What does lel refer to in combustible gas detectors?
As we all know, combustible gases that can be detected by combustible gas detectors include alkanes (such as methane, ethane, propane, isobutane, etc.), hydrocarbons (such as polyalkanes), alcohols (such as methanol, ethanol, etc.), aldehydes (such as formaldehyde, etc.), benzenes (such as toluene, xylene, etc.), acetylene, volatile organic compounds, etc. And in the process of detecting these combustible gases, sometimes we often involve some professional terms, such as lel. Do you know what the term 'lel' in a combustible gas detector refers to?
The term 'lel' in combustible gas detectors refers to the lower explosive limit of gases, which is a technical term for combustible gases.
When the concentration of combustible gases in the air reaches its lower explosive limit, we call the explosion risk of the combustible gas environment in this place 100%, which is 100% LEL.
If the combustible gas content only reaches 10% of its lower explosive limit, we call the explosion risk of the combustible gas environment at this location 10% LEL; The monitoring of combustible gas in the ambient air often directly gives the hazard level of the combustible gas environment, which is expressed as the percentage of the combustible gas content in the air and its lower explosive limit: [% LEL].
When flammable gases, flammable liquid vapors (or combustible dust) are mixed with air and reach a certain concentration, an explosion will occur when encountering a fire source. This concentration range that can cause an explosion is called the explosion limit.
The lower explosive limit of each gas is different. The explosion limit of hydrogen gas: lower limit 4.0%, upper limit 74.2%, combustion and explosion occur when encountering air and open flames. 4.0% is the low volume fraction of hydrogen gas that will explode when encountering an open flame. If it is less than this bottom line, it will not ignite and will not explode when encountering an open flame. 74.2% is the highest limit (or upper limit) for high volume fraction. When the volume fraction exceeds this upper limit, it can safely burn in the presence of air and open flames, and will not explode. In short, the range with a volume fraction below or below the explosion limit will not explode in the event of an open flame.
So, you don't have to worry about whether there is a danger at any time after the combustible gas detector alarms, as there is still a certain distance from reaching the explosion. Take corresponding measures immediately, such as opening the exhaust fan, cutting off some valves, or opening the sprinkler system, so that the risk of explosion does not occur. There is still a significant gap between the lower explosion limit where there is a real possibility of danger and giving an alarm, which will only serve as an alarm prompt.
