Section 6: Maintenance; Maintenance; Sensor Removal - Emerson Rosemount 398R Reference Manual

Reference Manual
00809-0100-3098

Section 6: Maintenance

6.1

Maintenance

The frequency at which a sensor should be inspected, cleaned, and calibrated can be determined
only by experience. Generally, the greater the tendency of the process liquid to coat or foul the
sensor, the more frequently maintenance should be done. Rosemount 398R and 398RVP sensors
are fouling resistant and, they usually require maintenance less often than other pH (or ORP)
sensors. Sensors exposed to extreme pH values or to high temperature require more frequent
inspection than sensors installed in less severe environments. The best way to evaluate a sensor is
to check its performance in buffers. If the sensor cannot be calibrated or has low slope, it is dirty or
has failed. Refer to the troubleshooting guide in this manual for assistance.
6.2

Sensor Removal

Please refer to the appropriate paragraph for instructions regarding removal of the sensor for
periodic maintenance.
6.2.1 Retractable Version
WARNING
System pressure may cause the sensor to blow out with great force unless care is taken during removal.
Make sure the following steps are adhered to.
A.
Figure 6-1: Example of Sensor Tube Replacement
Maintenance
Rosemount 398R-21 and 398RVP-21 (21" tube)
1. Be certain system pressure at the sensor is below 64 psig before proceeding
with the retraction. It is also recommended that the personnel wear a face
shield and have a stable footing. Refer to Figure 6-1. Push in on the cable end or
the top of the junction box and slowly loosen the hex nut (B) of the process end
male connector (A).
Maintenance
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