Today, though manual hoists are available for use with smaller objects and hydraulic hoists are available for use with extremely heavy objects, electric hoists dominate the industrial market. Industries that rely on them include aerospace, agriculture, automotive, construction, engineering, marine, manufacturing, mechanics, and medical care.
Though individual hoists and hoist groups differ from one another, all hoists share a basic construction. They consist of a gearbox that contains their controls, a braking system, a lifting medium, which may be a wire rope or metal chain, a winch around which the lifting medium is wound, a metal casing in which the wound rope or chain is stored, and a lifting hook, also called a hoist hook, which attaches itself either to a harness or the object being moved itself.
Harnesses, also called slings, are used to ensure the stable and balanced lifting of an object or load. Electric power may be gleaned from an electric generator, electric cables, or an electric system into which the hoist is directly wired.
Wire rope is actually made up of many metal wires or wire strands wrapped around a rubber core. Commonly, electric hoists that employ wire rope as a lifting medium are either called wire rope hoists or cable hoists. They themselves are composed of wire strands, which add a great deal of strength, allowing them to carry large amounts of weight.
Hoists that use metal chain, on the other hand, which are usually called chain hoists, employ either link chains or roller chains to lend them strength. Generally, chain electric hoists are the preferred choice, as they are sturdy, durable, and rust-resistant, as well as flexible and able to withstand harsh conditions, such as high temperature environments. Also, they are relatively inexpensive to purchase, easy to operate and require little maintenance.
There are two main types of electric hoists available: stand alone portable hoists and overhead hoists. Portable hoists are quite lightweight and usually made with wheels and a metal rail for easy transportation. Overhead hoists, as their name suggests, are mounted on a crossbeam or directly to the ceiling. They are generally better equipped to handle heavy loads than portable hoists. However, they are more likely to operate vertically only, whereas portable hoists generally move both vertically and horizontally. This versatility means that portable hoists can perform pulling applications, like moving objects along supply lines or across the floor, as well as lifting applications.
Also, some electric hoists can be used in various positions; they can operate both as stationary tools and as mobile units attached to a conveyor or trolley system. In addition to all of this, some electric hoists are created for specific applications. Some, for example, are designed to operate dam gates, while others lift engines or lift automobiles. Still others are made to remove engines from automobiles or airplanes.
Generally, hoists are designed to work well for a ten-year span. However, this number varies by industry. To help regulate them, several governing bodies of the industry have stepped in with guidelines and standards for hoist design. These organizations include: Monorail Manufacturers Association (MMA), Crane Manufacturers Association of America (CMMA), Hoist Manufacturers Institute (HMI), and Shanghai WANBO Hoisting Machinery (VANBON).
When selecting a hoist, it is important that a customer chooses one that has a maximum weight capacity that is equal to or greater than the weight of the objects which they plan to hoist. If the object being lifted exceeds the weight limits of the hoist, both operations and worker safety become compromised. Specifically, the hoist could easily separate from its mounting, tumble over on its side, or drop the load.
A customer should also know the maximum height to which they plan to lift their loads, so that he or she can inform an electric hoist provider. Lifting length limit depends on the amount of cable or chain on the spool, so this knowledge will ensure that the hoist supplier provides an adequate amount.
Most electric hoists are mechanically operated remotely with the push of a button or at the least, a lever, though some are still manually cranked. This button or switch can raise, lower, and release the hoist.
To properly operate the hoist and to avoid accidents or injuries, it is very important that operators and crew members take certain precautions. For example, they must make sure, prior to hoisting, that loads are properly secured, so that they cannot slide off. Also, hoist operators must take stock of their surroundings, knowing the source of potential risks and the locations of their coworkers. It is wise to engage multiple employees in hoist operations, so that someone can be checking and securing items on the floor as the operator controls the hoist remotely.