Performance Level – The Foundation of Machine Safety

Performance Level - when safety becomes measurable

1. What Is the Performance Level?

Machine safety is of central importance in industry. Machines should not only perform their intended task but also be designed in such a way that hazards to operators and other persons are avoided as much as possible. An important aspect of this is the safe design of control systems. In this context, the Performance Level (PL) plays a decisive role. It describes how likely a dangerous failure of the safety function is and to what extent any faults that occur can be detected and controlled.

For example, a safety function can ensure that a machine’s rotating tool cannot be touched or that it comes to a rapid stop when a hazard is detected. Both a drill/driver and a circular saw can cause injuries, although the severity of the potential injuries can vary significantly. While a drill/driver is more likely to cause minor injuries, a circular saw poses a significantly higher risk of serious cuts.

Depending on the existing risk, different requirements may therefore be placed on a safety function. The Performance Level makes it possible to define these requirements in accordance with the existing risk. This prevents safety measures from being designed to be either too weak or unnecessarily complex.

The basis for this is a risk analysis. This involves a systematic examination of the hazards that may be posed by a machine. These include, for example, hazards from moving machine parts, electrical hazards, high temperatures, pressure, or unexpected movements. Various operating conditions and foreseeable misuse are also considered.

The existing risk is then assessed. In particular, the following three points are considered:

• Severity of the potential injury
• Frequency and duration of exposure to the hazard
• Possibility of avoiding or limiting the harm

This assessment determines, among other things, the required Performance Level (PLr). This specifies the minimum safety level that a particular safety function must achieve. The technical implementation is then designed so that the actual Performance Level achieved is at least equal to the required PLr.

2. The Different Performance Levels

According to the EN ISO 13849-1:2023 standard, there are five performance levels, ranging from PL a to PL e.
PL a represents the lowest safety level and PL e the highest. Which level is required depends on the specific hazard. It is crucial that each safety function be designed in accordance with the respective risk.

To determine the required Performance Level (PLr), the procedure outlined in Annex A of the standard can be used. The following diagram illustrates how the PLr is determined based on the criteria S, F, and P.

For the user, this means:
If a failure of the safety function in question could lead to serious, normally irreversible injuries or death (S), at least PLr c is required according to the risk assessment. In cases of frequent to continuous exposure or prolonged exposure time (F), the requirement increases to at least PLr d. If, in addition, there is virtually no way to avoid the hazard or limit the damage (P), PLr e is required.

If, on the other hand, a failure can lead only to minor, normally reversible injuries (S), a PLr a through PLr c is required, depending on the exposure and the possibility of avoiding or limiting the harm.

3. Conclusion: Why the Performance Level Is Important

The Performance Level makes it possible to define safety requirements in a systematic and traceable manner. It is a key component for implementing the requirements of the Machinery Directive 2006/42/EC.

The five Performance Levels, from PLa to PLe, allow for a graded design of safety functions. The required Performance Level for each function is determined based on the risk analysis . This enables machine control systems to be specifically tailored to the existing risks and ensures that people are effectively protected.

The Performance Level thus provides an important foundation for the safe planning and design of machine control systems. The European legal framework for machinery is currently in transition: The Machinery Regulation (EU) 2023/1230 replaces the Machinery Directive 2006/42/EC and will take effect on January 20, 2027.

We would be happy to assist you in developing a safe and standards-compliant design for your machine control system in accordance with the required Performance Level. Contact us—we’d be happy to advise you.