Step by Step Preventive Maintenance Procedure for Zirconia Type Oxygen Analyzer with Checklist

Step 1: Review Manufacturer’s Instruction Manual

• Before initiating any maintenance procedures, thoroughly review the manufacturer’s manual provided with the zirconia type oxygen analyzer.
• The manual contains specific instructions and precautions relevant to your model, ensuring accurate and safe maintenance practices.
• Adhering to the guidelines outlined in the manual ensures the accuracy, safety, and efficacy of the maintenance procedures conducted on the analyzer.
• Consulting the manufacturer’s manual is the foundational step in executing effective preventive maintenance on the zirconia type oxygen analyzer.
• Reading through the manual will give you valuable information about how the analyzer works and give you the skills you need to do maintenance jobs properly.

Click here to know more about Exploring Zirconia Oxygen Analyzers in Industrial Applications 

Step 2: Safety Precautions

• Instruct the panel operator to set the MOS for both manual modes of the controllers’ (zirconia type oxygen analyzers control loop) and ESD loop before starting any preventive maintenance (PM) tasks.
• Ensure the operator understands the procedure for setting the MOS and its importance in preventing unintended disruptions to the analyzer’s operation during maintenance.
• Before maintaining the zirconia type oxygen analyzer, ensure that the system’s sample impulse tubes and calibration gas line are depressurized using proper techniques.
• Instruct operators to close the main sample inlet isolation valve of the zirconia type oxygen analyzer to depressurize the sample impulse tubes and calibration gas line safely.
• Explain how important it is to depressurize the system so that the risks of working with pressurized gas lines and possible leaks during repair are kept to a minimum.
• Refer to the instrument loop diagram to locate adjacent junction boxes or Marshaling Cabinets near the control room for isolating and powering off the zirconia type oxygen analyzers.
• Ensure operators are aware of the location and operation of isolation points to safely power off the analyzers before performing maintenance tasks.
• Always adhere to the manufacturer’s guidelines and local safety standards when working with zirconia type oxygen analyzers or any process equipment.
• Follow the specific maintenance instructions provided by the manufacturer to ensure safe and effective maintenance procedures.
• Wear appropriate PPE, including gloves, safety glasses, and protective clothing, in accordance with the company’s safety procedures and the manufacturer’s recommendations.
• Evaluate the specific risks associated with the maintenance tasks and ensure that adequate PPE is worn to mitigate these risks effectively.
• Follow lockout/tagout protocols to prevent unintentional restart of the zirconia type oxygen analyzers during maintenance.
• Examine relevant procedure documents, such as safety data sheets (SDSs), piping and instrumentation diagrams (P&IDs), and standard operating procedures (SOPs), for information on hazardous materials and proper handling procedures.
• Ensure clear communication with other personnel involved in the maintenance work on the zirconia type oxygen analyzers, including supervisors and maintenance technicians.
• Request a work permit for PM tasks on zirconia type oxygen analyzers to ensure proper authorization and adherence to safety protocols.

Step 3: General Inspections

Here’s a detailed breakdown of the general inspections for a zirconia oxygen analyzer

Visual Inspection:

Zirconia Measuring Probe:

• Check the zirconia measuring probe for any physical damage, including cracks, chips, or scratches. Even minor damage can compromise its functionality and accuracy.
• Inspect the probe’s protective casing for any signs of wear or deterioration. Ensure that it is intact and provides adequate protection to the zirconia sensor inside.

Converter Unit:

• Examine the converter unit for signs of wear, corrosion, or damage to the casing. Look for any cracks, dents, or discoloration that may indicate potential issues.
• Inspect all connections on the converter unit, including electrical connections and communication ports. Ensure they are clean, tight, and free from corrosion or damage.
• Pay close attention to the wiring and cable connections. Look for any fraying, exposed wires, or signs of overheating, which could indicate electrical problems.

Power Supply:

• Verify that the power supply to the converter unit is stable and within the specified voltage range. 
• Voltage fluctuations can affect the performance of the analyzer.

