Plant and machinery are present in most workplaces and working with moving plant or parts create exposure to the risk of injuries. The hazards associated with moving parts of machinery include the risk of crushing, shearing, entangling, trapping, hitting or abrading, or the uncontrolled release of pressure (energy). To successfully identify these hazards requires knowledge of how kinetic and potential energy and the interface between people and machinery that causes a loss of control of the energy.
In this article, we summarise the chapter on Mechanical Plant that is in the BOK Core Body of Knowledge for the Generalist OHS Professional. The discussion draws on the safety hierarchy of controls to develop ways to protect people when working with moving plant. We conclude with implications for health and safety practitioners.
What is Meant by ‘Moving Plant’?
The Australian Model Work Health and Safety Act describes moving plant as:
any machinery, equipment, appliance, container, implement and tool
However, the chapter on Mechanical Plant expands the definition to include:
- Plant that processes material by way of a mechanical action that
o Cuts, drills, punches or grinds the material
o Presses, forms, hammers, joins or moulds the material
o Combines, mixes, sorts, packages, assembles, knits or weaves the material
- Plant that lifts or moves people or materials, e.g. conveyors, robots, pumps
- Pressure equipment, e.g. boilers, air receivers, compressors, hydraulic hoses and cylinders
- Explosive-powered tools
- Amusement structures.
There is substantial regulation for working with moving plant, but even so, there remains a significant risk and a high number of workplace fatalities and injuries. In Australia in 2018, fifteen per cent of workplace fatalities were associated with machinery, plant or powered equipment when workers were hit by a moving object. A further 9% of workers’ compensation claims were related to coming into contact with fixed plant, powered equipment, tools and appliances. The long-term statistics indicate that over the past five years, the trend in fatality and injury numbers while working with moving plant, continues to remain the same with little improvement.
What Injuries Can Occur While Working With Moving Plant?
The injuries associated while working with moving plant or parts of plant commonly arise from the following outcomes:
• Crushing – where a person could be crushed between one or more moving machine components, e.g. between the ram and die of a press
• Shearing – where a person could be caught between two or more components moving past each other, e.g. scissor action
• Cutting or Severing – where a person could contact sharp surfaces or rapidly moving components
• Entanglement – where a person could become entangled in a rotating or moving component, e.g. a roller or conveyor
• Drawing-In or Trapping – where a person could be drawn in by a rotating or moving surface or surfaces, e.g. between two in-running rollers or between one roller and a fixed surface
• Impact – where a person could be struck by an object, either a controlled moving machine component or uncontrolled ejected material from a machine
• Stabbing or Puncture – where a person could contact a sharp machine protuberance, with either machine or person in motion
• Friction or Abrasion – where a person could contact a rough surface with either the surface or person in motion
• High-Pressure Fluid Injection (penetration of the skin) or Ejection – where a person may be struck by hydraulic fluid, steam or air.
What Are Kinetic and Potential Energies?
To understand the hazards associated with working with moving plant we need to understand kinetic and potential energy.
Kinetic energy hazards involve “things in motion” and “impact,” and are associated with the collision of objects in relative motion to each other. This includes the impact of objects moving toward each other, the impact of a moving object against a stationary object, falling objects, flying objects, and flying particles.
Potential energy hazards involve “stored energy”. This includes things that are under pressure, tension or compression; or things that attract or repulse one another. Potential energy hazards involve things that are “susceptible to sudden unexpected movement”. This category includes hazards associated with gravity and pertains to potential falling objects or persons. Also, the forces of gravity transferred biomechanically to the human body during manual lifting.
Risk Factors to Consider When Working With Moving Plant
There are several reasons while working with moving plant is highly hazardous and can lead to fatalities and injuries. Examples of contributory risk factors for the mechanical hazards associated with plant include:
• Shape – e.g. cutting elements, sharp edges, angular parts, even if stationary; deburred sheet metal edges, smooth rather than rough surfaces, protruding parts to catch clothing
• Relative Location – which can create crushing, shearing, entanglement zones when elements are moving, e.g. distance between in-running rollers for feeding material into a printing press, accessible by the press operator
• Stability Against Overturning – kinetic energy, e.g. suitable geometry of base, weight distribution, vibration, and external forces such as wind
• Mass and Stability – the potential energy of elements that can move under the effect of gravity, e.g. press ram or hoist platform held above other components during machine operation, and cranes
• Mass and Velocity – kinetic energy of elements in controlled or uncontrolled motion, e.g. from fast-moving light-weight components to slow-moving heavy components
• Acceleration and Deceleration – components that may accelerate quickly from rest
• Mechanical Strength – which when inadequate can generate hazardous breakages or bursts, e.g. grinder wheel disintegration or drive chain breakage, structural failure through loads and fatigue
• Potential Energy – of elastic elements (springs), or liquids or gases under pressure or vacuum, e.g. tyres under pressure, boilers, air receivers, hydraulic hoses, compressed air hoses.
