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Examples Of Dropped Objects

Guidance for the prevention of dropped tools and objects when working at height

Fallen tools can often cause harm to people, damage to machinery or create costs associated with lost production time. The following graph shows the likely-hood of injury or death from falling objects, relative to the mass and height from which a fall takes place

(* Graph Courtesy of Shell)


Example 1 Standard Bolt (¾ x 3½)
Weight 220 grams
Dropped Distance 11M (3 floors) 23M (6 floors)
Impact Velocity 31mph (50kph) 50mph (80kph)
Impact Force 23.7kgs 49.5kgs
Resulting Injury Hospitalised (Recordable) Fatality

A bolt dropped from 23 metres is equivalent of being dropped from the 6th floor of a building. The velocity attained is 50mph / 80kph on impact. The bolt achieves a mass impact weight of 49.5kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.


Example 2 Screw Driver
Weight 500 grams
Dropped Distance 10M (3 floors) 14M (4 floors)
Impact Velocity 31mph (50kph) 38mph (61kph)
Impact Force 49kgs 73.5kgs
Resulting Injury Hospitalised (Recordable) Fatality

A screw driver dropped from 14 metres is equivalent of being dropped from the 4th floor of a building. The velocity attained is 38mph / 61kph on impact. The screw driver achieves a mass impact weight of 73.5kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.


Example 3 Claw Hammer
Weight 2kgs
Dropped Distance 4M (1 floors) 6M (2 floors)
Impact Velocity 20mph (31kph) 24mph (39kph)
Impact Force 78kgs 117kgs
Resulting Injury Hospitalised (Recordable) Fatality

A claw hammer dropped from 6 metres is equivalent of being dropped from the 2nd floor of a building. The velocity attained is 24mph / 39kph on impact. The claw hammer achieves a mass impact weight of 117kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.


Example 4 Sledge Hammer
Weight 5kgs
Dropped Distance 1M 3M (1 floor)
Impact Velocity 10mph (16kph) 17mph (27kph)
Impact Force 49kgs 147kgs
Resulting Injury Hospitalised (Recordable) Fatality

A sledge hammer dropped from 3 metres is equivalent of being dropped from the 1st floor of a building. The velocity attained is 17mph / 27kph on impact. The sledge hammer achieves a mass impact weight of 147kgs at this point, resulting in a fatal injury even if struck on the head whilst wearing a hard hat.

This is a guide only and in fact even a light-weight object dropped from a considerable height may turn out to be fatal.



Author: Drew Beardmore October 2011



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