Scissors Approach in Human and Equipment Reliability Vis-A-Vis the Use of Alternative Fuel in Ship Propulsion

Abstract

This project looks deeply at the integration of human and equipment reliability in hydrogen bunkering operations, focusing on human corrective response actions (HCRAs) to unwanted events in the process. Human responses are also actions shaped by human performance thereby not totally devoid of human error. The possibility of the occurrence of accidents even when both personnel and equipment are reliable draws great attention to examine human responses to occurrences in the bunkering process of hydrogen. The Cognitive Reliability and Error Analysis Method (CREAM) is adopted alongside equipment reliability data from the maritime industry to assess the connection between system performance and human decision-making in the bunkering operation process. The findings show that enhanced equipment reliability significantly improves human corrective responses, leading to great operational efficiency. This study proposes an integrated reliability framework to optimize hydrogen bunkering procedures vis-à-vis an enhanced safety response, providing recommendations for improving safety regulations, and necessitate operator training, equipment management, and risk mitigation approaches. By ensuring industrial compliance and enhancing overall reliability in ship propulsion, these insights contribute to the use of hydrogen as an alternative fuel in the maritime sector for ship propulsion.

1. Introduction

1.1. Background

With the maritime embrace of the use of alternative fuels to ensure ecosystem sustainability to reduce carbon emissions, hydrogen has emerged as a promising solution for ship propulsion. However, the adoption of hydrogen bunkering operations places a lot of safety and reliability challenges.

Challenges are due to cryogenic storage needs, high flammability, explosion risks, leakage and diffusion, and compatibility of materials and equipment, as well as human factor risks, a lack of standard operating procedures, environmental and regulatory challenges, and pipeline and transfer risks.

Hydrogen has a wide range of flammability, increasing the risk of fire and explosion, and low ignition energy. Being a cryogenic liquid kept at an extremely low temperature poses dangers of frostbite and equipment failure. The safety challenges are not necessarily the production or the end-point use but the storage [1], which greatly concerns the bunkering system.

The investments in hydrogen pipelines for a given diameter are up to two times higher than those for Liquefied Natural Gas (LNG) pipelines [2]. Upon close consideration, because of the physical and chemical properties of hydrogen, the pipelines must be made of non-porous, high-quality materials such as stainless steel.

In the vein of bunkering procedures, clear procedural paths for its bunkering operation, step by step, have not been studied, raising a lot of uncertainties. There are several challenges in the bunkering of hydrogen, starting from the bunkering infrastructure; it is important to establish bunkering infrastructure to handle hydrogen, including storage facilities.

In the same vein, hydrogen is highly flammable, which can lead to combustion and possible explosions if not carefully handled. Considering its embrittlement nature also poses danger to maritime equipment, ranging from pipelines and storage tanks to avoid leakage.

The careful demand in the handling of this promising new alternative fuel (hydrogen) with a lot of safety issues requires high human cognitive reliability in its bunkering operation to bring it onboard. This careful handling, complex decision-making, need for situational awareness, and unexpected system failures makes CREAM the most suitable HRA method for the analysis.

1.2. Current Issue

The interesting goal set by the International Maritime Organization (IMO) for reducing greenhouse gas emissions from shipping advocates extreme measures by all relevant stakeholders [3]. Green hydrogen becomes a great interest for a cleaner environment as an alternative to fossil fuels. It is far more promising compared to other alternative fuels in the maritime industry for ship propulsion systems [4]. It will become the 21st-century version of oil [5].

To ensure the efficient and safe operation of the bunkering process of hydrogen, the reliability of both bunkering equipment and human operators becomes monumental. While technological advancement has improved safety, the reliability of both equipment and human corrective response as an intervention to uncertainties and unwanted situations remains important.

Existing studies have focused primarily on either equipment reliability or human reliability, without consideration of their integrated effects on the overall safety performance of the hydrogen bunkering process. Current risk assessment models lack a clear approach that considers human corrective response to unwanted events that integrate human and equipment reliability, leaving a gap in the hydrogen bunkering process.

