9 Step Zirconia Oxygen Analyzer Calibration Procedure

  • A zirconia oxygen analyzer is a device utilized to measure oxygen concentration in gas mixtures. It operates based on the conductivity of zirconia, which changes with varying oxygen partial pressures. 
  • The analyzer consists of a zirconia cell, reference and measuring chambers, electrodes, and a temperature control system. 
  • At high temperatures, zirconia becomes ionically conductive to oxygen ions, allowing them to migrate through the cell. 
  • The generated electrical current is proportional to the oxygen concentration, providing accurate measurements for various industrial applications.
  • The step-by-step calibration procedure outlined below offers a thorough guide for calibrating a Zirconia Oxygen Analyzer in a process area or analyzer room using instrument air supply as the reference & span gas and nitrogen as the zero gas. 
  • This detailed process ensures precise adjustments to achieve accurate and reliable measurements of oxygen concentration.
Prepare the Tools Required for Zirconia Type O2 Analyzer Calibration
  1. Sample Zero Gas Cylinder
  2. Span Gas – Clean Instrument Air Supply
  3. Calibration Documentation Forms
  4. O2 Analyzer data sheet / Specifications
  5. Communication Tools if necessary
  6. Calibration Gas Regulator
  7. Tubing and Connectors
  8. Necessary safety gear (e.g., gloves, safety goggles)
  9. Standard Tools and Cylinder Key
  1. Refer the following page for more information about the suggested calibration procedure and general safety issues for the process industry: Process Industry Calibration Methodology: Essential Safety and General challenges.
  2. Request that the panel operator switch the Zirconia Oxygen Analyzer’s MOS (Maintenance Override Switch) of the controller to manual mode.
  3. Verify whether the Zirconia Analyzer is part of an Emergency Shutdown (ESD) loop integration.
  4. Verify that the safety documentation contains any special procedures that belong to the ESD system.
  5. The particular Zirconia Oxygen Analyzer that needs to be calibrated should be identified and located.
  6. Verify the Zirconia O2 analyzer’s specifications, including the model number, manufacturer, tag number, and any other relevant information.
  7. In order to accommodate the specific characteristics of the Zirconia Analyzer and the location of the process, the fundamental safety procedure should be modified.
  8. When using the Zirconia Oxygen Analyzer, always follow the manufacturer’s instructions and local safety standards.
  9. In order to prevent the analyzer from being accidentally activated while it is being calibrated, lockout and tagout procedures should be implemented.
  10. It is essential that the Zirconia Analyzer be effectively isolated from the process in order to eliminate any potential safety risks.
  11. Make sure you wear the appropriate personal protective equipment (PPE) as much as possible when doing the calibration.
  12. Ensure that the surrounding area is clear of any flammable materials or potential ignition sources during the calibration process of the Zirconia Oxygen Analyzer.
  13. It is important to exercise caution when working with the Zirconia Analyzer and to adhere to all safety precautions in order to keep the working environment safe.
  14. Everyone who is involved in the calibration of zirconia oxygen analyzers should have safety training and awareness in order to ensure that safe procedures are followed for the calibration process.
Prepare the Calibration Setup for Zirconia type O2 Analyzer
  1. Ensure that the location chosen for calibrating the Zirconia type Oxygen Analyzer is free of electromagnetic interference and vibrations, as these may decrease calibration accuracy.
  2. To enable a precise and safe calibration process, make sure the calibration environment is well ventilated and well-lit.
  3. Gather all of the tools and supplies needed to calibrate the Zirconia Oxygen Analyzer, referring to the analyzer’s manual and instrument loop diagram for specific requirements.
  4. This contains calibration gas cylinders (zero and span gas), regulators, tubing, calibration adapters, relevant tools, and any personal protective equipment (PPE) required for gas and equipment safety.
  5. Verify the integrity and performance of all equipment to ensure a smooth and efficient calibration process that promotes accurate oxygen concentration measurements.

Note: Set the pressure of the reference gas, which in this case is instrument air, to the specified pressure as indicated on the nameplate located on the inside of the instrument panel or within the instrument data sheet of the Zirconia Oxygen Analyzer.

