Human reliability analysis plays a critical role in ensuring safety during hydrogen handling and maintenance operations. Given the unique properties of hydrogen—high flammability, low ignition energy, and propensity to leak—human errors can lead to severe consequences. Techniques such as THERP and CREAM provide structured methodologies to assess and mitigate these risks, particularly in high-stakes environments like pipeline inspections and electrolyzer maintenance.
One of the most established methods for evaluating human reliability is the Technique for Human Error Rate Prediction (THERP). This approach quantifies the probability of errors during procedural tasks, accounting for factors such as task complexity, environmental conditions, and operator experience. In hydrogen systems, THERP can be applied to maintenance tasks like valve operations, leak testing, or pressure checks. For example, during pipeline inspections, a missed defect due to inadequate visual examination may have an estimated error probability between 0.001 and 0.01, depending on inspection conditions and inspector training. THERP also incorporates recovery factors, such as secondary verification steps, which can reduce error probabilities by an order of magnitude.
The Cognitive Reliability and Error Analysis Method (CREAM) offers a more dynamic perspective by focusing on cognitive failures rather than just procedural slips. CREAM classifies errors into categories such as interpretation failures, planning mistakes, and execution errors. In hydrogen electrolyzer maintenance, a technician misinterpreting a pressure gauge due to poor labeling could lead to incorrect adjustments, increasing the risk of over-pressurization. CREAM assigns context-dependent control modes—from scrambled to opportunistic—to estimate error likelihoods. For instance, under time pressure, an operator may shift from a strategic mode (low error probability) to a tactical mode (higher error probability), increasing the chance of oversight during safety checks.
Training and procedural safeguards are essential to minimize human error probabilities. Standardized operating procedures with clear step-by-step instructions reduce ambiguity in tasks like hydrogen purging or compressor startups. For pipeline inspections, checklists that mandate ultrasonic testing alongside visual inspections can mitigate oversight risks. In electrolyzer maintenance, color-coded piping and digital monitoring systems provide additional layers of error prevention. Simulations and virtual reality training further enhance operator preparedness by replicating high-risk scenarios without real-world consequences.
Human reliability assessments must also consider organizational and environmental influences. Poor lighting in a hydrogen storage facility increases the likelihood of misreading instruments, while excessive noise during compressor maintenance may disrupt communication between team members. Fatigue is another critical factor; extended shifts in high-alert environments can elevate error rates significantly. Quantitative studies indicate that error probabilities in repetitive tasks may double after 10-12 hours of continuous work.
Case studies from hydrogen infrastructure highlight the effectiveness of structured HRA. In one incident involving a hydrogen refueling station, a procedural deviation during a filter replacement led to a minor leak. A subsequent THERP analysis revealed that adding a peer-verification step reduced the error probability from 0.05 to 0.005. Similarly, a CREAM-based review of an electrolyzer shutdown procedure identified that unclear alarm prioritization contributed to delayed responses. Redesigning the alarm system and conducting targeted training lowered cognitive error rates by 40%.
Despite these measures, residual risks remain. Redundancy in safety systems—such as dual pressure relief valves or automated shutdown triggers—acts as a final barrier against human errors. Regular audits of maintenance logs and incident reports help identify recurring issues, enabling continuous improvement in human reliability. For example, analyzing near-misses during hydrogen cylinder handling led to ergonomic redesigns of storage racks, reducing manual handling errors by 30%.
The integration of human reliability analysis into hydrogen safety protocols is not static. Advances in digital tools, such as real-time performance monitoring and AI-assisted diagnostics, are reshaping error mitigation strategies. Wearable sensors that detect operator fatigue or distraction can provide immediate feedback, preventing mistakes before they occur. In pipeline inspection drones equipped with AI-driven anomaly detection complement human inspectors, reducing reliance on subjective judgment.
In summary, human reliability analysis provides a systematic framework for addressing the inherent risks in hydrogen handling and maintenance. By leveraging THERP and CREAM, organizations can quantify error probabilities, implement targeted safeguards, and continuously refine operational procedures. The dynamic nature of hydrogen systems demands ongoing vigilance, ensuring that human factors are managed as rigorously as technical ones. Through structured training, procedural clarity, and technological augmentation, the hydrogen industry can achieve higher safety standards while maintaining operational efficiency.