Instruction Manual
D104483X012
785C Actuator
May 2022
8
actuator and any attached accessories and/or valve. Use caution during lifting and handling to prevent slippage, swinging,
faulty equipment connections, or sudden shock loads.
NOTICE
Special care must be taken when installing an actuator in a horizontal service orientation. To avoid cantilever loads on the
valve stem and yoke, it is the customer’s responsibility to ensure proper support for a horizontal actuator.
The actuator may be installed in any orientation, but normal installation is with the actuator vertical above the valve.
If using a manual override in double acting application, a bypass valve should be furnished, allowing balance the
pressure within both sides of the piston before operating the manual override.
If using a manual handpump, the handpump must be installed vertical above the valve (see figure 7).
If the supply source is capable of exceeding the maximum actuator operating pressure or instrument supply pressure,
appropriate steps must be taken during installation to protect the instrument and all connected equipment against
overpressure.
When an actuator and control valve are shipped together as a control valve assembly, the actuator is normally
mounted on the valve. Follow the valve instructions when installing the valve in the pipeline. If the actuator is shipped
separately or if it is necessary to mount the actuator on the valve, perform the actuator mounting procedures in this
instruction manual. Refer to the individual product instruction manuals for the installation or mounting of a FIELDVUE
DVC6200 digital valve controller.
If the actuator is being installed without a positioner, the cylinder loading pressures should be supplied through a
4-way solenoid valve or a switching valve.
Pressure connections are located on top of the pneumatic cylinder end flange (key 2210) and on the side of the
pneumatic cylinder head flange (key 2201).
D
The supply pressure medium should be clean, dry filtered air. If the supply source is capable of exceeding the
maximum actuator operating pressure or positioner supply pressure, appropriate steps must be taken during
installation to protect the positioner and all connected equipment against over pressurization.
D
The control valve should be located where it will be accessible for servicing. Space should be left above and below
the control valve to permit removal of the actuator and valve plug.
Actuator Earth Grounding
All Fisher 785C series actuators are provided with a threaded actuator earth grounding interface on the yoke (spool)
for the earth connection as shown in the figure 3
Note
Proper connection to the earth grounding interface is required for compliance with ATEX regulations.