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Wood chipper blade failure

Safety Alert
1 October 2012

Wood chippers are powerful machines used to reduce tree trunks and branches into small wood chips through the action of a cutting disc.

A wood chipper machine was in use when a sudden failure resulted in a cutting blade shattering with large fragments ejected through the solid metal guard. This incident had the potential to cause serious injury to the operator or other workers in the vicinity.

The chipper cutting disc, remaining blade and surrounding guarding sustained extensive mechanical damage, with debris piercing through the heavy duty metal guard.

Damaged metal guard

Damage metal guard on a woodchipper

Possible causes

  • failed main bearing supporting the cutting disc
  • low-grade bolt used in securing the blade to the disc
  • loose/incorrectly adjusted blade
  • blunt blade/poor blade sharpening technique
  • brittle blade material or wrong material selection
  • damaged or over-torqued blade retaining bolts
  • material fatigue that may have initiated cracks in the blade
  • different length blades
  • foreign material trapped between the blade and cutting disc during assembly
  • too high a timber feed rate into the machine
  • mulching of high hardness timber
  • metal/foreign object drawn into the chipper.

Other hazards

Operating wood chippers can be dangerous for operators and others in the vicinity of the machine:

  • workers feeding tree limbs and branches into chippers are at risk of getting caught in the material and being pulled into the cutting area
  • materials ejected from chippers, such as wood, metal fragments and stones, could cause serious injuries and even death.

Action required

  • use wood chippers in accordance with manufacturer’s instructions
  • ensure wood chippers have the appropriate safety devices installed, such as a feed control bar, and that they are regularly tested
  • check the condition of blades prior to startup, including the securing bolts
  • ensure workers wear the appropriate personal protective equipment (PPE)
  • ensure all repairs/servicing are done by competent persons
  • establish a regular servicing, maintenance and inspection program, and repair or replace faulty parts identified from inspections
  • identify and implement a hazardous work zone to exclude members of the public and non-essential workers.