While manual hoists are suited to lifting lighter or occasional loads, for repeated lifts of heavier loads, electric power-operated hoists become far more practical, improving speed and productivity while reducing manual strain, worker fatigue and workplace injuries in a variety of applications.
In factories and workshops, electric hoists might be involved in assembly line operations, lifting heavy machinery parts, raw materials or finished products. Construction sites may employ them to lift tools, equipment, building materials or structural components to higher floors. You will see electric power hoists being used for unloading trucks in a logistics facility or cargo on the docks, while in a busy warehouse you might find them helping in the frequent movement of pallets or bulky goods. They are a common sight in automotive facilities for lifting engines out of vehicles for repair or serving as well as handling other heavy mechanical components, such as transmissions.
Being electric powered means these hoists can incorporate variable speed control, smooth start/stop operation and pendant or remote control systems. These features allow precise position of loads overhead, which makes them particularly useful in entertainment venues to safely lift such things as lighting rigs, speakers or stage scenery. In fact, they enable delicate positioning for all kinds of equipment installation in tight spaces. There are also features that reduce risk compared to purely manual systems. These include overload protection, emergency stop functions, upper/ lower limit switches and braking systems.
Electric power-operated hoists are not always a suitable solution. Manual alternatives will need to be used where power unavailable and make more sense when lifting is infrequent, budgets are limited, loads are light and portability is critical. Power operated hoists are designed to lift in the vertical plane only and the application should be fully discussed with the supplier to ensure that the correct equipment is selected.
Irrespective of the application for which an electric hoist is to be used, always consider capacity, range of lift, speeds, suspension, operating levels, availability and suitability of power supply (including protection and isolation facilities), service conditions, nature of load and the documentation required by legislation.
A classification system for electric power operated hoists, which takes into consideration the operating cycles per hour, operating hours per day, magnitude of load and total range of lift, is set out in the standard to which it was made and should be marked on the hoist.
It is important to remember that hoists used frequently for high lifts may approach the limit of their motor rating. The greater the height of lift the longer the motor will run. Incorrect selection can result in extended running times leading to overheating. Single phase hoists are more susceptible to this.
Service conditions
Standard electric power operated hoists are manufactured to meet normal service conditions, with use assumed to be under cover, not directly exposed to the elements and at ambient temperatures between -10°C and 40°C without high local heating or cooling. Normal use conditions also assumes clean air that is free from excess of humidity, contamination and deposits. Any other service conditions requiring special attention will need to be discussed with the supplier to ensure the correct hoist is selected.
Environmental conditions requiring special attention include outdoor use, salt air, high humidity, ambient temperatures above or below the normal range, the presence of local heat sources such as furnaces and dust/ abrasives in the atmosphere.
Will the hoist be used in close proximity to any hazardous substances, such as corrosives, which can harm the hoist or its associated electrical equipment? Are there any substances that may be affected by the operation of the hoist, such as explosives? Hazardous substances requiring special attention include flammable or explosive gases, vapours or dust, corrosive vapours and liquids, volatile liquids, toxic substances and molten metal. Seek the specific advice of the manufacturer or supplier if power operated hoists are to be used in an acidic or alkaline environment because these conditions can cause stress corrosion cracking, for example, on some types of chain.
Other potential hazards may arise as the result of the work being carried out in the general location or by the hoist performing lifting and moving operations over the heads of personnel. Examples of potentially hazardous locations requiring special attention include mines and quarries, entertainment facilities, laundries, paint shops, galvanising and hot dipping processes as well as use over work areas, walkways and footpaths.
The design of electric power operated hoists should consider the requirements of the relevant standards for the hoist, trolley, runway or slewing jib and electrics. The marked SWL should be suitable for the load being handled.
At no time must the load applied to the hoist exceed the marked SWL and allowance must be made for any possible shock loading that may occur. As for the power supply to the hoist, it must be appropriate for the intended use.
For further guidance, consult the LEEA Code of Practice for the Safe Use of Lifting Equipment (COPSULE).
