Equalising equipment

Find out how to use equalising sheaves to support loads.

What is an equalising sheave?

Equalising sheaves are load supports. They transfer the weight of the load from one single point to two others using a wire rope or synthetic rope.

The two points then each take half the weight of the load.

Special chain equalisers can be available for some applications.

If the two points are of unequal capacity, the load on the single point should never exceed double the capacity of the weakest of the other two points.
 

Equalising sheave

What is a hauling sheave?

If one of the two lifting points remains stationary and the other hoists up, the sheave is then a hauling sheave not an equalising sheave.

Friction must be taken into account when working out the weight on the hauling part of line.

Note: The extra load due to the friction of the sheave system needs to be included in determining the required capacity of the crane.

Use of equalising sheaves

Equalising sheaves are often used on bridge or gantry cranes. These have a four-part purchase with two hauling parts attached to the hoist drum.

The opposite or stationary side passes over an equalising sheave, like in the image below:

Equalising sheave used with four-part purchase

The function of the equalising sheave is to move as the hoist block swings sideways.

The part of the hoist rope that passes over the sheaves is the hardest working part of the rope. It constantly runs back and forth through the sheaves. This means it can be subject to abrasion and fatigue along this area.

This section of hoist rope takes:

• half the weight of the hoist block at all times
• half the weight of the load
• half the weight of the hoist block when the crane is lifting.

It must be regularly inspected by operators and maintenance personnel.

Delta plates

Delta plates (load equalisation plates) are used to suspend multi-leg assemblies that may not have weight evenly distributed.
 

DELTA plates being proof tested