This study aims to analyze human corrective response to uncertainties in the hydrogen bunkering process and assess how equipment reliability influences human response decision-making. We develop an integrated reliability framework to enhance the hydrogen bunkering process and provide practical recommendations to improve operational efficiency.

1.3. CREAM

These corrective responses to uncertainties are cognitive in nature; therefore, there is a need to use a human reliability assessment method that marries the interest of human decision-making. First-generation human reliability analysis (HRA) methods often focus on mechanical tasks and procedural errors. However, the hydrogen bunkering process involves complex decision-making and cognitive workload management, calling for the CREAM HRA method as the most suitable strategy. The bunkering process involves real-time decision-making in response to uncertainties such as sudden and unexpected system failures. The CREAM looks at how human cognitive functions influence responses to uncertainties, where operators must respond dynamically to changing conditions in a changing environment.

The Cognitive Reliability and Error Analysis Method (CREAM) brought into the HRA industry is extensively used for identifying human error, supporting the regulatory framework, and enhancing crew performance [6]. This method focuses on task analysis, error reduction, and human performance [7].

Human error has been an extensive contributing factor to marine accidents, posing a high level of risk to operational integrity in the nuclear industry [8,9]. In the same vein of discussion, it will be interesting to note that human reliability analysis (HRA) has panned out to be so useful in extenuating human errors [8].

Several human reliability analyses have been carried out using the Cognitive Reliability and Error Analysis Method (CREAM) to examine the likelihood of human errors that are cognitive in nature, considering the context of operations in complex industrial cycles [6]. The CREAM human reliability assessment has widened its application to different industrial environments. In the maritime industry, its application has been adopted for operational efficiency and risk reduction. To improve the reliability of maritime transportation, a reliability analysis model was proposed using CREAM and a decision-making model [10]. In further instances, detailed human reliability analysis was carried out for the operational process of cargo oil pumps on tanker ships using a fuzzy-CREAM extended Bayesian Network to calculate human error probability [11].

Application of the CREAM framework was also conducted in emergency responses to engine room fires to evaluate specific scenarios associated with human error probability onboard shipping operations [12]. The objective interest is to see how human reliability on board the ship during operations can be enhanced. In an in-depth analysis, the CREAM was used for productive quantification of human error probability (HEP) for an LNG bunkering operation, integrating the Fuzzy Bayesian Network to indicate HEPs by means of on-site safety philosophical factors [13]. A weighted CREAM model for maritime human reliability analysis substantiated with axioms in a case study of an oil tanker was considered [8].

The CREAM HRA can be used both retrospectively and prospectively in its analysis, which evaluates the performance of the operator. It has four control modes and identifies cognitive functions like execution, planning, interpretation, and observation: The strategic control mode (long-term objectives and high-level planning), the tactical control mode (standard procedures and rules in carrying out a task),the opportunistic control mode (performing actions based on immediate intimation without much planning), and the scrambled control mode (often leading to errors due to unorganized chaotic response to an occurrence or situation). In addition, the CREAM has both Basic and Advanced versions in its analysis on a particular operation, giving room for better cognitive decision-making inclusive of context influence on human reliability.

The human element has often functioned as a safety adaptive agent in response to the occurrence of accidents or incidents in any industrial environment [14]. Human actions were the element of rescue that brought the situation under control during the blackout of Viking Sky in Hustadvika, Norway [15]. This is a clear indication that humans can be a positive safety tool to respond to unwanted situations if their capabilities are enhanced.

2. The Contribution of This Paper

The study will generally contribute to the enhancement of maritime safety vis-à-vis the use of alternative fuels in ship propulsion, focusing on the human corrective response to uncertainties and integrating human reliability assessment with equipment reliability. A developed and robust human–equipment reliability framework by applying the Cognitive Reliability and Error Analysis Method (CREAM) was used to assess human reliability in cognitive response to uncertainties within the bunkering process and to critically examine how the best equipment reliability influences human decision-making.

