Functional Safety Assessment- FSA

Functional Safety Assessment (FSA) is mandatory in accordance with IEC 61511. FSAs are undertaken in addition to the traditional activities of verification, validation and functional safety audits. FSA is performed to ensure that functional safety has been achieved within the specific scope of supply for the organisation in the context of the SIS Safety Lifecycle.

The FSA assesses if appropriate methods, techniques and processes have been used to achieve functional safety, in relation to design, implementation and installation of Safety Instrumented System. IEC 61508 Part 1, clause 8 defines as to when, how, who and why in addition to the levels of independence required of the organisation and staff implementing the FSAs.

An FSA enables the asset owner/operator to make a judgement on the completeness of the functional safety design activities and the compliance of the Safety Instrumented Function (SIF) design with IEC‑61511..

IEC-61511 states that FSAs are be carried out at the end of each phase of the safety lifecycle.

Below is a brief of the FSA stages as detailed in IEC-61511-

•  Stage 1: After the Hazard Analysis and Risk Assessment has been carried out, the required protection layers have been identified and the Safety Requirements Specification (SRS) has been developed.
•  Stage 2: After the Safety Instrumented System (SIS) has been designed.
•  Stage 3: After the installation, pre-commissioning and final validation of the SIS has been completed and operation and maintenance procedures have been developed.
•  Stage 4: After gaining experience in operating and maintenance.
•  Stage 5: After modification and prior to decommissioning of a SIS.

Some may argue that this only concerns the Logic Solver, but fail to realise the essence of Functional Safety Management and failure of SIS could be attributed to failure of Input sub-systems (i.e. sensors, transmitters) and equally to failure of Final Elements (ESD Valves, Contactor, I/R Relay, MCC Relays, etc). FSA is about assessing Each sub-system to ensure appropriate planning, recording, analysis has been performed, related to SIS, during Each lifecycle stage to reduce systematic and common cause failures.

An Audit is a systematic and independent examination to determine whether the procedures specific to the functional safety requirements comply with the planned arrangements, are implemented effectively and are suitable to achieve the specified objectives. SIS Audits are usually carried out to ensure that the SIS Implementation meets the requirements of SIS Design Requirements specified in SIS Requirements Specification, Plant Safety Philosophies, (SRS) Safety Requirements Specification and (PRS) Process Requirements Specification.

Our experienced Consultants have carried out FSA Stage 1, Stage 2, Stage 3 and Stage 4 FSAs. We have also identified gaps during the FSA and provided recommendations to customers to enable them to close those gaps.

Backed with a strong C&I Background, Elite Technical Consulting is very experienced in carrying out Functional Safety Assessments, SIS Audits and Independent Verification of SIS. Typically the documents that are reviewed include

• SIS Requirements Specifications
• Safety Requirements Specification.
• Process Requirements Specification.
• SIS Functional Design Specification.
• Relevant P&IDs and Cause and Effects.
• Datasheets.
• SIS I/O Schedules and Loop Drawings.
• Inspection and Test Plan.
• Factory Acceptance Test Documentation.
• SIS Integration Test Procedures.
• Test Plan.
• Functional Safety Management Procedure.
• SIS Safety Lifecycle Plan.
• Deterministic SIL Report, Risk Assessment Report.
• HAZOP, CHAZOP Report.
• SIL Verification Report (depending on FSA stage).