Electrical Connections:

• Inspect electrical connections between the measuring probe and converter unit. Ensure they are tight, secure, and free from corrosion.

Analog Signal and Communication:

• Verify the integrity of analog signal connections between the measuring probe and converter unit. Ensure proper data transmission for accurate readings.

Digital Signal Wiring:

• Inspect digital signal wiring between the measuring probe and converter unit. Ensure all connections are secure and functional for effective communication.

Gas Sampling System:

• Examine the gas sampling system for blockages, leaks, or contamination. Ensure that the sample inlet is clean and free from obstructions.

Step 4: Maintenance of the Calibration Gas Tube of the Detector Assembly

Following these steps will help maintain the calibration gas tube of the detector and ensure its optimal performance.

• Ensure the detector is disconnected from the power source and removed from the installation assembly for safety.
• Remove the Flame Arrestor Assembly from the Sensor Assembly. Refer to Figure 11.2 in the manual for guidance.
• Remove the four bolts (and associated spring washers) securing the sensor assembly, pipe support, and U-shaped pipe.
• Use a rod with a diameter of 2 to 2.5 mm to clean the calibration gas tube inside the probe.
• Maintain a flow of air from the calibration gas inlet at approximately 600 ml/min.
• Carefully insert the rod into the tube (3-mm inside diameter), ensuring not to insert it deeper than the specified depth (40 cm for general-purpose detectors, or 15 cm for high-temperature detectors).
• Move the rod back and forth within the tube to dislodge any dust or debris obstructing the flow.
• Rinse the U-shaped pipe with water. Ensure thorough drying before reassembly to prevent moisture-related issues.
• Restore all components to their original positions.
• Replace any O-rings with new ones to ensure proper sealing and prevent gas leaks.
• Tighten the bolts securely to reassemble the detector properly.
• Perform a functional test to ensure the detector operates correctly after reassembly.
• Verify that the calibration gas flows smoothly through the tube at the specified flow rate without any obstructions.
• Keep detailed records of the cleaning process, including the date, actions taken, and any observations or abnormalities noted during the inspection.

Step 5: Maintenance of the Zirconia Sensor Assembly

By following these steps, you can successfully replace the sensor assembly of a zirconia oxygen analyzer probe. Make sure to perform the sensor fault check and verify the specified values before and after replacement to ensure accurate measurements.

• Ensure the detector has cooled down from its high temperature before proceeding to avoid burns.
• Determine the parts needing replacement, typically including the sensor, metal O-ring, and contact. Consider replacing the U-shaped pipe, bolts, filter, and associated spring washers if necessary.

Sensor Fault Check:

• If the sensor is suspected to be faulty, perform a check to verify its condition. Check the zero correction ratio (100±30%) and span correction ratio (0±18%). 
• If the sensor cannot satisfy these ratios, or if it’s damaged and unable to operate during measurement, replacement is necessary.

Removal and assembly  Procedures:

• Use a special wrench to remove the flame arrestor assembly.
• Remove the four bolts and associated washers from the tip of the detector probe.
• Remove the U-shaped pipe support along with the U-shaped pipe. Remove the filter.
• Pull the sensor assembly while turning it clockwise. Remove the metal O-ring between the assembly and the probe. Be cautious not to damage the probe’s tip.
• Use tweezers to remove the contact from the groove in the probe’s tip.
• Clean the sensor assembly, particularly the metal O-ring contact surface, to remove any contaminants.
• Install the contact properly into the ringed groove on the probe’s tip.
• Ensure the O-ring groove on the sensor’s flange surface is clean. Install the metal O-ring in the groove and insert the sensor into the probe while turning it clockwise.
• Align the U-shaped pipe insertion holes with the bolt openings and fully insert the U-shaped pipe and its support into the probe.
• Apply anti-seize grease to the threads of the four bolts and screw them in with the washers. Tighten the bolts uniformly by hand, then use a torque wrench to ensure even tightening of the sensor flange to the probe’s O-ring working face.
• Tighten each bolt in rotating fashion, 1/8 turn at a time, until fully tightened with the torque wrench.
• Reattach and fix the flame arrestor assembly. Install the detector and restart operation. Calibrate the instrument before making any measurements.