This paper will bridge the research gap by addressing the lack of studies on the interaction between human corrective actions and equipment reliability in the hydrogen bunkering process, creating platforms for improving training, contributing to policy development, and regulations. This study will also enhance resilience, ensuring that both human and equipment work together to mitigate uncertainties and risks.

The overall impact of this is to provide empirical data and recommendations for policy makers and maritime stakeholders in the hydrogen bunkering process.

Hydrogen Bunkering Procedure

Proper procedural steps will greatly enhance safety during the bunkering operation of hydrogen. One of the greatest risks in hydrogen bunkering is leakage, which can be caused by equipment fault, operational fault, and procedural fault [16]. The loading of hydrogen into a fuel tank to be used onboard the ship for propulsion is different from the loading of HFO because it can be influenced by both temperature and pressure changes. Hydrogen is a cryogenic liquid at a temperature of about (−253 °C), making it highly brittle if it encounters equipment or personnel unsafely. Its storage in tanks and transportation through pipes and hoses posed a great risk to safety.

However, hydrogen embrittlement can be prevented using proper material selection and better welding techniques on the technical requirements of engineers [17].

Hydrogen may share some similarities with that of LNG in general areas of bunkering operation, but when it comes to filling, the situation is different because of the smaller molecules of hydrogen. These smaller molecule sizes of hydrogen place a high potential for leakage. Therefore, there is a need to be more cautious, considering ship-to-shore bunkering operation.

Figure 1 indicates the sequential step-by-step process of the hydrogen bunkering operation, discussing the transferring of hydrogen fuel to be used on a ship. However, the interest of this study is to carry out human reliability analysis on human corrective response actions. The operational procedures will benchmark for human corrective response actions.

3. Methodology

This study is described as a scissors approach as a metaphoric concept of considering the reliability of both human and equipment jointly in response to uncertainties. Scissors have two blades to cut and groom. Using scissors as a metaphor emphasizes that both equipment and human reliability are interdependent in the hydrogen bunkering operation and even in response to uncertainties.

The methodology of this study follows a suitable step-by-step approach.

The first step is to identify the possible incidents/accidents that might occur during the hydrogen bunkering operation. The next step is to critically look at, if such an incident occurs, what will the response of personnel be? The overview of the methodology is considered below:

Figure 2 is a flowchart to address human response to uncertainties in hydrogen bunkering by analyzing both human response actions and equipment behaviour, quantifying their individual and combined reliability, applying corrective measures based on data-driven insights, and ensuring a feedback loop for ongoing safety and performance enhancement. The integrated approach is critical for hydrogen operations, where both human judgement under pressure and equipment integrity under extreme conditions must be highly reliable, where response to uncertainties is a vital aspect to enhance safety in critical maritime operations.

3.1. Marine Case

The approach of the study is firstly to consider a marine case based on global maritime needs. This time, the hydrogen bunkering operation was of the greatest interest because of the global maritime need to decarbonize emissions from ships. The shipping industry alone accounts for approximately 2–3% of global gas emissions [18]. Contributing to the safe handling of hydrogen will enhance its use as a marine fuel due to the promising nature of hydrogen compared to other alternative fuels. It will be a great breakthrough in the maritime industry if hydrogen is safely used as a fuel for ship propulsion. There are several reasons of importance for considering hydrogen bunkering as a case study. It is a very promising emerging fuel, contributing to infrastructural development, enhanced safety regulations, technological innovation, and enhanced economic and operational feasibility.

3.2. Problem Definition

This phase clearly involved identifying safety challenges faced in the hydrogen bunkering process. The problem definition clearly outlines key challenges faced during the operation and is important for a detailed task analysis. This picture is of safety concerns, storage and transportation, environmental impact, and creative insights in response to uncertainties. Clearly defining the problem will improve the hydrogen bunkering process. A study was conducted to gain deep knowledge into risk levels associated with the bunkering operation of LNG and LH2, quantifying potential risks such as explosion and fire [19]. Cautious safety precautions must be adhered to during bunkering operations to prevent such risks. In addition to this, a human reliability analysis to establish a safe ship-to-ship bunkering operation was carried out under D-S evidence fusion HEART [20].

