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Three-point linkage connections

Safety Alert
1 February 2012

A worker was injured while clearing a log from beneath a slasher which had been attached to a tractor via a three-point linkage connection.

A chain and two D-shackles were used as the top link between the tractor and the slasher to provide a flexible connection for rough terrain. A pin had fallen out of a D-shackle and the slasher dropped onto the worker as he removed the obstruction.

The D-shackle pins had not been secured with a split pin or similar fastening device but had remained secure due to the distortion of the pin caused by the load.

Three-point linkages, commonly used to fit attachments behind tractors, are standardised mechanisms consisting of an adjustable top link centred above two lower lifting links

Three-point linkages, commonly used to fit attachments behind tractors, are standardised mechanisms consisting of an adjustable top link centred above two lower lifting links

Possible causes

  • The D-shackle pin may have worked loose during normal machine operation, as there was no secondary fastening system in place.

Action required

  • Never work or stand under suspended machinery unless it is supported by suitably designed props or stands. Do not use wood to support the machinery.
  • Replace chain connections with an adjustable bar or some other method, where possible.
  • If a chain must be used, secure all D-shackle pins with a secondary fastening device.
Disclaimer: While care has been taken to ensure the accuracy and currency of the information in this publication, at the time of reading it may not be sufficiently accurate, current or complete to suit your individual needs. Reliance on the information in this publication is at your own risk. SafeWork SA accepts no liability for any loss resulting from your reliance on it. To best meet your work health and safety obligations refer to current Acts, Regulations and Approved Codes of Practice.