Infrared Gas Analyzers: Working Principle, Types, and Expert Selection Guide
Infrared gas analyzers are high-tech measuring complexes designed for continuous or periodic monitoring of polyatomic gas concentrations in air and process environments. Amid constantly tightening regulatory requirements for industrial and environmental safety, traditional monitoring methods are gradually giving way to optical technologies. Optical infrared gas analyzers rightfully hold leading positions in the control and measuring instruments market due to their exceptional selectivity, durability, and ability to operate stably in the harshest conditions.
Comparative Analysis of Gas Analysis Technologies
To understand the place of infrared technologies in the overall industrial safety system, it is necessary to compare them with alternative detection methods. The table below outlines the key differences that engineers consider when designing gas monitoring systems.
| Sensor Technology | Operating Principle | Key Advantages | Application Limitations |
|---|---|---|---|
| Infrared (NDIR) | Selective absorption of IR radiation by gas molecules | High selectivity, service life of over 5 years, operation without oxygen, resistance to poisoning | High initial cost, inability to measure diatomic gases (O2, N2, H2) |
| Thermo-catalytic | Oxidation of combustible gas on a heated catalytic bead | Low cost, measurement of a wide range of combustible gases | Catalyst poisoning by silicon and sulfur compounds, requires oxygen presence, short service life |
| Electrochemical | Chemical reaction at the electrodes generating an electric current | High sensitivity to toxic gases, low power consumption | Limited service life (2-3 years), high dependence of readings on ambient temperature |
Physical Fundamentals and Operating Principle of NDIR Technology
The operation of these devices is based on the non-dispersive infrared analysis method. Unlike contact methods, optical infrared gas analyzers eliminate direct physical contact between the sensing element and the aggressive environment, which drastically increases their fault tolerance.
Bouguer-Lambert-Beer Law in Gas Analysis Practice
The foundation of the equipment’s operation is the Bouguer-Lambert-Beer law, which describes the exponential attenuation of a monochromatic light beam as it passes through an absorbing medium. Each polyatomic gas has a unique absorption spectrum in the infrared range. For example, methane maximally absorbs radiation at a wavelength of about 3.3 µm, propane in the 3.4 µm range, and carbon dioxide at 4.26 µm. By measuring the degree of IR flux attenuation at a strictly defined wavelength, the device’s microprocessor calculates the volume fraction of the target component in the gas mixture with high accuracy.
Dual-Beam Optical Scheme as a Reliability Standard
Modern optical infrared gas analyzers implement a dual-channel measurement scheme. The system simultaneously records the signal at the working wavelength, which is actively absorbed by the target gas, and at the reference wavelength, which is not absorbed by this gas. This engineering solution allows the device’s algorithms to compensate in real-time for the drift of the infrared radiation source characteristics, natural contamination of optical windows by dust or condensation, as well as pressure fluctuations in the measuring cuvette.
Classification of Infrared Equipment by Design
The market offers various modifications of the equipment adapted to the specific tasks of industrial enterprises and the architectural features of safety systems. The main types are presented in the following table.
| Equipment Type | Main Purpose | Key Design Features |
|---|---|---|
| Stationary Infrared Gas Analyzer | Continuous 24/7 monitoring in fixed zones | Reinforced explosion-proof enclosure, 4-20 mA output signals, relay outputs for automation control |
| Infrared Gas Analyzer Sensors | Integration into existing distributed control systems (DCS) | Modularity, compactness, hot-swappable measuring block without compromising explosion protection |
| Open-Path Optical Infrared Gas Analyzers | Monitoring of extended areas, perimeters, and pipe racks | Range up to hundreds of meters, integral measurement of gas cloud concentration along the entire beam path |
Key Advantages of Optical Systems
The popularity that infrared gas analyzers have gained in heavy industry is due to a number of undeniable technical advantages that directly impact the enterprise’s economics.
- Complete absence of the poisoning effect. The optical method is completely immune to catalytic poisons, which is critical for oil refineries and chemical plants.
