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Guarding Of Machines


  • Document Type: Guidance Note
    Keycode: web only
    Industry: General, Synthetics manufacturing, 
    Category: Plant, 
    Division Author: Manufacturing & Agriculture
    Publication Date: 06 June 2005
    Date First Published: 18 September 2000
    Summary: This guidance note provides general guidance to assist employers in safeguarding of machines for use in their workplaces.

Issued: September 2000


Purpose

To provide general guidance to assist employers in safeguarding of machines for use in their workplaces.

Background

Machines are used in workplaces to perform a wide range of functions which include cutting, drilling, punching, grinding, pressing, forming, hammering, joining, moulding, combining, mixing, sorting, packaging, assembling, knitting and weaving materials.

Machines generally have moving parts which perform rotating, sliding or reciprocating motion or a combination of these movements. These have the potential to cause injury to workers and those in the vicinity of the machine.

The Occupational Health and Safety (Plant) Regulations 1995 (Plant Regulations) require employers to ensure that:

  • hazards (potential for injury or illness) associated with the installation, commissioning, erection, operation, inspection, maintenance, repair, service and cleaning of any new and existing machine for use in the workplace are identified;
  • the risks (likelihood for injury or illness) associated with the identified hazards are assessed; and
  • any risk is eliminated, or where that is not practicable, reduced so far as is practicable.


The Plant Regulations require employers not to depend solely on the use of administrative controls (e.g. training, safety procedures, safety signs, supervision) or personal protective equipment (e.g. safety gloves, safety glasses) to control risk unless the following are not practicable measures:

  • Substituting the machine with one which has a lower level of risk; or
  • Use of engineering controls to change the physical characteristics of the machine to eliminate or reduce risk; or
  • Isolation of the machine from people.


The Plant Regulations require employers to consult with the relevant health and safety representative when undertaking hazard identification, risk assessment and risk control processes. Employers should also involve machine operators, people who carry out inspection, maintenance, repair, service and cleaning of machines in those processes. They are valuable source of information on hazards and measures for controlling risks because of their day to day experience.

Identifying Hazards

WorkCover's publication "Plant Hazard Checklist" can be used to identify hazards associated with machines for use in your workplace. This is available from WorkCover publications.

To help identify areas of the machine which can cause injury or illness, look for:

Mechanical hazards:

  • "drawing in" points
  • shearing points
  • impact and crushing areas
  • cutting areas
  • entanglement areas
  • stabbing points
  • abrasion areas
  • flying particles
  • any protrusions which could cause injury


Non-Mechanical hazards:

  • electrical shocks and burns
  • chemical burns, toxicity, flammability
  • noise, vibration
  • radiation
  • biological hazards, viral
  • manual handling (see also Occupational Health and Safety (Manual Handling) Regulations 1999 and Code of Practice for Manual Handling 2000)
  • mist, dust, fumes
  • suffocation


Assessing Risks

Once the potentially dangerous areas of the machine are identified, the risk (likelihood of injury or illness) associated with those areas should be assessed by considering:

  • whether any person (workers and visitors) would be exposed to those areas during installation, commissioning, erection, operation, inspection, maintenance, repair, service and cleaning of the machine;
  • what existing measures are in place to protect the health and safety of people who may be exposed; and
  • how adequate the existing measures are for protecting the health and safety of people who may be exposed.


In considering the issue of exposure, you need to consider:

  • Are any parts of the body likely to come into contact with the machine?
  • Are there any non-mechanical hazards present that may cause injury or illness?


If the answer to both questions is no, then there is no risk and no additional risk control measures are required.

If the answer to either of the questions is yes, consideration should be given to the adequacy of existing control measures for protecting the health and safety of people who may be exposed.

Existing control measures should not be regarded as adequate simply because an incident hasn't occurred. This particularly applies where the existing control measures are only administrative controls and/or by use of personal protective equipment. These types of control rely heavily on human behaviour in doing the right thing and any deviation in behaviour (e.g. machine operators not following the safe procedures because they are being distracted by some one or situation) could cause injury. The Plant Regulations require the risk assessment to take into account "any reasonably foreseeable abnormal operating conditions" of the machine. Experience shows that these are the events that eventually result in incidents.

