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Series 830/840/860 Instruction Manual Chapter 4 Maintenance
IM-83/84/86-H 4-11
Motor-Operated Rotary Valves
The electronic components in the Model 840 motorized valve flow
controllers require no maintenance with the exception of the motor,
which requires replacement when its service life has ended. This
will be evidenced by “hunting,” or the inability to maintain set
point without a constant motion back and forth, or outright failure.
The motor normally has a long service life, typically more than
five years, and all other possibilities should be explored before
considering replacement.
To disassemble the motor-operated rotary valve:
1. To allow for component removal, set the valve to the fully
open position before removing power.
2. Remove the unit from the system.
3. If desired, remove the valve from the flow body to make disas-
sembly easier. Unplug the connector and remove the four bolts
holding the valve assembly to the flow body. Inspect the sealing
O-ring and replace as necessary.
4. Unscrew the six 4-40 Phillips head screws from the valve mo-
tor enclosure and remove the lid. Loosen the lower set screws
in the motor shaft coupling (there are two set screws in each
location to prevent loosening during operation). Inspect the
valve rotor shaft and coupling for scoring and replace if neces-
sary.
5. Remove the three 8-32 screws holding the valve to the enclo-
sure and separate the valve body from the enclosure.
6. Unscrew the four 6-32 x 7/8 inch flat head screws from the top
of the valve and remove the valve base plate and spacer. Re-
move the valve bonnet, rotor and Teflon washers. Inspect the
valve rotor and body for wear and replace the O-ring and seal
in the valve bonnet.
7. Inspect and replace the Teflon valve leaves and upper and
lower Teflon washers if they are worn or damaged.
8. Re-assemble the components. When the controller is re-
installed in the system, leak test the connection.
Caution!
When using toxic or cor-
rosive gases, purge the
unit thoroughly with inert
dry gas before discon-
necting from the gas line.