Safety and Risk Assessment of Hydrogen Leaks and Ignition in Storage Facility

Abstract

This study evaluates the safety of hydrogen storage facilities by applying Hazard and Operability (HAZOP) analysis, What-If analysis (WIA), and Fault Tree Analysis (FTA). The HAZOP analysis identifies key deviations such as leakage, overpressure, and valve malfunction, which can lead to hydrogen accumulation, jet fires, and vapor cloud explosions. The What-If analysis considers broader operational scenarios, including relief valve failures, ventilation loss, and external ignition events, which demonstrate the potential for low-frequency but high-consequence accidents. The FTA shows that uncontrolled hydrogen release together with the presence of ignition sources represents the dominant pathway leading to catastrophic events, with electrical sparks, static discharge, and hot surfaces highlighted as significant contributors. The study shows that the combined application of HAZOP, WIA, and FTA offers a comprehensive framework for identifying accident scenarios and supports a deeper understanding of risks in hydrogen storage operations.

Introduction

Hydrogen is increasingly recognized as a clean energy carrier with applications in transportation, industry, heating, and energy storage. While technological advances and cost reductions have improved its competitiveness, safety remains a critical challenge. Key safety concerns include hydrogen's:

• Wide flammability range

• Low ignition energy

• High burning velocity

• Small molecular size, which increases leak potential

These factors necessitate comprehensive risk assessment in both hydrogen production and storage facilities.

Key Safety Challenges & Research Insights

• Risk of Accidents: Studies show hydrogen leaks can exceed flammability limits indoors, increasing explosion risks depending on release rate and space volume.

• Jet Fire & Explosion Hazards: Experiments show pit geometry affects flame behavior during jet fires; vapor cloud explosions may affect areas up to 280–301 meters, causing building damage and injuries.

• Knowledge Gaps: Mechanisms like electrostatic discharge and adiabatic compression in spontaneous ignition are not yet fully understood.

• High-Pressure Risks: Storage systems present major risks due to potential leakages and equipment failures.

Systematic Risk Assessment Need

Despite growing research, integrated application of risk assessment methods to hydrogen storage (as opposed to production or transport) is limited. To fill this gap, this study applies three complementary methodologies:

1. HAZOP (Hazard and Operability Study)

2. WIA (What-If Analysis)

3. FTA (Fault Tree Analysis)

II. Methodology

A structured, multi-method approach was adopted for analyzing a hydrogen storage facility:

A. System Description & Data Collection

Detailed characterization of storage types (e.g., high-pressure cylinders, cryogenic tanks), operating conditions, and safety systems using technical documents, historical data, and standards.

B. HAZOP Analysis

Divides the system into functional nodes (e.g., valves, vessels) and applies guidewords (e.g., “No,” “More,” “Other than”) to identify potential deviations in pressure, flow, etc., along with causes, consequences, and safeguards.

C. What-If Analysis

Poses hypothetical scenarios like equipment failure or external fire to capture low-frequency, high-impact events and factors not fully addressed by HAZOP (e.g., human error).

D. Fault Tree Analysis (FTA)

Quantifies accident probabilities, focusing on hydrogen explosion as the “top event.” Combines failure data to calculate the likelihood of critical scenarios, using logic gates and sensitivity analysis to identify key contributors.

E. Risk Evaluation

Synthesizes qualitative (HAZOP & WIA) and quantitative (FTA) findings to develop a comprehensive risk profile. Benchmarks results against safety standards like ALARP, and proposes mitigation strategies (engineering, administrative, emergency planning).

III. Results and Discussion

A. Findings from HAZOP

• Identified critical deviations like No flow, Leakage, Overpressure, and Reverse flow

• Root causes include valve failures, seal degradation, and equipment malfunctions

• Potential consequences include hydrogen accumulation, explosion, and fire risks

• Safeguards such as relief valves and leak detection systems exist, but additional measures (e.g., redundant sensors, better maintenance) are recommended

Conclusion

This study presented a structured risk assessment of hydrogen storage facilities by applying HAZOP, What-If, and Fault Tree Analysis. The HAZOP investigation identified key deviations such as overpressure, leakage, and valve failures across storage vessels, piping, and relief systems, with potential consequences including hydrogen accumulation, jet fires, and vapor cloud explosions. The What-If analysis complemented these findings by capturing broader operational scenarios such as relief valve malfunction, ventilation failure, and external ignition events. Fault Tree Analysis demonstrated that uncontrolled hydrogen release and the presence of ignition sources are the two critical conditions leading to major accidents, with static discharge, electrical sparks, and hot surfaces identified as significant contributors. Collectively, the results underline that hydrogen’s inherent properties demand comprehensive risk evaluation, and the integrated application of multiple assessment techniques provides a robust framework for understanding accident pathways in storage operations.

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Copyright

Copyright © 2025 Ayush Kumar, Anas K, Anshu Patel, Kaushlendra Singh Saini, Deepesh Kumar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.