Handwheel Operation - Emerson Fisher 785C Instruction Manual

785C Actuator
May 2022
Manual Handwheel Operation
If manual operation is required for actuator sizes 280, 335, and 385 a manual handwheel should be equipped as
standard construction.
NOTICE
To avoid damage to actuator parts and difficult operation of actuator handwheels, open the bypass valve before using a
handwheel. Do not disengage the handwheel if the spring thrust is not balanced by pneumatic load for spring return
actuator.
A bypass assembly is furnished only when an actuator with manual override is specified, see figure 4. The bypass
assembly allows the pressure to equalize on either side of the actuator piston, so that the manual override can be used
to position the control valve. Flow through the bypass tubing is controlled by an angle needle valve, which is operated
manually. This valve should be closed when air pressure is being used to operate the actuator.
Figure 4. Bypass Valve Examples for Double-Acting 785C Actuator with Manual Override
GH14579, sheet 1
10
ACTUATOR,
SPRING RETURN
GH14579, sheet 3
Instruction Manual
D104483X012
ACTUATOR,
SPRINGLESS