There are many common combustible gases found in chemical plant. These gases have one similarity. They may be sparked when their concentration in atmosphere are inside their flammability limits. What are flammability limits? Flammability limits or commonly called explosive limits are described as concentration of combustible gas in conjunction with air in which they may be ignited and exploded in the presence of source of ignition. The lowest concentration of a Combustible gas in conjunction with air where it can be ignited is known as by Lower Explosive Limit LEL or Lower Flammable Limit LFL. Whereas, the maximum concentration of it in conjunction with air it can be ignited is known as by Upper Explosive Limit UEL or Upper Flammable Limit UFL.
Each combustible gas has its own unique Lower Explosive Limit and Upper Explosive Limit. The info about LEL and UEL of a combustible gas are seen in its MSDS. What’s LEL of Common Combustible Gases data for? Lower Explosive Limit LEL Information of common combustible gases is extremely vital for safety. Let us take an example. When we plan to perform welding work on the surface of a pressure vessel containing one of the above mentioned common combustible gases, the first thing we must do is to assess the gas concentration within the vessel.
The concentration should be lower than LEL of the combustible gas. Even it is advised to set target concentration at 10 percent of LEL. It means that if the pressure vessel containing hydrogen, maximum hydrogen concentration within it must be 0.4percent before welding work is permitted. Normally, LEL of common combustible gases is included into hot work permit form. Each gas concentration is measured by combustible gas sensor or Paper Chromatography and the results are listed on the hot work permit form. Nitrogen substitution ought to be carried out if needed.
In case of combustible gas Purge, no functions are permitted to be performed during the gas purge. It is worried that the functions create fire or spark and ignite the purged gas, which is in its flammable limits. Middletown power plant explosion revealed just how dangerous natural gas purge operation that has been carried out improperly. It is advisable to install gas Purifiers in a vertical position as wall mounted kinds to prevent channeling. Channeling occurs when you put in the gas purifier at a horizontal position. Gas purifiers are available as compact panels using multiple purifiers or single panel which has multi-absorbent capabilities.