1.A3.4 SLING EQUALIZERS

To improve balance and ensure that the hook is positioned above the centre of gravity, slingers are increasingly using pulley blocks in the rigging arrangement. Although this can be beneficial where the COG may be difficult to estimate or when lifting multiple loads with a varying COG are to be lifted, the practice can introduce a number of risks that need to be properly planned and controlled, either by the rigging arrangement itself or through control and safe systems of work during the lifting operation.

Pulley blocks do not have a positive holding mechanism, so as the lifting machine hoists, they will naturally position themselves and the crane hook above the centre of gravity. However, this can only be safe if the position of the COG does not or cannot change during the lifting operation. For example, if during a lifting operation the load should collide or become snagged the COG will shift and when used with a pulley block this can result in destabilisation, uncontrolled movement and potentially loss of the load. Similarly, lifting dynamics due to horizontal travel can cause the load to tip or swing. Again, this can cause the COG to shift and again cause potential loss of load control.

If considering the use of load equaliser, it is important that these factors are properly assessed, and the associated risks are reduced to an acceptable minimum. This can be achieved through the rigging arrangement or by motion control devices or restraints.

When selecting sling equalisers use only those that have been designed specifically for the task. LEEA only supports the selection and use of equipment designed for the purpose. In the UK and EU such equipment shall be conformity marked as a lifting accessory, be issued with a declaration of conformity and suitable instructions for safe use.

If in any doubt with respect to load stability and balance when using pulley systems, LEEA recommends the use of other equipment that has been designed for the purpose, such as sling shortening devices, refer to SECTION 14 - CHAIN SLINGS – SECTION 18 - FIBRE ROPE SLINGS and SECTION 23 - RIGGING SCREWS AND TURNBUCKLES for further guidance and alternatives.