The incidents - at two separate, undisclosed sites - involved the crane operators inadvertently releasing the auxiliary hoist, launching the hook into an uncontrolled free fall.
The NSW Department of Primary Industries' investigation into the incidents revealed the cranes were from the same manufacturer and fitted with free-fall capabilities that could easily and inadvertently be activated because of the absence of fail-safe interlocking.
In the first instance the crane was being used to demobilise a demountable building. After the hoist was released the hook free-fell and landed in close proximity to the dogman.
Mine employees were also put at risk at the site of the second accident that came when maintenance personnel were attempting to remove the engine from an excavator using the main hoist and hook.
Again the hoist was inadvertently released, allowing the hook to free-fall, landing close to the workers.
The department has issued a safety alert to all sites to bring attention to the cranes and is asking all crane operators to review their machine to ensure it meets safety requirements in a bid to prevent other accidents of a similar nature that have the potential to result in serious injury or death.