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Functional safety

Functional safety: A very important aspect

Safety systems are becoming increasingly important and complex since machinery and plants are becoming more and more powerful and the hazards are generally also increasing with higher productivity. Standards and guidelines support plant operators to achieve the required safety level. Failure analyses and risk assessments serve as a basis for decision-making to reduce the risk of technical systems to an acceptable level by means of safety measures. EU regulation 2023/1230 and technical standards demand the minimisation of risks, making functional safety mandatory in many areas.

The more complex an electronic system is, the more diverse the error possibilities are. For this reason, the IEC 61508 series of standards demands the avoidance of systematic faults during development, monitoring during operation as well as the safe control and elimination of detected errors. Functional safety objectives therefore include the reduction of systematic or random errors to ensure the safety of people, the environment and plants.

Are there legal standards on functional safety with machinery?

The Machinery Directive 2006/42/EC is the most important guideline for functional safety. The most important standards are:

  • DIN IEC/EN 61508: Functional safety of safety-related electrical/electronic/programmable electronic systems
  • DIN IEC/EN 61511: Functional safety – Safety instrumented systems for the process industry
  • DIN EN ISO 13849: Safety of machinery – Safety-related components of control systems
  • DIN IEC/EN 62061: Safety of machinery – Functional safety of safety-related electrical, electronic and programmable electronic control systems

The last two standards are harmonised, which means that a presumption of conformity applies. In addition, the German Product Safety Act (ProdSG) and the German Act on Installations Requiring Monitoring (ÜAnlG) must be observed.

For security: two safety systems

Both the performance level (PL) and the safety integrity level (SIL) define the reliability of safety functions in machinery and plants. Each safety-related component of a control system has a specific PL or SIL, which represents the ability to reduce a risk. Also, each safety function has a specific target level that must be maintained in order to reduce the risk of a malfunction.

The PL is used primarily in machine building, which is why the Machinery Directive is taken into account. The SIL, on the other hand, was mainly developed by the process industry for plant construction.

Performance level

The standard DIN EN ISO 13849 defines the term performance level, which describes the ability of a control system to perform a safety function. A required risk minimisation is defined for each individual safety function of a machine, indicated by the value PL r (required). The performance level of the safety function must be greater than or equal to PL r. The scale ranges from PL a (lowest level) up to PL e.

Safety integrity level (SIL)

This value system originates from DIN IEC/EN 61508 and DIN IEC/EN 61511. The safety integrity level is used to assess the reliability of the safety functions of electrical, electronic and/or programmable electronic systems. Here, too, a SIL r (required) is defined, which must be complied with. The scale ranges from SIL 1 (lowest level) to SIL 4 (highest level).

By adhering to these standards and guidelines, the functional safety can be ensured in various industrial sectors and the risk of malfunctions can be minimised.

FAQ on functional safety

What is a functional safety concept?

A functional safety concept describes the measures and methods used to ensure the functional safety of a technical system, including the selection and validation of components and systems.

What is functional safety in accordance with ISO 26262?

ISO 26262 is a standard for functional safety of electrical and electronic systems in motor vehicles. It defines requirements and processes to ensure that vehicles function safely and that potential risks are minimised.