Which PHA method uses subjective judgment for SIL assignment based on team expertise?

• A. Consequence Only
• B. HAZOP
• C. Modified HAZOP
• D. Event Tree Analysis

Answer: (C)

The Modified HAZOP (Hazard and Operability Study) method is recognized for incorporating subjective judgment in the safety assessment process, particularly for Safety Integrity Level (SIL) assignments. This method builds upon the traditional HAZOP approach but adapts it to allow for a more nuanced evaluation that takes into account team expertise and experience.

In a Modified HAZOP, the analysis focuses on identifying potential hazards and operational issues by examining deviations from the design intent of systems. The involvement of team members with varying backgrounds and expertise leads to discussions rooted in their professional judgment, making it possible to arrive at SIL assignments that reflect the complexities of the system being studied.

This adaptability to incorporate subjective input is crucial when considering factors that may not be fully quantifiable or identifiable through purely objective methods. Such expertise allows the team to tailor the assessment to specific operational scenarios, resulting in a more comprehensive understanding of the risks and necessary safety measures.