● 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. For deviations from this,
DIN EN ISO 13849-1 refers to IEC 61508.
When combining several safety-related parts to form a complete system, the standard explains
how to determine the resulting PL.
Note
DIN EN ISO 13849‑1 and machinery directive
Since May 2007, DIN EN ISO 13849-1 has been harmonized as part of the Machinery Directive.
A.4.2.5 EN 62061
EN 62061 (this is identical to IEC 62061) is a sector-specific standard below IEC/EN 61508.
It describes the implementation of safety-related electrical control systems of machines and
takes into account the complete lifecycle - from the conceptual phase to de-commissioning.
The standard is based on the quantitative and qualitative analyses of safety functions,
whereby it systematically applies a top-down approach to implementing complex control
systems (known as "functional decomposition"). The safety functions derived from the risk
analysis are sub-divided into sub-safety functions, which are then assigned to real devices,
sub-systems, and sub-system elements. Both the hardware and software are covered. EN
62061 also describes the requirements placed on implementing application programs.
A safety-related control systems comprises different sub-systems. From a safety perspective,
the sub-systems are described in terms of the SIL claim limit and PFH
D
characteristic
quantities.
Programmable electronic devices (e.g. PLCs or variable-speed drives) must fulfill IEC 61508.
They can then be integrated in the controller as sub-systems. The following safety-related
characteristic quantities must be specified by the manufacturers of these devices.
Safety-related characteristic quantities for subsystems:
● SIL CL: SIL claim limit
● PFH
D
:
Probability of dangerous failures per hour
● T1:
Lifetime
Simple sub-systems (e.g. sensors and actuators) in electromechanical components can, in
turn, comprise sub-system elements (devices) interconnected in different ways with the
characteristic quantities required for determining the relevant PFH
D
value of the sub-system.
Appendix
A.4 Standards and specifications
Safety Integrated - SINAMICS G110M, G120, G120C, G120D and SIMATIC ET 200pro FC-2
426 Function Manual, 01/2017, FW V4.7 SP6, A5E34261271B AD
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