  1. Turn off the power of the zirconia O2 Analyzer to ensure safety during the calibration setup preparation
  2. For the Zirconia type Oxygen Analyzer, prepare the calibration gas cylinders accordingly:
    a. Use nitrogen with a minimum purity of 99% with 1% oxygen as the zero gas.
    b. Use instrument air with an oxygen content of 20.7 to 21% of the upper range value specified in the data sheet of the analyzer manufacturer.
  3. Mount the pressure regulator assembly, including the pressure regulating valve and needle valve, securely on the calibration cylinder.
  4. When setting up the calibration process for the Zirconia Oxygen Analyzer, ensure the calibration gas cylinder used is certified.
  5. On the certification label, look for particular information such as the name of the certifying agency, the certification date, and the expiration date (if applicable).
  6. Verify that the calibration gas’s oxygen content corresponds to the amount listed on the certification label.
  7. Ensure that the pressure regulator is set to deliver gas at an outlet pressure not exceeding the specified limit as per the data sheet of the Zirconia analyzer manufacturer.
  8. Install all setup components through the calibration control panel to facilitate convenient and efficient calibration procedures.
  9. Connect a multimeter to the analog output of the analyzer signal converter to monitor and verify the signal output during the calibration process. This ensures accurate calibration adjustments based on the signal readings.

Before proceeding with the calibration of the Zirconia Oxygen Analyzer, it’s essential to allow the instrument to warm up and stabilize to ensure accurate readings. Follow these steps for instrument warm-up and stabilization:

  1. Turn on the Zirconia Oxygen Analyzer and any associated equipment required for calibration.
  2. Allow the analyzer to reach its operating temperature, typically around 700-900°C, as specified by the manufacturer. This warming-up process may take some time, so be patient and refer to the instrument’s manual for the recommended warm-up duration.
  3. Once the instrument reaches its operating temperature, allow it to stabilize for a sufficient period to ensure consistent and accurate readings. 
  4. This stabilization period ensures that the analyzer settles into its operating conditions and minimizes any fluctuations in readings.
  5. During the stabilization period, monitor the readings displayed on the analyzer to ensure they remain consistent and within the expected range. 
  6. Any significant deviations may indicate a need for further adjustment or troubleshooting.
  7. Once the readings have stabilized and remained consistent for a predefined period, typically specified by the manufacturer, the instrument is ready for calibration.

Calibration for a Zirconia type Oxygen Analyzer typically involves a 2-point calibration process:

