Replacing The Differential Pressure Unit - Emerson Fisher 4194HA Instruction Manual

4194HA, HB, HC Controllers
July 2018
Figure 5‐2. Changing Controller Action
W3439

Replacing the Differential Pressure Unit

WARNING
Refer to the Maintenance WARNING at the beginning of this section.
Before performing any maintenance operations:
D Shut off the supply pressure to the controller.
D Disconnect any operating lines providing supply air pressure, a process input signal, or other pressure source to
the controller.
Refer to figures 6‐1 and 6‐2 for key number locations.
Use this procedure in reverse to connect a differential pressure unit to a controller.
1. Is the process under temporary control? If so, shut off the process differential pressure to the differential pressure
unit. Also, shut off the supply pressure to the controller. Carefully bleed pressure from the controller and differential
pressure unit.
2. Disconnect all tubing. Refer to the installation procedures for process and supply tubing connections to disconnect
when the differential pressure unit is removed from the pipestand.
WARNING
The combined weight of the controller and differential pressure unit is approximately 26 kilograms (57 pounds). Provide
adequate support for the unit during removal procedures to prevent personal injury or property damage.
3. Remove the controller and differential pressure unit from the mounting position. Figure 2‐1 shows the location of
the set screws connecting the differential pressure unit mounting bracket to the pipestand. Move the controller and
differential pressure unit to a maintenance area.
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Instruction Manual
D200156X012