Process Safety Analysis-HAZOP LOPA
Techniques for hazard identification and risk mitigation, including HAZOP, LOPA, and overpressure scenarios in process engineering.
Process Safety Fundamentals
Process safety ensures safe operations by identifying hazards and layering protections. Tools like HAZOP and LOPA systematically assess risks, complying with standards like API 521 for relief scenarios.
HAZOP (Hazard and Operability Study)
A structured brainstorming method reviewing process deviations (e.g., no/low/high flow) from design intent. Teams use guidewords (no, more, less) on nodes (P&IDs) to uncover causes, consequences, and safeguards. Primary goal: Spot operability issues early, preventing incidents like overpressure.
LOPA (Layer of Protection Analysis)
Semi-quantitative tool evaluating independent protection layers (IPLs)—e.g., alarms, interlocks, PSVs—against initiating events. Calculates risk reduction; if below tolerance, add IPLs. Targets scenarios like blocked outlets or controller failures.
Common Overpressure Scenarios
- Blocked Outlet: Closed discharge with continued inlet flow builds pressure.
- Tube Rupture: High-P fluid breaches to low-P side.
- Instrument Failure: Malfunctioning controllers cause imbalances.
- Thermal Expansion: Blocked liquids heat up (e.g., solar).
- Fire: Wetted area heat input; depressurize to cool.
Mitigations: Multiple relief paths, blowdown for emergencies. Accumulations limited (10% non-fire).
Integration with Design
Embed in P&IDs (e.g., car seals for locked valves). Test vessels hydrostatically (1.3x MAWP) or pneumatically (riskier due to energy release).
These flashcards build expertise in proactive safety.
What is the primary purpose of a HAZOP study in process engineering?
A HAZOP (Hazard and Operability) study systematically reviews a process to identify potential deviations from design intent that could lead to undesirable consequences.
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