Siemens SINAMICS V90 Operating Instructions Manual page 243

For electromechanical devices, a manufacturer specifies a failure rate λ with reference to the
number of operating cycles. The failure rate per unit time and the lifetime must be
determined using the switching frequency for the particular application.
Parameters for the sub-system, which comprises sub-system elements, that must be defined
during the design phase:
● T2: Diagnostic test interval
● β: Susceptibility to common cause failure
● DC: Diagnostic coverage
The PFHD value of the safety-related controller is determined by adding the individual PFHD
values for subsystems.
The user has the following options when setting up a safety-related controller:
● Use devices and sub-systems that already comply with EN ISO 13849-1, IEC/EN 61508,
or IEC/EN 62061. The standard provides information specifying how qualified devices
can be integrated when safety functions are implemented.
● Develop own subsystems:
– Programmable, electronic systems and complex systems: Application of EN 61508 or
– Simple devices and subsystems: Application of EN 62061.
EN 62061 does not include information about non-electric systems. The standard provides
detailed information on implementing safety-related electrical, electronic, and programmable
electronic control systems. EN ISO 13849-1 must be applied for non-electric systems.
Note
Function examples
Details of simple sub-systems that have been implemented and integrated are now available
as "functional examples".
Note
EN 62061 and machinery directive
IEC 62061 has been ratified as EN 62061 in Europe and harmonized as part of the
Machinery Directive.
SINAMICS V90, SIMOTICS S-1FL6
Operating Instructions, 09/2016, A5E36037884-002
EN 61800-5-2.
Safety Integrated function
8.1 Standards and regulations
243