Wood Chipper Machine Guarding
Industry: Forestry, Wood and wood products manufacturing,
Publication Date: 22 November 2006
Date First Published: 22 November 2006
Summary: This guidance note provides information on the use of guarding to control the risks associated with the operation of mobile wood chippers. Document Type: Guidance Note
This guidance note provides specific guidance on the use of guarding to control the risks associated with the operation of a mobile wood chipper.
In Western Australia (1999) a 16 year old employee received fatal injuries when he was dragged into a mobile wood chipping machine. The conclusion from the incident investigation was that the control bar that activates the in-feed rollers was being relied upon as an emergency device, which it was not designed for.
In the U.S. between 1992 and 1997, 11 people were fatality injured by wood chippers. The two most common causes of fatal injury were being fed through the chipper knives or being struck by the chipper disc hood. Minor amputations have been recorded in Victoria, including an employee who lost a toe while trying to stop the moving disc on run-down with this foot. Another recent injury involved an employee whose finger was amputated when he tried to free debris from the in-feed rollers of a chipper.
Wood chippers are most commonly used for tree trimming operations and are designed differently depending on the manufacturer and particular model. They all use the principle of a rotating disc or drum with hardened steel blades which chip the wood. The in-feed to the machine uses one or two feed rollers (usually hydraulic powered) and an exit chute at the rear of the cutting disc or drum.
Rotating in-feed rollers
A person is able to be caught in the in-feed rollers via the in-feed hopper or the side or top of the main body of the chipper unit. Entanglement, shearing, crushing are the potential hazards involved. There is also the risk that the person could be fed through to the cutting disc or drum. In past incidents this has caused a serious injury or fatality.
Rotating cutting disc or drum
All units require access to the cutting disc or drum for maintenance, operation and cleaning. An access hatch or cover allows the operator to potentially come into contact with the moving disc or drum. Potential hazards include cutting, crushing and entanglement. In addition, the structural integrity of the disc should be designed and maintained to correct specifications. Failure of a wood chipper disc resulted in a fatality in Western Australia in January 2004.
There are other hazards associated with the use of wood chippers which may not be listed here. These could include noise, manual handling, dangerous goods and dust inhalation. Refer to WorkSafe Victoria's publication Plant Hazard Checklist for guidance to identify these hazards.
Manufacturers/suppliers and operators of wood chippers should examine their machines to assess the effectiveness of their risk controls to prevent unintentional access to the hazard areas of the machine. Many chippers currently use a control bar to reverse the roller motion, distance guards and covers. However the injuries and fatalities have shown that these measures may be ineffective and additional safeguards are required. These feed control bars are operational controls and not emergency devices.
Existing control measures such as administrative controls and personal protective equipment should not be regarded as adequate simply because an incident hasn't occurred.
Entanglement with rotating in-feed rollers
Prevent access to the in-feed rollers
- Ensure design of the in-feed hopper includes a minimum distance from the edge of the feed hopper to in-feed rollers. (see AS 4024.1-2006, Safety of Machinery)
- Control access to the in-feed rollers whether from the side or top of the unit when the plant is in normal operation. Some wood chipper designs allow access to the in-feed rollers through the side or top of the hopper housing when they are in operation. Access should be prevented via a fixed or interlocked guard.
- Provide emergency shut-off devices to shut down all power on the machine. This should immediately stop the in-feed rollers and cut the power to the disc/drum (which will have a run-down time). These devices should be immediately accessible to the operator in an emergency and tested and verified to be functioning properly each time the chipper is to be used.
- Consider installing an electronic activating mechanism that is activated by sensors worn by the operator.
Rotating cutting disc or drum
Prevent access to the rotating cutting disc or drum for maintenance or cleaning purposes. One way to prevent access is to provide interlocked physical barriers. This could include:
- electronic interlocked systems (eg. motion control sensor, timed solenoid)
- mechanical interlocking systems. If there is a hatch cover over the disc/drum that is fixed with bolts or screws then consideration needs to be given to the time taken to remove the bolts (eg. use of a rattle gun). A disc/drum can have a run down time of up to five minutes if un-clutched.
In relation to the structural integrity of the wood chipper disc or drum the designer/manufacturer/supplier should conduct an engineering design assessment using engineering computations and finite element analysis (FEA).
