Glossary - Siemens DS III PROFIsafe Series Product Information

Glossary

Dangerous failure
Failure with the potential to bring the safety-instrumented system into a dangerous or non-
functional status.
Fail-safe
The capability of a control to maintain the safe state of the controlled device, e.g. machine,
process, or to bring the device to a safe state even when faults/failures occur.
Failure/fault
Failure
A resource is no longer capable of executing a required function.
Fault
Undesired state of a resource indicated by the incapability of executing a required function.
Fault
Failure/fault
→
Fault tolerance
Fault tolerance N means that a device can execute the intended task even when N faults
exist. The device fails to execute the intended function in case of N+1 faults.
Final controlling element
Converter that converts electrical signals into mechanical or other non-electrical variables.
Risk
The combination of probability of a damage occurring and its magnitude.
Functional safety for SITRANS P, series DS III PROFIsafe
Product information, 07/2006, A5E00849297-01
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