Elgas LPG Gas Blog

How Does LPG Work? Does LPG Work

LPG is called liquefied gas because it is easily transformed into a liquid. LPG needs only low pressure or refrigeration to change it into liquid from its gaseous state. As a gas, LPG expands to 270 times its volume as a liquid. This makes the liquid the ideal way to store and transport LPG.

LPG works as a fuel, providing energy.  It works by generating heat for cooking, heating, hot water and as a fuel for vehicles.

How LPG Works

LPG is stored under pressure, as a liquid, in a gas bottle.

It turns back into gas vapour when you release some of the pressure in the gas bottle by turning on your gas appliance.

Almost all of the uses for LPG involve the use of the gas vapour, not the liquefied gas. 

The LPG gas is ignited and burned to provide heat energy for various applications.

This short video (8:29) explains all of the basics of LPG gas...

But there is a bit more detail to this process…

Where Your LPG Comes From

The LPG pathway to you includes drilling of wells, refining, transport, storage, vaporisation, gas regulators and the gas appliances themselves.

LPG comes from drilling oil and gas wells.

LPG is found naturally in combination with other hydrocarbons, typically crude oil and natural gas.

LPG is produced from natural gas processing and petroleum refining.

How LPG is Transported to You

LPG exists as either a gas (vapour) or as a liquid, when it is under a modest amount of pressure in gas bottles, cylinders, tanks and larger LPG storage vessels.

Given that gaseous LPG has a volume 270x that of liquid LPG, it is almost always transported in its more compact liquid state.

LPG (propane) can be transported in a number of ways, including by ship, rail, tanker trucks, intermodal tanks, cylinder trucks, pipelines and local gas reticulation systems. 

Most homeowners receive their LPG either by exchange cylinders or tanker delivery into a large in situ tank.

LPG bobtail tanker

For BBQs, homeowners typically take their empty gas bottle to a retailer to be refilled or for a swap refill.

How Your LPG is Stored

LPG is compressed into liquid at relatively low pressures and stored in specially built gas bottles, cylinders or tanks.

LPG is generally stored, as a liquid, in steel or composite vessels ranging from small BBQ gas bottles to larger gas cylinders and LPG storage tanks.

How Liquid LPG Turns to Gas (Vaporisation) - How LPG Boils

LPG liquid boils and turns back into gas vapour when you release some of the pressure in the gas bottle by turning on your gas appliance.Vapourisation - How LPG boils

To boil, LPG vaporisation, the liquid LPG draws heat from the steel walls of the gas bottle which, in turn, get heat from the ambient air.

As with water, the more heat that is applied, the more rapidly it boils, vaporising at a faster rate.

So, as the steel of the bottle draws heat from the ambient air heat, cold weather will slow down the rate of vaporisation.

How Does a LPG Vaporizer Work

An LPG vaporizer works by adding more heat to the liquid LPG, for a higher vaporisation rate. How an LPG vaporizer (vaporiser) works can be nothing more than a serpentine coil of LPG filled tubing, absorbing heat from ambient air or a heated water bath of about 60°C or above. An LPG (propane) vaporizer is used when the steel walls of the vessel cannot provide sufficent heat to the liquid LPG to meet the required gas vaporisation load.

A heaterless LPG vaporizer works in much the same way except that the water is at ambient temperature. The liquid LPG is allowed to expand and cool rapidly and then the LPG extracts heat from the ambient temperature water tank.

Cooling tower water can also be used for further energy savings.

A direct fired LPG vaporiser heats the propane liquid with a direct flame, which hastens the vaporisation of the propane liquid for use in equipment that has a high vapour requirement. The propane liquid is pumped from the LPG tank to the vaporiser for the increased vaporisation flow.

Passing Through a Gas Regulator

After it leaves the bottle, the gas passes through a regulator.This is an LPG gas regulator with changeover valve and pigtails

Gas regulators automatically modulate high pressure gas to a maximum pre-determined regulator gas pressure.

LPG (propane) gas regulators reduce the LPG regulator gas pressure delivered to the gas appliances from the gas bottles.

The pressure within a gas bottle can be 800-900kPa as compared to the 2.75kPa regulator gas pressure typically required. 

LPG gas regulators are usually factory pre-set to the standard regulator gas pressure for the appliances.

Pressure Relief Valve for LPG Propane Tanks & Cylinders

Gas bottle pressure relief valveArguably, the single most important safety feature of a gas bottle or propane tank is the Pressure Relief Valve, which is a propane safety valve. It’s actually a propane safety valve within a valve.

The Pressure Relief Valve is incorporated into the main gas valve on the gas bottle (propane tank), as shown in the accompanying picture.

If the pressure of the gas inside the bottle increases, as the result of a fire or other heat source, the pressure relief valve releases some of the gas to relieve the pressure.

The propane safety valve prevents pressure build up, meaning no risk of an explosion.

Using LPG in Your Gas Appliances

Common in-home gas appliances include gas stoves, cooktops, ovens, gas heaters, fireplaces and gas hot water systems.  There are even gas clothes driers.

Outdoor gas appliances include BBQs, patio heaters, outdoor fireplaces, pizza ovens and fire pits.

Commercial and industrial usages get into the thousands of varied applications.

There are even some more exotic uses, such as LPG fuelled hot air balloons, Zamboni machines for ice rinks and use as propellant gas in various aerosol products.

When you turn on any of these gas appliances, gas flows to the appliances from the gas bottle, via the regulator.

The gas goes to a burner which may have an automatic ignition system or manual ignition.

The level of heat may be controlled by a thermostat or by a manual control valve knob. 

Some even have remote controls with multiple timers and thermostats, to make use even easier.

Once lit, the burner provides the heat to make the appliance operate, as designed.

Final Thoughts

Whilst there are a number of steps to explain how LPG works, it is actually a simple and easy-to-use technology for the consumer.

LPG has a myriad of applications, many of which make life easier and more enjoyable.

 

 

 

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The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.