Designers, manufacturers and suppliers of wood chippers should ensure that all components and alterations to any component are designed by competent persons and are suitable for the task.
Location of operator controls on the unit
In addition to the guarding of the wood chipper there is the issue of the location of operator controls on the wood chipper. If operator controls are not fitted kerbside for the operation of the chipper then a person is required to be on the road to access the controls. This exposes the person to a higher risk of being struck by passing traffic.
Possible risk control solutions for this include:
- Importers of machines from other countries offering the option of controls being fitted to either side of the machine for sale in Australia.
- If controls are non-kerbside, then the operator should implement a traffic management plan to ensure that the risk of being struck by passing traffic when accessing the controls is minimised.
There are other lower order controls that can be considered when assessing the risks with this plant. These might include:
- Develop written standard operating procedures based on a safe system of work and the manufacturer's recommendations for the particular model.
- Operators are competent through adequate training and appropriate supervision prior to and when using the machine
- Always stop the in-feed rollers prior to removing any debris from the in-feed hopper and use push sticks, brooms and branches to remove debris.
- Ensure the operator does not have loose items of clothing that may get caught or snag on pruning material as it is fed into the chipper.
- Feed the butt end of branches into the chipper in-feed rollers first
- Never climb onto, or stand on the in-feed hopper of the chipper
- Workers wear eye protection and ear protection
- Provide and maintain adequate warning signs as a constant reminder to operators and others of the potential hazards associated with the machine.
Legal responsibilities under the Occupational Health and Safety Act 2004
Employers and self-employed persons have a range of general duties under the Occupational Health and Safety Act 2004 (OHS Act) and the Plant Regulations 1995 to ensure equipment is safe (see sections 21, 23 and 24 of the OHS Act and sections 501–503; 601–606; 701–717 of the Plant Regulations).
Acts & Regulations
- Occupational Health and Safety Act 2004
- Occupational Health and Safety (Plant) Regulations 1995
- Occupational Health and Safety (Manual Handling) Regulations 1999
Acts and regulations are available from Information Victoria on 1300 366 356 or order on-line at www.bookshop.vic.gov.au . If you only want to view the legislation you can use the Parliament of Victoria web site; go to www.dpc.vic.gov.au, click on "Victorian Law Today" and scroll down to the "Search" window.
WorkSafe Victoria publications
- Plant (Code of Practice No.19,1995)
- Manual Handling (Code of Practice No.25, 2000)
- Plant Hazard Checklist
- Guidance Note ? Guarding Of Machines?(Sept 2000)
Copies of publications, including Codes of Practice, can be obtained by contacting WorkSafe Victoria on 03 9641 1333, visiting your local WorkSafe Victoria office or on WorkSafe Victoria's web site www.worksafe.vic.gov.au.
- AS 4024.1 – 2006: Safeguarding of machinery. Copies of standards can be obtained by contacting Standards Australia on 1300 654 646 or by visiting the web site at www.standards.com.au.
Special Note on Codes of Practice: Codes of Practice made under the Occupational Health and Safety Act 1985 provide practical guidance to people who have duties or obligations under Victoria's OHS laws. The Occupational Health and Safety Act 2004 allows the Minister for Workcover to make Compliance Codes which will provide greater certainty about what constitutes compliance with the OHS laws.
Codes of Practice will continue to be a practical guide for those who have OHS duties and WorkSafe will continue to regard those who comply with the topics covered in the Codes of Practice as complying with OHS laws. WorkSafe will progressively review all Codes of Practice and replace them with guidance material and in appropriate cases, with Compliance Codes.
Acts and Regulations
Acts and regulations are available from Information Victoria on 1300 366 356 or order online at www.bookshop.vic.gov.au.
View the legislation at Victorian Law Today at www.legislation.vic.gov.au.
Note: This guidance material has been prepared using the best information available to WorkSafe Victoria. Any information about legislative obligations or responsibilities included in this material is only applicable to the circumstances described in the material. You should always check the legislation referred to in this material and make your own judgement about what action you may need to take to ensure you have complied with the law. Accordingly, the Victorian WorkCover Authority extends no warranties as to the suitability of the information for your specific circumstances.