ENOTEC OXITEC 5000 Oxygen Analyzer Maintenance Guide

ENOTEC OXITEC 5000 Oxygen Analyzer Maintenance Guide

OXITEC 5000/5000+is a direct insertion flue gas oxygen analysis system used for combustion equipment, flue gas, and inert gas mixing processes. The system consists of SME-5 electronic units and KES series direct insertion probes, with zirconia sensors as the core measuring component. The probe is installed on the flue or combustion chamber, and the electronic unit is responsible for power supply, signal processing, gas path control, and human-machine interaction. For industrial sites that operate continuously for a long time, correct installation, regular calibration, and targeted maintenance are key to ensuring stable oxygen content data, reducing fuel costs, and minimizing downtime.

Measurement principle and system composition

The OXITEC 5000 series adopts the principle of zirconia oxygen measurement. The oxygen sensor at the tip of the probe is heated to about 800 ° C, and the reference side uses air with a known oxygen concentration, typically 20.95% O ₂; Measure the side contact process flue gas. When the oxygen partial pressure on both sides is different, the sensor generates a millivolt signal, which is logarithmic to the oxygen partial pressure ratio on both sides. The electronic unit converts the mV signal into the oxygen concentration in the flue gas based on the Nernst equation. The airtight isolation between reference air and process gas is extremely important. If the seal fails, the measured value will drift significantly.

The system typically includes electronic units, direct insertion measuring probes, pneumatic cables, probe signal cables, optional solenoid valves, flanges, and isolation components. The protection level of the electronic unit can reach IP66, and the probe is IP65. The ambient temperature of electronic units is generally -20 ° C to+55 ° C, and the probe junction box can adapt to -40 ° C to+80 ° C. Standard probes are suitable for smoke up to 600 ° C; When equipped with a cooling protection tube, it can cover higher temperature conditions. If the flue gas contains combustible components such as CO and H ₂, they may react with oxygen on the sensor surface, resulting in low measurement values. Therefore, it is necessary to evaluate the process conditions and, if necessary, choose protection schemes such as CSP.

Safety and on-site inspection before installation

The system is powered by line voltage, and the power must be cut off before removing the terminal cover. Only trained and authorized personnel are allowed to carry out electrical installation, commissioning, and maintenance. The installation location should avoid the accumulation of flammable gases, as the working temperature of the sensor can reach up to 800 ° C, posing a risk of ignition. The surface temperature of the probe during operation can reach 150 ° C to 800 ° C. When disassembling, it is necessary to wear insulated gloves and turn off the power supply of the electronic unit first. The probe should be stored after cooling to below 35 ° C.

Before installation, it should be checked whether the system numbers of the probe and electronic unit are consistent; Is the voltage on the nameplate consistent with the on-site power supply; Whether the electrical wiring is correct; Is the gas path connection sealed; Whether the flange is welded airtight, whether the bolts are tightened, and whether the gaskets are intact; Whether the on-site conditions match the technical data. The electronic unit should be installed at a height that is easy to observe, with sufficient space left around: at least 200 mm above and below, and at least 50 mm left and right. Avoid vibration greater than 2g and maintain IP protection level.

Electrical wiring and cable requirements

The maximum length of the probe signal cable FEP-0001 can reach 150 m, and the minimum bending radius is 96 mm. The temperature range during installation is -5 ° C to+50 ° C, and the operating temperature range is -40 ° C to+90 ° C. The signal cable should intersect with the power cable at a right angle to avoid interference caused by parallel wiring. The cable shielding layer can only be connected at the PE terminal of the electronic unit and cannot be grounded at the probe end at the same time.

The functions of each wire of the probe cable are clear: the O ₂ sensor uses white/brown and brown; Thermocouples use green and white; Probe heating uses black, blue, green/yellow; The solenoid valve uses gray and gray blue. The electronic unit terminals include power supply L/N/PE, O ₂ sensor signals, thermocouple signals, analog output 4-20 mA, relay contacts, probe solenoid valves, measurement range switching, calibration release, and process pressure input. The analog output is active 4-20 mA, with a maximum load of 500 Ω. Relay contacts are typically 24 V AC/DC, 1 A; The probe solenoid valve contacts can withstand up to 230 V AC/DC, 1 A.

The internal fuse of the electronic unit needs to be replaced according to the specifications. Common specifications include: F3 and F4 are 0.5 A; F5 is 1.0 A; F12 is 2.0 A; F1 and F2 are 4.0 A. Before replacing the fuse, the power must be turned off and the voltage, current, and characteristics of the new fuse must be confirmed to be consistent.

Gas path connection and flow rate setting

The instrument air version requires clean, dry, oil-free compressed air with an input pressure typically between 2-10 bar. The reference air continuous flow rate should be maintained at 30-40 l/h, and the test air should be maintained at 150-180 l/h during calibration. The maximum pressure of the test gas cylinder is 3 bar, and the commonly used test gas is a nitrogen mixture of 2.1% O ₂, with a flow rate of approximately 180 l/h (under 1.1 bar conditions). If using the pump version, with ambient air as the reference source, usually only the test air flow rate is adjusted.

In the gas path connection of the probe, use a blue tube for reference air and a green tube for testing gas. The bottom or back of the electronic unit is equipped with test air inlet/outlet and reference air inlet/outlet interfaces. The minimum bending radius of pneumatic cable FEP-0002 is 138 mm, with an installation temperature of -5 ° C to+50 ° C and an operating temperature of -40 ° C to+90 ° C. All air circuit joints should be correctly assembled using support sleeves, snap rings, and nuts to ensure no leakage.

