LOPA (Layer of Protection Analysis) is a risk assessment method used to evaluate whether sufficient protection layers exist to reduce risk to an acceptable level.
In BowTiePro, the LOPA module helps users:
- Analyze threats and consequences
- Apply protection layers
- Configure risk reduction values
- Evaluate acceptance criteria
- Determine whether calculated risk levels are acceptable
LOPA assessments work alongside BowTie diagrams and help provide a more quantitative approach to risk analysis.
What LOPA Does
The LOPA module allows users to:
- Define initiating threat frequencies
- Apply enabling factors
- Configure condition modifiers
- Add Independent Protection Layers (IPLs)
- Configure Probability of Failure on Demand (PFD) values
- Apply acceptance criteria
- Calculate overall consequence frequency
This helps organizations better understand whether existing safeguards are sufficient.
Key Components of LOPA in BowTiePro
LOPA assessments in BowTiePro are built using several key elements.
Threat Frequency
Threat frequency defines how often a threat or initiating event may occur within a given period.
Example:
- 0.1 events per year
Enabling Factors
Enabling factors increase the likelihood of a threat occurring under specific conditions.
Example:
- Lack of level transmitter
- Poor maintenance conditions
Condition Modifiers
Condition modifiers are additional factors that influence consequence probability or severity. These are applied during LOPA calculations to refine the overall assessment.
Independent Protection Layers (IPLs)
IPLs are safeguards or controls designed to reduce risk independently.
Examples may include:
- Emergency shutdown systems
- High-level shutoff systems
- Safety instrumented systems
Each IPL may contain a Probability of Failure on Demand (PFD) value.
Acceptance Criteria
Acceptance criteria define whether calculated risk levels are considered acceptable.
BowTiePro supports configurable criteria such as:
- SIL 1
- SIL 2
- SIL 3
- SIL 4
These values help determine whether additional controls are required.
LOPA Results
After all values are configured, BowTiePro calculates:
- Consequence frequency
- Overall risk values
- Acceptance status
- Whether the assessment meets defined criteria
Results are displayed within the LOPA assessment screens and related hazard views.
Relationship Between BowTie and LOPA
LOPA assessments are linked directly to hazards, threats, and consequences already defined within BowTie diagrams.
This allows users to:
- Visualize hazards using BowTie methodology
- Validate protection effectiveness using LOPA calculations
- Identify areas requiring additional safeguards