Step 6: Maintenance of the Heater Assembly

Preventive maintenance of the heater assembly in a zirconia analyzer probe is essential to ensure accurate and reliable operation. Here’s a guide to preventive maintenance for the heater assembly:

Regular Inspection:

• Schedule regular inspections of the heater assembly to detect any signs of wear, damage, or malfunction. Inspect for loose connections, corrosion, or physical damage.

Cleaning:

• Clean the heater assembly periodically to remove any dust, dirt, or contaminants that may accumulate over time. Use a soft brush or compressed air to gently clean the heating elements and surrounding areas.

Temperature Calibration:

• Calibrate the heater assembly temperature regularly to ensure it operates within the specified range. Use a calibrated thermometer or temperature sensor to verify the accuracy of the heater temperature.

Heater Element Replacement:

• Replace heater elements according to the manufacturer’s recommended schedule or if they show signs of deterioration. Damaged or worn-out heater elements can affect the stability and performance of the analyzer.

Electrical Connections:

• Check all electrical connections associated with the heater assembly for tightness and corrosion. Loose connections can lead to overheating or electrical failure.

Ventilation and Airflow:

• Ensure adequate ventilation and airflow around the heater assembly to prevent overheating. Clear any obstructions that may restrict airflow and cause temperature fluctuations.

Heater Housing Inspection:

• Inspect the heater housing for any cracks, leaks, or damage. Replace the housing if necessary to maintain the integrity of the heater assembly.

Step 7: Maintenance of the Flame Arrester in zirconia Analyzer Probe

• Schedule regular inspections of the flame arrester to detect any signs of wear, damage, or blockage. 
• Inspect for soot buildup, corrosion, or physical damage to the flame arrester components.
• Clean the flame arrester periodically to remove any debris, soot, or contaminants that may accumulate over time. 
• Use compressed air or a soft brush to gently clean the flame arrester mesh and surrounding areas.
• Inspect the flame arrester for any blockages that may restrict the flow of gasses. Ensure that the mesh is free from obstructions and allows for proper gas flow through the probe.
• Check to make sure the flame arrester’s gas flow is unrestricted. Check for any irregularities in gas flow that may indicate a blockage or malfunction.
• Inspect the mounting of the flame arrester to ensure it is securely attached to the probe. 
• Check for any loose or damaged mounting hardware and tighten or replace as necessary.
• Replace the flame arrester if it shows signs of damage, corrosion, or significant blockage that cannot be cleaned effectively.

Step 8: Cleaning the High Temperature Probe Adapter

• Allow the probe adapter to cool down completely before cleaning.
• Disconnect the probe adapter from the zirconia oxygen analyzer probe and any power source.
• Prepare a cleaning solution suitable for high-temperature materials, such as a mild detergent solution or recommended solvent.
• Gently scrub the surface of the probe adapter using a soft brush or cloth soaked in the cleaning solution.
• Pay attention to any debris or buildup, especially in areas prone to accumulation.
• Thoroughly rinse the probe adapter with clean water to remove any residue from the cleaning solution.
• Allow the probe adapter to air dry completely before reassembly or reinstallation.
• Alternatively, use a soft, dry cloth to pat the adapter dry.
• Follow the manufacturer’s instructions for reassembly of the probe adapter.
• Ensure all components are securely fastened and properly aligned.
• Conduct a final visual inspection to ensure the probe adapter is clean and free from any remaining debris.
• Verify that all parts are correctly reassembled and ready for use.

Step 9: Inspection and Maintenance of the Converter Unit

• Conduct a visual inspection of the converter unit for signs of wear, damage, or corrosion.
• Check for loose connections or components.
• Regularly inspect the fuse in the converter unit for any signs of damage or wear.
• Replace the fuse if necessary according to manufacturer specifications.
• Clean the exterior of the converter unit using a soft, dry cloth to remove dust or debris.
• Avoid using harsh chemicals or abrasive materials.
• If applicable, adjust the contrast of the LCD screen according to manufacturer instructions.
• Ensure optimal visibility under varying ambient conditions.
• Monitor the operating temperature of the converter unit to ensure it remains within the specified range.
• Address any overheating issues promptly.
• Inspect all electrical connections within the converter unit for tightness and signs of corrosion.
• Tighten connections if necessary to ensure proper conductivity.