3.3. Task Analysis

A proper task analysis was carried out to break down the hydrogen bunkering operation into steps where potential uncertainties may arise, such as leaks. From the task analysis, possible human corrective actions in response to identified uncertainties were developed. The task analysis also helps in optimizing safety standard operating procedures, which leads to better decision-making. The first step was to develop the procedure for the hydrogen bunkering operation, and later, to critically look at the possible human response to such uncertainties in each node. This enhances response decision-making.

Figure 3 outlines a logical flow of human decision-making during hydrogen bunkering.

• Operational Procedures of a Task: This represents the standard operating procedures (SOPs) involved in hydrogen bunkering: Connecting and disconnecting fuel lines, pressure and leak checks, ventilation protocols, and emergency shut-off readiness. These procedures are predefined and should be followed strictly by operators. A clear understanding and execution of tasks reduces human error and enhances safety.
• Identifying Potential Uncertainties: Here, operators must recognize possible deviations or unexpected conditions during the operation, such as the following: Sudden pressure drops or surges, the detection of minor hydrogen leaks, sensor malfunctions, or alarm failures. These uncertainties might not indicate immediate danger but can escalate if not managed. Early identification allows pre-emptive responses rather than reactive crisis management.
• Possible Human Corrective Responses: Based on the identified uncertainties, trained personnel may adjust the flow rate or pressure, pause or stop the operation, isolate a section of the system, initiate an emergency shutdown, notify the control room, or initiate evacuation if required.

The task analysis creates a better pathway to understand and deduce the corrective human responses, leading to the creation of a safety table showing possible human corrective responses to uncertainty such as leaks. The safety table can be expanded further to include more possible human corrective interventions. Structuring a safety table can provide systematic risk identification, enhanced decision-making, easy response time, and the proactive management of uncertainties.

Table 1. Safety table shows possible human actions and potential hazards.

TASK	Bunkering Operation	Human Actions	Possible Hazards
1	Hose/loading arm connection	Establish hose connection	Possible hose misalignment
2	Inert bunker lines, hoses, pumps	Start inert of lines and cargo pump with nitrogen	Possible wrong opening of inert gas line valves
3	Purging of lines	Start purging of lines with hydrogen vapour	Possible valve lines damaged
4	Filling of receiver tank with hydrogen	Open manual bunker valves on both sides	I. Possible misinterpretation of gauges or indicators II. Possible tank overfilling
5	Completion of transfer capacity	Verify required quantity	Possible tank overfilling
6	Draining of lines	Ensure liquid line stripping	Possible switch button failure
7	Purging of lines after completion	Purge lines with hydrogen vapour	Possible loss of valve connection
8	Inert lines after completion of bunkering	Ensure supply of inert gas (nitrogen)	Possible confusion of nitrogen with other gases
9	Hose/loading arm disconnection	Ensure proper disconnection	Possible hose misalignment

gives an overview of the possible operational steps in the bunkering process, identifying possible human actions and human corrective response actions. The human corrective actions are possible human responses to restore the bunkering process to an operational state if any unwanted incident occurs.

Table 2. Safety table showing possible human corrective response actions.

Causes	Consequences	Preventive Measures	Human Corrective Response Actions (HCRAs)
Improper assembly; not correctly matching hose with fitting	Hose rupture	Take care not to bend the hose beyond the minimum bend radius (MBR)	Ensure to replace the hose assembly
Lack of coordination among crew	Potential leakage	Proper communication	Proper labelling of inert gas lines, hoses, and gas cylinders
Possible wrong closing and opening of valves	Potential leakage	Use proper equipment such as valves and fittings	I. Activate the emergency shutdown system on both sides II. Identify and repair the source of the leak
I. Poor visibility or lighting II. Lack of standardization or calibration	Potential leakage	Ensure adequate illumination	Replace faulty lighting, gauges, and indicators
Failing to check level of hydrogen in both tanks	Potential leakage	Proper communication	Determine the maximum filling limit for the hydrogen fuel tanks
Mechanical or electrical failure of the switch button	Potential leakage	Regular inspection and maintenance	Activate emergency shutdown system (ESD)
Possible wrong closing and opening of valves	Potential leakage	Proper watchkeeping	Initiate emergency shutdown system (ESD)
Connecting the wrong hose to the nitrogen supply line	Potential gas leakage	Use dedicated hoses for nitrogen supply	Clearly label the inert gas line, gas cylinders, and hoses
Lack of supervision	Potential hose rupture	Hose should not be dragged over rough surfaces	I. Replace the hose assembly II. Complete a planning stage checklist

