A surprising number of Australian manufacturers are running machinery that would fail a formal AS 4024 audit. Not because they are reckless, but because the standard has evolved significantly over the past decade and most existing risk assessments have not kept pace. This article explains the current requirements and where the common gaps are.
Most machinery safety non-conformances found in Australian manufacturing facilities are not the result of negligence. They are the result of well-intentioned engineers applying standards that were current when the machine was installed but have since been revised, or applying controls-based safety solutions to hazards that require physical safeguarding under the current standard hierarchy.
The Legislative Foundation: What the Law Actually Requires
The Work Health and Safety Act 2011 (the model law adopted by NSW, Queensland, South Australia, Tasmania, ACT, and the Northern Territory) places a primary duty on persons conducting a business or undertaking to ensure, so far as is reasonably practicable, that the workplace and anything arising from the workplace does not present a risk to the health and safety of any person. The key phrase is "so far as is reasonably practicable", which is defined by reference to the likelihood of the hazard, the degree of harm, what the person knows (or ought reasonably to know) about the hazard, and the availability and cost of ways to eliminate or minimise the risk.
Victoria operates under the Occupational Health and Safety Act 2004, with substantively similar duties but state-specific regulations under the OHS Regulations 2017, including specific provisions for plant (machinery) in Part 5.1. Western Australia adopted the Work Health and Safety Act 2020 in March 2022, aligning with the model law framework. In all jurisdictions, non-compliance with an applicable Australian Standard (such as AS 4024) is not automatically a breach of the WHS Act, but it is strong evidence that a risk was not managed "so far as is reasonably practicable" if a relevant standard existed and was not followed.
The AS 4024 Standard Series: What Each Part Covers
AS 4024 is Australia's adoption of the ISO 12100 and associated standards for safety of machinery. The series is structured into parts that address different aspects of machinery safety. For a practical compliance programme, the most relevant parts are:
| Standard | Title | Practical Application |
|---|---|---|
| AS 4024.1201 | Design of Controls, Interlocks, and Guarding | Sets out design requirements for guards and control systems, hierarchy of risk reduction measures |
| AS 4024.1301 | Guards | Physical guard types, construction requirements, fastener specifications for fixed and movable guards |
| AS 4024.1302 | Interlocking Guards | Requirements for movable guards with interlocking, including guard locking where required by risk assessment |
| AS 4024.1601 | Design of Controls — Risk Assessment | Risk assessment methodology, hazard identification, risk evaluation framework (equivalent to ISO 12100) |
| AS 4024.1902 | Safety Distances | Minimum distances for safeguards to prevent reaching hazardous zones; table-based calculations for light curtains and pressure-sensitive mats |
| AS 4024.3301 | Safety-Related Parts of Control Systems | Australian adoption of ISO 13849-1; Performance Level determination methodology |
Risk Assessment Methodology Under ISO 12100
The risk assessment process under AS 4024.1601 (ISO 12100) follows a defined sequence: determine the limits of the machine, identify hazards for each life cycle phase (including installation, commissioning, operation, cleaning, maintenance, and decommissioning), estimate the risk for each hazard considering severity and probability of harm, evaluate whether the risk is acceptable, and apply risk reduction measures in the prescribed hierarchy until acceptable risk is achieved.
The hierarchy of risk reduction in AS 4024.1201 is: inherently safe design first (eliminate the hazard through design), then safeguarding and protective measures (guards, safety devices), then information for use (warnings, instructions, training). Safeguarding and information for use only achieve acceptable risk reduction when inherently safe design is not reasonably practicable. This hierarchy is frequently inverted in practice, with "warning label applied" used as the primary risk control for hazards that a design change or guard could eliminate.
Performance Level Determination Under ISO 13849-1
For safety functions implemented in control systems (such as guard interlocking, emergency stop, two-hand control, or enabling device functions), ISO 13849-1 (adopted in Australia as AS 4024.3301) requires determination of the required Performance Level (PLr) and verification that the achieved Performance Level (PL) meets or exceeds it.
PLr is determined by the risk graph in ISO 13849-1 Figure 3, considering severity of injury (S1: reversible, S2: irreversible), frequency of exposure (F1: seldom, F2: frequent), and possibility of avoidance (P1: possible, P2: scarcely possible). A safety function protecting against an irreversible injury from frequent exposure where avoidance is scarcely possible requires PLr e, the highest level.
The free SISTEMA software from the German IFA (Institut fur Arbeitsschutz) calculates achieved PL from component B10d values (the number of operations at which 10 percent of components have failed dangerously), mission time, and architecture category. A safety function using a single safety relay with OSSD outputs (Category 2 architecture) can achieve a maximum of PLd. A PLe requirement needs a Category 3 or 4 architecture with redundant channels and cross-monitoring, typically implemented with a safety PLC or dual-channel safety relay.
The most common non-conformance we find in Australian audits
Guard interlocking logic implemented in the standard (non-safety-rated) PLC, using a single input from an interlocking switch wired directly to a standard digital input card. This architecture fails to achieve any meaningful Performance Level under ISO 13849 because a single component failure (switch contact welding, wiring fault, or PLC I/O card failure) cannot be detected and may result in loss of the safety function without a fault signal. This non-conformance typically requires either a safety relay module or a safety PLC channel to correct.
A Practical Compliance Roadmap
- Commission a documented risk assessment for each machine or work cell, conducted by a competent person with AS 4024.1601 knowledge. Maintain these documents as living records, updated when the machine is modified.
- For each safety function (guard interlock, emergency stop, two-hand control, enabling device), determine PLr from the risk graph and verify that the current implementation achieves at least that PL using SISTEMA or equivalent calculation.
- Audit guard construction against AS 4024.1301 and 1302. Fixed guards secured only with simple tools (requiring a tool to remove) satisfy AS 4024.1301. Movable interlocking guards on access points to dangerous zones must meet AS 4024.1302 requirements for interlock type and guard locking if residual risk requires it.
- Verify safety distances for light curtains and area scanners using AS 4024.1902 Tables 2 and 3. A 14mm minimum object resolution light curtain at 500mm from a 200 mm/s hazard motion requires a minimum safety distance of 850mm from the hazard. Many existing installations have light curtains mounted closer than the calculated safety distance.
- Document the residual risks that remain after all reasonably practicable measures have been applied. Provide this information to operators and maintenance personnel in a format they can access and understand.