Plant that is moving or in operation presents mechanical hazards when people interact with the machine. It is vital to understand where, when and how people are likely to interact. You must consider all stages in the life cycle of people and machine interaction. For example, machine construction, transportation, installation, commissioning, operation, maintenance, troubleshooting, cleaning, repair, decommissioning and removal.
How Can You Control Hazards When Working With Moving Plant?
The Australian Model Work Health and Safety Act requires organisations to work through the Hierarchy of Controls and use the highest level of control that is practicable to remove or reduce the risks associated with working with moving plant. The highest level of control is Elimination to control plant hazards at the design stage. For example, designing a pop-out roller of the conveyor to eliminate pinching of the hand. If this is not reasonably practicable, the use of low-speed, low-pressure or low-energy components may reduce risks from mechanical hazards.
Also, you can use clever design to eliminate direct access to machine hazards, e.g. by enclosing the hazards within the body of the machine, and by providing controls and machine adjustments away from the hazards. As well, you can reduce the exposure of maintenance personnel by positioning equipment so that it can be serviced and repaired without the need to access hazardous areas or operate the machine during set up or maintenance.
On the Tap into Safety Training Platform, there is a microlearning course on the Hierarchy of Controls. The course unpicks the levels of the hierarchy pyramid and provides practical examples of each stage.
Also, see our article, Workplace Hazards and the Hierarchy of Controls.
If You Can’t Eliminate the Hazard, What Engineering Controls Can You Use?
Where eliminating the hazards when working with moving plant is not practicable, you can use engineering controls. You can do that by preventing people from entering the zone where the damaging energy can be transferred to them. This may be by fixed guarding, or by controlling the damaging energy when people need to enter the zone by using interlock guarding or presence sensing systems. For example, you might use:
- A permanently fixed guard where access is not required
- An interlocked physical guard where access is required
- A physical barrier that can only be altered or removed with tools where a fixed guard or interlocked guard is not reasonably practicable
- A presence-sensing system where a fixed guard, interlocked guard or physical barrier that can only be removed with tools is not reasonably practicable.
When Should You Use Isolation Controls?
There are times when you should use isolation controls. Isolation is usually required for major intervention access such as maintenance work or clearing of major jams in the machine. In such cases, you must isolate energy sources and dissipate or contain all stored energy to prevent hazards from arising while personnel are in the hazard zone. Energy isolation is usually an integral part of a Permit To Work System including Lockout/Tagout (LOTO) Procedures.
On the Tap into Safety training platform, there is a comprehensive course that trains on Isolating Energy Sources and a short course that refreshes on Personal Locks and Safety Tags. These courses use microlearning videos together with a robust assessment for the most effective control measures to use when working with moving plant. The Isolating Energy Sources course includes training on:
- Mechanical Energy
- Thermal Energy
- Chemical Energy
- Electrical Energy
- Gravitational Energy
- Hydraulic Energy
- Pneumatic Energy
- Locks and Safety Tags
Also, see our courses on Access Egress Barrier Selection that trains on operating moving mobile plant and workers on foot and Blind Spots and Vision Shadows that teaches about line of sight limitations when operating heavy mobile plant.
What About Administrative Controls?
The hazards when working with moving plant are very high and the potential severity of injuries is extreme. As such, you should focus your risk control efforts on good design and use guarding or machine controls wherever you can. But, there will be a residual risk and, while less reliable than higher-level controls, administrative controls are essential to control plant-related hazards. For example, testing and isolation, permit-to-work and lockout/tagout (LOTO) processes as well as information, instruction, training and supervision.
How Effective is PPE When Working With Moving Plant?
While PPE is a requirement in many organisations, it generally doesn’t provide protection against the kinetic energy of moving machine parts. Indeed, when there is an in-running movement of machine parts, the wearing of gloves can increase the risk of entrapment. However, the wearing of safety footwear and suitable clothing can assist in reducing the likely consequences of coming into contact when working with moving machinery or machine components.
What Are the Implications for Health and Safety Professionals?
All generalist Health and Safety professionals should have a basic understanding of the types of mechanical hazards associated with machinery and the typical risk controls to use. They should be able to recognise the potential for safeguarding systems to be defeated or compromised and be familiar with the means by which such actions can be eliminated or minimised.
If working with moving plant occurs in their workplace, they should ensure that plant design and control systems, including procedures, are appropriately designed for the purpose of the machine. Finally, Health and Safety professionals should always consult with others who are familiar with the use of the plant.