JVL MAC050 User Manual page 391

6.7 Emergency stop considerations
DS/EN ISO 13849-1 utilizes another criterion for safety level called "Performance level"
- PL – in which both the architecture and the component's failure rate are included. 5 PL
levels are defined: a, b, c, d, and e, where a represents the lowest level and e the highest.
If DS/EN ISO 13849-1 is used, information regarding the components' failure rates
(MTTF – mean time to failure) must be obtained from the component manufacturer.
For a more detailed description of the principles and requirements above, see the rele-
vant standards.
The following drawings illustrates examples of the design of safety circuits for an emer-
gency stop and enclosure system, stop category 0, which fulfils the requirements of
category 4 in accordance with DS/EN 954-1.
The achievable PL level in accordance with DS/EN ISO 13849 will depend on the MTTF
of the components used; using the solutions shown, typically a minimum PL level d would
be achieved.
JVL A/S - User Manual - Integrated Servo Motors MAC050 - 4500 387