Regardless of your industry, it\u2019s good to know how combustion occurs. So here\u2019s a brief outline:<\/p>\n
Combustion is the exothermic chemical reaction of a fuel in the presence of oxygen which results in the release of energy in the form of heat and light. The reaction zone between burnt and unburnt products is known as a flame.<\/p>\n
For combustion to occur and a flame to be present, the reaction requires three elements: oxygen, ignition and fuel.<\/p>\n
When a flammable mixture is ignited the flame will propagate from the ignition source within the volume of the combustible fuel-air mix. Within pipeline systems this propagation is usually upstream (known as flashback) against the flow of gas.<\/p>\n
The flammability of gas<\/strong><\/p>\n The flammability of gas can be defined by its explosion limit. Each fuel gas has an explosive range defined by an upper (UEL) and lower (LEL) explosion limit in the presence of oxygen outside of which it is not combustible.<\/p>\n Lower Explosion Limit<\/strong><\/p>\n The lowest concentration at which a fuel\/air mixture will burn. Below this the mixture is too lean or the fuel is Insufficient. <\/strong><\/p>\n Upper Explosion Limit<\/strong><\/p>\n The highest concentration at which a fuel\/air mixture will burn. Above this the mixture is too rich i.e. there is not enough oxygen.<\/p>\n When the concentration of fuel is neither too low (lean), nor too high (rich) you get perfect, or stoichiometric conditions. In other words, complete combustion.<\/p>\n As well as this, some fuels have LEL of <1% (Kerosene, Jet A) in air, meaning a small mixture\/leak can result in dangerous conditions. Some fuels such as hydrogen have very wide explosive ranges (4% – 75%) in air, making them particularly hazardous. Start-up\/shut down conditions must be taken account of, as most accidents take place during upset conditions.<\/p>\n <\/strong>Explosion risks<\/strong><\/p>\n When it comes to navigating explosion risk factors, Elmac should be the first company you turn to. We\u2019re experts at helping companies work out the risk factors involved: the likelihood that explosive atmosphere will occur, and the potential for ignition.<\/p>\n The types of questions we use to assess the risk include:<\/p>\n\n