Bryan Phillips, age 12, of Butte, Mont., for his question:
HOW LONG IS THE LONGEST CONVEYOR BELT?
A conveyor belt is a device that carries or conveys large quantities of material from place to place. It consists of an endless belt that is looped over two pulleys. Longest conveyor belt in the world is located in Oklahoma. It is five and a half miles long. The belt carries limestone from a quarry to a cement mill.
Most conveyor belts are powered by electric motors. Of the two pulleys needed, one is called the drive pulley and it supplies the power that keeps the belt moving.
The belt travels over a series of rollers that reduce friction and support the belt. The material moves along the belt at a moderate speed and in a straight line.
A conveyor belt can carry material at a much steeper grade, or slant, than can a truck or a railroad train. The steepness of the grade is limited only by the slant at which the material will slide down the belt.
Conveyor belts are regularly used in mines and quarries. Many of them are a mile long or even longer.
The belt of a conveyor may be flat and wide, and the materials simply placed on the belt and carried away. But for moving bulk materials, such as sugar or salt, the belt forms a trough so the material can be moved without spilling.
Other conveyor belts consist of chains that have buckets hanging from the chain. Some chain belts have either hooks or scoops that pick up the material and carry it along.
Many times a conveyor belt makes up only a part of a much larger conveyor system. If the system must change directions or turn a corner, the material is dropped from one belt to another belt that moves in the desired direction. In such a system, each belt is called a flight.
Different flights are needed for each change of direction required. Conveyor belts play important parts in most industrial mass production systems.
In an assembly line operation, such as an automobile factory, the workers stand in one place and the materials to be worked on move past them.
In airports, conveyor belts carry luggage from the ticket counter to the baggage room. And in many buildings, including airports, conveyor belts form moving sidewalks.
An escalator is a conveyor belt designed to form stairs as it moves around an endless belt.
In meatpacking plants, conveyor belts carry the carcasses of the animals from one station to another to be processed.
Conveyor belts are also widely used to load and unload ships, trucks and railroad cars. One such system moves over 6,000 tons of coal an hour in a steady stream from railroad cars to the belt. The belt carries the coal to a spading tower that distributes the coal to the various parts of the ship.
Large bakeries use conveyor belts to speed up the baking of bread. The mixed dough is placed in pans and put on an endless belt that passes through a walled oven over 100 feet long. It takes about 30 minutes to carry the pans through the oven.
The continuous movement of a number of these belts allows large bakeries to bake over 30,000 loaves of bread an hour.