Machinery Risk Assessment to EN ISO 12100

EN ISO 12100, “Safety of machinery – General principles for design – Risk assessment and risk reduction”, is the basic safety standard for machinery. It describes how the hazards of a machine are identified, how the risks are estimated and evaluated, and in which order they are reduced. Every machine placed on the EU or Turkish market with a CE marking must have a documented risk assessment, and EN ISO 12100 is the method used for it.

For an EN ISO 12100 risk assessment and CE marking of your machine, apply to CE Danışmanı (CE Consultant); we manage the whole process for you.

EN ISO 12100 at a glance

Why a risk assessment is required

The Machinery Directive requires the manufacturer to carry out a risk assessment in order to determine the health and safety requirements that apply to the machine. The machine is then designed and built taking the results into account. The documentation of the assessment is a mandatory part of the technical file.

The order matters: the risk assessment is done at the design stage, not after CE marking. The CE marking and the EU Declaration of Conformity are the result of this work. A technical file without a risk assessment is incomplete, and market surveillance authorities treat it as a non-conformity.

The standard itself is voluntary, but EN ISO 12100 is the established method for the risk assessment the legislation asks for.

Type A, B and C standards

Machinery safety standards form three layers. EN ISO 12100 sits at the top and gives the method the others rely on.

Where a type C standard exists for your machine, it is applied first. For hazards the type C standard does not deal with, the manufacturer goes back to EN ISO 12100.

The steps of a risk assessment

1. Determine the limits of the machine: Intended use, reasonably foreseeable misuse, the training level of users, the space the machine needs, its lifetime and maintenance intervals.
2. Identify the hazards: Hazards, hazardous situations and hazardous events are listed for every phase of the life of the machine.
3. Estimate the risk: For each hazard, the severity of the possible harm and the probability of its occurrence are assessed.
4. Evaluate the risk: It is decided whether the risk needs to be reduced.
5. Reduce the risk: Measures are taken and the process is repeated. It is also checked whether a measure has created a new hazard.

The process is not a one-off; it runs in a loop until the risk has been adequately reduced.

Life phases of the machine

A risk assessment does not cover normal operation only. A large share of accidents happens during setting, cleaning and maintenance. The phases assessed are:

• Transport, assembly and installation
• Commissioning
• Use: setting, programming, operation, cleaning, fault-finding and maintenance
• Decommissioning, dismantling and disposal

Types of hazard assessed

How the risk is estimated

The standard defines risk as the combination of two elements:

• Severity of harm: The possible outcome, from slight injury to death, and the number of persons affected.
• Probability of occurrence of that harm: How often and how long persons are exposed to the hazard, how likely the hazardous event is, and whether the harm can be avoided or limited.

EN ISO 12100 does not impose one scoring method. A risk matrix, a risk graph or numerical scoring can be used; ISO/TR 14121-2 gives practical guidance on these methods. What matters is that the chosen method is applied consistently to all hazards and that the reasoning is written down.

The risk graph method

A risk graph is a decision tree that splits the risk into branches with three questions. Its most common use is in EN ISO 13849-1: where a protective measure depends on the control system (an interlocked guard, a light curtain, an emergency stop), the reliability required from that safety function is determined with this graph. The result is a required performance level (PLr) from “a” to “e”.

The graph is read from left to right:

• S, severity of injury: S1 slight, normally reversible injury; S2 serious, irreversible injury or death.
• F, frequency and duration of exposure: F1 seldom and/or short exposure; F2 frequent, continuous and/or long exposure.
• P, possibility of avoiding the hazard: P1 possible under specific conditions; P2 scarcely possible.

Example: on a press where the operator reaches into the die area in every cycle, the injury is irreversible (S2), exposure is continuous (F2) and escaping the closing die is scarcely possible (P2). The graph gives PLr “e” on this branch, and the protective system has to be designed to reach that level.

This graph applies only to measures that depend on the control system. For the overall risk estimation of all hazards of the machine, risk graphs or risk matrices that work on the same logic are used; ISO/TR 14121-2 gives examples.

Risk reduction in three steps

The most important rule of the standard is the order of the measures. The next step is used only where the previous one cannot reduce the risk enough.

1. Inherently safe design: The hazard is removed or reduced by design. Examples: a geometry that removes the trapping point, lower force and speed, no sharp edges.
2. Safeguarding: For risks that design cannot remove, guards, interlocking devices, light curtains and complementary measures such as the emergency stop.
3. Information for use: For the residual risks, warning signs, audible and visual signals and the instruction handbook.

A warning label or personal protective equipment is not accepted as the solution for a risk that could be removed by design or by a guard. This is the gap most often found in inspections.

Example: how one hazard line is written

The line below is an example prepared to show the method; the rating scale depends on the method the manufacturer has chosen.

What the risk assessment report contains

• Description of the machine, its intended use and its limits
• Data and assumptions used: loads, strengths, safety factors
• The hazards, hazardous situations and hazardous events considered
• The risk estimation for each hazard and the method used
• The protective measures taken and the standards applied
• The residual risks and the information given to the user
• The result of the assessment, its date and the persons who prepared it

The report lives with the machine. It is updated when the design is changed or a new hazard is noticed.

High-risk machinery

Some types, such as presses, plastics injection moulding machines and hand-fed woodworking machines, are on the list of high-risk machinery of the Directive (2006/42/EC Annex IV). The risk assessment is done with the same method for these machines; the conformity assessment route is determined separately.

What changes with the new Machinery Regulation?

Regulation (EU) 2023/1230, which applies from 20 January 2027, keeps the risk assessment obligation. Topics such as software, cybersecurity and self-learning systems also come within the assessment. For machines placed on the market after that date the risk assessment has to be reviewed against the new requirements.

Frequently asked questions