AdBlue® freezes at about −11°C. For most of Australia that never comes into play, but for fleets and sites in alpine country, on the tablelands and across parts of the inland where winter nights get properly cold, it is worth knowing what happens when it freezes and how to handle it.
What happens when AdBlue freezes
AdBlue is 32.5% urea in de-ionised water. That concentration isn't arbitrary: it is the mix of urea and water with the lowest freezing point. Because of this, the urea and water freeze together, rather than the water freezing first and leaving concentrated urea behind. When it thaws, the concentration is the same as before.
- Freezing point: about −11°C.
- Expansion: roughly 7% by volume when frozen.
- Quality after thawing: unchanged. Freezing and thawing doesn't damage the product.
So the practical risk isn't the AdBlue itself. It is the container or equipment holding it.
Where Australian operators run into it
Temperatures cold enough to freeze AdBlue are uncommon in most Australian cities, but they do happen in:
- Alpine and high-country areas, including resort operations, road maintenance and hydro works.
- Tablelands and elevated inland regions, where clear winter nights bring hard frosts.
- Remote inland sites where overnight minimums drop sharply in winter.
Even where the air doesn't quite reach −11°C, exposed equipment can get colder than the recorded air temperature on clear, still nights. A hose lying on the ground or a nozzle on an open stand is usually the first thing to freeze.
Operators who move plant between regions, for example from a coastal depot to an inland project in winter, sometimes get caught out because their dispensing gear has never seen a hard frost before.
Vehicles are designed for it
Vehicle SCR systems are built to cope with freezing. The AdBlue tank, lines and dosing pump have heaters, and many systems purge the lines when the engine is switched off. If a vehicle starts with frozen AdBlue, in most cases the engine runs normally while the heater thaws enough fluid for the SCR system to begin dosing.
What not to do:
- Don't add anything to AdBlue to stop it freezing: no antifreeze, alcohol, diesel or water. Anything added takes it out of spec and can damage the SCR system.
- Don't fill the vehicle's AdBlue tank past the manufacturer's full mark, so there is room for expansion.
- Don't try to thaw a tank or line with a naked flame or heat gun.
If you're unsure how a particular vehicle behaves in the cold, the owner's manual or dealer will have the manufacturer's advice. You can read more about how the system works on our What is AdBlue page.
Storage and dispensing in cold conditions
For drums, IBCs and tanks on cold sites:
- Leave headspace. Don't fill containers to the brim. That 7% expansion needs somewhere to go, or it can split a drum or strain fittings.
- Store indoors where you can. Even an unheated shed usually stays warmer than open ground overnight.
- Protect hoses and nozzles. Hang hoses so they drain, or bring handheld gear inside overnight. A frozen nozzle or meter is the most common cold-weather nuisance.
- Don't run a pump against ice. If a line is frozen, let it thaw first or you risk damaging the pump.
- Thaw gently. Move frozen containers somewhere warmer and let them thaw at room temperature. Once fully thawed, the product can be used as normal.
If a container has split, don't try to salvage the product from it. The AdBlue itself is fine, but a cracked container has almost certainly let in dirt and moisture. Rinse the area with plenty of water and replace the container.
Insulated IBC covers, usually thought of as summer heat protection, also slow cooling on cold nights.
One check before winter: look at every vehicle-mounted tank, transfer container or decanted container that could be exposed to a hard freeze, and make sure none is filled to the neck. Sealed drums from the supplier normally have some headspace; problems usually come from containers topped up on site. It takes a few minutes and avoids split containers and spills later.
How Liquidia can help
Liquidia supplies AdBlue and dispensing equipment to sites across Australia, including hoses, nozzles and pumps for exposed sites. Browse the accessories range or find more answers in our FAQs.