 

Controlling Risks
If there is a likelihood of injury or illness associated with certain areas of the machine when all existing control measures are considered, the Plant Regulations require employers to eliminate or reduce the risk so far as is practicable by adopting the hierarchy of control as outlined in the Background section.

Provision of appropriate guarding for danger areas of a machine is a form of engineering control designed to:

  • prevent access to the danger areas of the machine; or
  • contain flying particles generated from the materials which the machine processes; or
  • contain workpieces ejecting or disintegration of machine parts


Guarding a machine's danger areas is one of several options available to you for controlling risks. Other options in the descending order of effectiveness are as follows:

  • Eliminate the process all together and therefore the need for the machine.
  • Replacing the machine with another with a safer design.
  • Isolate the machine from people.
  • Develop safety procedures and signs for the installation, commissioning, erection, operation, inspection, maintenance, repair, service and cleaning of the machine and make sure the relevant people are familiar with the procedures and signs.
  • Make sure the work is adequately supervised.
  • Provide appropriate personal protective equipment for workers and visitors and make sure they are used.


Before any decision is taken as to which type of risk control measures ought to be used, consideration should be given to the severity of injury that could occur. If the severity of injury is high (i.e. fatality or serious injury), the higher hierarchy order of control (i.e. elimination, substitution, engineering control, isolation) that should be used in combination with administrative control and in some cases personal protective equipment. It is not always practicable to immediately implement the higher hierarchy of control and there may still be a need to keep the machine operation going. In such situations interim control measures (in the form of administrative control in combination with personal protective equipment) may be used until the higher hierarchy of control can be implemented.

Note: If there is an immediate risk to health or safety, the employer must make sure the machine in question is not used until measures are taken to remove the immediate risk.

Selection and Design of Guards
The following is a description of the common types of guards available, their design considerations and limitations of use. Each type of guard is designed to suit a particular purpose. You should consider which type of guard is best suited for your needs. For some applications, you may need to use a combination of guards in order to achieve the safety outcome.

Irrespective of which guard you select, you need to ensure that:

  • the guard is such that it makes by-passing or disabling, whether deliberately or by accident, as difficult as is reasonably possible; and
  • the guard does not cause a risk in itself and cause injury.


Permanently fixed physical barrier (Figure 1)
This consists of a physical barrier welded to the machine to completely enclose the danger points or areas. This type of guard is the most effective in eliminating risks associated with those machine areas. This guard type is not suitable where access to those areas is necessary for cleaning and maintenance.


Cut-away view of a permanently fixed physical barrier encasing the gear assembly and heavy duty electric motor.

Figure 1 Cut-away view of a permanently fixed physical barrier encasing the gear assembly and heavy duty electric motor.

Interlocked physical barrier (Figure 2)
This consists of a physical barrier which is connected to either the power or control system of the machine. The interlock prevents the machine from operating unless the guard is closed. The interlocking system may be mechanical, electrical, hydraulic, pneumatic or a combination of these. This type of guard is ideal for situations where regular operational access to the area requiring guarding is required (e.g. to clear material jam). It is also very effective in minimising risks associated with danger areas of the machine provided that:

  • the interlocking system* is reliable or has a back-up system;
  • the interlocking system is designed to fail to safety (i.e. if there is a failure in the interlocking system, the machine can not operate); and
  • in cases where the moving parts of the machine requiring guarding take a period of time to come to rest, the interlock prevents access to the moving parts until they come to rest.


* Note: The type of interlocking system required should be dependent on the likelihood and severity of injury. See AS 4024.1-1996 for selection of category of control system for the interlocking system.


Interlocked physical barrier

Figure 2


Non-interlocked physical barrier (Figure 3)
This type of guard is normally used where access to the machine during operation, maintenance or cleaning when the machine is stopped or isolated, is less frequent.

There are 2 types of non-interlocked physical barrier:
1. Fixed guard
2. Moving guard

A fixed guard is a physical barrier(s) attached to the machine in a way that can only be removed by use of a tool. For some machines the physical barrier may be adjustable. The fixed guard is designed to:

  • prevent access to the area of the machine requiring guarding by completely enclosing the danger area using solid or mesh material; or
  • reduce access to the area of the machine requiring guarding by virtue of its physical dimensions and its distance from the danger area (commonly known as distance guard).