Step 10: Verification of Calibration and Performance

After completing the maintenance procedures outlined in the previous steps, it’s essential to verify the calibration and performance of the zirconia oxygen analyzer to ensure accurate measurements and reliable operation.

Calibration Verification:

• Perform a zero calibration: Ensure that the analyzer reads zero oxygen concentration when exposed to a zero oxygen environment. 
• Perform a span calibration: Introduce a calibration gas with a known oxygen concentration to the analyzer and verify that it reads the expected value. 
• Check calibration drift: Monitor the analyzer’s readings over time to detect any significant drift from the calibrated values. If drift occurs, recalibrate the analyzer as necessary.
• Document calibration results: Keep detailed records of the calibration procedures performed, including the date, calibration gas used, measured values, and any adjustments made.

Click here for 9 Step Zirconia Oxygen Analyzer Calibration Procedure

Performance Verification:

• Conduct a functional test: Ensure that the zirconia oxygen analyzer responds correctly to changes in oxygen concentration within its operating range. Introduce varying concentrations of oxygen to the analyzer and verify that it provides accurate and consistent readings.
• Check response time: Measure the time it takes for the analyzer to reach stable readings when exposed to changes in oxygen concentration. Compare the response time to the manufacturer’s specifications to ensure it meets performance requirements.
• Verify alarm functionality: Test the alarm system of the analyzer to ensure it activates appropriately when oxygen concentrations exceed preset thresholds. Confirm that alarms are audible and visible as per safety requirements.
• Monitor stability: Observe the stability of the analyzer’s readings over an extended period to ensure consistent performance. Any fluctuations or irregularities may indicate underlying issues that require further investigation.
• Review data logging: If the analyzer is equipped with data logging capabilities, review logged data to identify any patterns or anomalies in oxygen concentrations. Use this information to assess the analyzer’s long-term performance and identify any potential issues.

Step 11: Environmental Considerations

• Ensure the zirconia type oxygen analyzer operates within specified temperature ranges by monitoring ambient conditions and implementing temperature control measures such as insulation.
• Seal access points and use drying agents or humidity control devices to keep humidity low.
• Regularly clean the analyzer to remove dust and debris, and consider installing filters or air purifiers to minimize particle accumulation.
• Protect the analyzer from chemical exposure with coatings or barriers, and promptly address any signs of chemical damage.
• Minimize the impact of vibration and mechanical shock by using isolation measures and ensuring secure mounting.
• By addressing these environmental factors, you can maintain the performance and longevity of the analyzer in industrial environments.

Step 12: Documentation and Reporting

• Keep a detailed log of all maintenance activities performed on the zirconia type oxygen analyzer. Include the date, time, nature of maintenance, parts replaced (if any), calibration results, and any observations or abnormalities noted during the process.
• Document the results of visual inspections, including findings related to the condition of various components such as the zirconia measuring probe, converter unit, heater assembly, flame arrester, and other critical parts. Note any issues identified and actions taken to address them.
• Record the results of functional tests, response time measurements, alarm tests, and stability monitoring conducted to verify the performance of the zirconia oxygen analyzer. Include any deviations from expected values and actions taken to rectify them.
• Provide recommendations for future maintenance tasks, replacement schedules, or improvements to enhance the performance and reliability of the zirconia type oxygen analyzer. Document any follow-up actions required and their completion status.
• Obtain signatures and approvals from authorized personnel, such as supervisors or quality assurance personnel, to validate the completion of maintenance tasks and adherence to safety protocols.

Downloadable PM Checklist for Zirconia Type Oxygen Analyzer

Please follow the link below to access the downloadable PM Excel Checklist for Zirconia Type Oxygen Analyzer

Click here for more  Collection of Preventive Maintenance (PM) Procedures for Instrumentation and Control Systems