Lifecycle Thinking
Each stage of a project exists to mature a specific set of decisions. The gate is there to bring clarity to them.
Focusing on Decisions Rather than Activities
Front-end loading literature is consistent on one point: project stages are best separated by the information produced and the decisions taken, not by the activities performed.
Aligning technical risk management with plant design phases builds on the same principle — each stage exists to mature a specific set of decisions, and its risk activities exist to inform those decisions at the right level of detail.
So, the same HAZOP-style question tests quite different things at FEL and at detailed design.
The decisions listed here are fundamental ones. The point of this framing is a reminder: design maturity at each stage should be sufficient to feed the decisions that belong to it.
Front-End Loading (FEL) Phases
‘‘Focus on direction and definition’’
Early stages are where the project’s risk profile is built and where inherent safety flexibility is greatest — and steadily disappearing. Not every detail can be final at these gates. But decisions that will be costly or impossible to reverse must not pass unexamined — that is what the gate is for. These may include:
- The selected process configuration
- Major inventories and hazardous-system boundaries
- Operating, isolation and shutdown philosophies
- Relief and depressurisation strategy
- Principal utility dependencies
- Plot-space and layout constraints
- Major vendor and package interfaces
- The intended balance between inherent design, control systems, alarms, operator action and independent protection
Detailed Design Phase
‘‘Focus on execution and verification’’
At detailed design, the emphasis changes from choosing the right direction to proving that it has been applied consistently. Agreed philosophies should be traceable through:
- Final P&IDs
- Equipment specifications
- Control narratives
- Cause-and-effect and shutdown logic
- Relief calculations
- Vendor packages
- Operating assumptions
Contradictions between these documents are not minor drafting matters when they affect the validity of the risk assessment.
An important reminder for early phase HAZOPs:
HAZOP has a systematics and does not rely on arguments or future projections without evidence. HAZOP discussions can be only structured as per the proposed datasheets, drawings and reports which contradicts with discussing an idea freely in a group.
However, even the guidelines for HAZOP execution dictates frozen documentation before the workshop, by nature of design they can’t and potential modification, simplification or rejection on philosophies brings value to this safety gate. Yet, it does not mean HAZOP to be used as a room for leaving too many and major design decisions immature until the workshop.
"Which design and project decisions are now clearer because this HAZOP was performed?"
The critical question to be asked at early phase HAZOPs
by the project managers