Several products of different types from various vendors communicate within a PROFIsafe island. The products must be implemented conform to the PROFIsafe specification to ensure that this communication works correctly. Usually the conformance is documented through a certificate from the PI certification office based on the test report of one of the PI test laboratories.
The PROFIsafe tests
The PROFIsafe protocol mechanisms are based on finite state machines. Thus it was possible via a validation tool for finite state machines to mathematically prove that PROFIsafe works correctly even in cases where more than two independent errors or failures may occur. This systematically was achieved by generating all possible cases for "test-to-pass" and "test-to-fail" situations. They have been extracted as test cases for a fully automated PROFIsafe layer tester, which is used to check the PROFIsafe conformance of F-Devices and F-Hosts. It is part of a three-step-procedure within the overall safety certification process according IEC 61508 by notified bodies (Figure 13).
It is important to note that the PI test laboratories perform the approved PROFIsafe layer tests on behalf of notified bodies such as, for example
- TÜV (worldwide)
- INRS (France)
- BGIA (Germany)
- SP (Sweden)
- SUVA (Switzerland)
- HSE (United Kingdom)
- FM, UL (USA)
These are the only ones to be responsible for the safety assessments according IEC 61508.
The mandatory safety manual of each and every F-Device shall provide information about the SILCL (claim limit) and the PFHd (probability of dangerous failure per hour).
PROFIsafe provides a specification for test & certification. Currently two PI test laboratories are accredited for the PROFIsafe testing.