Mineral Mines & Quarries Inspectorate | Bulletin | No.219 V 1 | 22 April 2024
Tow Hitch Failures
What happened?
In a 14-month period, there have been eight High Potential Incidents relating to tow hitches. Trailers detaching while in motion present a significant hazard to persons on mine sites.
| Incident Date | Incident Description | Failure Mechanism | Primary Causes |
|---|---|---|---|
| 21/2/24 | A loaded truck and dog was travelling between mines on public roads when the trailer separated. | A-frame drawbar structure failed behind the hitch. | Fatigue loading failure. |
| 11/2/24 | A loaded B double travelling on a site haul road - rear trailer has separated. | Bolt-in drawbar eye sheared. | Fatigue loading failure. |
| 13/12/23 | Light vehicle towing a fuel trailer along a site road - trailer has separated. | Tow hitch insert sheared - safety chains not attached. | Tow hitch underrated for duties. |
| 10/12/23 | A loaded quad road train was travelling on a regional road. Three trailers have separated. | Bolt-in drawbar towing eye failed at thread. | Lock pin / bolt for the castellated nut sheared. |
| 20/7/23 | Light vehicle towing a dual axle trailer - trailer has separated from the tow vehicle. | Detached from tow ball - safety chains not connected. | Coupling not fastened securely during latching. |
| 18/4/23 | After proceeding through a boom gate, the rear trailer of a chemical delivery road train has separated. | Trailer kingpin uncoupled at turntable. | Coupling not fastened securely during latching. |
| 7/4/23 | A loaded triple road train was travelling on a haul road when the third trailer has separated. | Bolt-in drawbar eye sheared. | Fatigue loading failure. |
| 14/1/23 | Loaded road train travelling on a haul road. The second trailer has separated. | Bolt-in drawbar towing eye has sheared. | Fatigue loading failure. |
Key issues
The hitch arrangements for road trailer are often a high stress point and tend to fail in situ if operation and maintenance processes are not effective at maintaining a healthy hitch.
- Operation of on-road trucks in a mining environment can often result in increased wear and tear on equipment such as couplings due to harsh conditions, higher loading, and road construction different from that typically seen on public roads. Maintenance strategies must ensure this is taken into account. Inspection and maintenance frequency often needs to be increased.
- Signs of wear and premature failure of couplings, towing eyes, and drawbars can be detected visually or through the use of measuring equipment such as 'go, no-go' gauges available from coupling manufacturers and third-parties.
- Appropriate knowledge / information on sites regarding standards applicable to on-road trucks and haulage.
Recommendations
The hitch point is a safety-critical component. Consider if hitch arrangements on site are designed, operated, and maintained in a manner which reflects the operating environment with specific focus on:
Design: Appropriately robust and durable for the operating conditions, subjected loads, and life of product.
Operate: Vehicle speeds, acceleration, braking, cornering rates, road surfaces, safety chains / devices in place. Wet weather considerations, slopes / grades, QA for coupling / uncoupling activities.
Maintain: Lubrication, cleaning, inspection regime. Replacement of high stress components as a suitable frequency, assembly methods, QA of functions, tensioning, and corrosion management.
References and further information
NHVR – Vehicle Standard Guide 4 (VSG4)
NHVR – Vehicle Standard Guide 31
Heavy Vehicle (Vehicle Standards) National Regulation
National Heavy Vehicle Inspection Manual
Contact: Mark Genge, Inspector of Mines - Mechanical qldminesinspectorate@rshq.qld.gov.au
Issued by Resources Safety & Health Queensland
Placement: Place this announcement on noticeboards and ensure all relevant people in your organisation receive a copy, understand the content, findings and recommendations as applicable to their operation. SSEs should validate that recommendations have been implemented.
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