Lower Explosion Limit (LEL) Test

The purpose of the lower explosion limit (LEL) test is to determine the lowest concentration of dust that can ignite. The lower explosion limit is used in processes where dust concentration is controllable, such as some types of dryers and pneumatic conveying systems. The lower explosion limit is an important parameter when classifying a facility as a hazardous area.

This test is carried out according to the European standard EN 14034-3 (EN 14034-3 Determination of the explosion characteristics of dust clouds - Part 3: LEL determination of the lower explosion limit of dust clouds).

This standard describes a test method for determining the lower explosion limit of dust clouds in a closed container under defined initial pressure and temperature conditions. However, this test method is not considered suitable for use with conventional explosives such as gunpowder and dynamite, explosives that do not require oxygen for combustion, pyrophoric substances or, in some cases, substances or mixtures of substances that behave similarly.

During testing, dust samples of various sizes are dispersed in a 20 liter blast apparatus and exposed to a 2kJ ignition source. The test is repeated by changing the dust concentration in the apparatus until the lower explosion limit (LEL) is found.

For the purposes of this standard,

• Dust refers to small solid particles that collapse under their own weight in the atmosphere but can remain suspended in the air for a while.
• Combustible dust refers to dust that can react exothermically with air when ignited.
• Burst pressure refers to the highest overpressure that occurs during the explosion of a dust cloud in a closed container.
• An explosive atmosphere refers to the mixture of flammable substances in the form of gases, vapors, mists or dusts with air, in which combustion spreads to the entire unburned mixture after ignition occurs, under atmospheric conditions.
• Ignition delay refers to the time between the start of powder dispersion and activation of the ignition source.
• Initial pressure refers to the pressure in the detonation vessel at the moment of ignition.
• Initial temperature refers to the temperature in the detonation vessel at the time of ignition.
• The lower explosion limit (LEL) refers to the lowest concentration of combustible dust in a mixture with air at which an explosion occurs.

Our company also provides lower explosion limit (LEL) testing services with its trained and expert staff and advanced technological equipment, among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.