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Failure Analysis and Maintenance of Oxygen Analyzer

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Oxygen analyzer troubleshooting check

① The filter in the oxygen analyzer probe filter station should be cleaned frequently. If it is blocked, the cooling water pump cannot be started or it will stop shortly after starting.

② If the oxygen content is high and the measurement results are not improved by manually purging the sampling probe and filter multiple times and by repeatedly correcting the oxygen span, the possibility that the oxygen analyzer is sampling all air should be suspected. Example analysis: The central control shows that the analyzer 02 is reporting high, and the sample gas flow is normal on site. After repeated calibration of 02 span, it is still reporting high. Checking the sampling gas circuit carefully, it is found that the gas pipe entering the oxygen analyzer is flushed, and returns to normal after processing. The O2 content is about 8.6%.

③ The heat exchanger of the oxygen analyzer cannot start normally. Most of the failures of the temperature controller contacts cause the PLC monitoring unit to have no input / output. After processing the contacts, it can return to normal.

④ If the control head is often blocked or stuck, you must change the automatic probe purge time and automatic probe movement time in the program according to the changes in the working conditions in the kiln.

⑤ After the PLC program is lost, you can copy and restore it as follows: first turn off the power of the PLC, remove the lithium battery, take out the electrically washable memory unit “EPROM”, and then put it back. Restore the PLC power, set the switch on the programmable controller to the “stop” position for at least 5S, and then to the “copy” position until the red light stops flashing. Then turn the switch to the “Run” position and put back the lithium battery. The green light should glow at this time, and the input signal light of the PLC should also show normal status. In the worst case, the PLC central processing unit needs to be replaced.

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Failure Causes and Maintenance of Oxygen Analyzer

  1. Measurement value drifts irregularly

Cause ①: The sample gas pressure and flow are unstable.

Treatment ①: Set a pressure-stabilizing and steady-flow valve to ensure that the pressure and flow rate of the sample gas entering the analyzer is constant.

Cause ②: The zero position of the measurement circuit or the poor contact of the range potentiometer caused the output signal to drift.

Solution ②: Check and maintain or replace the potentiometer.

  1. The measured value is unstable or swings repeatedly

Cause ①: The performance of the DC stabilized power supply is not good, which causes the working current of the measuring bridge to be unstable.

Solution ①: Overhaul or replace the stabilized power supply to improve the accuracy of the stabilized voltage.

Reason ②: Detector’s constant temperature performance is not good, and the temperature fluctuation range is too large. Due to the unstable heat dissipation condition of the hot wire, the measurement value drifts irregularly.

Solution ②: Check and maintain or replace the potentiometer.

Cause ③: The zero potentiometer fails or has poor contact.

Treatment ③: Replace or maintain.

  1. Water mist and droplets will cause damage to the thermal element

Cause ①: There is water mist or liquid droplets in the detector.

Solution ①: Power off the instrument, blow dry air or clean the detector. Purge pressure: 0.05MPA.

Cause ②: The detector is oily or sticky.

Treatment ②: After the instrument is powered off, the detector is cooled to room temperature, then washed with cleaning solution, cleaned, and then dried with dry air.

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Daily failure analysis of oxygen analyzer

  1. The indicated value is too low

If the secondary meter of the oxygen analyzer displays “OXYGENLOW”, indicating that the oxygen content is less than 1%, the following checks should be performed:

  1. When the meter is used, the reference air flow must reach 0.7kg / cm2. To this end, it is necessary to check whether the air flows through the zirconia platform or the reference air flow is low. If the above two situations occur, they should be adjusted appropriately.
  2. Check whether the setting status is “YES” in the “AUXILIARYAIR” column under the “UTILITY” menu. If it is set to “NO”, the setting error in the program is corrected.
  3. Unable to verify

Sometimes when the instrument is periodically checked, it is found that the gas-filled sample instrument does not respond, which may be caused by the following reasons.

  1. The flow rate of the sample gas used for calibration does not meet the requirements of the instrument for the sample gas flow rate, ie 600 ± 20ml / min. Because the flow rate is too small, the sampling sensitivity of the system is reduced, and the detection process will fail.
  2. The setting range of the check tolerance value in the software parameter is too small. Improper setting of the tolerance value will cause the meter to fail to respond to the gas sample being measured during the calibration and measurement process. If the meter shows that the oxygen content is 5%, it is suspected that there is a deviation by analysis. Add 0.3% concentration of sample gas, and the meter display does not change. Check the software parameter and find the calibration tolerance value is 0.5%. When the above situation occurs, the tolerance value should be appropriately increased first, and then the tolerance value should be gradually reduced until the instrument calibration is accurate.
  3. The flue gas or reference air of the heating furnace is not clean, which causes the gas path to be blocked. Even if the gas to be measured is added, the sensor cannot detect the change in the oxygen content on both sides of the zirconia platform. The entire pneumatic section of the instrument is carefully cleaned.

Oxygen analyzer daily maintenance precautions

  1. The calibration cycle of the oxygen analyzer is half a year. The calibration process shall be carried out in strict accordance with the calibration steps of the product operating instructions.
  2. In the routine inspection, you can enter the VIEW item to observe the parameter values ​​and judge whether the meter is running well.
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