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AS/NZS 4024 seriesCurrent series — parts have different editions

Safety of machinery

A practical guide to the machinery-safety logic: identify hazards, reduce risk by design first, then use safeguarding and safety-related controls, and validate the complete safety function.

Start with risk reductionSee fixed access
Pathway at a glance

Guarding change pathway

Machine guarding failures often come from changes: a new task, bypassed interlock, speed change or safety-function retrofit.

Open guarding change check
Machine change — does the guarding need revisiting? Three gates: a bypassed guard or interlock means restore first, then redesign the task; new access to a danger zone means rerun the risk assessment; a touched safety function means specify and validate PL or SIL performance. Otherwise verify stopping distances and document the decision. Machine change on the table Guard or interlock bypassed? yes Restore first then redesign the task no New access to a danger zone? yes Rerun risk assessment task-based, all modes no Safety function touched? yes Specify and validate PL / SIL performance no Verify and document stopping distances, records Red — act immediately · Amber — assessment needed · Green — record and proceed
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How to use this summary

  • A bypassed safeguard is an immediate control issue and a design finding.
  • Changed exposure means the risk assessment needs to be revisited.
  • Changed safety functions need specification and validation, not just wiring.
  • Even when no impact is indicated, record the decision basis.

This is a screening summary only — it is not a machine risk assessment or validation.

01

“Does this old lathe need a new physical guard, or is a light curtain enough?”

The answer should not begin by choosing a safety product. It begins with the machine, task, hazard, access need and required risk reduction.

02

The practical answer

The AS/NZS 4024 series provides a machinery-safety framework and specialist requirements. The general logic is to reduce risk by inherently safer design first, then safeguarding and complementary measures, then information for use for the residual risk.

A guard, interlock, light curtain or safety control is only one part of a safety function. The hazard, stopping performance, access frequency, foreseeable defeat, fault behaviour and reset logic all matter.

Modifying an old machine can create new hazards or invalidate existing controls, so the change should trigger a structured machinery risk review.

The series contains general principles and many specialist parts. The right part depends on the machine and technology — for example robots, presses or specific machine tools.

AS Applied rule of thumbChoose the scope, design basis and evidence pathway first. Do not start by hunting for a single clause, percentage or formula that makes the preferred answer work.
03

Where this Standard fits

Common starting points
  • New machinery design and procurement
  • Machine guarding and interlocking
  • Safety-related control systems
  • Unexpected start-up and energy isolation issues
  • Machine modifications and control upgrades
  • Robots, presses and other machine-specific applications
Do not assume
  • A rule that every hazard needs a physical fence
  • Permission to use a light curtain without checking stopping distance and access
  • A substitute for electrical, hydraulic or pneumatic safety requirements
  • A one-time risk assessment filed away after commissioning
  • A reason to ignore foreseeable misuse and guard defeat
  • A single document that contains every machinery-safety requirement
04

Choose controls only after understanding the risk

Start with the hazardous situation and task. A safety device is the output of the risk-reduction process, not the starting point.

1Define machine limits and tasksNormal operation, setting, cleaning, jam clearing, maintenance, fault finding and foreseeable misuse.
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2Identify hazards and hazardous situationsMechanical movement, stored energy, unexpected start, ejection, heat, pressure, electricity and task-specific hazards.
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3Reduce risk by design firstEliminate hazards, reduce forces and speeds, improve visibility and access, or move routine tasks away from danger zones.
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4Select safeguarding and safety functionsFixed or movable guards, interlocks, presence sensing, two-hand controls and other measures should suit the access need and hazard.
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5Design fault behaviour and control reliabilityDetermine the required safety performance and design input, logic and output so faults do not create unacceptable loss of the safety function.
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6Validate and maintain the complete functionCheck stopping, reset, defeat resistance, interfaces, documentation, inspection and future change control.
The most common failure is a broken chain of assumptions.

A good result needs the equipment definition, loads, design method, fabrication, inspection and operating limits to describe the same real system.

05

Key engineering concepts to understand

01

Inherently safer design comes first

A well-designed machine can remove a hazard or reduce exposure before guards and warning signs are considered.

02

Access frequency changes the safeguarding solution

A fixed guard may suit rare access; frequent intervention may require an engineered movable guard or protective device with a validated safety function.

03

An interlock is a system

Sensor, logic, contactors or valves, stopping behaviour, reset and fault detection all contribute to whether the safety function works.

04

Higher category is not a universal shortcut

Control-system reliability should be selected from the risk and architecture, not by automatically choosing the highest number without understanding the application.

05

Unexpected start-up is a recurring failure mode

Control changes, stored energy, power restoration and maintenance modes need deliberate prevention and isolation logic.

06

Machine-specific parts can override generic assumptions

Robots, presses and machine tools have hazards and safety functions that need their relevant specialist requirements.

06

Detailed engineering case studies

The examples below show how the Standard changes a real engineering decision. They are not clause summaries or universal answers; each case starts with the equipment, task and evidence available.

Case study 1 · Existing machine upgrade

Old lathe with frequent chuck access

01
Project context

A workshop upgrades a manually operated lathe after a safety inspection. Operators frequently access the chuck area for setup and say a fixed guard would make the machine unusable.

Why this Standard matters

The problem is not 'guard or light curtain?'. The design should start with tasks, hazards, access frequency and stopping behaviour, then select and validate the safeguard.

