GE Masoneilan 4700E, Maintenance Manual

Page: 56 / 80

© 2015 General Electric Company. All rights reserved
.
56 | = GE Oil & Gas
Air to Close/Reverse Acting Positioner (4700P/4800P only)
See Figure 19 on page 68.
1. Disconnect air line from positioner to actuator at actuator. Run an independent
regulated air line to the actuator. Slowly apply proper air pressure through the
regulator to close the valve. (Handwheel may be used to open valve instead of
regulated air line.) Align the travel indicator with the
closed end of travel scale. Do
not overtravel.
2. Place cam (26) on to cam shaft with selected cam lobe facing forward and low
signal line approximately aligned with positioner case raised reference line.
Secure cam to shaft using washer (27) and screw (28).
3. Slowly reduce pressure applied to actuator to zero (If handwheel was used, back if
off fully). Cam will now be at high signal line.
4. Disconnect the independent regulated air line and connect the positioner output
line to the actuator. Connect supply pressure and signal to the positioner.
5. Apply low value of instrument signal. (3 psi if 3-15 psi signal range) Unlock zero
locknut (4C) and turnbuckle locknut (107). Adjust zero by turning both the zero nut
(4B) and turnbuckle (106) until the low signal line of the cam is aligned with the
positioner case raised reference line and the travel indicator shows
closed
position. Refer to Figure 5 on page 23 and Figure 19 on page 68. Re-tighten both
locknuts.
6. Apply full scale value of instrument signal (i.e. 15 psi) and note position of stroke
scale indicator. If travel is not correct, perform span adjustment. Refer to “Span
Adjustment” on page 48.
7. Repeat zero and span adjustments per “Zero Adjustment” on page 48 and “Span
Adjustment” on page 48 until travel range is correct. After adjustments are
satisfactory, re-tighten the spring locking screw (8), zero locknut (4C), and
turnbuckle locknut (107).
NOTE Although this procedure is written for 87/88 actuators, it is, in
general, applicable to calibration of any reciprocating actuator.
Damping Adjustment
The airflow to the actuator may be reduced by turning screw (20) clockwise. This adjustment may
be required for smaller volume actuators if instability is observed. Turn clockwise until desired
stability is obtained.
CAUTION
Screw must never be backed out further than top flush with
housing.