Maintenance - Emerson Rosemount 499Atrdo Quick Start Manual

November 2019
5

Maintenance

Periodic maintenance and cleaning are required for best performance of the
sensor. Generally, the membrane and fill solution should be replaced every
four to six months. The optimum maintenance frequency is best determined
by experience. Periodically check the zero current and sensitivity. If the zero
current is less than about 5 nA, and the current in the air is between 30 and
45 nA with a variability of less than two percent, the sensor does not need
maintenance.
WARNING
Pressurized spray injury
Before removing the sensor, be absolutely certain that the process pressure
is reduced to 0 psig and the process temperature is lowered to a safe level!
5.1 Cleaning the membrane
Keep the membrane clean and free from solid corrosion products. Clean the
membrane with water sprayed from a wash bottle or gently wipe the sensor
with a soft, clean tissue.
5.2 Replacing the electrolyte solution and membrane
WARNING
Harmful substance
Fill solution may cause irritation. May be harmful if swallowed.
Read and follow the instructions.
Procedure
1. Unscrew the membrane retainer.
2. Remove the membrane assembly and O-ring.
See
3. Hold the sensor over a container with the cathode pointing down.
4. Remove the fill plug.
5. Allow the electrolyte solution to drain out.
6. Inspect the cathode.
Quick Start Guide
Figure 1-1.
a) If it is tarnished, clean it by gently rubbing in the direction of
the existing scratches (do not use a circular motion) with
400-600 grit silicon carbide finishing paper.
Quick Start Guide
15