Endress+Hauser Oxymax COS61D, Operating Instructions Manual

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Maintenance Oxymax COS61D
26 Hauser
10 Maintenance
Take all the necessary precautions in time to ensure the operational safety and reliability
of the entire measuring system.
NOTICE
Effects on process and process control!
‣
When carrying out any work on the system, bear in mind any potential impact this
could have on the process control system and the process itself.
‣
For your own safety, only use genuine accessories. With genuine parts, the function,
accuracy and reliability are also ensured after maintenance work.
10.1 Maintenance schedule
Maintenance cycles depend to a great extent on the operating conditions.
The following rule of thumb applies:
• Constant conditions, e.g. activated sludge basin = long cycles (1/2 year)
• Widely varying conditions, e.g. fluctuating process pressure = short cycles (1 month and
shorter)
The following method helps you determine the necessary intervals:
1. Inspect the sensor one month after commissioning. To do so, remove the sensor from
the medium and dry it carefully.
2. After 10 minutes, measure the oxygen saturation index in air.
 Decide using the results:
a) Measured value not 100 ± 2 % SAT? → Service the sensor.
b) Measured value = 100 ± 2 % SAT? → Double the length of time to the next
inspection.
3. Proceed as indicated in Step 1 after two, four and eight months.
 This allows you to determine the optimum maintenance interval for your sensor.
Particularly in the case of widely fluctuating process conditions, damage may occur to
the fluorescence layer even within a maintenance cycle. You can recognize this by
implausible sensor behavior. (→  25)
10.2 Maintenance tasks
The following tasks are mandatory:
1. Clean the sensor fluorescence cap . →  26
2. Replace wear parts or consumables. →  27
3. Check measurement function. →  28
4. Recalibrate (if desired or necessary).
 Follow the Operating Instructions for the transmitter.
10.3 Cleaning exterior of sensor
The measurement can be corrupted by sensor fouling or malfunction due to the following,
for example:
Deposit buildup on the fluorescence cap
 This results in a longer response time and, under certain circumstances, a reduced
slope.
For reliable measurement, the sensor must be cleaned at regular intervals. The frequency
and intensity of the cleaning operation depend on the medium.