What made the job difficult

  • Operators need frequent access for setup and measurement.
  • The chuck can continue rotating after power is removed.
  • A simple interlock may be defeated if it makes normal work impractical.
  • Reset and restart behaviour are not clearly defined.

How the engineering review should proceed

  1. Break the work into operating, setup, cleaning, fault-finding and maintenance tasks.
  2. Reduce the hazard by design where practical before selecting guarding.
  3. Choose a guard/interlock concept compatible with access frequency and stopping time.
  4. Define and validate the safety-related control function, including faults, reset and restart.
Practical outcome

A practical upgrade may use a movable interlocked guard with defined stopping and restart behaviour rather than a fixed guard that operators will remove. The safeguard succeeds only if the complete machine system is validated.

Also investigate
Relevant guarding and interlocking parts of the AS/NZS 4024 seriesElectrical machine control requirementsOperator consultation and foreseeable misuse
Case study 2 · Production conveyor access

Guarding a conveyor where operators regularly clear jams

02
Project context

A packaging line has fixed perimeter guarding, but product jams occur several times per shift. Operators open a bolted panel or reach through gaps to clear the blockage quickly.

Why this Standard matters

The repeated task shows that the safeguarding concept does not match the real work. The risk assessment has to include jam clearing as a normal foreseeable task.

What made the job difficult

  • Hazardous motion can restart unexpectedly after a jam is cleared.
  • Access frequency makes tool-removable fixed guards impractical.
  • The operator cannot see all moving parts from the reset location.
  • Production pressure encourages defeat of existing controls.

How the engineering review should proceed

  1. Observe the actual jam-clearing task and identify every hazardous movement that remains possible.
  2. Consider design changes that reduce the jam frequency before adding more safeguarding.
  3. Where access remains necessary, define interlocking, isolation or safe limited-motion modes appropriate to the task.
  4. Validate restart prevention and ensure reset does not itself initiate hazardous motion.
Practical outcome

The best solution may combine process improvement, accessible guarding and a validated control function. A stronger padlock on the existing panel would not address why workers bypass it.

Also investigate
Lockout and isolation proceduresAS 1657 if elevated access is neededHuman factors and production task design
Case study 3 · New automation cell

Robot cell modified for collaborative loading

03
Project context

A manufacturer wants operators to load parts closer to an industrial robot to reduce cycle time. The proposal is to remove part of the fence and rely on a scanner.

Why this Standard matters

Collaborative operation is an engineered application, not a label applied to a robot. The robot, end effector, workpiece, speed, separation and control functions all matter.

What made the job difficult

  • The robot itself is safety-rated, but the end effector has sharp tooling.
  • The scanner field changes with product size and operator approach direction.
  • Stopping distance varies with robot speed and payload.
  • Maintenance and teaching modes create different exposure from production loading.

How the engineering review should proceed

  1. Define the intended collaborative task and all non-collaborative modes.
  2. Assess the complete robot application, not only the robot controller certification.
  3. Determine the required safety functions, speed/separation limits and verification methods.
  4. Validate the integrated cell in realistic worst-case configurations.
Practical outcome

The final design may retain physical separation for some modes while allowing controlled collaborative loading in others. Removing fencing is the end of a risk-reduction process, not the starting point.

Also investigate
AS 4024.3301 robot requirementsAS 4024.3302 system integrationSafety-related control-system validation
07

Common mistakes

Buying the safety device first

A light curtain, scanner or interlock is selected before the hazard and stopping behaviour are understood.

Risk assessment by checklist only

The assessment lists hazards but does not connect them to real tasks, access and control measures.

Ignoring maintenance modes

The machine is safe in automatic production but hazardous during setup, cleaning or fault finding.

Treating emergency stop as safeguarding

An emergency stop is relied on instead of preventing or controlling normal exposure to the hazard.

No validation after control changes

PLC logic, sensors or drives are modified without proving the complete safety function still performs as intended.

Guarding creates new access hazards

Poorly coordinated platforms, reach paths or awkward manual handling are introduced while solving the original hazard.

08

Information to gather before making the decision

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Machine description and intended use

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All operating and maintenance tasks

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Existing drawings and control schematics

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Hazardous movements and stored energies

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Access frequency and whole-body access potential

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Existing guards and protective devices

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Stopping times and distances

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Safety-related control architecture

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Reset, restart and mode-selection logic

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Foreseeable misuse and defeat history

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Previous incidents and risk assessments

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Proposed modification and validation plan

09

What should happen next?

1

New machinery

Specify machinery-safety and validation requirements during procurement, not after delivery.

2

Old machine upgrade

Assess the actual tasks and changed hazards; do not simply copy the latest guard arrangement from another machine.

3

Control-system modification

Revalidate affected safety functions, fault behaviour, stopping and restart logic.

4

Frequent guard defeat

Treat defeat as design feedback: understand why access is needed and redesign the task or safeguarding system.

5

Complex automated cell

Use specialist machinery-safety and functional-safety engineering, including the relevant robot or machine-specific parts.

Related AS Applied content

AS 1657

Safe machine access should be coordinated with guarding and danger zones.

Open →AS 1418

Cranes and hoists have their own safety and control requirements.

Open →AS 3990

Machine frames and mechanical equipment steelwork may need a separate structural design basis.

Open →
10

Source basis & limitations

  • This page explains the risk-reduction and safety-function logic without reproducing category tables, machine-specific clauses or control-system diagrams.
  • Additional AS/NZS 4024 parts are likely to be required for detailed content on guards, interlocks, emergency stops, safety distances and particular machine types.
Project-specific engineering

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