Masoneilan 4700P/E & 4800P/E Positioners Manual =| 49
© 2015 General Electric Company. All rights reserved
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Cam Lobe Change
If it is necessary to change the cam lobe only (without changing actuator action or positioner ac-
tion) then proceed as follows:
NOTE Do not disturb cam holder (36) setting on rotary actuators. [i.e. do
not touch set screws (35)].
CAUTION If cam is not at low signal line on lobe (low end of range), do not
attempt to remove cam. The cam must be at low signal line. Select
correct actuator and positioner action and proceed as follows.
Air to Open / Direct Acting Positioner
See Figure 19 on page 68 and Figure 20 on page 71.
1. Shut off supply pressure and signal to positioner. Valve is now closed and cam (26)
is at low signal line on lobe.
2. With cam at low signal line remove screw (28) and washer (27). Note the relative
position of the cam lobe being changed and then remove the cam (26).
3. Select the desired cam lobe and replace cam (26) on cam shaft with low signal line
of desired lobe against cam follower. Ensure the newly selected cam lobe is in the
same relative position as the lobe noted in Step 2.
4. Replace washer (27) and screw (28). Turn on supply pressure and signal to
positioner. Check zero and span adjustment. Refer to “Zero Adjustment” on
page 48 and “Span Adjustment” on page 48.
Air to Open / Reverse Acting Positioner
See Figure 19 on page 68.
1. Shut off supply pressure and signal to positioner. Valve is now closed and cam (26)
is at high signal line on lobe. Do not remove.
2. Run an independent regulated air line to the valve actuator in place of positioner
output line. Slowly apply proper air pressure through the regulator to open the
valve. Do not exceed designated supply pressure. (Handwheel may be used to
open the valve in place of regulated air line). Align the travel indicator with the
open end of travel scale. Do not over travel. Cam is now at low signal line on lobe.
3. With cam at low signal line remove screw (28) and washer (27). Note the relative
position of the cam lobe being changed and then remove the cam (26).
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