12 Feb 2020

Functional Safety

With Industry 4.0, new technologies have also found their way into everyday working life. Humans and machines are working together closer and closer and production processes are becoming increasingly networked.

LOTO experts at a clinets factoryThis of course has an impact on occupational safety – especially on the Performance Level (PL), which indicates how reliable a safety function is. You can find out what you need to consider here.

A risk assessment is to be carried out as part of the certification procedure in accordance with the Machinery Directive, not only for new machinery. Any modification of machines requires a consideration of possible risks in addition to the question of the type of modification – significant or not. All measures to reduce these risks should be chosen according to the 3-step procedure.

Determination of the Performance Level

Protective measures should be implemented according to the state of the art as best as possible. This means the Performance Level (PL) must be taken into account for measures that are part of so-called functional safety. If a designer decides, for example, to install a light curtain, a safety mat or a safety switch on a safety door, he or she must specify the required Performance Level (PLr) for the design of the safety function. This is determined in a risk assessment, taking into account the extent of damage, the exposure time in the danger zone and the probability of the damage occurring. Only by specifying the PLr is the designer able to design the safety function correctly. Decisive factors in this regard are the selection of components used, above all the type of wiring and the system’s ability to detect errors.

All this data is then used to determine the performance level reached by a safety function. The safety requirements are only fulfilled and functional safety is only given if the reached PL is equal to or higher than the PL that was assumed as required during the risk assessment.

Errors in the actual performance level – how so?

CE-CON expert for ce markingErrors are possible which, if they occur, can have dangerous consequences. For example, a PL of “e” can be achieved with certain safety components, but this depends, among other things, on the category, i.e. the design. If, for example, a safety switching relay that can achieve a PL=e is used in an emergency stop chain with a single-channel structure, “e” will never actually be achieved in the end. That would be like putting a 300hp engine into an old VW Beetle to reach speeds of 290km/h – impossible!

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