5 Stages of Functional Safety Assessment | FSA Lifecycle

What is a Functional Safety Assessment (FSA)?

Functional Safety Assessment (FSA) is a systematic and structured process to evaluate the functional safety of a process unit across different phases of its lifecycle. It is a key requirement of functional safety standards, such as IEC 61508 and IEC 61511, ensuring that all activities are executed as planned. FSAs are critical to demonstrating that a Safety Instrumented System (SIS) fulfills its Safety Instrumented Functions (SIFs) and Safety Integrity Levels (SILs).

The primary objective of the FSA is to verify compliance with safety standards and practices through independent assessments, ensuring that the SIS effectively mitigates potential risks. These assessments occur at various lifecycle stages and include:

• Comprehensive hazard and risk analysis.
• Verification of safety requirements.
• Ongoing performance evaluations.

Why is Functional Safety Assessment Important?

1. Ensure Compliance: FSAs confirm adherence to applicable safety standards, such as IEC 61508 and IEC 61511.
2. Identify Gaps: They help uncover errors or non-conformities in the safety lifecycle, enabling corrective actions.
3. Enhance Safety: By verifying safety measures, FSAs minimize hazardous events, protecting people, assets, and the environment.
4. Promote Independence: Independent evaluations enhance credibility and trust in the safety management process.
5. Lifecycle Assurance: FSAs maintain safety objectives throughout the lifecycle, from design to decommissioning.
6. Demonstrate Due Diligence: They provide documented proof of thorough risk management for legal and regulatory purposes.

Key Attributes of a Successful FSA

To ensure the effectiveness of an FSA, the following best practices should be followed:

Planning: A plan should be generated for each FSA, identifying arrangements such as the scope of the assessment, the assessors, their competencies, and the information to be generated by the assessment.

Standards Alignment: The FSA should consider other standards and practices, which may be contained within external or internal corporate standards, guides, procedures, or codes of practice. The FSA plan should define what will be assessed for the particular assessment/ system/application area.

Evidence-Based: The frequency of FSAs may vary across different system developments, but they should always take place before the hazards are presented to the system. Some companies also like to conduct an assessment before the construction/installation phase to prevent costly rework later in the life cycle.

Risk-Based Frequency: FSA frequency and rigor should be defined taking into account system attributes such as:

• Complexity
• Safety Significance
• Previous experience with similar systems
• Standardization of design features.

Ensuring Evidence Availability for Assessment: Sufficient evidence of design, installation, verification, and validation activities should be available before the assessment. The availability of sufficient evidence could itself be an assessment criterion

The 5 Stages of Functional Safety Assessment

FSA 1: After the analysis phase and SRS development

• Ensures the hazard and risk analysis is thorough and that the Safety Requirements Specification (SRS) adequately captures the functional and integrity requirements for the Safety Instrumented System (SIS).

FSA 2: After the SIS detailed design is completed

• Verifies that the detailed design of the SIS aligns with the SRS and meets the required Safety Integrity Levels (SILs).

FSA 3: After installation and commissioning, but before startup

• Confirms that the SIS has been implemented as per design, tested, and is ready for safe startup.

FSA 4: After gaining operational and maintenance experience

• Evaluate the ongoing performance of the SIS during operation to ensure it continues to meet safety requirements.

FSA 5: After any changes to the SIS and before decommissioning

• Ensures the safety impact of changes is assessed and that the SIS remains compliant with safety standards up to decommissioning.

Safety Lifecycle and FSA Stages

How FSAs Safeguard Operations

FSAs are essential to maintaining high safety and operational reliability. By aligning with industry standards and following a structured approach, organizations can:

• Prevent costly errors and rework.
• Ensure system compliance at every lifecycle stage.
• Protect lives, assets, and the environment.

Conducting FSAs at the appropriate stages fosters a culture of safety and reliability, ensuring long-term success in achieving functional safety objectives.