Definition:
Proven In Use (PIU), directly tied to Route 2S, is an argument that a device’s reliable operating history can demonstrate its fitness for safety applications. The data would be manufacturer driven, and is driven by IEC 61508-2 §7.4.10. It is strict what is needed.
Proven is use is the foundational concept of route 2S, and route 2S is essentially proven in use.
Note proven in use, prior use, and routes are notoriously confusing in functional safety circles!
Key Points:
- Requires detailed records of failures and operating conditions from the manufacturer.
- A valid pathway to achieve systematic capability level, although 1S is the more common way.
- This is associated with Route 2S.
- PIU is not just history — it is qualified, statistically justified operational experience under defined conditions.
- To claim a Route 2S SIL capability for a product, a certification body is required.
Example:
An emergency shutdown relay has been on the market for 10+ years. The company wants to get a SIL 2 certification. Since they have over 1 million hours of successful operation, they might qualify under Proven In Use. This analysis would be done by a certification body (CB) and the CB would issue the SIL Certificate under route 2S.
Cited Source:
- IEC 61508-2:2010, Clause 7.4.10
- The 61508 Association –Proven in Use – policy paper