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3710 and 3720 Positioners
OUTPUT CONNECTIONS
A6056/IL
TOP VIEW
Figure 21. Output Connections
Changing Positioner Action
WARNING
Avoid personal injury or equipment
damage from sudden release of
process fluid. Before changing
positioner action:
D Wear protective eyewear, gloves
and clothing whenever possible.
D Disconnect any operating lines
providing air pressure, electric power,
or a control signal to the actuator and
accessories. Be sure the actuator
cannot suddenly open or close the
valve.
D Use bypass valves or completely
shut off the process to isolate the
valve from process pressure.
D Vent the actuator loading
pressure.
D Use lock-out procedures to be
sure that the above measures stay in
effect while you work on the
equipment.
D Check with your process or safety
engineer for any additional measures
that must be taken to prevent against
process media.
24
Single-Acting/Double-Acting
See figure 21 for positioner output connections. See
figure 23 for the positioner schematic.
Use 3/8-inch tubing between the positioner and
actuator.
D For single-acting output, plug positioner
OUTPUT A. Refer to the actuator instruction manual
for the specific connection for positioner OUTPUT B.
Connect positioner OUTPUT B to the actuator
connection for single-acting. For Fisher diaphragm
actuators, this connection is known as the
diaphragm casing connection.
D For double-acting output (with direct-action),
refer to the actuator instruction manual for the
specific connections for positioner OUTPUT A and
B. Connect positioner OUTPUT A to the actuator
cylinder connection where actuator air pressure is
exhausted during the initial actuator stroke. Connect
positioner OUTPUT B to the actuator cylinder
connection where supply pressure enters the
actuator during the initial actuator stroke. For Fisher
piston actuators, OUTPUT A connects to the lower
actuator cylinder connection and OUTPUT B
connects to the upper actuator cylinder connection.
Direct-Acting/Reverse-Acting
This section explains changing the positioner action
from direct to reverse or reverse to direct. With
direct-action, the actuator stem extends as the input
signal to the positioner increases. With
reverse-action, the actuator stem retracts as the
input signal to the positioner increases.
See figure 21.
1. Turn off supply pressure. Reverse the piping
connections between the actuator and the positioner
output connections (OUTPUT A and OUTPUT B).
D For single-acting output, disconnect piping from
OUTPUT B. Unplug OUTPUT A and connect the
piping to it. Plug OUTPUT B.
D For double-acting output, disconnect piping
from both positioner outputs. Connect piping from
OUTPUT A to OUTPUT B. Connect piping from
OUTPUT B to OUTPUT A.
It may be necessary to bend new lengths of tubing if
rigid tubing is used.
2. After reversing the piping connections, remove
the positioner cover assembly (key 7) and reverse
the cam (key 36). To reverse the cam, unscrew the
Instruction Manual
Form 5300
July 2005
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