
dered, a tool is supplied with the valve. It can also be
ordered individually by referencing the tool part num-
ber included in the Parts List of this manual. A tool can
also be machined for a specific valve using the dimen-
sions shown in figure 6.
Machine the tool from a material listed in
figure 6, or from a material with a yield
strength of at least 827 MPa (120,000
psi). Using a tool of lower strength may
result in damage to the valve body
threads.
CAUTION
Careful handling and installation of trim
parts is extremely critical on all Design
CAV4 valves. Any damage to gasket and
seal surfaces of the cage or valve body,
or valve plug and cage seating surfaces
can result in leakage that can cause
eventual damage to the cage and valve
body due to erosion and cavitation.
1. Remove the actuator (not shown), bonnet (key 12)
and packing by following steps 1 through 7 of the
Packing Replacement section.
CAUTION
When lifting the valve plug and stem as-
sembly out of the valve body, be certain
the upper cage (key 3) remains in the
valve (key 1). This will prevent damage
that might be caused by the upper cage
dropping back into the valve after being
lifted part way out. Use care to avoid
damaging gasket sealing surfaces.
The 6-inch Design CAV4 graphite piston
rings (key 11) are brittle and in two
pieces. Use care to avoid damage to the
piston rings caused by dropping or
rough handling.
Note