LNG Quantitative Risk Assessment (QRA) Study

Client

Gujarat State Petronet Limited (GSPL)

Industry

Natural Gas Infrastructure | LNG Transportation | LNG Storage & Regasification | Energy Transition

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Challenge

As India’s natural gas infrastructure expands to support cleaner energy adoption, the safe transportation, storage, and regasification of Liquefied Natural Gas (LNG) has become a critical operational and regulatory requirement. LNG transportation by road tankers introduces potential hazards associated with traffic accidents, tanker rollover, cryogenic releases, vapor cloud formation, fire escalation, and explosion scenarios. Similarly, LNG regasification facilities contain cryogenic storage tanks, transfer systems, vaporizers, pressure regulation skids, and associated equipment that require rigorous assessment of potential loss-of-containment events.

Gujarat State Petronet Limited (GSPL) sought a comprehensive Quantitative Risk Assessment (QRA) to evaluate risks associated with multiple LNG transportation corridors and LNG regasification infrastructure. The objective was to demonstrate that both transportation and facility operations comply with internationally accepted risk acceptance criteria, support regulatory approvals, validate emergency preparedness strategies, and ensure that risks remain within Acceptable or ALARP (As Low As Reasonably Practicable) regions.

The study required a detailed evaluation of potential fire, explosion, thermal radiation, blast overpressure, and societal risk impacts affecting:

LNG transport tanker operations
Public road users
Nearby communities and commercial establishments
Sensitive receptors
Facility operators and maintenance personnel
LNG unloading, storage, vaporization, and pressure regulation systems

Study Scope

iFluids Engineering performed an integrated Quantitative Risk Assessment covering both LNG transportation routes and LNG regasification infrastructure.

LNG Transportation Assessment

The transportation study covered LNG movement from the Petronet LNG Terminal at Dahej to multiple downstream LCNG stations across Gujarat. The assessment evaluated route-specific hazards and societal exposure associated with LNG road tanker transportation.

The scope included:

LNG tanker transportation operations
Route-based population exposure assessment
Accident frequency evaluation
Collision and rollover scenarios
Loss of containment (LOC) events
LNG release and dispersion modelling
Fire and explosion consequence assessment
Societal risk quantification
Route-specific F-N curve development

LNG Regasification Facility Assessment

The LNG Regasification Station assessment included the complete LNG receiving and regasification system, including:

LNG transport tanker unloading systems
Flexible cryogenic transfer hoses
LNG unloading pumps
LNG storage tanks
LNG transfer pipelines
Ambient air vaporizers
Pressure Regulation Skids (PRS)
Associated piping and process equipment

The study evaluated both onsite and offsite risk impacts resulting from credible release scenarios throughout the LNG handling process.

Methodology

The assessment followed internationally recognized Quantitative Risk Assessment methodologies in accordance with industry best practices, TNO Purple Book guidance, BEVI Risk Assessment methodologies, and accepted LNG risk modelling standards.

Phase 1 – Hazard Identification

A systematic hazard identification process was undertaken to identify credible loss-of-containment events associated with transportation and facility operations.

Key initiating events assessed included:

Transportation Hazards

Road traffic collision
Tanker rollover
Mechanical impact damage
Catastrophic tanker failure
LNG release following accident

Facility Hazards

LNG storage tank failure
Transfer hose rupture
Pipeline rupture
Pump-related release events
Vaporizer system failure
Pressure regulation skid release scenarios

Only credible scenarios contributing to individual or societal risk were considered, ensuring compliance with accepted QRA practices.

Phase 2 – Consequence Modelling

Advanced consequence modelling was performed to quantify potential physical effects resulting from accidental LNG releases.

The following hazardous outcomes were evaluated:

Fire Scenarios

Jet Fire
Flash Fire
Pool Fire
Tank Fire
Fire Ball

Explosion Scenarios

Vapor Cloud Explosion (VCE)
Overpressure Explosion
BLEVE-type escalation scenarios

Dispersion Scenarios

Cryogenic vapor dispersion
Flammable cloud formation
Delayed ignition events

Impact distances were evaluated using internationally accepted damage criteria, including:

Thermal Radiation Criteria

4 kW/m² – Pain threshold and skin blistering
12.5 kW/m² – Equipment damage and ignition threshold
37.5 kW/m² – Indicative fatality threshold

Blast Overpressure Criteria

0.01 bar – Glass breakage
0.10 bar – Structural damage
0.30 bar – Major equipment damage

Meteorological modelling incorporated local weather conditions, wind patterns, atmospheric stability classes, temperature, and humidity to ensure realistic consequence predictions.

