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MAINTENANCE
CLEANING THE MEMBRANE.
Keep the membrane clean and free from dirt. Clean the
membrane with water sprayed from a wash bottle. Use
a soft tissue to gently wipe the membrane.
REPLACING THE ELECTROLYTE SOLUTION AND
MEMBRANE.
1. Unscrew the membrane retainer and remove the
membrane assembly and O-ring. See Figure 16.
2. Hold the sensor over a container with the cathode
pointing down.
3. Remove the fill plug and allow the electrolyte solu-
tion to drain out.
4. Inspect the cathode. 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. Rinse the
cathode thoroughly with water.
5. Wrap the plug with one or two turns of pipe tape
and set aside. Remove old tape first.
6. Prepare a new membrane. Hold the membrane
assembly with the cup formed by the membrane
and membrane holder pointing up. Fill the cup with
electrolyte solution. Leave the membrane assem-
bly filled with electrolyte solution and set it aside.
7. Hold the sensor at about a 45-degree angle with the
cathode end pointing up. Add electrolyte solution
through the fill hole until the liquid overflows. Tap the
sensor near the threads to release trapped air bub-
bles. Add more electrolyte solution if necessary.
8. Place the fill plug in the electrolyte port and begin
screwing it in. After several threads have engaged,
rotate the sensor so that the cathode is pointing up
and continue tightening the fill plug. Do not over-
tighten.
9. Place a new O-ring in the groove around the cathode
post. Cover the holes at the base of the cathode
stem with several drops of electrolyte solution.
10. Insert a small blunt probe, like a toothpick with the
end cut off, through the pressure equalizing port.
See Figure 16.
NOTE
Do not use a sharp probe. It will puncture
the bladder and destroy the sensor.
Gently press the probe against the bladder several
times to force liquid through the holes at the base
of the cathode stem. Keep pressing the bladder
until no air bubbles can be seen leaving the holes.
Be sure the holes remain covered with electrolyte
solution.
11. Place a drop of electrolyte solution on the cathode,
then place the membrane assembly over the cath-
ode. Screw the membrane retainer in place.
12. The sensor may require several hours operating at
the polarizing voltage to equilibrate after the elec-
trolyte solution has been replenished.
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MODEL 499A OZ MAINTENANCE
Periodic maintenance and cleaning is required for best performance of the sensor. Generally, the membrane and
fill solution should be replaced every four to six months. Sensors installed in harsh or dirty environments require
more frequent maintenance. The optimum maintenance frequency is best determined by experience.
WARNING
Before removing the sensor from the process
stream for maintenance, be sure the process
pressure is reduced to 0 psig and the process
temperature is at a safe level.
Fill solution may cause irritation. May be harmful if
swallowed. Read and follow manual.
CAUTION