Definition
A combustible gas concentration meter is a safety instrument used to detect and measure the concentration of combustible gases in the air. It helps prevent the risk of fire or explosion caused by gas buildup by identifying the presence of specific gases and quantifying their concentration. This type of instrument is widely used in industrial and civil environments where there is a hidden danger of combustible gas leakage, and is an important technical tool to ensure safe production.
Principle
The core working principle of a combustible gas concentration meter is based on sensor technology. Common sensor types include catalytic combustion and infrared absorption. Catalytic combustion sensor uses the principle of Wheatstone bridge: when the combustible gas diffuses to the detection element (platinum wire coil coated with catalyst), flameless combustion occurs under the action of the catalyst, causing the temperature of the element to rise, and its resistance value changes, breaking the balance of the bridge and generating a voltage signal directly proportional to the gas concentration. This signal is converted into a concentration reading by circuit processing. The basic relationship can be expressed as: ΔV ∝ C, where ΔV is the output voltage change and C is the gas concentration.
Infrared absorption sensors are based on the selective absorption of infrared light at a specific wavelength by gas molecules. According to Lambert-Beale's law, there is a quantitative relationship between gas concentration and light intensity attenuation: I = I0 · e-αCL, where I is the intensity of transmitted light, I0is the incident light intensity, α is the absorption coefficient, C is the gas concentration, and L is the path length. The gas concentration can be calculated by measuring the degree of infrared light absorption.
Measurement method
According to the sampling method, the measurement can be divided into diffusion type and pump suction type. Diffusion type relies on natural gas diffusion contact sensor, suitable for open space or continuous monitoring; The pump suction type actively pumps gas samples into the sensor chamber through the built-in pump, and is suitable for areas that are difficult to diffuse such as pipelines and closed containers. The measurement process usually includes calibration, sampling, signal conversion and display. The instrument needs to be calibrated with standard gas at regular zero point and range to ensure measurement accuracy. Readings are usually expressed as a percentage of the lower limit of explosion or a percentage concentration by volume.
Influencing factors
Measurement accuracy is affected by several factors. Environmental conditions such as temperature and humidity changes may alter sensor sensitivity or cause baseline drift; Air pressure fluctuations affect the gas diffusion rate and sensor response. Cross-interference is noteworthy, as some non-target gases may react with the sensor, causing biased readings or false alarms. Sensor aging or poisoning (e.g., catalyst deactivation due to silicides, sulfides) can gradually degrade detection performance. In addition, field conditions such as instrument installation location, airflow velocity, and dust accumulation may also play a role in the measurement results.
Applications
Combustible gas concentration meters play a significant role in several industries. In the petrochemical field, it is used to monitor combustible gas leakage around storage tanks, pipelines, and reactors; In the gas industry, check the concentration of natural gas or liquefied petroleum gas in the pipeline network, pressure regulating station, and user end; In the power sector, hydrogen or methane accumulation in generator rooms and cable trenches is monitored; In municipal engineering, the biogas level in sewers and underground pipe galleries is detected; In a laboratory setting, monitor fume hoods or storage areas where flammable solvents are used. These applications are all aimed at preventing accidents and ensuring the safety of personnel and facilities.
Selection considerations
When choosing an instrument, technical parameters and application requirements should be comprehensively considered. It is necessary to clarify the type of gas to be measured and its lower explosion limit, and confirm whether the instrument range matches the resolution. According to the use environment, judge whether the protection level meets the requirements of explosion-proof, waterproof and dustproof. Consider whether response time and recovery time meet monitoring frequency requirements. Evaluate sensor life expectancy and replacement costs. For mobile applications, instrument weight, endurance, and durability are worth paying attention to; For fixed installations, it is necessary to consider the output signal type, communication interface and system integration capabilities. Ease of maintenance, calibration intervals and supplier technical support are also reference factors for long-term reliable operation.