Combustible Gas Detectors – Overview

Combustible gas detectors are ones of the basic safety equipments required when there is combustible gas inside the plant site. Auto-ignition temperature and Lower Explosive Limit (LEL) describe the potential dangers of combustible gases.

Auto-ignition temperature is the lowest temperature at which combustible gas could be ignited spontaneously (self-sustained combustion), without the presence of source of ignition. Meanwhile, Lower Explosive Limit or LEL is the lowest concentration of combustible gas in the air that will propagate flame when exposed to a source of ignition.

There are two types of combustible gas detectors in market. The first type is electrocatalytic (catalytic bead), which is also referred to passive type of gas detector. The second type is infrared detector, which uses infrared absorption as detecting technology. It is the active type.

Electrocatalytic type is widely used in various industries and generally applied as single-point detectors for combustible gases. The operating principle is based on oxidation reaction of combustible gas and oxygen from the air on the heterogeneous catalytic element. Heat from the reaction heats the platinum coil embedded in the catalyst and this change resistance of the coil. Then, it is measured and monitored.

There are two factors that affect the sensitivity of catalytic type gas detectors, i.e. blockage of the flame arrestor by which combustible gas flows through and poisoning of the active bead. Besides, mechanical failure may be possible caused by vibration. Vibration can break the platinum wire.

Benefits of electrocatalytic sensors are relatively low unit cost, simple and better accuracy compared with other detection methods.

On the other hand, infrared type combustible gas detectors detect the presence of any combustible gas based on infrared radiation absorption at a certain wavelengths.

Some key benefits of infrared type are free of maintenance because calibrated by the factory, can be used for single-point and open path devices, can be located at inaccessible location in the plant site, no chemical poisoning possibility, fail to safe technology, does not require oxygen to measure combustible gas concentration, internal compensation virtually eliminates span drift and appropriate for continuous gas environment.

When you need to choose which combustible gas detectors you should purchase, read the following tips. You need a short research before making any selection. Here are tips.

  1. Determine clearly your specific requirements of combustible gas detectors.
  2. Select multiple or single combustible gas detectors. Some gas detectors can also detect other gases instead of only combustible gases, such as sulfur dioxide, carbon monoxide, ammonia and so on.
  3. Check the detection range of combustible gases. It means check its percentage of Lower Explosive Limit (LEL). The combustible gas detectors at least should be capable of detecting 10%~15% of the lower LEL. Give this specification more attention, since this will give you more time for you to take actions when gas leak is detected.
  4. Select which type of detecting sensors is appropriate for your needs.
  5. Get information about battery and sensors lifetime. This is especially important when you need to replace them.
  6. Select which alarms are required to alert gas leakage. Sound or light, or may be both.
  7. Get the spare parts price of the combustible gas detectors, especially the sensors. Do not select a gas detector when unit price of the combustible gas detectors is nearly same with sensor’s price.
  8. Select only combustible gas detectors that certified by common standards or the government.
  9. Purchase combustible gas detectors from trusted manufacturers only. Look for testimony from others.

The following combustible gas detectors are recommended for your chemical plant needs. See the features which one can fulfill your requirements.

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