Background

Chain hoists are the most widely used devices for lifting loads. They are standard equipment in almost every shop and rigging department. They usually cost less than other types of hoisting equipment. They are also dependable and, usually, portable.

There are three basic types of chain hoists: differential, screw-geared, and spur-geared.

Differential hoists

The differential hoist is the simplest type of chain hoist. This hoist is made up of two sheaves on the upper block (labeled large wheel and load wheel in the figure) and one on the lower block (labeled small wheel). The chain is a one-piece unit (labeled continuous chain).

The throat and grooves of the upper sheaves are made with pockets that fit the links of the chain. One of the sheaves has one or two pockets less than the other. This difference in the number of pockets is called the differential. Each time the sheaves rotate one full turn, one side of the chain becomes one link shorter. This differential, as the sheaves are turned, provides the mechanical advantage necessary for lifting the weight.

The upper sheave, having the fewer pockets, is slightly smaller than the other sheave. The small sheave is the load side of the hoist. The differential hoist is the least efficient of all hoists, but probably the most common.

Screw-geared chain hoists

The screw-geared chain hoist uses two separate chains. The hand chain is an endless chain which drives a single sheave with pockets that fit the chain. As this sheave on the handwheel turns, it drives a worm-and-screw-gear arrangement which furnishes the power to raise or lower the chain. The load chain is fitted at one end with a hook connected to the load.

Spur-geared hoists

The spur-geared hoist is the most efficient type of hoist. This hoist uses an endless chain (hand chain) to drive a pocketed sheave which in turn drives a gear reduction unit that is fitted with the second or load chain. One end of the load chain is fitted with a hook.

The gear reduction unit reduces the friction so much that a brake is required to hold the load once it is raised. The brake is built into the gear box (labeled spur and pinion gear casing) or onto the sprocket that moves the load chain. One form of a brake is a ratchet arrangement that permits the sprocket of the load chain to turn in only one direction. This type of brake is released manually before lowering the load.

Some models of this hoist use a roller chain for the load chain. These models operate the same as other types. Their increased load capacity results from the use of various types of load chains. This hoist is about three times as efficient as the differential hoist.

Comealongs

The comealong is another type of chain hoist. It uses a ratchet operated by a lever rather than a pocketed sheave. The load chain is regular or roller chain.

The comealong, a tool normally used to stretch wire or cable, can be used to lift loads short distances.

Use of chain hoists

All of the hoists above are attached to the overhead or attachment point and to the item being moved. Pull the chain clockwise for hoisting or counterclockwise for lowering.

If the capacity plate is missing, do NOT use the hoist. Notify the shop supervisor.

Depending on their rated capacities, chain hoists'  mechanical advantages vary from 5 to 250, in a range from 1/2 ton to 40 tons. Chain hoists are identified by a capacity listed on the plate. Chose the one that fits your needs.

Hoist safety precautions

Observe all safety rules during hoisting operations. Many of the loads are very heavy. With these kinds of loads, accidents happen quickly. Typical accidents results are fractures, such as; broken arms and legs, crushed fingers, broken backs, and death. BE CAREFUL so that accidents do NOT happen.

Protective clothing is absolutely vital to your safety. Always wear a hard hat, safety glasses or goggles, and safety shoes when performing rigging tasks. Wear them even when you don't think you need them. Make them as much a part of your routine dress as a coat in cold weather.

NEVER exceed the rated capacity of hoisting equipment. Check every piece of hoisting equipment to determine its rated capacity. Most hoisting equipment will have a capacity plate firmly attached to the device. NEVER exceed the capacity listed on this plate. Hoisting loads in excess of rated capacity invites accidents. If the capacity plate is missing, consult your supervisor for instructions before starting any hoisting operation. Never gamble; it can cost you your life or the life of a shipmate.