is part of Table 1; it is an overview of the possible causes, consequences, and most importantly, possible human corrective response actions during the bunkering operation of hydrogen. These tables give room for the inclusion of more possible human corrective response actions.

3.4. Human Error Analysis

This was to critically look at the points of possible human errors in the hydrogen bunkering operation. The point of interest is to identify possible human errors in the human corrective responses. A proper human error analysis was carried out involving maritime experts with more than 10 to 15 years of working experience onboard the ship as crew. To ensure a proper analysis of the hydrogen bunkering operation and human response to actions to uncertainties, the CREAM HRA was adopted with the use of eight maritime experts in the study, amongst whom are five maritime officers in key roles such as Captains of a ship, Chief Engineers, and Chief Officers. Their in-depth experience helps in analyzing the bunkering operation. They also help in identifying sub-tasks and common performance challenges. Additionally, three certified human reliability analysis experts helped in this study, with specified knowledge on the application of CREAM methodology. They systematically contributed to the interpretation of control modes and clearly rated the common performance conditions (CPCs). The whole process was achieved through diverse expert workshops, semi-structured interviews, and visiting maritime companies. Detailed operational insights about the bunkering operation were provided by the experienced onboard maritime experts while the HRA practitioners supervised the use of the CREAM.

Identifying human involvement in the operation: First, applying a CREAM which is a second-generation HRA method, in identifying possible human errors during human corrective actions. Thereafter, gathering data on equipment reliability from standardized maritime industries. Secondly, integrating marine equipment reliability data into the human error probability values, and from there, drawing possible conclusions and possible recommendations.

3.5. The Screening Phase

Screening was performed in the task analysis to identify high-risk decision points in the cognitive human response to uncertainties during the hydrogen bunkering process. Points where the emergency shutdown system is employed become very vital areas to pay serious attention to; in other words, where more human errors are likely to occur. This creates a platform to ensure that the safety-critical task receives the most attention. The screening phase, in a nutshell, supports detailed proactive cognitive responses in a situation of the occurrence of uncertainties. The screening creates a pathway to quantify possible human errors. It is like a stethoscope, used to map out possible human errors where they are more likely to occur. This guides quantification.

3.6. Quantification

To quantify human error during cognitive responses, the application of the Cognitive Reliability and Error Analysis became so useful. The CREAM is solely applied to the response actions, not to the operational procedure of the bunkering operation.

By quantifying the human error in the response actions, it better estimates the likelihood and impact of potential failures. This gives room for accurate prediction and proactive risk management.

The following parameters were used in their abbreviated form for mathematical representation in this study:

CFP: Adjusted cognitive failure probability (modified estimate of the likelihood that a person will experience a cognitive failure while performing a task).

ERDo: Nominal equipment reliability data (quantitative or qualitative information that describes how reliable a piece of equipment is over time).

EFP: Adjusted equipment failure probability (the probability or chance that a specific piece of equipment will fail to perform its intended function within a given time frame).

HCMs: Human corrective measures (actions taken by humans—operators, technicians, or supervisors—to correct, mitigate, or recover from abnormal or unsafe situations in a system or process).

CFPo: Nominal cognitive failure probability (probability that a human will experience a cognitive failure while performing a specific task under standard or ideal conditions).

W.F: Weighting factor (used to adjust cognitive or equipment failure probabilities based on influencing conditions).

