YOKOGAWA DOX8HS, User Manual, Page: 27 / 32

< 4. Maintenance >
4-1
IM 19H1D2-01E
4. Maintenance
When the DOX8HS submersion type holder operates normally, maintenance and inspections
need not be performed.
Perform inspection and maintenance procedures described in this chapter in conjunction with
calibration and sensor maintenance.
4.1 Inspecting Sensor Retaining O-ring
The sensor is designed such that it can be immersed in the solution up to the sensor cable and
the entry of solution in the holder does not lead to a breakdown. However, damage to the sensor
cable sheathing could lead to poor insulation and for that reason the solution should as much as
possible not be allowed inside the holder.
The sensor retaining O-ring prevents the entry of solution into the holder to reduce the risk of
insulation problems. If solution enters the holder, make the following inspections.
1. Has dirt adhered to the O-ring reducing its sealing function?
2. ls the O-ring damaged from wear (deformed or cracked)?
Replace the O-ring when the above inspection shows that cause of solution entering the
holder was caused by O-ring damage. O-ring replacement normally requires sensor cable
disconnection. Be sure not to soil the prepared end of the sensor cable.
To replace the O-ring without disconnecting the sensor cable, the O-ring has to be from the
sensor front end and across the sensor body. Remove all dirt accumulated on the sensor. Before
inserting the O-ring to prevent that it is damaged (rust) through exposure to dirt. See Figure 4.1.
O-ring
Sensor body
Sensor securing nut
Submersion type holder
(sensor holder)
Turn the O-ring to move it. Position it so that elongation
in the flange is minimized.
Note: Remove all drift accumulated
on the sensor before replacing
the O-ring.
Figure 4.1 Replacing Sensor Retaining Ring (inserting it from the sensor front end)