Quantitative Risk Analysis (QRA)

Objective of QRA Study:

The primary objective of Quantitative Risk Analysis (QRA) is to assess and mitigate the risks associated with hazardous activities. This systematic approach provides a detailed evaluation of potential risks, helping organizations make informed decisions about safety, operational efficiency, and risk reduction. Key objectives include:

1. Definition of Key Terms in QRA: Clear explanation of the critical terms used in the QRA study.
2. Document Identification: Identifying the documents and data required to carry out the QRA.
3. QRA Methodology: Describing the step-by-step methodology used in conducting the QRA.

Key Purpose of QRA Study:

The QRA study is essential for evaluating the risks posed to personnel, assets, and production, and for determining how best to reduce these risks. Specific purposes include:

1. Assessing Risk to Personnel and Assets: Evaluating the potential risks to individuals, facilities, and production systems, and determining their significance.
2. Risk Acceptability: Determining if calculated risks are acceptable and identifying key risk contributors (source and location).
3. Design Evaluation: Comparing different design options and selecting the one with minimal risk based on technological, commercial, and safety considerations.
4. Risk Prioritization: Ensuring resources are allocated efficiently to implement the most effective safety measures.
5. Assessing Societal and Individual Risks: Evaluating the potential societal impact of risks and assessing individual risks within the facility.
6. Safeguard Evaluation: Critically reviewing existing safety measures and ensuring their adequacy to manage identified risks.
7. ALARP Principle: Demonstrating that risks are in the tolerable range and determining if additional risk reduction measures are feasible.
8. Cost-Benefit Analysis (CBA): Evaluating risk reduction measures by weighing their costs against the potential benefits.

QRA Methodology:

The QRA study is carried out using a step-by-step methodology, focusing on the identification and analysis of credible accident scenarios, consequence modeling, frequency analysis, and risk evaluation.

1. Identification of Credible Accident Scenarios (CASs):
   • Identify potential events such as jet fires, pool fires, vapor cloud explosions, and toxic cloud dispersion.
   • Exclude natural calamities (e.g., earthquakes, lightning) from frequency analysis but consider their impact on the risk analysis.
2. Facility Segmentation and Inventory Calculation:
   • Divide the facility into isolatable sections (IS).
   • Calculate the inventory of materials for each section based on operating parameters and material properties.
3. Consequence Analysis:
   • Perform consequence modeling to estimate the effects of toxic materials or fires.
   • Utilize DNV PHAST software for modeling toxic dispersion, heat radiation, and overpressure magnitude.
4. Frequency Analysis:
   • Assess the likelihood of accidents using relevant databases.
   • Obtain failure frequencies for each isolatable section using standards such as OGP Risk Assessment Data Directory.
5. Risk Modeling:
   • Combine consequence and frequency analysis results using risk modeling software like DNV SAFETI.
   • Risk results are presented as:
     • Individual Risk (IR): Risks faced by an individual, typically presented as IRPA or LSIR contours.
     • Societal Risk: Presented using F-N curves or PLL (Potential Loss of Life).
6. Risk Evaluation:
   • Compare risk results against established risk acceptance criteria.
   • Carry out sensitivity analysis to evaluate uncertainty in assumptions.
7. Risk Reduction Measures (RRMs):
   • Identify and implement measures to reduce risks to acceptable levels.
   • Evaluate the cost-effectiveness of safety measures using Cost-Benefit Analysis (CBA).

Hazard Identification and Assessment:

The QRA study identifies potential hazards and credible accident scenarios (CASs) based on the materials handled and facility operations. Some common accident scenarios include:

• Jet Fires
• Pool Fires
• Vapor Cloud Explosions
• Toxic Gas Dispersion

The QRA process evaluates these events using international databases to assess failure frequencies and to model potential consequences effectively.

Consequence Modeling:

Consequence analysis evaluates the impact of hazardous material releases. Key aspects include:

1. Source Term Modeling: Determine the release rate of hazardous materials.
2. Physical Effects Modeling: Analyze the dispersion of gases, flame geometry, thermal intensity, and overpressure magnitude.
3. Impact Criteria: Compare the results of the physical effects model to safety standards and impact criteria.

Consequence modeling is carried out using DNV PHAST software, ensuring accurate prediction of hazard impacts.

Frequency Analysis:

Failure frequencies for facility components (pipelines, vessels, storage tanks) are determined using international databases. The procedure includes:

• Base Failure Frequencies: Sourced from recognized databases using methods such as the parts count method.
• Risk Reduction Factors: Adjusting frequencies based on safety measures and mitigation strategies.
• Generic Data: Applied when site-specific data is unavailable.

Risk Assessment and Evaluation:

1. Individual Risk (IR): The risk to a single individual, considering potential exposure to hazards.
2. Societal Risk: The collective risk to society, typically assessed using F-N curves or PLL.
3. Risk Acceptance: Risks are evaluated against acceptable thresholds. If risks exceed acceptable limits, mitigation measures are required.
4. Sensitivity Analysis: Assumptions made during the assessment are tested to evaluate the uncertainty in results.

Cost-Benefit Analysis (CBA):

CBA compares the costs of implementing additional safety measures with the benefits in terms of reduced risk. It evaluates the monetary value of reducing risks, including the potential loss of life, and helps decide whether the safety measures are cost-effective.

Deliverables of the QRA Study:

1. QRA Assumption Register: Document outlining assumptions made during the study.
2. ALARP Workshop & Draft Report: Initial draft report after conducting the risk analysis.
3. Final QRA Report: Incorporates company feedback and presents the final recommendations and risk mitigation strategies.

QRA Report Structure:

1. Executive Summary: High-level overview of the QRA study.
2. Introduction/Objectives: Purpose and scope of the study.
3. Facility Description: Overview of the facility and its operations.
4. Hazard Identification: List of credible accident scenarios.
5. QRA Assumptions: Basis for analysis.
6. Consequence Analysis: Impact analysis of identified hazards.
7. Failure Frequencies: Frequency data for potential accidents.
8. Risk Assessment: Evaluation of individual and societal risks.
9. Recommendations/RRMs: Suggestions for mitigating risks.
10. Appendices: Additional data and information.

Conclusion:

The QRA study provides a detailed and systematic approach to risk management, offering critical insights into potential hazards, risk mitigation strategies, and cost-effective safety measures. This process ensures that all identified risks are managed within acceptable limits and that the facility operates safely and efficiently.

By employing advanced modeling techniques and rigorous analysis, the QRA study provides actionable recommendations to mitigate risks and improve overall safety performance.