MTBF: Mean time between failure (average time elapsed between one failure of a system or piece of equipment and the next failure during normal operation).

MTTF: Mean time to failure (used for non-repairable items; unlike MTBF, which applies to repairable systems, MTTF is for devices or parts that are replaced after failure rather than repaired).

TCPC: Total influence of CPC on cognitive functions (combined or overall effect that CPC has on cognitive functions).

FFP: Final failure probability (overall probability that a system, component, or process will fail after considering all relevant factors and adjustments).

3.7. Human Error Probability (HEP)

The human corrective response involves a more cognitive nature. The human error probability phase clearly explains in detail how the response involves elements of human error probability. The cognitive failure probability (CFP) is a subset of human error probability (HEP). However, the human cognitive response actions are directly married to cognitive reliability, involving reacting to dynamic and interpreting complex situations, a better thinking process, reasoning, and judgement in the response actions during uncertainties in the hydrogen bunkering operation. This links the quantification phase to the cognitive interpretation of the response actions of the hydrogen bunkering operation.

3.8. Collection of Data from the Maritime Industry

Conducting of interviews and surveys and organizing of expert panel discussions were carried out. Gathering data from standard maritime organizations to understand detailed information about the bunkering process was performed using the LNG bunkering process as a benchmark. A map of expert stakeholders, such as operators, engineers, maritime crew, and regulatory authorities, to ensure comprehensive coverage was created. The specialized knowledge possessed by the maritime experts in ship operations provides insights into a better understanding of the bunkering process.

3.9. Application of Statistics to Determine the Failure Rate of Equipment

This is to determine the failure rate of the critical equipment used in the human corrective response to uncertainties during the bunkering process of hydrogen, giving room to proper predictive maintenance by focusing on equipment with higher failure risks, and understanding how equipment functions is a better way to manage it. The collection of historical data from maritime organizations concerning the failure rate of equipment during the bunkering process was performed. Descriptive statistics to calculate the Mean Time Between Failures (MTBF), Mean Time to Repair (MTTR), Failure Frequency, and rate. Also, the failure rate estimation, can be expressed as Failure rate = Number of failures/Total operating time:

$$\mathsf{\lambda }=\mathrm{n}/\mathrm{T}$$

(1)

where

λ = Failure rate;

n = Number of failures;

T = Total operational time.

Also, to determine the average time between the consecutive failures of this equipment, we consider the Mean Time Between Failures (MTBF).

MTBF = Total Operating Time/Number of Failures

A higher MTBF shows greater reliability and a lower MTBF shows frequent failures. This will guide in the maintenance activities of the whole system.

The relationship between the MTBF and the failure rate gives an overview of predicting and improving the performance of human response to any uncertainties during the bunkering operation. This relationship is mathematically defined as

$$\mathsf{\lambda }={\displaystyle \frac{1}{\mathrm{M}\mathrm{T}\mathrm{B}\mathrm{F}}}$$

(2)

Here, MTBF represents the average time between two consecutive failures for repairable systems or equipment. For non-repairable systems, this metric is referred to as Mean Time To Failure (MTTF), indicating the average operational time before failure.

The failure rate (λ), expressed in failures per hour, reflects the constant likelihood of failure over time for systems that follow an exponential distribution of failures.

Understanding this relationship supports the broader concept of reliability, particularly in the context of safety and risk mitigation during bunkering operations. This includes aspects such as system design and redundancy, equipment maintenance, and response planning.

The reliability function, denoted as R(t), describes the probability that a system or component will perform its intended function without failure up to time, t. It is defined as

$$\mathrm{R}\left(\mathrm{t}\right)=1-\mathrm{F}\left(\mathrm{t}\right)$$

(3)

where $\mathrm{F}\left(\mathrm{t}\right)$ is the cumulative distribution function representing the probability of failure by time $\mathrm{t}$. Thus, reliability is interpreted as one minus the probability of failure.

Further analysis was conducted using reliability data obtained from standard maritime industry sources, aligning with the above reliability functions to evaluate and improve system response effectiveness during bunkering operations.

