Technical data

Safety Integrated Functions
8.1 Standards and regulations
Function Manual
Function Manual, 06/2012, 6SL3097-4AB10-0BP4
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8.1.2.4 EN ISO 13849-1 (previously EN 954-1)
A qualitative analysis (to EN 954-1) is not sufficient for modern controllers due to their
technology. Among other things, EN 954-1 does not take into account time behavior (e.g.
test interval and/or cyclic test, lifetime). This results in the probabilistic basis in EN ISO
13849-1 (probability of failure per unit time).
EN ISO 13849-1 is based on the known categories of EN 954-1. It now also takes into
account complete safety functions and all the devices required to execute these. With EN
ISO 13849-1, safety functions are investigated from a quantitative perspective going beyond
the qualitative basis of EN 954-1. Performance levels (PL), which are based on the
categories, are used. The following safety-related characteristic quantities are required for
devices/equipment:
● Category (structural requirement)
● PL: Performance level
● MTTF
d
: Mean time to dangerous failure
● DC: Diagnostic coverage
● CCF:
Common cause failure
The standard describes how the performance level (PL) is calculated for safety-related
components of the controller on the basis of designated architectures. In the event of any
deviations from this, EN ISO 13849-1 refers to EN 61508.
When combining several safety-related parts to form a complete system, the Standard
explains how to determine the resulting PL.
Note
Since May 2007, EN ISO 13849-1 has been harmonized as part of the Machinery Directive.
EN 954-1 will continue to apply until 30.12.2011.