What is LPG?

Definition

LPG is a mixture of hydrocarbons consisting mainly of commercial propane and butane. It is generally known as “Liquefied Petroleum Gas” or simply LPG.

LPG is different from NG (Natural Gas), which consists mainly of methane and ethane. The Calorific Value of LPG is about 3 times of NG. NG is piped through the natural gas distribution network, whereas LPG is supplied to consumer with storage in a cylinder or bulk tank.
 

A vapour at ambient temperature and atmospheric pressure, LPG is liquefied by compression at ambient temperature to enhance distribution. LPG is used extensively for domestic, commercial, vehicle as well as for industrial applications.

LPG has been formed over millions of years beneath the ground. Gas rigs produce the gases as a mixture, which is then separated into methane (main gas), liquified petroleum gases (Propane and Butane) and other gases. LPG is also produced from crude oil at refineries.

Pressure

LPG exists as a gas at normal atmospheric pressure, and only existing in a liquid form at very low temperature or under pressure. When the pressure is released (e.g. when the gas supply valve is turned on), the liquid will boil and form a vapour. It is this vapour (gas), which is used to fuel appliances.

Heat is needed to convert the liquid to gas, known as the latent heat of vapourization; As the liquid boils, it takes heat energy from itself and its surroundings. This is why the containers feel cold to the touch and if there is heavy gas take off, frost may appear on the outside.

Pressure increases with temperature, so if the temperature around the tank increases, so will the pressure inside the tank as the liquid expands. Tanks are normally fitted with a pressure release valve to release any extreme pressure build up safely.