A safety alert has been issued after three recent incidents involving tower cranes in Queensland.
In March 2019 two separate free fall incidents occurred on Comansa hammerhead tower cranes. In the first incident the hoist rope catastrophically failed, dropping a hook block weighing approximately 500 kilograms to the ground. It is understood the hoist rope failed when the hook block was being hoisted up and contacted the hook trolley (also known as two blocking). The falling hook block caused the hook trolley to travel along the jib at speed and collide with the jib end, causing significant damage to the crane. The trolley rope was also cut in the incident. Both the hoist rope and trolley rope ends dropped onto the roof of a house on the other side of the street next to the site. The hoist rope was rigged in double fall, with the end of the hoist rope anchored to the end of the tower crane jib.
In the second incident a rubbish skip of approximately 7 tonnes dropped 11 metres when the crane operator was attempting to lower the skip onto the road. The load started to free fall and the hoist brake was unable to hold the load.
The third incident occurred in October 2018 on a luffing tower crane, but was not caused by two blocking. The cause of this incident was still being investigated when this alert was issued.