Phase 3 – Frequency Analysis

Scenario frequencies were established using:

TNO Purple Book failure data
Industry LNG transportation statistics
Historical accident databases
Event Tree Analysis (ETA)
Equipment-specific failure frequencies
Ignition probability modelling

The analysis quantified both low-frequency/high-consequence events and higher-frequency operational release scenarios.

Phase 4 – Risk Quantification

Risk calculations combined consequence modelling and frequency analysis to determine:

Individual Risk Assessment

Location Specific Individual Risk (LSIR)
Individual Risk Per Annum (IRPA)
Worker risk assessment
Occupancy-based risk evaluation

Societal Risk Assessment

Population vulnerability analysis
Route-based societal exposure
F-N Curve development
Potential Loss of Life (PLL) assessment
Community risk evaluation

The results were benchmarked against internationally recognized risk acceptance criteria and ALARP principles.

Software Used

To ensure high-fidelity modelling and industry acceptance, the study utilized globally recognized risk assessment software platforms.

DNV PHAST Version 8.71

Used for:

LNG release modelling
Cryogenic dispersion analysis
Thermal radiation calculations
Fire consequence modelling
Explosion consequence modelling

DNV SAFETI Version 8.71

Used for:

Quantitative Risk Assessment
Individual Risk Analysis
Societal Risk Analysis
LSIR contour generation
F-N Curve development
Potential Loss of Life calculations

The use of PHAST and SAFETI enabled rigorous, defensible, and regulator-accepted risk quantification.

Key Findings

The integrated study generated a comprehensive understanding of LNG transportation and regasification risks across the project lifecycle.

LNG Transportation Routes

The assessment confirmed that:

Transportation-related accident scenarios were effectively identified and quantified.
Thermal radiation and blast effects remained localized for the majority of credible accident cases.
Individual risk levels remained within acceptable thresholds along assessed transportation corridors.
Route-specific societal risks were demonstrated to fall within internationally accepted risk criteria.
F-N curve evaluations confirmed societal risk remained within the broadly acceptable region.

LNG Regasification Facility

The facility assessment demonstrated that:

Existing engineering safeguards significantly reduced escalation potential.
LNG storage, transfer, and regasification operations satisfied applicable risk acceptance criteria.
Individual risk levels for workers remained within Acceptable or ALARP regions.
Control room occupants and operating personnel were adequately protected by existing facility safeguards.
Offsite societal risk was negligible and remained outside significant risk contours.
Potential Loss of Life (PLL) values were within tolerable limits for the assessed population.

Risk Acceptance Verification

The study demonstrated that:

Individual risk levels complied with accepted risk tolerability criteria.
Societal risks were within acceptable limits.
No intolerable risk conditions were identified.
Existing safeguards provide effective risk reduction.
LNG transportation and regasification operations can be safely conducted when existing controls are maintained.

Benefits Delivered

The study provided GSPL with significant technical, operational, and regulatory value.

Enhanced Regulatory Compliance

The QRA established compliance with recognized risk assessment methodologies and provided a defensible basis for demonstrating regulatory conformance.

Quantified Risk Visibility

The study transformed potential hazards into measurable risk metrics, enabling informed decision-making and risk-based planning.

Improved Emergency Preparedness

The assessment provided a robust basis for:

Emergency Response Planning
Disaster Management Planning
Resource allocation
Incident preparedness strategies

Safer LNG Transportation Operations

The route-specific risk evaluation enabled better understanding of transportation risks, population exposure, and accident consequences.

Risk-Informed Asset Management

The study supported:

Integrity management programs
Inspection planning
Maintenance prioritization
Risk reduction initiatives

Future Infrastructure Expansion Support

The risk assessment framework provides a scalable foundation for future LNG transportation and regasification projects.

Client Outcome

Through this integrated Quantitative Risk Assessment, GSPL obtained a comprehensive and technically robust understanding of risks associated with LNG transportation and LNG regasification operations.

The study demonstrated that:

LNG transportation routes satisfy societal risk acceptance criteria.
LNG regasification facilities operate within acceptable individual and societal risk limits.
Existing engineering and operational safeguards provide effective risk reduction.
Risks are maintained within Acceptable and ALARP regions.
LNG infrastructure can be safely operated while supporting expanding natural gas distribution requirements.

By combining advanced consequence modelling, frequency analysis, LSIR evaluation, F-N curve assessment, and ALARP verification, iFluids Engineering delivered a risk-based decision-making framework that supports operational excellence, regulatory compliance, emergency preparedness, and the continued expansion of LNG infrastructure across Gujarat.