- Correct operation in oxygen-deficient environments. Infrared gas analyzer sensors accurately measure gas concentration even in an inert atmosphere or in the complete absence of oxygen, where catalytic sensors are useless.
- Protection against false alarms. Optical systems are selective and do not react to high concentrations of non-combustible gases or vapors that can cause malfunctions in thermo-catalytic elements.
- Minimal operating costs. The absence of burnout elements and consumable chemical reagents ensures calibration stability over many years.
Selection Criteria: Checklist for Engineers
To correctly specify the equipment and avoid procurement errors, it is necessary to formalize technical requirements at the design stage. The following table serves as a practical selection guide.
| Selection Criterion | Recommendation for the Specialist |
|---|---|
| Target gas and measurement range | Clearly define the measured component (CH4, CO2, CxHy) and the required range (from LEL percentages to volume percentages) |
| Environmental conditions | Choose a stainless steel enclosure for aggressive environments, enclosure protection rating of at least IP66 |
| Explosion protection requirements | Availability of a valid certificate of conformity to the technical regulations of the Customs Union (TR CU 012/2011) for Zone 0, 1, 2 areas |
| Communication interfaces and integration | Support for necessary industrial protocols: HART, Modbus RTU, or RS-485 for seamless integration into DCS |
| Metrological support | Mandatory presence of a certificate of inclusion of the model in the State Register of Measuring Instruments |
Industries Using Infrared Gas Analyzers
The implementation of the equipment is dictated by strict industry regulations for industrial and environmental safety, as well as the need to optimize technological processes.
- Oil and gas sector and oil refining. Monitoring methane and light hydrocarbon leaks on offshore platforms, main pipelines, and primary oil processing units.
- Chemical and pharmaceutical industries. Monitoring technological reactions with the release of carbon dioxide or volatile organic compounds in sealed reactors.
- Power generation and metallurgy. Analysis of flue gas composition to optimize the excess air coefficient and control harmful emissions.
- Environmental monitoring and biogas plants. Measuring methane and carbon dioxide concentrations at municipal solid waste landfills and wastewater treatment plants.
Economic Justification: Total Cost of Ownership (TCO)
When evaluating the total cost of ownership, the initial price of a stationary infrared gas analyzer may exceed the cost of basic catalytic analogs. However, the real economic efficiency is revealed over a three-to-five-year operation horizon. The service life of the optical sensor ranges from 5 to 10 years without significant sensitivity degradation, which eliminates regular costs for purchasing replacement elements. The calibration interval reaches 12 months, and the calibration procedure is performed quickly and does not require disassembling the device.
Expert Support and Supplies from LET
LET specializes in the comprehensive equipment of industrial facilities with modern gas analysis and industrial safety means. We do not just supply equipment; we also provide a full cycle of engineering support: from auditing existing systems and developing detailed technical specifications to commissioning and metrological maintenance.
The company’s catalog features proven solutions that meet the strictest industry quality standards. Our engineers will help select the optimal configuration that guarantees measurement reliability and full compliance with regulatory authorities’ standards.
For detailed technical consultation, cost calculation, or requesting an individual commercial proposal, please contact us:
- Email: let@eca.ru
- Phone: +7 (495) 232-00-66
Entrust industrial safety to professionals: choose infrared gas analyzers that will ensure uninterrupted and safe operation of your enterprise for decades to come.
FAQ
Can an infrared gas analyzer be used to measure oxygen?
No, oxygen (O2) molecules are diatomic and symmetrical, so they do not absorb infrared radiation. Electrochemical or paramagnetic sensors are used to measure oxygen concentration.
How often does the optical sensor require calibration?
Due to the high stability of the optical system, the calibration interval is usually 1 year, and technical calibration may be required no more than once every 6–12 months, depending on operating conditions and the enterprise’s regulatory documentation requirements.
Does high dustiness affect measurement accuracy?
Modern optical infrared gas analyzers are equipped with an optical contamination compensation function. The system compares signals from the measuring and reference channels, neutralizing the effect of dust, dirt, or condensation on the final accuracy of the result.