NORSTAT Safety Relays - Handbuch (Seite 13)

application guide safety relays from riese electronic page 13
1.
Definition of the safety-
technological requirements
2.
Selection of the required
performance
3. Safety design
4.
Definition of the achived
performance
5. Verification
6. Validation
3.2.1 Functional safety – the single steps:
1. Definition of the safety-technological requirements
The required safety function characteristics are defined e.g. ESPD-function with automatic start, no
simultaneity, etc. and a detailed description with the necessary interfaces to the other parts of control
systems will be prepared.
2. Selection of the required performance
The definition is done with a risk graph. For new systems it can be generally done with two
standards:
EN 13849-1 (Safety of machines – safety-related parts of control systems, part 1: General
design principles)
With the risk graph it is possible to investigate all safety-related functions and areas of a machine
respectively. The results are the so-called Performance Level / PL (
a-e). The PL is needed for the
selection of the safety setup and the corresponding components including wiring.
The
a stands for low safety and the e for high safety.
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