Is AZ25 always better than AZ20?
No. They address different conditions. The temperature range and probe construction must match the application.
ABB · Analytical measurement
Oxygen and combustion analysis
Oxygen measurement for combustion control. We assess temperature, atmosphere, installation and the need to measure residual combustibles.
Selecting from the Endura range
| Model | Measurement / construction | Application to assess | Reference |
|---|---|---|---|
| AZ20 | O₂ · in-situ zirconia | Combustion control; process temperatures up to 800 °C | AZ20 |
| AZ25 | O₂ · high-temperature zirconia | Applications above 600 °C, up to 1400 °C depending on version | AZ25 |
| AZ30 | O₂ · flameproof system | Hazardous areas; process temperatures up to 700 °C | AZ30 |
| AZ40 | O₂ or O₂ + CO equivalent; close-coupled sampling | Control of excess oxygen and unburnt combustibles | AZ40 |
| AZ10 | O₂ · close-coupled sensor with sample guide tube | Small boilers and marine applications; process temperatures up to 800 °C | AZ10 |
These limits guide initial selection. Check length, sheath, mounting and permitted conditions against the datasheet for the selected configuration.
AZ20 · O₂ in flue gas
Probe with a zirconia cell at the tip inserted into the duct. ABB specifies process temperatures up to 800 °C and lengths up to 4 m. The range includes diagnostics, HART communication and automatic calibration options.
A useful starting point for in-situ combustion measurement where temperature, materials and gas conditions are compatible.
AZ25 · High temperatures
For furnaces and processes above 600 °C, ABB offers AZ25 versions up to 1400 °C, with protective sheaths selected for the application. Specified lengths reach 1250 mm.
Selection also depends on furnace atmosphere and sheath resistance: replacing AZ20 with a probe that has a higher temperature rating is not sufficient by itself.
AZ30 · Hazardous areas
AZ30 is the flameproof combustion measurement system in the range. ABB specifies ATEX/IECEx certification, process temperatures up to 700 °C and lengths up to 2 m.
Check the full marking, external environment and permitted process conditions. Certification does not remove the need to assess the gas reaching the cell.
AZ40 · Oxygen and combustibles
AZ40 combines zirconia oxygen measurement with combustibles measurement expressed as CO equivalent, depending on configuration. It uses close-coupled sampling with a heated path; filtration and blowback-cleaning options are available.
COe is not a selective measurement of CO alone. The value is used to assess residual combustibles and must be interpreted according to the analyser’s principle and calibration.
AZ10 · Small boilers and marine applications
ABB datasheet revision E describes AZ10 for small industrial boilers and marine applications. The system includes a remote transmitter and a zirconia sensor outside the duct, supplied through a sample guide tube; direct installations are provided for small ducts.
Process temperatures up to 800 °C, with a 400 °C limit at the mounting flange. Reference air reaches the sensor by diffusion, without a dedicated external compressed-air line.
For replacement, provide the nameplate, mounting details and application conditions. For marine use, check the certification required by the project for the proposed configuration.
Selecting the installation point
- Choose a representative process location and assess possible stratification.
- Avoid interpreting air ingress through the duct or mounting as a change in combustion.
- Allow space for probe withdrawal, maintenance and test gas connections.
- Assess dust, deposits and the probe’s chemical compatibility.
- Follow the manufacturer’s heating, start-up and calibration procedures.
O₂ in process gas, flue gas or water?
A combustion probe is not automatically suitable for nitrogen purity or trace oxygen. The range and sample matrix require a dedicated selection.
Information for a quotation
To select an Endura oxygen analyser, send us the following information, even if preliminary:
- Application and fuel; residual combustibles or a reducing atmosphere.
- Minimum, normal and maximum temperature; duct pressure.
- Required O₂ range and need for combustibles/COe measurement.
- Dust, corrosive components, moisture and start-up conditions.
- Insertion length, flange, orientation and space to withdraw the probe.
- Area classification, utilities and control system interfaces.
Frequently asked questions
Does AZ40 measure only CO?
No. Combustibles measurement is expressed as CO equivalent. It must not be presented as a selective measurement of carbon monoxide alone.
Why does the reading differ from an extractive analyser?
Check sampling location, wet or dry basis, air ingress and delays. Comparison requires equivalent conditions.