Initial power on and display interface

After turning on the power, the system first displays a startup message, followed by prompts to select language, set date and time, enter TAG number, and optional ENOTEC REMOTE code. Afterwards, the probe enters the heating stage, and the display screen will show the current temperature, heating progress bar, and status. After heating is completed, enter measurement mode. After the first debugging, a two-point calibration should be performed 24 hours later.

The measurement interface usually displays TAG, O ₂ measurement value, current range, alarm indication, soft key menu, etc. The keyboard area includes three LEDs: Alarm, Maint., and Error. Alarm is orange, indicating a limit alarm; Maint. is orange, indicating maintenance mode; Error is red, indicating a system error. The system code defaults to 0000 at the factory. It is recommended to make changes after debugging and save them properly.

SYS-MENU and Key Parameters

SYS-MENU can view actual measurement values, including O ₂ value, mA output, sensor mV, reference air flow rate, probe temperature, heating power, thermocouple mV, terminal temperature, internal temperature, process pressure, sensor life, and Lambda. In the calibration results, the calibration date, method, offset, slope, test gas data, and response time can be viewed. Equipment operation data includes power on times, operating hours, and internal minimum/maximum temperature.

The O ₂ range can be freely configured, with a common range from 0-2% to 0-25%. The analog output can be set to 0-20 mA or 4-20 mA. In case of system error, the mA output can be set to 0-3.55 mA or 20.41-20.80 mA. The O ₂ limit alarm supports min/max and hysteresis settings; If the delay is 0.00%, it needs to be manually reset after triggering. The default test gas application time is 10 minutes, which can be adjusted within 5-30 minutes. If the sensor is not stable within the maximum time, it will prompt calibration failure. ACAL automatic calibration can be timed, triggered through digital input or "time+digital input". Two ACAL points need to be permanently connected to the test gas cylinder and kept open.

Key points of calibration operation

One point calibration is used to determine sensor offset, usually only test air is introduced. Two point calibration simultaneously determines offset and slope, requiring the introduction of test air and test gas. When manually calibrating, enter CAL-MENU and select either 1-point or 2-point calibration. The system will prompt to apply test air or test gas, displaying trends, flow rates, target values, and progress. During the calibration process, if the difference between the measured value and the test air concentration exceeds 3.00%, the system will prompt to return to the process. The calibration result can be displayed for up to 1 minute before resuming measurement.

The stability criterion is based on the final measurement value: if the new value exceeds the tolerance, the internal timer will reset and save the new value; If the timer is not reset, the signal is considered stable. Usually, the unit constant or slope is calculated using the final stable value after 2 minutes. The response time of mA output to changes in O ₂ sensor input is less than 200 ms.

Maintenance and replacement of vulnerable parts

The maintenance cycle depends on the flue gas conditions. Corrosive components such as SO ₂ HCl、 Continuous reducing atmosphere, dust, and solid particles can accelerate probe aging, filter clogging, and sensor drift. It is recommended to check the sensor every six months using test gas and test air; If the deviation is significant, perform two-point calibration; Visually inspect the probe and clean the filter at least annually.

When replacing filters, only ceramic, basalt, or sintered metal filters can be replaced. After removing the old filter, mix the supplied adhesive with water according to the instructions, apply it to the contact surface between the seat groove and the filter, push in and rotate the filter, evenly smooth and remove excess adhesive. The glue dries at room temperature for 24 hours. When replacing the probe, first turn off the power, open the junction box, loosen the flange bolts, use a new gasket, pay attention to the direction of the smoke, and adjust the V-shaped cover. Replacing the O ₂ sensor is usually only carried out when there is a leak or abnormal measurement value. The flange needs to be cleaned, new metal gaskets and four new screws need to be used, and the wires need to be connected before reinstalling and waiting for the working temperature. After 24 hours, perform two-point calibration.

Common faults and troubleshooting

If the O ₂ display fluctuates greatly, it may be caused by intermittent wiring, poor mV connection inside the probe, damaged filters, incorrect installation of V-shaped covers, or lack of filter heads. If the display shows full range or higher than expected, the probe and sensor flange sealing, flange welding, and bolt fastening should be checked. If the local display is correct but the output is incorrect, check the range setting and mA output terminal. If O ₂ displays 0%, possible reasons may include heater failure, thermocouple failure, damaged heating fuse, cable short circuit, transformer failure, poor mV contact, influence of combustible components, or damaged measuring cell.

Common error messages include: hardware errors 1-7, thermocouple open circuit, probe set temperature not reached, temperature too low, temperature too high, O ₂ sensor open circuit, calibration failure, test gas flow too low/too high, offset too low/too high, slope too low/too high, unstable signal, abnormal process pressure mA input, and REMOTE module error. The alarm information includes low/high reference air flow, O ₂ limit alarm 1/2, low/high electronic unit temperature, and low clock battery. When an error that cannot be handled occurs, service personnel should be contacted.

Technical Data Summary

The electronic unit displays a 240 × 64 dot matrix and supports 2 configurable O ₂ ranges, with an accuracy better than 0.5% or 0.02 Vol% O ₂ of the measured value. The power supply is 230 V AC or 115 V AC, 50/60 Hz. The power consumption during the heating stage is about 400 VA, and the measurement mode is about 200 VA. The output signal is active 0/4-20 mA, with a maximum load of 500 Ω. The standard on-site shell size is approximately 300 × 440 × 240 mm, with a weight of approximately 19 kg. The probe measurement principle is zirconia, with a process pressure of ± 50 mbar, a flow rate of 0-10 m/s, a reaction time of less than 1 s, a T90 of less than 5 s, and a probe material of SS316.