A fixed guard offers protection only if it is properly fixed in an appropriate position and maintained in that position. If mesh is used, it is critical to select the appropriate grid size of the mesh for preventing access of bodily parts such as fingers (of children in some cases) to the danger area of the machine.

A moving guard is a physical barrier(s) which moves or has moving parts. The physical barrier is mechanically connected to the machine so that as the machine moves or as the workpiece moves, the guard also moves and takes up a safe position. Because this type of guard is not interlocked to the machine controls or power source, its removal, incorrect adjustment or other failure does not prevent the machine operating or prevent access to the danger area of the machine when the machine is operating. Therefore, this type of guarding requires stringent compliance with setting and maintenance procedures.

Mesh guard, Use of flat plate or angle section to prevent access to in-running nips

Mesh guard
Use of flat plate or angle section to prevent access to in-running nips
Figure 3

Distance guard, Adjustable guard


Distance guard
Adjustable guard
Figure 3

Presence-sensing system (trip devices) (Figure 4)
A presence-sensing system is a device that causes working machine to stop or assume a safe condition when a person or object is in the area being guarded.

This type of guard is normally used where regular access to the area of the machine requiring guarding is required (e.g. to clear material jam or for die setting).

There are 3 types of trip devices:
1. mechanical
2. photoelectric
3. pressure-sensitive

The key component of a mechanical trip device is a barrier (e.g. a trip edge) which is moved by part of the body as a danger area is approached. This movement of the device operates controls which may be electrical, mechanical, hydraulic or pneumatic.

A photoelectric trip device uses a beam(s) of light (visible or invisible), a curtain of light or any combination of these, to detect the approach of persons or objects to danger part of the machine where, so long as a person or object is detected, the danger part of the machine cannot be set in motion. Its effectiveness depends on the electrical integrity of the device and the location of the light beam(s)/curtain relative to the dangerous part of the machine. Where a high level of integrity is required, the device may need to monitor certain machine functions such as the stopping performance and the performance of the devices controlling the dangerous motions.

A pressure-sensitive device (e.g. pressure mat) contains sensors which are activated when a person or object applies pressure to the device. By its nature, the device is exposed to potential damage which can result in failure. For the device to be effective, its dimensions need to take into account of a person's speed of approach, length of stride and the overall response time of the device. The device needs to be sensitive over the whole sensing area.


Mechanical trip device, Photoelectric guard
Mechanical trip device
Photoelectric guard
Figure 4


Perimeter guard (fence guard) (Figure 5)
A perimeter guard is a fence which completely surrounds a machine. It is regarded as a form of engineering control if a portion of the machine is incorporated as part of the fence, otherwise it is a form of isolation in the hierarchy of control. For the guard to be effective the distance from the danger area of the machine, the height of the fence and the material used for the fence are important considerations. A perimeter guard can be fitted with an interlocked gate(s) or photoelectric trip devices interlocked to the machine controls to allow people access to the machine. Re-closing of the interlocked gate(s) must not cause an automatic restart of the machine. Manual reset/restart outside the safeguarded space is then necessary. Where the access gate(s) is not of the interlocked type, appropriate danger tags and lockout mechanisms should be used whenever it is necessary for a person to have access to the machine.


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Figure 5

Maintenance of Guards and Review
After the appropriate guard(s) is selected and installed, you need to make sure that it is maintained. All employees should be instructed to report any faults and the faults need to be addressed as a matter of urgency. You should conduct regular meetings with machine operators, people who carry out inspection, maintenance or cleaning of the machine to identify whether there are new hazards requiring attention. If there are new hazards, you should repeat the hazard identification, risk assessment and risk control processes.


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.


Standards Australia


  • AS 4024.1-1996 Safeguarding of machinery Part 1: General principles
  • AS 4024.2-1998 Installation and commissioning requirements for electro-sensitive systems-Optoelectronic devices.
  • AS 4024.3-1998 Manufacturing and testing requirements for electro-sensitive systems-Optoelectronic devices.
  • AS 4024.4-1998 Installation and commissioning requirements for electro-sensitive systems-Pressure sensitive devices.
  • AS 4024.5-1998 Manufacturing and testing requirements for electro-sensitive systems-Pressure sensitive devices

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.


Further information


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.