(132c) Beyond HAZOP: Analyzing Common Cause and System Scenarios

A production operation often consists of multiple unit operations, supported by plant-wide services, such as instrument air, power, electronic communications, and cooling water. Likewise, a production operation can be covered by multiple risk studies that are divided up based on numerous non-technical reasons, such as unit management, study length and convenience. The use of multiple evaluations is particularly common when associated with large production units or integrated packaged equipment. Traditional process hazard analysis techniques, such as HAZOP and LOPA, focus on pairing individual causes with deviations and consequences. The “divide and conquer” approach is good for planning and execution, but the resulting “pieces and parts” analysis can allow significant common cause scenarios to get lost in the clutter. This traditional approach commonly results in missed hazard scenarios, such as:

• Concurrent safe states
• Global loss of service
• Transference of risk

These complex situations are often interrelated and thus are not well suited for analysis by tools that assume a simple cause-consequence relationship. This paper will propose an advanced hazard analysis technique that may be used to address these challenges in a more holistic manner.