Glossary · Protective devices and interlocks
Safety-rated interlock
In machine safety, a safety-rated interlock is an interlocking device designed and validated for use in a safety-related control function, with documented safety characteristics such as failure data and suitable architecture.
- Machine safety
- Technical documentation
In one sentence
A safety-rated interlock is designed and validated for safety functions; being safety-rated does not by itself achieve the required Performance Level.
Example
A machine builder selects a coded safety interlock switch with a manufacturer-stated B10D value and uses it in a dual-channel circuit to reach the required Performance Level.
How it applies
- Functional safety: A safety-rated device supplies the data needed to calculate the Performance Level (PL) or SIL of the safety function. The achieved level still depends on the architecture, diagnostics and the other components in the chain.
- Design: Select interlocking devices according to ISO 14119, including coding level and measures against defeat (tamper resistance).
- Evidence: Keep the manufacturer's safety data, the calculation and the validation of the complete function in the technical file.
- Technical documentation: Specify replacement only with the same or an equivalent safety-rated device, and the test interval stated in the safety calculation.
Safety-rated interlock vs. standard switch
A standard position switch may work in normal operation, but it has no documented failure behavior for safety use. Using it in a safety function requires justification such as fault exclusion or a redundant architecture.