Semi-automatic quick hitches on excavators

Background

A young worker's leg was crushed when an excavator bucket unexpectedly detached from height during a house demolition.

Early indications are that the bucket was connected to an excavator via a semi-automatic quick hitch attachment when the incident occurred.

A quick hitch enables mounting and removal of attachments on machinery such as excavators. It's also called a quick adapter or quick coupler. There are different types of quick hitches, including half-hitch, mechanical, semi-automatic and automatic.

Safety issues

Quick hitches have safety systems to prevent attachments from coming away if the hydraulics or excavator control system malfunctions or fails. It's important to ensure the safety system is always used.

In semi-automatic quick hitches, the safety system consists of a safety pin located where the attachment joins the machine. This pin has to be manually inserted and secured with a fastener such as a lynch pin.

Quick hitch devices should comply with AS 4772 – 2008 or another equivalent standard (such as ISO13031 – 2016). AS 4772 requires that a safety system is used to ensure the attachment does not unintentionally disconnect from the quick hitch in event of failure of the primary retention system.

Every time an attachment is changed, the safety system (safety pin) must first be removed to enable the attachment to be disconnected, then re-inserted and secured once the replacement attachment is engaged. This usually requires the machine operator to get out of the machine and install the safety pin and fastener. When attachments are being changed regularly, operators may not get out of the machine and install the safety pin and fastener every time. This means that, if the primary retention system malfunctions or fails, the attachment can unexpectedly detach.

Recommended ways to control risks

If excavators, backhoes or similar items of plant are being used on your site, or if you operate excavators with quick hitches, ensure that:

• any quick hitch devices are fitted with the safety system, and
• it is used in accordance with the manufacturer's instructions

The safety system MUST be installed to prevent uncontrolled release of buckets or other attachments when the machine is in operation. This requirement must be reflected in documented site safety procedures and induction for plant operators.

Other measures to prevent accidental detachment

• Replace the semi-automatic quick hitch with a fully automatic quick hitch.
• Ensure attachments and hitches are compatible with the machine.
• Connect and operate equipment in accordance with the manufacturer's instructions.
• Check that the hydraulic system provides the correct pressure to retain attachments.
• Verify correct engagement of the primary retention system prior to use.
• Ensure safe systems are in place to prevent accidental activation of the controls used to disengage the hitch.
• Ensure the machine and attachments are inspected regularly, including checking for wear and checking the hydraulic system, in accordance with the manufacturer's instructions.
• Ensure that the operator has been trained in the use of the machine and attachments, and is provided with the necessary information and instructions.
• Ensure that the operator has access to the attachments user manual.

Legal duties

Under the Occupational Health and Safety Act 2004, employers must, so far as reasonably practicable, provide and maintain a working environment that is safe and without risks to the health of employees. This includes identifying risks to health or safety and eliminating or reducing those risks, so far as is reasonably practicable.

Employers must, so far as is reasonably practicable, provide or maintain plant or systems of work that are safe and without risks to health.

Self-employed persons must ensure, so far as is reasonably practicable, that persons are not exposed to risks to their health and safety arising from the conduct of their undertaking.

Under the Occupational Health and Safety Regulations 2017, employers are required to conduct risk assessments on plant. Employers must then, so far as is reasonably practicable, eliminate the specific risks identified for powered mobile plant or, if it is not reasonably practicable to eliminate the risks, reduce them so far as is reasonably practicable.

Further information

• AS1418.8 – 2008, Cranes, hoists and winches – Special purpose appliances
• AS2550.1 – 20011, Cranes, hoists and winches – Safe use – General requirements
• AS4772 – 2008, Earth-moving machinery – Quick hitches for excavators and backhoe loaders
• ISO13031 – 2016, Earthmoving machinery – Quick couplers