Machine safety and CE

An earlier article looked at the basic safety considerations around emergency stop and shutdown. This article goes one level deeper: which rules and standards actually underlie the requirements for a system to be safe enough — and how do you determine how safe a given safety function needs to be? This is the core of learning objective no. 7, which requires that the apprentice can perform assembly and replacement tasks based on applicable directives and standards for machine safety including electrical safety.

§From machine directive to machine regulation

Since 2023, all household-like waste from companies must be sorted into 10 fractions, on an equal footing with private households: food waste, paper, cardboard, glass, metal, plastic, food and beverage cartons, hazardous waste, textiles and residual waste. Some fractions may legally be collected in the same container — e.g. paper and cardboard, or metal and plastic — but the basic principle is separate sorting at source.

§Performance Level — how safe should safety be?

When building a safety function—for example, an emergency stop or a door switch that stops a robot—the question isn't just whether it works, but how reliable it must be relative to the danger it's meant to protect against. That's what the standard EN ISO 13849-1 is about. The standard operates with five Performance Levels, PL a through PL e, where PL a covers low risk and PL e covers high risk and serious consequences. Performance Level is determined based on a risk assessment of injury severity, how often you're exposed to the danger, and whether the danger can be avoided.

• 01PL a — lowest level, less serious, rare hazards
• 02PL b–d — increasing reliability and redundancy requirements
• 03PL e — highest level, serious and frequent hazards, requires high redundancy and error monitoring

§Categories — how the system is built

Beyond Performance Level, the standard works with categories (B, 1, 2, 3 and 4) that describe how the safe control itself is designed — whether it has dual channels, monitoring of its own faults and protection against a single fault making the entire safety function ineffective. The higher the category, the more robust the design is against a single defective component compromising safety without being detected.

§Electrical equipment on machinery: EN 60204-1.

Alongside the safety functions, the standard EN 60204-1 sets requirements for the electrical equipment on machines themselves — cable routing, labelling, control cabinet structure, protection against unexpected restart and the design of emergency stop circuits. Together with the Danish Working Environment Authority's guidance on machines and machinery systems (AT-Guide B.1.3), which requires that an emergency stop be easy to spot and accessible, and that machines be protected against unintended start after e.g. a power failure, these standards and regulations form the complete rule set the automation technician works within.

“The CE mark is not proof that someone guessed well. It is proof that someone calculated how badly it could go — and built accordingly.”