Grit Bins

Gritters

Gritters are winter service vehicles that are used to clear the ice and snow from public highways and places such as airports. Gritters are the service vehicles that we get used to seeing whenever there is a lot of snow and ice. Vehicles are usually run by local authorities whose responsibility it is to clear the roads and public spaces in their area. The gritter is used to spread grit which is a mixture of rock salt and sanded grit. The salt works on the snow to melt it and the grit makes it easier for vehicle tyres to grip the roads in icy conditions.

Most gritters have what is known as a hopper on the back of the vehicle with a cover over the top to prevent any objects entering the grit and messing up the operation and jamming the spreading mechanism. Snow is spread through a kind of tube that increases the flow of the substance and is known as an impeller. The gritters also have hydraulic drive systems which consist of a hydraulic pump or generator, a combustion engine and a motor that drives the machinery. Years ago, grit used to be spread by men with spades working from the back of a truck to distribute the grit on the roads.

Salt is used in gritters because it lowers the point at which ice melts meaning that the salt acts as a sort of anti-freeze and makes it stay liquid at a lower temperature and this is known as the freezing-point depression. The freezing point depression causes the ice to melt at lower temperatures than it would naturally (providing it is higher than minus five degrees centigrade) and then the liquidised ice runs off the road. Grit increases the friction between the road and the tyres of a vehicle, giving them more grip on the road.

Gritters drop varying amounts of salt on roads, depending on the amount of ice and snow that is on the road. Gritters are used on main road and motorways and they are also used to clear the ice off of airport runways. Airport gritters have to use a different type of salt to that which is used on the road because it can corrode parts of the plane and interfere with some of the aeroplane’s navigation systems, which are very sensitive.

Sea salt tends to be too fine for use in gritters because it dissolves a bit too quickly, which means that the salt that is used in gritters has to come from salt mines, which is not renewable. Gritting can be damaging and so local authorities tend to keep the use of gritters as low as possible. Because the salt for gritters cannot be reused it means that local councils need to have a constant supply of rock salt as well as grit. One of the problems with grit is that when the snow and ice melt the grit ends up at the side of the roads, making it difficult for vehicles to pull in.