Tags: Wireless gas monitoring system , Infrared gas detector "LEL" refers to the lower explosive limit. The lowest concentration of combust…
Tags:Wireless gas monitoring system ,Infrared gas detector
"LEL" refers to the lower explosive limit. The lowest concentration of combustible gases that explode in air when exposed to an open flame is called the lower explosive limit—abbreviated as %LEL. The highest concentration of combustible gases that explode in air upon exposure to an open flame is called the upper explosive limit—abbreviated as %UEL. So, what is the lower explosive limit? If the concentration of flammable gases is too low or too high, it is not dangerous; it only combusts or explodes when mixed with air to form a mixture, or more precisely, when it meets oxygen to form a certain proportion of mixed gas.
Combustion is a violent oxidation reaction accompanied by luminescence and heat, and it must have three elements: a. Combustible material (gas); b. Combustion aids (oxygen); c. Ignition source (temperature). Combustible gas combustion can be divided into two categories: one is diffusion combustion, which involves volatile combustible gas that is emitted or leaked from equipment and combusts together when it meets an ignition source. The other type of combustion is combustion when combustible gas and air mix. This combustion reaction is intense and fast, usually producing tremendous pressure and noise, also known as an explosion. There is no strict distinction between combustion and explosion. Relevant authorities and experts have conducted combustion and explosion analyses on the currently discovered combustible gases and established the explosion limits for combustible gases, which are divided into upper and lower explosive limits. If the content of combustible gas in the mixture is insufficient below the upper limit and cannot cause combustion or explosion, and if the oxygen content is insufficient above the upper limit, it will also not cause combustion or explosion.
Additionally, the combustion and explosion of combustible gas are also related to factors such as gas pressure, temperature, and ignition energy. The explosion limit is generally expressed by the volume percentage concentration. The explosion limit refers to the lower and upper limits of explosions. The concentration of combustible gases in the air only occurs between the lower and upper limits of the explosion. Explosions will not occur if the explosion is below or above the upper limit. Therefore, when measuring explosions, the alarm concentration is generally set below 25% LEL of the lower explosion limit.
All kindsCombustible gas detectorThe measurement range is 0-100% of LEL. Fixed combustible gas detectors usually have two alarm points (depending on the model of the alarm host): 10% LEL is a primary alarm, 25% LEL is a secondary alarm. Portable combustible gas detectors usually have an alarm point: 25% LEL as the alarm point. For example, if the lower explosive limit of methane is 5% by volume, that means dividing this 5% volume ratio into 100 equal parts so that the 5% volume ratio corresponds to 100% LEL. In other words, when the detector reading reaches the 10% LEL alarm point, the methane content at that time is equivalent to 0.5% by volume. When the detector reaches the 25% LEL alarm point, the methane content is equivalent to 1.25% by volume.
Therefore, you don't need to worry about danger at any moment after the alarm. This is a reminder to take immediate action, such as turning on the exhaust fan or shutting off some valves. This is still far from the lower limit of the actual potential explosion, which serves as an alarm warning.
(2) ppm is the specific concentration by volume: parts per million.
ppm is a method of expressing solution concentration (solute mass fraction), with ppm being one part per million.
For solutions: i.e., 1/1000 milliliter of solute in 1 liter of aqueous solution, its concentration (solute mass fraction) is 1 ppm.
For gases: one of the methods for expressing the concentration of pollutants in the ambient atmosphere (air).
Volume concentration notation: the volume of pollutants contained in one million volumes of air, i.e., ppm
Most of itGas DetectorsThe gas concentrations measured by the instrument are all volumetric concentration (ppm). According to Chinese regulations, especially environmental protection departments, gas concentrations are required to be expressed in units of mass concentration (e.g., mg/m³). Our country's standards and specifications also use mass concentration units (e.g., mg/m³; ) stated.
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