The purpose of this health and safety alert is to inform workers, employers, builders and designers of the risk of failure of lifting clutches associated with tilt-up and pre-cast concrete erection.
In October 2019, the lifting clutch link on a 5-tonne lifting clutch failed when a 100-tonne crawler crane was lifting a 16-tonne concrete wall panel. The panel was rigged with four face lifting inserts (lifters) at the time with equalising sheaves each fitted between two inserts. When the lifting clutch link broke, it caused two of the lifting points to become ineffective and the panel dropped onto the casting stack below. Although no workers were injured, the incident caused extensive damage to the panel and had the potential to cause serious injuries.
It appears the primary cause of the lifting clutch link failure was that it had a substantial, undetected crack through its cross-section. Rust on the failure surface indicates that the crack may have been present for some time (refer to Photograph 2). The crack was close to a weld and started on the inside of the lifting clutch link, so it may have been difficult to notice the crack by visual inspection. The lifting clutch link was inspected and proof tested by a third-party lifting gear organisation six months prior to the incident.
This incident highlights the serious consequences of lifting gear element failure. Although it occurred on a tilt-up site, the same type of lifting clutches are commonly used for pre-cast element erection. The incident is a reminder of the need for a back-up lifting system for the lifting of pre-cast elements as highlighted in Section 13.2 of the Tilt-up and pre-cast construction Code of Practice 2003.
The lifting clutches had been supplied by a company that specialises in gear associated with the erection of concrete elements and has a quality assurance program. The lifting gear was not owned by the company employing the crane and rigging crew.
A rigorous inspection and testing program is needed on lifting clutches, possibly beyond the current minimum industry benchmarks. Australian Standard AS3850.1:2015 Prefabricated concrete elements: Part 1 General requirements specifies non-destructive testing (NDT) of lifting clutches at manufacture, but does not specify any NDT during the 12-monthly inspection. Therefore to help prevent unexpected failures, consider carrying out NDT to inspect for cracks at the 12-monthly inspection. The inspection should include dimensional checking to determine that tolerances remain within the manufacturer’s specifications.
Inspection records should be maintained for every lifting clutch and the records should include the:
- identification number of each clutch assembly
- inspection organisation carrying out the 12-monthly inspection
- name of the competent person carrying out the inspection
- inspection method used (including the NDT method if used)
- results of the inspection (e.g. pass/fail).
The rigging crew erecting concrete elements should carry out a detailed visual inspection of the lifting gear prior to use.