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GE Oil & Gas
4.4 VARIPAK 28002 Cv ADJUSTMENT
This adjustment is carried out by moving adjustment
knob (24) along adjustment plate (25) fastened to the
top of lever No. 1 (21). See section “Adjusting the Cv
of a Varipak 28002 valve for each plug and seat ring
combination”, page 7.
4.5 POSITIONER START-UP PRESSURE ADJUSTMENT
(Figures 7, 25, 26 and 27)
A. Connect the air supply and signal lines to the 7700P
or 7700E (with electrical signal) positioner.
B. Set the supply pressure according to the valve Cv
value (see the table in figure 3).
C. Set the signal to the minimum value for an Air-to-
Open actuator, and to the maximum value for an Air-
to-Close actuator. Turn take-up screw (116) until the
piston rod just begins to move. Tighten locknut (117).
5. Maintenance
Caution: Always ensure that there is no
pressure in the valve, actuator, or positioner
before maintenance or disassembly.
5.1 ACTUATOR DIAPHRAGM REMOVAL
(Figures 17, 24, 25, 26 and 27)
A. Unscrew the two pressure connection nuts (138a)
and pull tubing (140) out. Remove the four cap screws
(139) and diaphragm cover (137). Remove the worn
diaphragm. Form new diaphragm (136) and fit it on
the piston as shown in figure 17. Fit the diaphragm
roll into the bracket groove. Take care not to twist
or bend the diaphragm during replacement. Refit
diaphragm cover (137) with the four screws (139)
and reconnect the tubing with the two pressure
connection nuts (138a). Check that all connections
are leaktight.
Figure 17 - Diaphragm replacement
5.2 ADDING PACKING RING (Figures 18, 26 and 27)
A. Before adding packing ring, the valve must be
isolated and all pressure released. Remove packing
flange nuts (8b), lift the packing flange and follower,
and insert a new packing ring. Tighten nuts (8b)
finger tight and then tighten one full turn with the
wrench.
Figure 18 - Adding a packing ring
