Quantitative Risk Assessment (QRA) for Process Facilities in Oman

What is Quantitative Risk Assessment (QRA)?

Quantitative Risk Assessment (QRA) is a method used to calculate and evaluate the risks of hazardous events in industries. It uses data and models to estimate the likelihood and impact of incidents, helping organizations improve safety and comply with regulations.

Introduction

Quantitative Risk Assessment (QRA) is a vital process in ensuring the safety and reliability of operations at process facilities. In Oman, this assessment helps identify potential hazards, evaluate risks, and implement measures to mitigate them. This document outlines the QRA methodology used to assess location-specific individual risks (LSIR) at process facilities in Oman.

1. Objective

The primary objective of this Quantitative Risk Assessment (QRA) is to evaluate the location-specific individual risk (LSIR) associated with process facilities in Oman. This assessment aids in informed decision-making by analyzing potential hazards and their impacts on safety and operations.

2. Software Tools

• SHELL FRED v7.1
• SHELL SHEPHERD v3.2
• DNV PHAST v8.22
• DNV SAFETI v8.22

3. Standards

• IP Ignition probability Review Model Development & Look up Correlations (Jan 2006).
• EP Forum Hydrocarbon leak and ignition database, Report No. 11.4/180, (1992)
• UKHSE, Guidance on ALARP Decisions in COMAH.
• Effects of Thermal Radiation, Centre for Chemical Process Safety, (CCPS) 1994.
• OGP Risk assessment Data Directory
• CPR 18E Guideline for quantitative risk assessment
• SP-1258 Specification: Quantitative Risk Assessment & Physical Effects Modelling

4. QRA Methodology

The methodology adopted for the same has been described below

      Figure 1 – QRA Methodology

4.1  Identification of Hazards & Release Scenarios

Hazard identification involves recognizing undesired events that could lead to hazardous conditions. For process facilities in Oman, the primary hazards include uncontrolled releases of flammable or toxic materials. Key tasks include:

• Identifying potential leaks and major releases from process pipelines and vessels.
• Collecting data on
  • Material composition in vessels/pipelines
  • Inventory levels
  • Flow rates
  • Conditions of vessels/pipelines (phase, temperature, pressure)
  • Dimensions of piping and connections

4.2 Consequence Analysis

The consequence modelling evaluates the resulting effects if the accidents occur, and assessing their impacts. Estimation of the consequences of each possible event is performed using QRA software tool.

Following consequence outcome events are considered for process releases:

For each hazardous scenario, consequence modelling is conducted to determine the area impacted by each consequence event. For each consequence event, the extent of the impact of the effects depends on the conditions specified for the hazardous scenario. These include:

• Process conditions (e.g. temperature, pressure, flowrate);
• Material properties;
• Release source (elevation, orientation) and
• Atmospheric conditions (wind speed, atmospheric stability, surface roughness)

4.3 Frequency Analysis

Frequency analysis estimates the likelihood of each failure scenario. This includes:

• Developing leak frequencies using parts count and event tree analysis.
• Evaluating the potential for detection and isolation of leaks.
• Considering factors such as gasket failures, valve issues, corrosion, and other external factors.

4.4 ALARP

The risk criteria are based on the HSE Corporate risk of the company. The IRPA has been compared against the individual risk tolerability criteria as defined in the HSE corporate risk is used to determine whether the total IRPA is considered broadly acceptable, tolerable or intolerable.

SHELL SHEPHERD RESULTS

DNV PHAST RESULTS

Conclusion

This QRA methodology provides a comprehensive framework for assessing risks associated with process facilities in Oman. By utilizing advanced software tools and adhering to established standards, this assessment helps ensure the safety and reliability of operations.