Quantitative Risk Assessment (QRA) for Ammonia Storage & Handling Facility

CASE STUDY

Quantitative Risk Assessment (QRA) for Ammonia Storage & Handling Facility

Project Overview

A leading specialty chemical manufacturing company engaged Sigma HSE to conduct a Quantitative Risk Assessment (QRA) for its ammonia storage and handling facility. The objective was to evaluate potential risks associated with ammonia unloading, transfer, storage, and pumping operations, and to verify that risks to personnel, assets, and the environment remained within acceptable limits.

Key Challenges

The facility handled 25% aqueous ammonia, a hazardous chemical with toxic and corrosive properties. Potential concerns included:

1. Accidental release during tanker unloading operations
2. Leakage from pumps, piping, and storage systems
3. Exposure of personnel to ammonia vapors
4. Environmental contamination of soil and groundwater
5. Assessment of emergency preparedness and risk mitigation measures

Scope of Study

Sigma HSE carried out a comprehensive QRA covering:

1. Hazard Identification and Scenario Selection
2. Consequence Modelling using DNV PHAST software
3. Toxic Dispersion Analysis
4. Failure Frequency Assessment
5. Individual and Societal Risk Assessment
6. Evaluation against internationally accepted risk criteria
7. Recommendations for risk reduction and emergency preparedness

Scenarios Evaluated

The study considered multiple release scenarios from:

1. Ammonia road tanker unloading system
2. Transfer pumps and associated piping
3. Ammonia storage tank

Leak sizes ranging from small leaks to catastrophic ruptures were analyzed under various meteorological conditions.

Methodology

The assessment followed internationally recognized QRA methodologies and included:

1. Hazard identification and credible accident scenario development
2. Toxic consequence modelling
3. Release frequency estimation using historical industry databases
4. Individual Risk (IRPA/LSIR) assessment
5. Societal Risk evaluation
6. ALARP (As Low As Reasonably Practicable) assessment

Industry-standard software (DNV PHAST & PHAST Risk) was utilized for consequence and risk calculations.

Key Findings

Risk Assessment Results

1. No significant off-site or on-site fatality risk was identified from the evaluated ammonia release scenarios.
2. Individual Risk and Societal Risk levels were found to be negligible and well within acceptable criteria.
3. No risk contours requiring additional land-use restrictions were generated.
4. The facility demonstrated an inherently low-risk profile for the ammonia storage system.

Recommendations Implemented

Although overall risk levels were low, Sigma HSE recommended several proactive safeguards to further strengthen safety performance:

✓ Enhanced PPE requirements for operators and emergency responders

✓ Improved spill containment systems around storage and transfer areas

✓ Protection of soil and groundwater through effective drainage management

✓ Proper venting arrangements for relief devices

✓ Continued inspection, testing, and preventive maintenance programs

✓ Periodic review of emergency response procedures

Client Benefits

Improved Process Safety

Verified that ammonia storage operations met acceptable risk levels.

Regulatory Compliance

Supported compliance with recognized risk assessment and process safety requirements.

Enhanced Emergency Preparedness

Provided data-driven emergency planning and response guidance.

Environmental Protection

Identified measures to prevent accidental contamination of soil and water resources.

Risk-Informed Decision Making

Enabled management to prioritize safety investments based on quantified risk results.

Conclusion

The QRA demonstrated that the ammonia storage and handling facility operated within acceptable risk limits. Through systematic hazard assessment, consequence modelling, and risk quantification, Sigma HSE helped the client validate the safety of its operations while identifying practical measures to further enhance personnel, environmental, and asset protection.

Sigma HSE delivers comprehensive QRA studies, Hazardous Area Classification (HAC), HAZOP, LOPA, SIL, DHA, QRA, and Process Safety Management solutions for chemical, pharmaceutical, FMCG, oil & gas, and manufacturing industries.