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GE Oil & Gas
N. Admit the signal and supply pressure and complete
calibration. Refit cover (110) using the two screws
(109). If the valve is equipped with a handwheel, refit
the cover, then turn the handwheel clockwise until
it is engaged in lever arm stop (122). Tighten cover
screws (109).
O. If the valve body has been removed, reinstall it taking
the precautions given under "Valve Installation" on
page 10. Put the valve back into service.
5.5 PACKING QUICK CHANGE METHOD (ONLY FOR
VALVES WITH MAX. Cv OF 0.6 TO 3.8)
(Figures 21, 26 and 27)
The quickest and easiest way to replace packing is
to remove the entire actuator from the valve body,
taking care not to modify the actuator setting. This
method is not recommended, however, for valves with
a maximum Cv less than 0.6 because of their extremely
fine plugs. For these valves, disassemble the valve to
replace the packing (see "DISASSEMBLY", page 15).
Figure 21 - Packing replacement (for Cv maxi ≥ 0.6)
Vent the valve pressure and proceed as follows:
A. Check that the plug is not resting on the seat ring.
For valves equipped with an Air-to-Open actuator,
admit air pressure under the diaphragm and turn the
handwheel to move the plug off its seat ring.
B Remove safety pin (11) from the valve body. The
safety pin stub engages with the hole in packing
spacer (5). The function of the safety pin and spacer
is to prevent the plug from being pushed out if the
actuator is accidentally removed while the valve is
still pressurized. The internal parts of the valve cannot
be removed unless the safety pin is removed first.
Remove the two packing flange nuts (8b) and back off
the two actuator bracket mounting nuts (8a) as far as
possible.
C. Remove the actuator-plug assembly from the valve
body, tapping it off with a block of wood and mallet if
necessary. Clean the packing box in the valve body.
Remove the worn packing, then clean the plug stem
thoroughly. Carefully fit new packing rings around
the stem, positioning the skive cut of each ring 120°
from that of the adjacent ring.
D. Refit the actuator-plug assembly on the valve body,
taking care to: - align hole in packing spacer (5) with
safety pin (11) hole,
- and refit the two mounting nuts (8a).
- Take extra care when guiding each packing ring
into the packing box.
E. Wind two layers of PTFE tape around the safety pin.
Screw the pin into the bonnet five and a half to six
turns as from the thread engagement point.
Note: To determine the thread engagement point:
- Screw the safety pin about one turn,
- Pull the safety pin out while unscrewing it.
F. Refit the packing follower, packing flange, and flange
nuts (8b). Tighten the packing assembly correctly. If
the valve is equipped with an Air-to- Open actuator,
release the air pressure or turn the handwheel to
bring the plug back into contact with the seat ring.
Put back into service.
5.6 7700P OR 7700E POSITIONER MAINTENANCE
(Figures 22, 23, 24, 25, 26 and 27)
Caution: Shut off the signal and supply
pressure. Isolate and depressurize the valve
body.
A. Disconnect the two pressure connection nuts (138a)
and pull tubing (140) out.
