Glossary · Functional safety
Performance Level e (PLe)
Also known as: PLe, PL e
German: Performance Level e (PLe)
In ISO 13849-1, Performance Level e (PLe) is the highest of the five performance levels, corresponding to an average probability of dangerous failure per hour from 10^-8 to less than 10^-7.
- Functional safety
- Verification
In one sentence
Performance Level e (PLe) is the highest ISO 13849-1 level, with a dangerous failure probability of 10^-8 to under 10^-7 per hour.
Example
The risk graph for manually loading a press yields a required PLr e for the two-hand control and light curtain functions.
How it applies
- Risk: PLr e results from the risk graph when injuries are serious, exposure is frequent or long, and avoidance is scarcely possible.
- Architecture: PL e requires Category 3 or 4 with high MTTFd, adequate diagnostic coverage and measures against common-cause failure. Software and systematic requirements become more demanding as well.
- Components: Devices certified as suitable for PL e only support the function. The complete safety function must be verified.
- Documentation: State PLr and achieved PL per safety function in the technical file and calculation report. The documentation team should avoid marketing phrases such as a machine being PL e; PL applies to individual safety functions.
PL e vs. SIL 3
The PFHd range of PL e corresponds to that of SIL 3 in high-demand or continuous mode. The two levels come from different standards and methods, so the correspondence is approximate and does not replace verification under the chosen standard.