Functional Safety Assessment Services
Functional Safety Assessment
The Functional Safety Assessment (FSA) is investigation to determine if the safety function under study achieves the required level (SIL) of functional safety. Within IEC 61511 it is defined as.
"an investigation, based on evidence, to judge the functional safety achieved by one or more SIS and/or other protection layers”
This involves demonstrating that the safety instrumented function (SIF) within a Safety Instrumented System (SIS) provides a safe outcome from all scenarios it is protecting against and that it does this with sufficient reliability. The FSA process requires a systematic review of all functional safety documentation to ensure that there is linkage between the hazard identification and risk assessment phases through to the current safety lifecycle phase.
The FSA is an in-depth review process that requires the functional safety assessors extensive experience and careful judgement to ensure that any SIF meets the design, engineering and installation requirements of IEC 61508 or IEC 61511. Independence and competence are key attributes of a Functional Safety Assessor and therefore Functional Safety Assessments are often carried out by 3rd party organisations.
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Our functional safety assessors can provide the independence and expertise required to conduct these assessments. Outputs are issued in a clear, understandable Functional Safety Assessment Report.
Functional Safety Assessor
FSA 1 (Stage 1 Assessment)
FSA 1 is performed following the completion of the Hazard Identification, Risk Assessment and development of the Safety Requirements Specification (SRS).
This assessment should ensure that a quality hazard identification study has been performed which has clear links to the specification within the SRS.
FSA 2 (Stage 2 Assessment)
FSA 2 is carried out once the detailed design is complete.
This assessment ensures that the SIF / SIS design meets the SRS along with any Safety Integrity Level (SIL) ratings. Performing an assessment at this stage while the system is still “on paper” provides an opportunity to avoid costly re-designs and delays later.
FSA 3 (Stage 3 Assessment)
FSA 3 is performed following installation, commissioning and site acceptance of the SIS, and before the introduction of the hazards to the system.
This assessment reviews work performed during the installation and commissioning stages in addition to reviewing the completion of findings from earlier stage FSA 1 and FSA 2 studies. Once the stage 3 assessment confirms that the requirements of IEC 61511 have been met, the SIS can be handed over to the operations and maintenance teams.
FSA 4 (Stage 4 Assessment)
FSA 4 is performed periodically during the life of the SIS to ensure that relevant functional safety activities are being conducted in a suitable manner.
A key aspect of this assessment is to look at inspection, maintenance and proof testing activities and how these are being used to collect the relevant performance data for the SIS.
Additionally, while the stage gate approach to Functional Safety Assessment works well with new project sites are often faced with legacy installed safety instrumented systems without a history of assessments. A good starting point if faced with this is an FSA 4.
FSA 5 (Stage 5 Assessment)
FSA 5 is performed when the SIS is subject to a change.
The term subject to a change could imply that it is a modification to the SIS only. Strictly speaking, modifications to the plant, process or organisation which can have an impact on Functional Safety require an assessment.
This assessment consists of two phases. The initial phase evaluates the Modification plan and assesses its suitability for the proposed change. The subsequent phase evaluates the implementation of the Modification and determines if it aligns with the intended plan. Many organisations refer to their existing management of change systems to cover these requirements, however such systems are often lacking aspects required for SIS modification.
Frequently Asked Questions
Please reach us at info@processsafetyconsulting.com if you cannot find an answer to your question.
It is a common misconception that only the Stage 3 assessment is a mandatory requirement of Functional Safety Standards such as IEC 61508 and IEC 61511. While this stage is necessary prior to the introduction of hazardous fluids into the process, if the earlier stages of FSA 1 and FSA 2 have not been completed, then the scope of the stage 3 assessment must include these two earlier stages. Understanding this, it becomes clear that by performing FSA 1 and FSA 2 earlier in the project lifecycle, costly issues and delays can be avoided.