Machine Safety & Risk Assessment: Meeting ISO 13849

Every machine carries risk — moving parts, stored energy, automated motion. Machine safety is the discipline of reducing that risk to an acceptable level without making the equipment unusable. And it always begins in the same place: a structured risk assessment. Here is how machine safety works and where ISO 13849 fits in.

Why risk assessment comes first

You cannot protect against hazards you have not identified. A risk assessment is the foundation of machine safety, and the international standard ISO 12100 defines the process:

1. Determine the limits of the machine — how it is used, and foreseeable misuse.
2. Identify the hazards at every lifecycle stage — mechanical, electrical, thermal, noise and more.
3. Estimate the risk for each hazard, considering severity, frequency of exposure and the possibility of avoidance.
4. Evaluate the risk — is it acceptable, or must it be reduced?
5. Reduce the risk and repeat until the residual risk is tolerable.

The hierarchy of risk reduction

Not all safeguards are equal. Good practice follows a hierarchy:

• Inherently safe design first — eliminate the hazard where possible.
• Safeguarding & protective measures next — guards, light curtains, interlocks and safety-related control functions.
• Information for use last — warnings, training and procedures for the residual risk.

Relying on warning signs where a guard is needed is a classic — and dangerous — shortcut.

Where ISO 13849 comes in

When risk reduction depends on the machine’s control system — for example, an interlocked guard that stops motion when opened — that safety function must be reliable enough for the risk it addresses. ISO 13849-1 is the standard that governs the safety-related parts of control systems.

It introduces the Performance Level (PL), from PL a (lowest) to PL e (highest). The required Performance Level (PLr) is derived from the risk using three factors: severity of injury, frequency and duration of exposure, and the possibility of avoiding the hazard. The safety function must then be designed — through architecture, component reliability and diagnostics — to achieve that PL.

From assessment to compliant machine

The full path looks like this: assess the risk (ISO 12100), decide which safety functions are needed and their required PL (ISO 13849), design and build those functions, then validate that they perform as intended. Properly documented, this evidence supports conformity with machinery regulations such as the EU Machinery Directive and CE marking.

Machine safety also increasingly overlaps with OT cybersecurity — a compromised controller must not be able to defeat a safety function.

How iSquare helps

iSquare provides machine risk assessments, safety-function design to ISO 13849, and validation as part of our safety studies and engineering services. We help you build machines and lines that are both productive and demonstrably safe. Talk to our safety engineers to get started.