Understanding FSA Stage 2
Continuing from part one of our Functional Safety Assessment (FSA) series, FSA Stage 2 is a critical checkpoint after design and engineering of the Safety Instrumented System (SIS).
At this pre-installation stage, the FSA team assesses that the SIS will perform reliably once operational. It means ensuring that the design and engineering of the SIS meet the requirements as defined in the Safety Requirements Specification (SRS) developed during earlier phases of the SIS safety life cycle as described in the process industry consensus ISA / IEC 61511 standard. According to the ISA / IEC 61511 standard, it is recommended to perform an FSA Stage 2 after the SIS has been designed and factory acceptance tested.
Conducting a thorough FSA Stage 2 ensures that potential safety issues are identified and resolved before the SIS is operational, preventing costly changes, rework, and unexpected project delays.
What are the Goals of FSA Stage 2?
The success of any SIS hinges on whether the design makes sense for real-world considerations.
During FSA Stage 2, every component of the SIS goes through rigorous verification and testing for any field installation problems. This stage verifies compliance with the requirements as defined in the SRS while also identifying potential issues that could compromise safety.
Table 1: What FSA Stage 2 Accomplishes
Design Verification | Implementation Review | Prepare for Installation |
Confirm that the SIS design meets the requirements as defined in the SRS | Assess the SIS hardware and software components to ensure they are correctly designed and engineered for field installation | Establish a strong foundation for the successful execution of subsequent phases of the SIS safety life cycle. |
What is the FSA Stage 2 Process?
At the heart of every FSA Stage 2 is a thorough review of the SIS design and engineering. This involves evaluating the SIS logic solver(s), input/output (I/O) modules, communication system(s), control panel(s), and other critical components, including field instrumentation, to ensure they meet the design specifications provided in the SRS.
The assessment also verifies that the SIS components are configured to fulfill their intended Safety Instrumented Functions (SIFs). Any discrepancies or gaps are identified and corrected before they can impact the SIS performance.
A common misconception is that FSA Stage 2 can serve as a substitute for Factory Acceptance Testing (FAT), where the SIS logic solver(s) hardware and software are tested in a controlled environment prior to field installation. In reality, they are complementary processes that work together to ensure system reliability. FAT tests the SIS logic solver(s) hardware and software, while FSA Stage 2 provides an independent assessment of these tests, ensuring the system is robust, meets all requirements, and is ready for the field installation.
Proper documentation is the backbone of an effective FSA. In addition to reviewing the output of the FSA Stage 1, the FSA Stage 2 will review the documentation developed during the SIS design and engineering. One of the most important aspects of the FSA Stage 2 is to confirm all the findings from the FSA Stage 1 are addressed. By verifying that all findings from previous stages are documented and addressed, teams can maintain continuity and avoid costly delays ensuring that the SIS evolves smoothly from design to implementation and beyond.
What is the Stakeholder Involvement for an FSA Stage 2?
FSA Stage 2 is a team effort, and results are highly dependent on the involvement of key personnel including the following essential roles:
Table 2: Roles & Responsibilities
Role | Responsibilities |
Ensures that the outcomes of the hazard and risk assessments are accurately reflected in the SIS design and engineering. | |
Operations Representative | Verifies the practicality and effectiveness of their operational processes implemented in the SIS design and engineering. |
Maintenance Representative | Assesses the maintainability and testability of the SIS, ensuring that future maintenance needs are considered during the SIS design and engineering. |
SIS Engineer | Oversees the technical aspects of the SIS, ensuring that all components meet the required specifications and performance standards provided in the SRS. |
FSA Stage 2 | An aeSolutions Case Study
Recently, aeSolutions conducted an FSA for a fired equipment modernization program which involved multiple thermal oxidizers/incinerators.
The project faced several challenges, including inconsistent safety requirements and the complex integration of new SIS components with the existing systems. By conducting a thorough FSA Stage 2, the team identified and corrected design flaws early, preventing potential safety hazards and ensuring the SIS met updated regulatory standards and design requirements.
The FSA Stage 2 process included a comprehensive review of the SIS design and engineering documentation including the FAT records and an independent assessment to ensure the new SIS equipment was ready for the field installation. The lessons learned from the first thermal oxidizer were applied to subsequent fired equipment, streamlining the FSA process and reducing overall project costs. This proactive approach not only enhanced safety but also fostered collaboration among the project engineering, operations, and maintenance teams, contributing to a more robust and reliable SIS.
The success of this project demonstrated the value of performing a meticulous FSA Stage 2, particularly in complex modernization efforts. The insights gained have been integrated into the company’s standard procedures for future projects, ensuring that similar initiatives can be managed more efficiently while maintaining the highest safety standards.
The Takeaway
Per the ISA / IEC 61511 standard, FSAs provide a five-stage, evidence-based investigation to judge the functional safety achieved by one or more SIS and/or other protection layers. FSA Stage 2 is the critical step in ensuring that the SIS is ready for field installation. By thoroughly verifying the SIS design and engineering, FSA Stage 2 helps to identify and address potential issues before they escalate into costly rework and project delays. It safeguards the integrity of the SIS, verifying that all components meet safety standards and are configured for optimal performance.
This stage supports bridging the gap between design and construction, ensuring that all SIS components are aligned with safety requirements — readying them for the field installation. As organizations continue to adopt more complex and integrated systems, the value of a thorough FSA Stage 2 becomes even more critical — laying the groundwork for safer, more efficient, and ultimately more successful projects. Be sure to check out the next blog in our FSA series that discusses how an FSA Stage 3 confirms your Safety Instrumented System (SIS) is ready for operational use.
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