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

EW Valve
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 13. Lower (Valve Plug to Seat Ring) and Upper
(C-sealt Plug Seal to Cage) Seating Surfaces
Remachining Metal Seats (C-seal
Constructions)
See figure 14. 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 the valve closes and the
C-seal retainer will strike the seating
20
RETAINER
1
CAGE
CAGE
SEAT
RING
C-seal
RETAINER
PLUG
(4)
1 0.010 INCH
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
3 REMOVAL OF 0.020 INCH FROM THE UPPER
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 14. Example of Machining the Lower
(Valve Plug to Seat Ring) and Upper (C-sealt Plug Seal to
Cage) Seating Surfaces
area of the cage, preventing the valve
from closing.
Trim Replacement (C-seal
Constructions)
1. Apply a suitable high-temperature lubricant to the
inside diameter of the C-seal plug seal. Also,
lubricate the outside diameter of the valve plug
where the C-seal plug seal must be pressed into the
proper sealing position (figure 9).
2. Orient the C-seal plug seal for correct sealing
action based on the process fluid flow direction
through the valve.
D The open interior of the C-seal plug seal must
face up in a valve with flow-up construction
(figure 9).
Instruction Manual
Form 2376
March 2007
UPPER SEATING
SURFACE
(4)
0.020 INCH 3
MACHINING OF THE UPPER
SEATING SURFACE MUST
EQUAL THE TOTAL MACHINING
OF THE LOWER SEATING SUR-
FACE (PLUG PLUS SEAT RING).
IF NOT, THE RETAINER MAY
STRIKE THE UPPER SEATING
SURFACE BEFORE THE VALVE
PLUG PROPERLY SEATS ON
THE LOWER SEATING SUR-
FACE.
CAGE
SEAT
RING
(4)
0.010 INCH 2