Properties of LPG
Properties of LPG
LPG vapour is heavier than air, which has important safety implications. Any leakage will sink to the ground and accumulate in low lying areas and may be difficult to disperse, so LPG should never be stored or used in cellars or basements.
LPG has no smell and so a strong "stenching " agent is added before delivery to help detection of any leaks.
LPG is a high performance fuel, but will only ignite if mixed with air in a gas:air ratio of between 1:50 and 1:10. The low limit for flammability means that even small leaks could have serious results.
The ignition temperature of LPG in air is around 500ºC – lower than that of mains gas but actually requiring more energy to cause ignition. This means that some gas lighters may not work with LPG.
LPG is chemically reactive and will cause natural rubber and some plastics to deteriorate. Only equipment and fittings specifically designed for LPG should be used.
LPG has been formed over millions of years beneath the ground. Gas rigs produce the gases as a mixture, where they are separated into methane (mains gas), the LPG’s of propane and butane and other gases. LPG is also produced from crude oil at refineries.
LPG exists as a gas at normal atmospheric pressure, only existing in a liquid form at very low temperatures, or under pressure. Normally, the gas is stored in liquid form under pressure in a steel container.
When the pressure is released (e.g. when the gas supply valve is turned on), the liquid will boil and form a vapour. It’s this vapour (gas) which is used to fuel appliances.
Heat is needed to convert the liquid to gas, known as the latent heat of vapourisation. As the liquid boils, it needs to take heat energy from itself and its surroundings. This is why containers feel cold to touch and if there is a heavy gas off-take; frost may appear on the outside.
There are two types of LPG (propane and butane), which have similar properties but are very different in storage requirements. Propane has a lower boiling point than butane, so will continue to convert from a liquid to a gas even in very cold conditions. This makes it suitable for domestic and commercial heating, hot water and cooking, as well as a whole range of uses in agriculture and industry.
