Last edit: 06/08/2025
During the revision of IEC 62061, several discussions took place regarding the effectiveness of a Proof Test in high demand mode; especially for electromechanical components.
The first aspect to consider is that for Electromechanical components, manufacturers do not normally provide indications how a Proof Test on their components should be done. Moreover, a Proof Test on those components can only be partial, due to the presence of degraded failures. In high demand mode applications for electromechanical components, it is recommended not to use the concept of Proof Test. That is, for example, clearly stated for Basic Subsystem Architecture A.
[IEC 62061] 7.5.2.1 Basic subsystem architecture A: single channel without a diagnostic function
[…] In high or continuous mode of operation, architecture A shall not rely on a Proof Test.
For the other architectures, the Proof Test interval is inside a parameter called T1, that is the smaller between
- Proof Test interval of the perfect Proof Test and
- The useful lifetime, which is the smaller between the component Mission Time and the parameter T10D.
In high demand mode, for electronic components, normally the PFH is provided by the manufacturer; therefore, the determination of the proof test interval is normally not required for the calculation of the reliability of the safety system.