Hazard Management Bulletin - Use of Gravlocks in Rigging
Incident
In October 2004, a scaffold tube and attached rigging weighing 21.5 kg, fell 12 m from its attachment to the ground. It hit two workers below seriously injuring them.
Circumstances
In October 2004, a scaffold tube and attached rigging weighing 21.5 kg, fell 12 m from its attachment to the ground. It hit two workers below seriously injuring them.
The scaffolding was part of a system to raise and lower two large lighting platforms, which were suspended from universal beams in the roof. The platforms were raised and lowered by chain hoists and motors. Moving the platforms horizontally along the set required manual hauling on a rope through a pulley system. This pulley system was anchored at each end of the building and attached to the universal beams using a girder clamp known as a ‘gravlock’. Only one gravlock was used at each end of the scaffold tube and attached to the inside flange on each beam.
As the platform was being lowered to the ground, the rope became caught. The tension ripped one of the scaffold tubes off the universal beam causing it to bring down the lighting stage and injuring the workers below.
Investigation Findings
The scaffold tubes were incorrectly attached to the beam. Only one gravlock was used at the point of contact.
Manufacturers’ instructions are clear that gravlocks must be used ‘in pairs’. This means that two gravlocks should have been used at the point of attachment to the universal beam.
Had there been two gravlocks used correctly as a pair, on the inner and outer flanges of the beam, this accident would have been avoided.
This investigation has identified confusion amongst riggers and scaffolders in regard to the interpretation of what a ‘pair’ of gravlocks means. The following clearly shows the recommended use of a pair of gravlocks.
Recommendation
Ensure all gravlocks are used in pairs as indicated below.
Which industries/sectors or matters will this information be relevant to?
Construction industry.
Note: This material has been prepared using the best information available to the Department of Labour at the time of publication. Information may change over time and it may be necessary for you to obtain an update. This material is also only intended to provide general advice and does not constitute legal advice. You should make your own judgement about action you may need to take to ensure you have complied with your workplace health and safety obligations under the law.
Issued by the Department of Labour, New Zealand
http://www.osh.govt.nz
February 2010
