Lapping Metal Seats (C-Seal Constructions); Remachining Metal Seats (C-Seal Constructions) - Fisher Design ED series Instruction Manual

C-seal METAL
PLUG SEAL
VALVE PLUG
UPPER SEATING SURFACE
PLUG
LOWER SEATING SURFACE
NOTE:
1
UPPER SEATING SURFACE IS THE AREA OF
CONTACT BETWEEN THE C-seal METAL PLUG
SEAL AND THE CAGE.
A6780 / IL
Figure 10. Lower (Valve Plug to Seat Ring) and Upper
(C-seal Plug Seal to Cage) Seating Surfaces
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 10).
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 10).
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 10)
following appropriate procedures in the Lapping Metal
Seats section of this manual.
Design ED & EAD Class 125-600
RETAINER
1
CAGE
CAGE
SEAT
RING
C seal
RETAINER
PLUG
(4)
0.010 INCH
1
LOWER SEATING SURFACE
NOTE:
REMOVAL OF 0.010 INCH FROM THE VALVE PLUG
1
REMOVAL OF 0.010 INCH FROM THE SEAT RING
PLUS
2
MUST EQUAL
REMOVAL OF 0.020 INCH FROM THE UPPER
3
SEATING SURFACE IN THE CAGE
4. THESE VALUES ARE FOR EXAMPLE ONLY. REMOVE ONLY THE
MINIMUM AMOUNT OF MATERIAL REQUIRED TO REFURBISH THE
SEATS.
A6781 / IL
Figure 11. Example of Machining the Lower
(Valve Plug to Seat Ring) and Upper (C-seal Plug Seal to
Cage) Seating Surfaces
Remachining Metal Seats (C-seal
Constructions)
See figure 11. A valve plug with a C-seal metal plug
seal features two seating surfaces. One seating
surface is found where the valve plug contacts the
seat ring. The second seating surface is found where
the C-seal plug seal contacts the upper seating
surface in the cage. If you machine the seats on the
seat ring and/or plug, you must machine an equal
dimension from the seating area in the cage.
CAUTION
If metal is removed from the seat ring
and plug and a corresponding amount is
not removed from the cage seating area,
the C-seal plug seal will be crushed as
UPPER SEATING
SURFACE
(4)
0.020 INCH
3
MACHINING OF THE UPPER
SEATING SURFACE MUST
EQUAL THE TOTAL MACHINING OF
THE LOWER SEATING SURFACE
(PLUG PLUS SEAT RING). IF NOT, THE
RETAINER MAY STRIKE THE UPPER
SEATING SURFACE BEFORE THE
VALVE PLUG PROPERLY SEATS ON
THE LOWER SEATING SURFACE.
CAGE
SEAT
RING
(4)
0.010 INCH
2
15