Haulage mainly consists of trailers pulled by tractors or trucks.
A) Haulage trucks can be classified as:
- For construction project dump truck is very common and essential equipment and is available in various sizes and types.
- These trucks are classified as Volumetric or tonnage payload capacity.
- The capacity ranges from 3 to 25 cu.m are commonly used with a speed upto 80 km per hour.
- The dump trucks having capacity of more than 200 cu.m have also been manufactured.
- These trucks have chasis, prime mover and power transmission system similar to that of truck whereas body of dump truck is heavy duty type and is capable of tilting towards one side by means of hydraulic jack.
- Tail gate is provided at the rear so that while moving on highway materials do not fell on the road.
- The speed of these trucks is high and can be upto 80 km/hr depending on the condition of the road.
- These trucks do not have tail gates, therefore the body floor slopes upward at a slight angle toward the rear.
- These are used off the highway specially for earth moving and mining applications.
- These are commonly known as Dumpers.
- The body is specially designed to absorb high-impact loading.
- The floor of the body is high tensiled to reduce abrasion damage.
- The ratio of gross vehicle weight to HP is generally lower than for on-highway truck.
- Top speed of the truck is also slow about 30-40 km/hour.
- Off highway trucks can also be classified as:
- Rear dump trucks.
- Bottom dump trucks.
- Side dump trucks.
- From speed considerations, the wheeled tractors are the machine intermediate between the heavy trucks and the crawler tractor.
- As a haulage unit, the wheeled tractor has to depend entirely upon its own weight for its tractive reaction.
- A tractor for the better traction must have high weight/HP ratio.
- The two types of trailers mostly used are Full trailers and Half trailers.
- Full trailers also known as wagons are self supported and are provided with a swivelling axle and a draw bar for connecting the prime mover.
- Semi-trailers are supported on their own wheels only at the rear, while front end is supported on the prime mover.
- The semi trailers have more maneuverability as compared to full trailers.
- The braking system of a trailer or semi-trailer may be operated by either hydraulic or vacuum or by air pressure.
- Trailers for haulage of heavy equipment and machinery may have drop level or level deck.
- In drop deck, trailer loading and unloading is done from sides.
- Level deck or flat bed trailers have abundant space on the deck and it is easy to load and unload them from the rear.
- The trailers are tadem axle(2 axle) arrangement with 8 wheels and 3 axle arrangement with 12 wheels for haulage of heavy loads.
Factors affecting performance of Hauling equipments:
- Size and specifications of loaders.
- Type and condition of materials loaded.
- Capacities of shovels and haulage vehicles.
- Skill level of operators.
- Efficiency of shovels and haulage vehicles.
- Hauling distance.
- Haulroad condition.
- Manoeuvrability of vehicles.
- Job efficiency.