  • Zero Calibration: Setting the baseline reading when no oxygen is present. This is done using nitrogen gas with 0.5 to 1% oxygen.
  • Span Calibration: Setting the upper limit of the analyzer’s measurement range using gas with a known oxygen concentration(instrument air which is normally having 21% of O2).
Zero Calibration of Zirconia type O2 Analyzer 
  1. Set the desired oxygen concentration for zero-point calibration using the calibration settings. Normally 0.5 to 1%.
  2. Make sure that the analyzer is in maintenance mode in order to make calibration process.
  3. Open the zero calibration gas isolation valve to allow the flow of zero calibration gas to the analyzer, crucial for introducing the known concentration gas.
  4. Open the zero gas cylinder containing nitrogen with 0.5 to 1% of oxygen.
  5. Allow the analyzer to stabilize to ensure accurate zero calibration.
  6. Observe the specified flow rate in the rotameter (flowmeter with regulation) as per the instrument datasheet.
  7. Record the readings displayed on the analyzer.
  8. During zero calibration, note the mA output value from the analyzer.
  9. Measure the mA current output from the analyzer using a multimeter and compare it with the expected mA during zero calibration.
  10. Observe the Oxygen concentration values displayed on the analyzer and in the control room during zero calibration.
  11. Compare these values against the estimated zero concentration found with the zero gas.
  12. Refer to the instrument datasheet for the expected range of readings during zero calibration.
  13. Ensure that the readings fall within the specified range and meet the instrument’s accuracy criteria for zero calibration as per the calibration control plan.
  14. In the event that errors are found in zero calibration measurements, modify the analyzer’s parameters to bring it into conformity with the calibration values and the specifications of the instrument.
  15. After completing the zero calibration, close the Zero calibration gas isolation valve to stop the flow of calibration gas and also close the zero gas cylinder containing nitrogen.
Zero Calibration of Zirconia type O2 Analyzer  1
  • The concentration of oxygen maintained in the reference side of a Zirconia Oxygen Analyzer is typically 20.9%. 
  • This concentration is achieved by utilizing air as a reference, which naturally contains approximately 20.9% oxygen. 
  • The zirconia cell, integral to the analyzer, is situated inside a furnace, where the temperature is controlled at 650°C to ensure optimal performance.
Span Calibration of Zirconia type O2 Analyzer 
  1. Set the oxygen concentration for span calibration. If instrument air is used as the span gas, enter 21% O2. 
  2. Open the span gas isolation valve containing the known concentration gas as instrument air 
  3. Open the calibration gas isolation valve and apply the  instrument air at the specified flow rate
  4. To ensure the correct span calibration, give the analyzer time to stabilize.
  5. Observe the concentration values displayed on the analyzer during both span calibration.
  6. Compare these values with the expected concentrations based on the known 21% of concentrations
  7. Ensure that the readings fall within the specified range and meet the instrument’s accuracy criteria as per the calibration control plan.
  8. During span calibration, note the measured mA output value.
  9. Measure the analyzer’s current output using a multimeter and compare it to the anticipated mA during span calibration.
  10. Ensure that the readings fall within the specified range and meet the instrument’s accuracy criteria for span calibration as per calibration control plan.
  11. Adjust the analyzer parameters to match the calibration values and instrument specifications if errors are found in the span calibration results.
  12. After completing the Span calibration, close the Span calibration gas isolation valve to stop the flow of instrument air.
  1. Perform multiple calibration runs to assess repeatability, repeating both zero and span calibration procedures.
  2. Ensure that instrument readings remain consistent across these calibration runs, with repeated tests yielding similar results.
  3. If repeatability checks indicate that the Zirconia Oxygen Analyzer does not meet acceptable standards, implement necessary corrective actions.
  4. Following repairs or replacement, conduct comprehensive tests to confirm resolution of the repeatability issue.
  1. When the calibration is successful, attach a label with the date, personnel, and calibration data to the Zirconia O2 analyzer.
  2. Ensure that all residues have been removed from the calibration area  and the zirconia O2 analyzer equipment is fully clean. Maintain the equipment’s safety by placing it in the proper storage space.
  3. All essential calibration data, including the beginning and finishing readings, any adjustments made, and any errors found, should be kept on file. For later use, store this information in the analyzer log.
  4. Make Sure and Close all the calibration gas valves.
  5. Place the analyzer in measurement mode in order to start capturing process readings.
  6. Take down any barriers or isolation measures that were put in place during calibration.
  7. The O2 analyzer should be allowed to resume its normal operation within the processing area.
  8. Confirm that the Zirconia O2 analyzer provides accurate and reliable measurements in real time. Evaluate the present data in relation to the calibration-based expected values.
  9. Ensure safety interlocks or control systems are normalized.
  10. Confirm that any interlock systems that have been temporarily modified or interrupted have been returned to their normal functioning configurations.
  1. Generate a calibration report specifically tailored for the Zirconia Oxygen Analyzer.
  2. Provide a clear and concise overview of the calibration process, detailing the gases utilized and any adjustments conducted.
  3. Utilize a standardized template within Excel for systematic and organized documentation.
  4. Make sure the report includes all necessary information that will be needed for future maintenance and reference. For reference, please see the sample calibration report attached below for a Zirconia Oxygen Analyzer.
 Calibration Report Preparation
  • Our detailed process ensures accurate measurements of oxygen levels in industrial settings.
  • We follow NIST standards for precise measurements.
  • Compliance with IEC 61508 ensures safety at all stages of the analyzer’s use.
  • Our calibration method, based on industry best practices, improves accuracy.
  • Our procedure satisfies the testing and calibration competency standards of ISO/IEC 17025.
  • Following ISO 6143 guidelines ensures accurate gas mixtures for calibration.
  • Our approach aligns with industry standards for dependable oxygen level measurements.

Click here for 10 Step Oxygen Analyzer Calibration Procedure: Paramagnetic Type

Click here for more Calibration Procedure

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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