Replacement Of Installed Bore Seal Trim; Trim Removal (Bore Seal Constructions) - Fisher EHD Instruction Manual

Instruction Manual
April 2009
appropriate instructions in the Trim Replacement
section of this manual.
7. Install piston rings by following instructions in the
Trim Replacement section of this manual.
8. Remove the existing valve actuator and bonnet
following the appropriate instructions in the
Replacing Packing section of this manual.
CAUTION
Do not remove the existing valve stem
from the valve plug unless you are
planning to replace the valve stem.
Never reuse an old valve stem with a
new plug or reinstall a valve stem after
it has been removed. Replacing a valve
stem requires drilling a new pin hole in
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.
9. Remove the existing valve stem and plug, cage,
and seat ring from the valve body following the
appropriate instructions in the Trim Removal section
of this manual.
10. Replace all gaskets according to appropriate
instructions in the Trim Replacement section of this
manual.
11. Install the new seat ring, cage, valve
plug/retainer assembly, and stem into the valve body
and completely reassemble the valve package
following the appropriate instructions in the Trim
Replacement section of this manual.
CAUTION
To avoid excessive leakage and seat
erosion, the valve plug must be
initially seated with sufficient force to
overcome the resistance of the Bore
Seal plug seal and contact the seat
ring. You can correctly seat the valve
plug by using the same force
calculated for full load when sizing
your actuator. With no pressure drop
across the valve, this force will
adequately drive the valve plug to the
seat ring, thus giving the Bore Seal
EH Valves (NPS 8 through 14)
plug seal a predetermined permanent
set. Once this is done, the
plug/retainer assembly, the cage, and
the seat ring become a matched set.
With full actuator force applied and the
valve plug fully seated, align the
actuator travel indicator scale with the
lower end of valve travel. Refer to the
appropriate actuator instruction
manual for information on this
procedure.
Replacement of Installed Bore Seal
Trim

Trim Removal (Bore Seal Constructions)

1. Remove the valve actuator and bonnet following
the appropriate instructions in the Replacing Packing
section of this manual.
To avoid leakage when the valve is
returned to service, use appropriate
methods and materials to protect all
sealing surfaces of the trim parts
during maintenance.
Use caution when removing piston
ring(s) and the Bore Seal plug seal to
avoid scratching any sealing surface.
Do not remove the valve stem from the
plug/retainer assembly unless you are
planning to replace the valve stem.
Never reuse an old valve stem with a
new plug or reinstall a valve stem after
it has been removed. Replacing a valve
stem requires drilling a new pin hole in
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 Bore
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 7). The staked thread secures the retainer.
CAUTION
CAUTION
15