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LPG freezing point

19 Apr, 2024 | Residential LPG Blogs

In this article:

Understand what happens to LPG at its freezing and why you see ice on LPG bottles, is it harmful and what to do next.

LPG Freezing Point: Propane Tank Regulator Freezing – LP Gas Regulator Freezing

LPG (propane) freezing point is -188 °C (-306.4°F). This would only ever occur under laboratory conditions. There is no place on the planet where temperatures this low occur in nature.
LPG-propane does not freeze in winter.
LPG-propane BOILS at -42°C (-43.6°F), which means that liquid propane does not vaporise – turn to gas – below that temperature. So, unless you live in Antarctica, you should have no problem.
The causes propane tank frost and propane regulator freezing are the same. Under the right circumstances, condensation, ice or frost can form on a propane tank (LPG gas bottles) and a propane regulator freezing but the LPG gas does not freeze.

Does LPG Gas Freeze in Winter

In answer to the question, “No, LPG gas does not freeze”, as the freezing point is at -306.4°F (-188 °C). However, what many really want to know is if the LPG-propane tank ever gets too cold to work. The average winter temperature at the South Pole is about -56.2°F (-49°C).

LPG does not freeze in the winter. And if you get propane, and you don’t live in Antarctica, it should work fine. However, if you get butane and the temperature drops below freezing, the butane will stop vaporising.

Propane Tank Frost

Propane tank frost is a result of the vaporisation process when the liquid gas draws heat from the steel walls of the tank to boil and vaporise. This make the tank walls cold, as the boiling occurs at -42°C (-43.6°F). Combine this with some ambient humidity and the result is propane tank frost.

Ice on Propane Tank

LPG-propane boils at -42°C (-43.6°F) at 1 atmosphere of pressure. The propane draws heat from the ambient air, through the tank steel walls. This makes the tank walls cold and, combined with ambient humidity, you get ice on a propane tank.

Ice on propane tank is a result of the vaporisation process, when the liquid gas draws heat from the steel walls of the tank to boil and vaporise. This makes the tank walls cold, as the boiling occurs at -42°C (-43.6°F). Combine this with some ambient humidity, leave it long enough and the result is ice on a propane tank.

LPG-Propane Gas Bottle Freezing – Propane-LPG Freezing Point – Does LPG Gas Freeze in Winter

LPG freezing point is -188 °C (-306.4°F). So, whilst frost or ice may form on an LPG system, the LPG-propane itself does not freeze, as the LPG freezing point is so low. So, LPG does not freeze in winter, as temperature never get that low outside of a laboratory.

In summary:

♦ Vaporisation, the process of the liquid LPG-propane turning into vapour (gas), is what makes the gas bottle cold and propane tank frost.

♦ The LPG-propane gas bottle draws in ambient heat to make the LPG-propane vaporise (boil).

♦ The LPG (propane) boils at -42°C.

♦ The LPG-propane gas bottle gets colder when you are actually using the gas.

♦ Frost, condensation or ice can form on the LPG-propane gas bottle (propane tank frost) with sufficient humidity and when you are using gas very rapidly.

♦ The visible condensation or propane tank frost line indicates the level of the liquid LPG-propane gas remaining in the gas bottle.

♦ The LPG-propane itself does not freeze, as that would require temperatures below the freezing point of -188°C (-306.4°F ).

Why is There Frost on the Outside of My Propane Tank – Propane Tank Frost

There is propane tank frost because condensation forms when the temperature of the LPG-propane gas bottle or gas regulator drops below the dew point. As the temperature continues to drop, the condensation on the LPG gas bottle or propane tank may turn to ice or propane tank frost.

This propane tank frost is exactly the same as the condensation you get on a humid day with a glass of ice water, just colder.
But why do the gas bottle and regulator get cold in the first place?

Why is LPG-Propane Gas Bottle So Cold – LPG Freezing Point

To make sense of why is LPG-propane gas bottle so cold, it helps to first explain how LPG-propane works. LPG-propane is cold, or feels cold, because of the same vaporisation process. Why is propane cold might be better asked as why is propane gas bottle cold or why is there propane tank frost.

