22 October, 2020
One of the most important tools in various industries, ports and machine shops when it comes to lifting, unloading and moving heavy materials are hoists. It is an ancient mechanism designed in the 3rd century BC. and its use allows to minimize the effort and the energy necessary to carry out these movements.
Hoist: What is it?
Hoist (or rigging) is defined as the mechanism used to lift or move a load mechanically, applying a lesser force than the weight to be moved. It is used for lifting or lowering a load by means of a drum or lift-wheel around which rope or chain wraps. It may be manually operated, electrically or pneumatically driven and may use chain, fiber/lifting slings or wire rope as its lifting medium. These units are typically used in an industrial setting and may be part of an overhead crane.
They are usually attached by a lifting hook to a rotating arm that is attached to a machine. They can also be mobile guided by rails placed on ceilings of industrial buildings. Small hoists can be handled by hand, but heavier hoists are electrically powered by motors, which is essential to establish their lifting power.
How do Hoists Work?
Hoists are used in the construction industry, as well as industries such as steel, in mechanical workshops, in airports, in mines, in warehouses and in sea ports. They are generally used to load and unload very heavy materials that cannot be handled by one person and that must be placed in transport trucks, boats, fixed spaces and many other locations.
The responsibility for moving the load rests with the system of pulleys and cables, which can be fixed and/or mobile. This system varies the forces and speed, needing to apply a lesser force than the load to be moved. The effort is also less than what we would need if the load were lifted freehand or with small hoists.
A specific overhead hoist configuration is usually defined by the lifting medium, operation and suspension. The lifting medium is the type of component used to transmit and cause the vertical motion and includes wire rope, chain or synthetic strap, or rope. Operation defines the type of power used to operate the hoisting motion and includes manual power, electric power, hydraulic power or air power. The suspension defines the type of mounting method used to suspend the hoist and includes hook, clevis, lug, trolley, deck, base, wall or ceiling.
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Types of Hoists
Manual hoists, are lever-actuated or hand chain operated lifting devices. A manual lifting hoist uses two different chains: the hand chain used to control the lifting and lowering action and the load chain, which supports the load. The manual chain hoist is characterized by having a compact, lightweight and easy-to-handle design that allows the lifting of up to aprox. 2 tons of weight. It is ideal for vertical load lifting.
Powered hoists come with 3 different settings: electric, air/pneumatic and hydraulic.
Electric hoists follow the same principle as manual ones, only the chain drive is replaced by an electric control. Pneumatic chain hoists or otherwise known as air hoists are very similar in features to an electric hoist except the hoist is powered by a compressed air feed as opposed to being restricted by the need for a suitable electric power supply. Finally, hydraulic chain hoists are very similar in features to pneumatic hoists except the hoist is powered by hydraulic oil as opposed to being powered by a compressed air line.