Important mechanical components on rear dump mining trucks are most easily accessed by raising the dump body. To allow safe work under the raised body, holdback slings are installed between the tail of the body and the rear axle.
The strength requirements for this sling are dictated by the Australian Standard AS ISO 13333:2021, entitled Earth-moving machinery — Dumper body support and operator’s cab tilt support devices. Unfortunately, this standard is poorly written, leaving room for misinterpretation and potentially resulting in dangerous outcomes.
In relation to strength, the standard states, “the device… shall be designed to withstand the static load imposed…”. While there is more to the requirements, the essence is that the applied loads are those expected in service, and the strength requirement is “designed to withstand”.
Properly designed structures have a significant safety margin on the basic loads. Competent suppliers of body holdback equipment interpret “designed to withstand” to mean that any device will have an adequate safety factor at the design load. For example, fibre ropes should be used with a five times safety factor on failure at their design load.
However, due to the imprecise wording of the standard, some suppliers have interpreted “designed to withstand” to mean that the device only needs to survive this loading and nothing more. Therefore, they are confusing the breaking strength and the safe working load.
To compensate for load uncertainty and possible variation in component strength, it is critically important that end users of body holdback slings understand that sling components should have appropriate margins of safety at the design load.
A failure to do so could lead to mines unknowingly putting their workshop personnel at risk of serious injury, or worse.
Ready to safeguard your maintenance team?
If you need clarification about the safety and compliance of your rear dump truck holdback slings, get in touch with CMP Engineers.
For over 30 years, CMP Engineers has been delivering innovative mechanical engineering solutions and specialised equipment design to some of the biggest names in mining, including BHP, Glencore, Rio Tinto, and Anglo American. From concept to commissioning, our team ensures quality, durability, and efficiency in every project to address your unique challenges.
For more information or a confidential discussion about your holdback slings, contact us today.