LPG-propane is stored under pressure, as a liquid, in a LPG-propane gas bottle. It turns back into a gas by ‘boiling’ into gas vapour.

LPG-propane boils at the very low temperature of -42°C (-43.6°F) .

LPG (propane) freezing point is -188 °C (-306.4°F). Another way of saying that is that the LPG (propane) melting point is -188 °C (-306.4°F).

To boil, the liquid LPG-propane draws heat from the steel walls of the gas bottle, making a LPG-propane bottle cold to the touch.

This, in turn, makes the LPG-propane gas bottle feel colder than the ambient temperature.

The LPG-propane 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, frost or ice can form on the LPG gas bottle or propane tank.

The visible condensation or frost line indicates the level of the liquid LPG-propane gas remaining in the gas bottle.

The picture shows this on a small dark coloured gas bottle, so it is easier to see.

The LPG-propane gas vapour that forms in the gas bottle moves downstream to the point at which it is used.

Propane Tank Regulator Freezing – LP Gas Regulator Freezing Up – Gas Regulator Freezing

During normal use, a propane tank regulator (LP gas regulator) may appear to be freezing up, causing concern. Under the right humidity conditions, condensation, frost or ice can form on gas regulators. A gas regulator freezing is typically not a problem.

LPG Gas Regulators Get Very Cold – Propane Regulator Freezing

But before making its way to the LPG appliances in your home, it passes through your LPG-propane gas regulator, where the pressure is reduced to the appropriate level.  As the LPG-propane passes through the regulator, it expands, resulting in very cold gas vapour temperatures and propane regulator freezing.

The LPG-propane gas regulator delivers a constant safe pressure while the gas bottle pressure can significantly vary, depending on the ambient temperature and the amount of liquid LPG-propane gas remaining in the bottle.

This causes the LPG-propane gas regulator to also reach extremely cold temperatures, as the cold gas vapour passes through it, causing propane regulator freezing.

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 LPG-propane gas regulator.

The faster the gas is used, the colder the LPG-propane gas regulator will get.

This is why, under normal operation in warm and humid climates, the outside of a LPG-propane gas regulator will feel cold to the touch and may also be wet, frozen or frosted.

Now, the exact OPPOSITE problem…

LPG-Propane Gas Bottles in the Sun

Many people worry about leaving their BBQ gas bottles in the sun.

Should you be worried?

LPG-Propane Gas Bottles have Built-In Room for Expansion

LPG-propane BBQ gas bottles and larger tanks are designed to be full while allowing 20% of the space, called “ullage”, for the natural expansion of the LPG-propane .
In other words, they are oversized.

LPG-Propane Gas Bottles have Reflective Colours

In addition, LPG-propane 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 LPG-Propane Gas Bottles

Overfilling LPG-propane gas bottles 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-Propane Gas Bottles in Artificially High Temperatures

The Australian Standard maximum fill levels are conservative but there can still be issues in certain situations, where LPG-propane gas bottle temperatures reach extremes. LPG-propane gas bottles should not be stored near fires, appliances, machinery or any other heat source nor should they be stored indoors.

Transporting LPG-Propane Gas Bottles Inside of Vehicles

Temperatures can reach high levels within the interior of cars or where the LPG-propane gas bottle is subject to artificial or reflected heat sources. LPG-propane gas bottle  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.

LPG-Propane Gas Bottle Pressure Relief Valve

If a LPG-propane 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 releasing some of the LPG-propane gas.

If the gas bottle is stored safely outdoors, and away from any ignition source, the released gas should just harmlessly dissipate.

Normal Situations with LPG-Propane Gas Bottles 

If you think about it, 45kg LPG 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.

BBQ size gas bottles are no more prone to sun heat problems than other gas bottles and tanks.

The nominal maximum fill levels for LPG-propane gas bottles is 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 LPG-propane gas.

You can refer to AS2030.5-2009 and AS1596-2008 for more information regarding fill levels.

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