Written by Eric Hahn
Gas Bottles in the Sun - High Temperatures
Many people worry about leaving their BBQ gas bottles in the sun.
What about LPG storage temperatures that are artificially high, including being left inside of cars?
LPG gas bottle pressure rises with temperature.
Should you be worried?
Built-In Room for Expansion
LPG BBQ bottles and larger tanks are designed to be full while allowing 20% of the space, called “ullage”, for the natural expansion of the LPG.
In other words, they are oversized.
In addition, gas bottles are always white, silver or light grey in colour, to reflect radiant heat.
In combination with the ullage design feature, it makes it exceedingly unlikely that you would ever have a problem in a typical sunny outdoor environment.
Overfilling an LPG Bottle
Overfilling can cause problems, as it would reduce the ullage expansion space.
Overfilling is extremely unlikely with gas bottle exchange programmes, like SWAP’n’GO®, as they fill the gas bottles on digital scales.
However, it is possible to overfill a gas bottle when utilising the decanting method, as used by service stations.
LPG Storage & Artificially High Temperatures
The Australian Standard maximum fill levels are conservative but there can still be issues in certain situations, where LPG storage temperatures reach unacceptable extremes.
Gas bottles should not be stored near fires, appliances, machinery or any other heat source nor should they be stored indoors.
Transporting Gas Bottles Inside of Vehicles
Temperatures can reach high levels within the interior of cars or where the cylinder is subject to artificial or reflected heat sources.
Gas bottles should only be in vehicles whilst being transported.
They should be removed as soon as they reach their destination and always transported upright and secured.
Pressure Relief Valve
LPG vapour pressure rises with temperature.
If a gas bottle is exposed to abnormally high temperatures, the gas will expand.
If it exceeds the maximum safe pressure, the pressure relief valve, built into the main valve, will release some of the pressure by venting some gas.
If the gas bottle is stored safely outdoors, and away from any ignition source, the released gas should just harmlessly dissipate.
Normal Sun Exposure
If you think about it, 45kg home gas bottles are sitting in the sun for hours a day without any problems.
Service stations have massive LPG autogas tanks that are also exposed to the sun for virtually the entire day, yet still no problems.
The nominal maximum fill levels specified in the Australian Standards are calculated for normal storage and use anywhere in Australia, regardless of climate.
The maximum fill level is a complex calculation which takes into account the size of the container, the maximum pressure and the expansion ratio of the gas.
You can refer to AS2030.5-2009 and AS1596-2008 for more information regarding fill levels.
Gas Bottles in the Sun – Should You be Worried?
• LPG (propane) gas bottles are designed to be in the sun or shade.
• Gas bottles use reflective colours to reduce solar heat gain.
• LPG gas bottles have built-in room for expansion, with 20% ullage space for the natural expansion of the gas.
• 9kg or 20lb BBQ gas bottles are no more prone to sun heat problems than other gas bottles and tanks.
• Gas bottles have pressure relief valves that will release some of the pressure by venting a small amount of gas, in the unlikely event that the vapour pressure gets too high.
• Avoid LPG gas bottle storage temperatures that are artificially high. This includes storage inside of cars or near fires, appliances, machinery or any other heat source.
Now, the exact OPPOSITE problem...
Why Does Ice Form on Gas Bottles & Regulators?
Under the right circumstances, condensation or ice can form on gas bottles and/or gas regulators.
But why does this happen?
Condensation Turns to Ice
Initially, condensation forms when the temperature of the gas bottle or regulator drops below the dew point.
This is exactly the same as the condensation you get on a humid day with a glass of ice water.
As the temperature continues to drop, the condensation may turn to ice.
But why do the gas bottle and regulator get cold in the first place?
Why the Gas Bottle Gets So Cold
To make sense, it helps to first explain how LPG works. LPG is stored under pressure, as a liquid, in a gas bottle.
It turns back into a gas by 'boiling' into gas vapour. This happens at the very low temperature of -42°C.
To boil, the liquid LPG draws heat from the steel walls of the gas bottle. This, in turn, makes the gas bottle feel colder than the ambient temperature.
The gas bottle gets even colder when you are actually using the gas.
So, with sufficient humidity and when you are using gas very rapidly, condensation or ice can form on the gas bottle.
The visible condensation or frost line indicates the level of the liquid gas remaining in the gas bottle.
The picture to the right shows this on a small dark coloured gas bottle, so it is easier to see.
The gas vapour that forms in the gas bottle moves downstream to the point at which it is used.
Regulators Get Very Cold
The regulator delivers a constant safe pressure while the gas bottle pressure can significantly vary, depending on the ambient temperature and the amount of liquid gas remaining in the bottle.
As the LPG passes through the regulator, it expands, resulting in very cold gas vapour temperatures.
This causes the regulator to also reach extremely cold temperatures, as the cold gas vapour passes through it.
Depending on the humidity of the surrounding air and the rate at which the gas is being used, condensation or even ice will form on the regulator.
The faster the gas is used, the colder the regulator will get.
This is why, under normal operation in warm and humid climates, the outside of a gas regulator will feel cold to the touch and may also be wet, frozen or frosted.
BBQ Gas Leak Test
It is important to regularly leak test your BBQ gas bottle, regulator and hose.
Leaks from these items are frequently the cause of BBQ gas fires.
How to Test for Gas Leaks
Put some soapy water in a spray bottle.
Turn on the gas bottle without turning on the BBQ.
Next, spray the entire valve, regulator and hose assembly with the soapy water.
Bubbles will form if there is a gas leak and you may also smell the gas.
For more details, please see: BBQ Gas Leak Test
Hot To Safely Attach or Change Your BBQ Gas Bottle
Changing gas bottles is not difficult but you do need to know how and you should always test for leaks, when done.
Connecting & Disconnecting Your Gas Bottle
The male connector of a POL regulator has a reverse or left-handed thread.
So, to detach, you turn it clockwise and then anti-clockwise to re-attach. Remember to do a leak test when done.
For full step-by-step instructions, please see:
How to Attach or Change Your BBQ Gas Bottle
Comments, questions or feedback?
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.