The second edition IEC 61511

Last edit: 26/06/2023

The Second Edition reinforces the need to design for Functional Safety management rather than a narrow focus on calculations and it can be used to manage the actual performance of the SIS over time. IEC/TR 61511-4 was written to provide a brief introduction to the above issues, with more detailed content remaining in the main parts of the standard. Management of Functional Safety addresses systematic failures, mostly caused by humans, that are not quantifiable with mathematical models. These activities, covering the whole safety lifecycle, are applied through processes and procedures.

In this second edition there is the idea that Safety in not only based upon reliable components but it comes from an holistic approach given by the concept of the Safety Life Cycle. To ensure that Functional Safety can be achieved, several activities (done by different stakeholders, like end users, engineering company, vendors, etc..) need to be done. They are all connected to each other like a chain and the strength of this chain will be only as strong as the weakest link. It is crucial to consider Functional Safety as a lifecycle, which starts with hazard identification and ends with the decommissioning of SIS: all activities in the safety lifecycle are impacted by upstream and downstream activities.

Every SIS project has clear roles and responsibilities. All involved parties are aware of their responsibilities and are competent to fulfil the related activities necessary for Functional Safety. Competencies are kept up to date. All necessary activities in a project are described in a safety plan which can be project specific or a general company specific document. For all relevant activities, a Functional Safety assessment is carried out to demonstrate that a SIF fulfils all requirements and it is compliant to the agreed standards. Performance management during operation is done by collecting field data for SIS Reliability and SIS process demand information. Functional Safety audits are done at regular intervals to demonstrate that the organization remains capable of fulfilling the defined Functional Safety requirements. Assessment and auditing activities are done by individuals independent of the project team. Meaningful documentation of the assessment and audit results are generated, and recommendations tracked for effective closure.