Chain hoists are an invaluable asset for lifting heavy equipment, reducing the effort and manpower required. Chain hoists are available in a variety of sizes, from the small versions found in automobile repair shops to the huge hoists found on bridge cranes and jib cranes. For lifting car engines and shipping containers, manual chain hoists and electric chain hoists soon repay the investment for businesses and homeowners alike.

The history of chain hoists can be traced back as far as the Ancient Greeks and Romans, who developed the principle of using pulleys to shift heavy loads. These cultures developed the familiar 'block and tackle' to move and manipulate heavy loads, including huge blocks of marble and ships. This technological advance helped to develop the reputation of these advanced cultures as master architects and engineers.

These ancient machines used wooden pulleys and ropes, but they were the direct ancestors of the familiar chain hoist. Modern technology ensures that high tensile steel and electric motors make the process more efficient, but the underlying principles are exactly the same.

Chain hoists were derived from the rope or wire cable pulley, which operate by multiplying the force applied. Fixed pulleys allow the direction of pull to be changed, and movable pulleys and compound pulleys multiply the amount of force, called gaining a mechanical advantage, by a factor of two or more. However, wire cable pulleys do carry some inherent disadvantages.

• Rope and wire cable pulleys are subject to friction, so adding more ropes to further multiply effort becomes counterproductive as frictional forces increase.

• Pressure must be maintained upon the rope or cable, otherwise the load will slip, undoing all of the good work and posing a threat to safety. Using an electrical winch reduces the chance of this happening.

• Cables and ropes are prone to fraying and breaking, ad the sheer forces and imparted velocity can seriously maim or kill.

The chain hoist was a natural development of the pulley system, bypassing these disadvantages. Chain hoists are a much more reliable way of manipulating heavy loads and are now a mainstay in construction, warehousing and a whole range of other industries and homes.

Chain hoists operate via an endless chain looped over a dual pulley system, adding a mechanical advantage in the same way as a pulley. The hoist incorporates a tooth and ratchet system, which prevents the load from slipping. Whilst chain can also break, it does not 'whip' at high velocity as is the case with high tensile steel cable.

For smaller tasks, such as lifting an engine block, manual chain hoists are common, but electric chain hoists are an option for heavy and awkward cargoes. For huge loads, hydraulic hoists and compressed air chain hoists are much more common, and these types are usually incorporated into cranes and jibs. This vertical lifting power of these hoists, coupled with the enhanced safety, makes them the only choice, but the difficulty lies in selecting from the variety of types available.

Chain hoists are designed to handle extreme weight, but they are still dangerous and exceeding the recommended safety margins can be a serious risk to life and limb. Before investing in a chain hoist, make sure that you and your staff are aware of the correct procedures, because most chain hoist accidents are caused by overloading or poor maintenance procedures.

Overloading a chain hoist soon leads to metal fatigue of the chain, erosion or breaking of the teeth and damage to the motor, hydraulic or air system. For this reason, it is essential to buy a hoist with more capacity than is needed, allowing a larger degree of tolerance. Buying a low budget hoist is false economy, because they are much more likely to fail or need replacing after a couple of years. A hoist with a chain and teeth made from cheap and inferior steel is an accident waiting to happen, so look for the relevant safety certifications, such as CE and GS marks.

The next stage is to select a reputable and reliable brand, which can be a little difficult considering the huge range of manufacturers building hoists. You should take your time and consider all of the options, deciding whether you want a manual chain hoist or a powered one.

Look at review sites and forums rather than taking the word of the salesman, looking for how happy customers were with the machinery and the aftercare. Searching for a range of opinions and views makes sure that you will buy a reliable and efficient chain hoist that will give many years of service.