Hazards when utilising the free fall feature on mobile cranes

What happened?

A 20-tonne rough terrain mobile crane was being used to erect a transmission tower.

It was lifting part of the tower when the auxiliary winch went into free fall.

The load fell, striking a worker and fatally injuring them.

Why did it happen?

The freefall mechanism was accidentally activated, which allowed the load to descend uncontrollably.

Hoist winches on some mobile cranes are fitted with a free fall feature that allows the hook and load to fall in an uncontrolled manner (traditionally used for clamshell dredging and dynamic compaction).

The risk of activating this feature by accident is high.

Some crane owners have installed physical locks to prevent this, but the locks are not always installed correctly (see image – example for informational purposes only - crane may inadvertently go into free fall if the hoist brake pedal on the crane is depressed).

What did they learn?

Where free fall features are present, a competent person should install physical locks to prevent unintentional activation and test them to ensure they are functioning as intended.

The test should be carried out in a controlled environment where people cannot be injured, and the crane cannot be damaged.

Crane owners should consider deactivating the free fall function permanently. The deactivation should include the removal of the switches and should be certified by the crane manufacturer or a professional engineer.

The use of the free fall function on mobile cranes should be extremely rare and only be permitted where a documented safe work method statement has shown there is no other reasonable alternative.

Always stay out of the line of fire! Workers should not be under suspended loads, or nowhere near the lift zone when free fall operations are being carried out.

Ask yourself or your crew

Have you ever been on site when an incident like this has happened?

Do any of the mobile cranes you work with have a free fall functionality? Is it enabled or disabled?

What is your work procedure for using the free fall functionality?

How do you know where the ‘drop zone’ is when working around mobile cranes?

What happened?

A 20-tonne rough terrain mobile crane was being used to erect a transmission tower.
It was lifting part of the tower when the auxiliary winch went into free fall.
The load fell, striking a worker and fatally injuring them.
Why did it happen?

The freefall mechanism was accidentally activated, which allowed the load to descend uncontrollably.
Hoist winches on some mobile cranes are fitted with a free fall feature that allows the hook and load to fall in an uncontrolled manner (traditionally used for clamshell dredging and dynamic compaction).
The risk of activating this feature by accident is high.
Some crane owners have installed physical locks to prevent this, but the locks are not always installed correctly (see image – example for informational purposes only - crane may inadvertently go into free fall if the hoist brake pedal on the crane is depressed).
What did they learn?

Where free fall features are present, a competent person should install physical locks to prevent unintentional activation and test them to ensure they are functioning as intended.
The test should be carried out in a controlled environment where people cannot be injured, and the crane cannot be damaged.
Crane owners should consider deactivating the free fall function permanently. The deactivation should include the removal of the switches and should be certified by the crane manufacturer or a professional engineer.
The use of the free fall function on mobile cranes should be extremely rare and only be permitted where a documented safe work method statement has shown there is no other reasonable alternative.
Always stay out of the line of fire! Workers should not be under suspended loads, or nowhere near the lift zone when free fall operations are being carried out.
Ask yourself or your crew

Have you ever been on site when an incident like this has happened?
Do any of the mobile cranes you work with have a free fall functionality? Is it enabled or disabled?
What is your work procedure for using the free fall functionality?
How do you know where the ‘drop zone’ is when working around mobile cranes?