Catalogs > Safety Products Catalog > Principles, Standards and Implementation > System Design According to IEC/EN 62061
System Design According to IEC/EN 62061
| Introduction |  |
Subsystem Design: IEC/EN 62061 | |
Affect of the Proof Test Interval | |
Affect of Common Cause Failure Analysis | |
Common Cause Failure (CCF) | |
Diagnostic Coverage (DC) | |
| Hardware Fault Tolerance | |
Management of Functional Safety | |
Proof Test Interval | |
Safe Failure Fraction (SFF) | |
Systematic Failure | |
The proof test interval represents the time after which a subsystem must be either totally checked or replaced to ensure that it is in an “as new” condition. In practice, in the machinery sector, this is achieved by replacement. So the proof test interval is usually the same as lifetime. EN ISO 13849-1 refers to this as Mission Time.
A proof test is a check that can detect faults and degradation in a SRCS so that the SRCS can be restored as close as practical to an “as new” condition. The proof test must detect 100% of all dangerous failures. Separate channels must be tested separately.
In contrast to diagnostic functional tests, which are automatic, proof tests are usually performed manually and off line. Diagnostic functional testing is usually performed often (typically over a few hours) as compared to proof testing which is done infrequently (typically over many years). For example, the circuits going to an interlock switch on a guard can be functionally tested automatically for short and open circuit conditions with diagnostic (e.g., pulse) testing.
The proof test interval must be declared by the manufacturer. Sometimes the manufacturer will provide a range of different proof test intervals.