Lapping Metal Seats (C-Seal Constructions); Remachining Metal Seats - Fisher EWS Series Instruction Manual

Instruction Manual
Form 2376
March 2007
INSTALLATION
TOOL
C-SEAL
METAL
PLUG
SEAL
FLOW DOWN
NOTE:
PRESS INSTALLATION TOOL OVER VALVE PLUG
UNTIL THE TOOL CONTACTS THE HORIZONTAL REFERENCE SURFACE
OF THE VALVE PLUG.
A6778 / IL
Figure 11. Installing the C-sealt Plug Seal Using
the Installation Tool
DEFORM THREAD TO
STAKE C-SEAL RETAINER
PISTON
RING
RETAINER
C-SEAL
METAL
PLUG
SEAL
FLOW DOWN
A6779 / IL
Figure 12. Stake the Threads of the C-sealt Retainer
VALVE
PLUG
HORIZONTAL
REFERENCE
SURFACE
VALVE
PLUG
the stem. This drilling weakens the
stem and may cause failure in service.
However, a used valve plug may be
reused with a new valve stem.
2. Remove the plug/retainer assembly (with C-seal
plug seal), cage, and seat ring from the valve body
following the appropriate instructions in the Trim
Removal section of this manual.
3. Locate the staked thread on top of the valve plug
(figure 12). The staked thread secures the retainer.
Use a drill with a 1/8 inch bit to drill out the staked
area of the thread. Drill approximately 1/8 inch into
the metal to remove the staking.
4. Locate the break between sections of the piston
ring(s). Using an appropriate tool such as a
flat-blade screwdriver, carefully pry out the piston
ring(s) from the groove(s) in the C-seal retainer.
5. After removing the piston ring(s), locate the
1/4-inch diameter hole in the groove. In a retainer
with two piston ring grooves, the hole will be found in
the upper groove.
6. Select an appropriate tool such as a punch and
place the tip of the tool into the hole with the body of
the tool held tangent to the outside diameter of the
retainer. Strike the tool with a hammer to rotate the
retainer and free it from the valve plug. Remove the
retainer from the plug.
7. Use an appropriate tool such as a flat-blade
screwdriver to pry the C-seal plug seal off the plug.
Use caution to avoid scratches or other damage to
the sealing surfaces where the C-seal plug seal
makes contact with the valve plug (figure 13).
8. Inspect the lower seating surface where the valve
plug contacts the seat ring for wear or damage
which would prevent proper operation of the valve.
Also, inspect the upper seating surface inside the
cage where the C-seal plug seal contacts the cage,
and inspect the sealing surface where the C-seal
plug seal makes contact with the plug (figure 13).
9. Replace or repair trim parts according to the
following procedure for lapping metal seats,
remachining metal seats, or other valve plug
maintenance procedures as appropriate.
Lapping Metal Seats (C-seal
Constructions)
Before installing a new C-seal plug seal, lap the
lower seating surface (valve plug to seat ring,
figure 13) following appropriate procedures in the
Lapping Metal Seats section of this manual.
EW Valve
19