Minimising the risk of boil-over

The risk of these kinds of accidents, known as boil-over, is particularly high if hot bitumen is loaded into a tanker that previously transported emulsion or another product with a high water  content. Other risk factors are if the tank has not been used for a long time, as  condensation can easily form, or if it has been left  standing open. In just a few seconds, 10 litres of water can expand to form 20,000 litres of steam. When the  pressurised steam passes through the liquid bitumen, a hot foam is formed that is forced out through the manhole or, if the tank is closed, causes an explosion. 

In other words, it is extremely important that the driver always makes sure that the tank is free of water or aqueous products before loading.