Split-Range Operation; Changing The Spool Valve - Emerson Fisher 3710 Instruction Manual

3710 and 3720 Positioners
September 2017
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 cam locknut (key 37). Remove the cam, turn it over, and reinstall it, making sure
the cam is positioned for the proper input signal range.
3. Set the initial cam position following the cam alignment procedure given in this manual. Tighten the cam locknut.
4. Turn on supply pressure. Perform the zero and span adjustment procedure given in this manual.
5. Replace the positioner cover assembly.
Split‐Range Operation
The positioner can be used for split‐range operation with the input signal from a single control device split between
two positioner/actuator/control valve packages. One positioner will fully stroke one actuator with an input signal
range from:
D 0.2 to 0.6 bar (3 to 9 psig)
D 0.6 to 1.0 bar (9 to 15 psig)
D 0.4 to 1.2 bar (6 to 18 psig)
D 1.2 to 2.0 bar (18 to 30 psig)
1. Turn off supply pressure. Remove the positioner cover assembly (key 7).
2. Loosen the cam locknut (key 37). Rotate the cam to the desired split‐range value: either "0-50%" or "50-100%".
3. Before tightening the cam locknut, perform the cam alignment procedure given in this manual.
4. Turn on supply pressure. Perform the zero and span adjustment procedure given in this manual. Use the proper
input signal range to match the cam split‐range value selected in step 2, above.
5. Replace the positioner cover assembly.

Changing the Spool Valve

WARNING
Avoid personal injury or equipment damage from sudden release of process fluid. Before changing the spool valve:
D Wear protective eyewear, gloves, and clothing whenever possible.
D Do not remove the actuator from the valve while the valve is still pressurized.
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. Relieve process pressure
on both sides of the valve.
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Instruction Manual
D101728X012