Failure of a quick hitch mechanism

Mine type

All mine types

Incident

A person was seriously injured while working in a trench, when a bucket detached from an excavator and fell into the trench striking the person. At the time of the incident the excavator's engine was not running and the work being carried out resulted in the person being in close proximity to the elevated boom and bucket of the excavator.

Equipment

Hyundai Robex 360C excavator fitted with an RDW quick hitch mechanism

Hazard

Moving equipment, falling equipment and a collapse or slump of the trench walls.

Cause

A number of causes contributed to this incident:

• The safety pin was not refitted to the excavator quick hitch mechanism when the bucket was changed.
• The excavator boom and bucket were positioned so that they were over an area where a person could be working.
• The quick hitch hydraulic locking ram was worn causing oil to by pass the piston, which allowed the ram to retract when the engine was switched off.
• The position of the boom and bucket were such that when the hydraulic locking ram retracted it allowed the bucket to detach from the quick hitch.
• The site supervisor failed to inspect the job and operations appropriately.

Comments

• The use of quick hitch mechanisms on excavators and other earth moving equipment is common practice, as these allow operators to easily change buckets or attachments.
• The failure to adequately inspect, maintain and operate these mechanisms according to the manufactures recommendations could lead to the introduction of unacceptable levels of risk. In this case had the safety pin been fitted then the bucket could not have detached from the quick hitch.
• Additionally the investigation found that the quick hitch activation switch was a simple push pull type and was positioned so that it could easily been bumped during the operation of excavator controls. This could have led to an accidental release of the attachment.

Recommendations

All mining and quarrying operations are reminded of their obligations under the Mining and Quarrying Safety and Health Act 1999, and the Coal Mining Safety and Health Act 1999 and their Regulations, especially those related to the management of risk and the need to ensure that plant is operated, serviced and maintained so that it is capable of performing its intended function. To achieve this all mines should consider the following:

1. Review operating procedures and standard work instructions to ensure that where quick hitch mechanisms are used on equipment, the inspection and use of any associated safety-locking device is clearly identified and mandated.
2. Review maintenance and inspection practices to ensure that quick hitch mechanisms are maintained in a fully serviceable condition.
3. To prevent accidental activation, where quick hitch release mechanisms are electrically activated, consider the use of a switch that requires two actions to operate it.
4. Ensure appropriate supervision is available to ensure compliance with work procedures.

Authorised by Peter Minahan - Chief Inspector of Mines

Contact: minesafetyandhealth@dnrm.qld.gov.au

Issued by Queensland Department of Natural Resources and Mines