Emerson PN 51A-499AOZ Maintenance, Cleaning The Membrane, the bladder and destroy the sensor

MODEL 499A OZ MAINTENANCE

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.

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.

CAUTION

Fill solution may cause irritation. May be harmful if swallowed. Read and follow manual.

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.

6