Posted 10 Dec 2010 22:59
LEL; is the lower explosion limit. Case of combustible gas in the air blast out the lowest concentration of fire, known as the lower explosion limit - referred to as% LEL. English: Lower ExplosionLimited. Case of combustible gas in the air next highest concentration of fire explosion, called the upper explosive limit - short% UEL. English: UpperExplosion Limited. So what is the lower explosion limit? Combustible gas concentration is too low or too high it is not dangerous, it is only the formation of mixed gas mixed with air or, more precisely meet a certain percentage of oxygen mixed gas fire or explosion will occur . Combustion is accompanied by intense heat and light oxidation, it must have three elements: a, fuel (gas); b, combustion material (oxygen); c, ignition source (temperature). The burning of combustible gas can be divided into two categories, one is a diffusion combustion, the volatile or ejected from the device, gas leakage can be encountered sources of ignition combustion. Another burning, combustible gas and air mixture is ignited, this intense and rapid combustion, generally have an enormous pressure and sound, also known as an explosion. Combustion and explosion no strict distinction. Relevant authorities and experts have found to the current explosion of gas were burned, worked out a flammable gas explosion limit, it is divided into upper explosive limit (short for the English upper explodelimit UEL) and lower explosive limit (short for English lower explodelimit LEL?). Below the lower explosive limit, the gas mixture can be less than the content of gas and can not cause a fire or explosion, the gas mixture above the upper limit of the content of oxygen deficiency, it can not cause a fire or explosion. In addition, the burning of combustible gas and gas with the blast of pressure, temperature, ignition energy and other factors. Explosion limit of the percentage concentration by volume, said the general. Lower explosion limit of the explosion, the explosion limit of the general term for combustible gas concentrations in the air only in the lower explosion limit, an explosion will occur between the upper explosive limit. Below the lower explosion limit or above the upper explosive limit will not explode. Therefore, when an explosion measurement, alarm concentration is generally set at 25% LEL lower explosion limit or less. Fixed combustible gas detector alarms usually have two points (on models with alarm host): 10% LEL as an alarm, 25% LEL for the second alarm. Portable combustible gas detector with an alarm point, usually: 25% LEL for the alarm. For example, methane explosion limit is 5% volume ratio, that means that 5% of this volume, a hundred equal parts corresponding to 5% of the volume ratio of 100% LEL, that is, when the values reach the detector 10 % LEL alarm point, the equivalent time of 0.5% methane content of volume. When the detector values to reach 25% LEL alarm point, the equivalent time for the methane content of 1.25% volume. So, you do not have to worry about the alarm is not in danger at any time, at this time is prompted to immediately take appropriate measures to you, such as cutting open the exhaust fan or a number of valves, from the real danger of an explosion may occur there is a great gap between the lower section, so alarm will play a role.