Online trace oxygen analyzerThe key points of daily maintenance (focusing on extending service life) are as follows:
1、 Core component maintenance: specialized management of sensors
Electrochemical sensor
Avoid overload: Prolonged exposure to high concentrations of oxygen (>1000ppm) or corrosive gases (such as Cl ₂, H ₂ S) is prohibited, as it may cause irreversible damage to the electrode. After accidental contact, it is necessary to immediately blow with high-purity nitrogen gas (99.999%) for 30 minutes, and then check whether the output is normal.
Electrolyte management: Check the electrolyte level every 3-6 months. If the level is below the scale, turbid, or discolored (such as transparent turning brown or yellow), immediately replace it with the same type of electrolyte (avoid mixing different brands). After replacement, let it stand for 2 hours until the sensor stabilizes before calibration.
Oxygen permeable membrane maintenance: Check the oxygen permeable membrane (such as polytetrafluoroethylene membrane) for damage, deformation, or oil stains every 6 months. If there are pollutants, gently wipe with a dust-free cloth dipped in anhydrous ethanol; If the membrane is damaged, it needs to be replaced as a whole and recalibrated.
zirconia sensor
Temperature control: Ensure a smooth heating process during startup (avoid sudden heating), and turn off the power after the temperature drops to room temperature to prevent ceramic components from cracking.
Heater and thermocouple inspection: Use a multimeter to measure the resistance of the heater every quarter (usually 50-100 Ω). If the resistance is abnormal (such as infinite or close to 0), the heater needs to be replaced; At the same time, check if the thermocouple is loose. If the temperature display deviation exceeds ± 5 ℃, it needs to be recalibrated or replaced.
Zirconia tube cleaning: Every 6-12 months (shortened to 3 months in high dust environments), remove the zirconia tube and use a soft bristled brush or compressed air (pressure ≤ 0.3MPa) to remove dust and carbon deposits inside and outside the tube; Stubborn stains can be soaked in a 5% citric acid solution for 10 minutes, then rinsed with pure water and dried. Scratching the pipe wall with hard objects is prohibited.
Paramagnetic sensor
Anti vibration: Avoid severe vibration (magnetic circuit deviation can cause accuracy decrease), and check the installation and fixation for firmness every week.
Cleaning of optical components: Check the laser emitting end and receiving end lenses (or fluorescent probes) every 3 months. If there is dust or oil stains, use specialized optical lens paper or dust-free cloth dipped in isopropanol to gently wipe in the same direction. Do not use ordinary paper towels.
2、 Maintenance of gas system: leak prevention and pollution prevention
leak detection
Conduct a monthly gas leakage test: turn off the analyzer, introduce 0.2MPa high-purity nitrogen gas into the gas path, close the intake valve and observe the pressure change. If the pressure drops by ≤ 0.01MPa within 1 hour, it is considered qualified; If there is a leak, it is necessary to check whether the joints (such as card sleeves, threaded interfaces) are loose, replace the aging sealing rings (such as nitrile rubber rings, fluorine rubber rings for high temperature environments), and tighten them again.
Filter cleaning and replacement
Pre filter (such as PP cotton filter element, sintered metal filter element): Disassemble and inspect every 2-3 months. If there is obvious dust or oil on the surface of the filter element, it needs to be replaced (replaced monthly in high dust environments).
Precision filter (aperture ≤ 0.2 μ m): Replace every 6 months to prevent impurities in the standard gas from contaminating the sensor.
Condensed water and impurity treatment
If the moisture content of the sample gas is high (such as smoke or fermentation gas), it is necessary to check the liquid level of the condenser separator daily and drain the condensate water in a timely manner (to avoid water entering the sensor, causing short circuit or electrode failure); In cold environments, it is necessary to turn on air path tracing (temperature set at 5-10 ℃ to prevent condensation water from freezing and blocking the pipeline).
3、 Calibration and Verification: Ensuring Measurement Accuracy
Daily calibration
Perform single point calibration every 1-2 weeks (using zero gas to calibrate the zero point). If the zero drift exceeds ± 2% FS, two-point calibration (zero gas+range gas) is required.
Regular full calibration
Perform two-point calibration every 3-6 months, and record calibration data (such as zero offset and range error) after calibration. If the error exceeds 5% FS, check whether the sensor is malfunctioning or contact the manufacturer for professional calibration.
Calibration gas management
The calibration standard gas (such as zero point gas 99.999% N ₂, range gas 10/100ppm O ₂) should be used within its validity period. Before each use, the dead volume at the outlet of the steel cylinder should be emptied (open the valve to release air for 3-5 seconds) to avoid residual air in the pipeline affecting the calibration accuracy; When the pressure of the steel cylinder is lower than 0.5MPa, it needs to be replaced.
4、 Environment and Operating Standards: Reduce External Damage
Working temperature and humidity
It is recommended to maintain the working temperature between 0-40 ℃ and avoid high temperature or humid environments; In high humidity environments (humidity>85%), desiccants (such as silicone desiccants, replaced once a month) can be placed inside the equipment to prevent the circuit board from being affected by moisture and short circuiting.
Sample gas pressure and flow rate
The sample gas pressure should be lower than 0.2MPa (recommended 0.05MPa), as excessive pressure may cause damage to the sensor; The flow rate of the sample gas should be controlled at 200-400 milliliters per minute, as high or low flow rates can affect measurement accuracy.
Installation and anti-interference
Confirm that the equipment is securely installed (such as whether the bracket of the wall mounted equipment is loose), to avoid displacement of sensors or air circuit joints caused by vibration; Stay away from strong electromagnetic interference sources (such as frequency converters and high-voltage cables). If it is not possible to stay away, install electromagnetic shielding covers for the equipment.
5、 Long term shutdown and storage: preventing performance degradation
Pre shutdown processing
Before shutting down, blow the gas path with high-purity nitrogen for 10 minutes to remove any residual sample gas in the sensor and avoid long-term contact of the electrode or zirconia tube with corrosive gases; After disconnecting the power, seal the sensor in an inert gas environment (electrochemical sensors should avoid drying and can be kept slightly moist).
Ready to power on again
When restarting after a long-term shutdown (more than 1 week), the preheating time should be extended (30 minutes more than usual) to ensure that the sensor temperature is stable before measurement.
6、 Data and Record Management: Tracing the Root of Problems
data backup
Export historical data monthly and back it up to avoid data loss caused by storage medium damage; Check whether the communication interface (such as RS485, Ethernet) is normal. You can send instructions through the upper computer to confirm whether the data transmission is stable (if packet loss occurs, check the cable shielding or replace the interface module).
Maintenance Log
Establish a maintenance ledger to record the time, content (such as sensor replacement, air leakage testing, calibration results), and operators of each maintenance, in order to trace the equipment status and promptly identify potential problems (such as the need to check for corrosive impurities in the sample gas if the frequency of sensor replacement is too high).
7、 Consumables and consumables management: advance planning for replacement
Sensor life assessment
When using electrochemical sensors for more than 1 year and zirconia sensors for more than 2 years, it is necessary to confirm whether the accuracy meets the standard through multiple calibrations. If frequent calibrations still cannot meet the requirements, the sensor should be replaced in a timely manner (expired use can lead to unreliable data).
Filter element and desiccant replacement
The pre filter element is replaced every 2-3 months (for high dust environments, it is replaced every month), and the precision filter is replaced every 6 months; Check the status of desiccants (such as silica gel desiccants) monthly. If the silica gel changes from blue to pink, it needs to be replaced or regenerated in a timely manner (such as heating activated silica gel).