Important – and little-known – facts about the inner workings of a LEL System

A LEL system is a complex safety monitor, capable of measuring the percentage of different gases in a specific chamber's atmosphere, thus allowing for those gases which pose a significant risk of explosion to be lowered in quantity until such danger no longer stands. Such monitoring is vital in several industrial situations, the printing industry above all; however, the way LEL systems actually work is often not well known to many operators. Here are a few important facts regarding these monitors: A LEL system is a complex safety monitor, capable of measuring the percentage of different gases in a specific chamber's atmosphere, thus allowing for those gases which pose a significant risk of explosion to be lowered in quantity until such danger no longer stands. Such monitoring is vital in several industrial situations, the printing industry above all; however, the way LEL systems actually work is often not well known to many operators. Here are a few important facts regarding these monitors:

1. There is more than one type of LEL system, depending on the kind of analysis required for a specific application. Some models mount a single sensor, and can only monitor the presence of a single kind of gas, while others are equipped with a suite of different sensors and can do a more throrough atmospherical analysis, detecting oxygen, hydrogen sulfide, and many other gases.

2. The structure of the sensor in an LEL system is, in itself, quite simple. It consists of two solid state catalytic sensors (made of two porous ceramic beads, one active and one inert) which surround a coiled wire.

3. LEL sensors are usually non-specific. This means that most LEL systems are capable of reacting to exposure to any single combustible gas.

4. Calibration of an LEL system is essential: sensors will indicate incorrect values if used to measure a different gas than the one they were originally calibrated for. For this reason, most manufacturers of LEL systems provide tables of correlation factors to obtain correct measurements for different gases based on the originally calibrated type.

5. The LEL in LEL systems stands for “Lower explosion level”. LEL systems express a value that is the percentage of LEL of a combustible gas – that is, how much gas there is in the atmosphere compared to a dangerous level of concentration.

8. LEL system sensors aren't eternal: their normal operating life lasts about one or two years at most, and that is how long they are usually guaranteed by manufacturers. Several factors may shorten that time, such as impacts (the coiled wire in the sensors is very fragile) or applications in atmospheres which are rich in combustible gas but poor in oxygen (since it causes carbon and tar to accumulate on the active bead).


By: Michele Ansoni

NIRA Instruments' LEL systems are among the best known and most used in the printing industry, striking an ideal balance between efficiency and investments.

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Article Tags: LEL Systems

Submitted On Oct 05, 2016. Viewed 263 times.

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