3.10. Integrating the Cognitive Failure Probability with Equipment Reliability

This was the aspect of the study where both human and equipment functions were considered together in response actions during the bunkering operation of hydrogen. A decrease in the probability of cognitive failure is an increase in human performance. To enhance human performance in cognitive human actions, it was necessary to integrate equipment reliability. The weighting factor differentiates the impact of the various CPCs on human reliability; considering the same impact on equipment reliability, we could have a final reliability value as

$$\mathrm{F}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{S}\mathrm{u}\mathrm{c}\mathrm{c}\mathrm{e}\mathrm{s}\mathrm{s} \mathrm{P}\mathrm{r}\mathrm{o}\mathrm{b}\mathrm{a}\mathrm{b}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{y}=\left(1-\mathrm{C}\mathrm{F}\mathrm{P}\right)\times (1-\mathrm{E}\mathrm{F}\mathrm{P})$$

(4)

$$\mathrm{F}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{F}\mathrm{a}\mathrm{i}\mathrm{l}\mathrm{u}\mathrm{r}\mathrm{e} \mathrm{P}\mathrm{r}\mathrm{o}\mathrm{b}\mathrm{a}\mathrm{b}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{y}=1-(\left(1-\mathrm{C}\mathrm{F}\mathrm{P}\right)\times \left(1-\mathrm{E}\mathrm{F}\mathrm{P}\right))$$

(5)

where (1 − CFP) is the probability that the human operator makes no cognitive error and (1 − EFP) is the probability that the equipment works as intended, meaning the equipment does not fail.

The combination of the two indicates that both the equipment and the human operator work successfully in the operation without failure. Their product gives better risk management as organizations will focus their attention on looking out for both human and equipment more intentionally.

There is no ideal human, and equipment does fail as well. Also, the relationship between the operational time of each piece of equipment and of reliability can be determined using reliability functions, assuming a constant failure rate:

$$\mathrm{R}(\mathrm{t})={\mathrm{e}}^{-\mathsf{\lambda }\mathrm{t}}$$

(6)

where R(t) is defined as the reliability at time, t. Lambda defines the constant failure rate, regarding failures per unit time, and t is the operational time.

Using equipment reliability data from the maritime industry and failure rate, the operational time can also be mathematically calculated, assuming a constant failure rate, placing the target on a particular level of reliability:

$$\mathrm{t}=\ln \left(\mathrm{R}\right)/\mathsf{\lambda }$$

(7)

3.11. Application of More Corrective Actions

Further corrective actions were carried out to further reduce any identified errors both on equipment and human involvement. This gives room for continuous monitoring to improve the overall system, such as continuous routine checks, implementing preventive maintenance after a rescue mission. The whole process can serve as quality assurance and documentation for both industrial output and stakeholders.

4. Case Study

4.1. Application of the CREAM HRA to the Human Corrective Actions of the Hydrogen Bunkering Operation

The Basic CREAM is applied in determining the control mode of the operator. The contextual influence index provides a structural way of evaluating the common performance conditions on the mode of the operator quantitatively.

Determining the weighting factor will help to identify the total influence of CPC on the cognitive functions (TCPC) of the operational task, placing humans as the major decision-makers for other human(s) and equipment involved in the process. The same weighting factor is applied to equipment reliability data to evaluate the whole operation. Weighting factor (W.F) = Total influence of CPC on cognitive functions (TCPC).

$$\mathrm{W}.\mathrm{F}=\mathrm{T}\mathrm{C}\mathrm{P}\mathrm{C}$$

(8)

Applying the extended CREAM is performed to determine the cognitive failure probability (CFP), which is considered the human error probability (HEP) in the CREAM. Cognitive failure probability is the weighted factor.

$$\mathrm{C}\mathrm{F}\mathrm{P}=\mathrm{W}.\mathrm{F}\times \mathrm{C}\mathrm{F}\mathrm{P}\mathrm{o}$$

(9)

$$\mathrm{E}\mathrm{F}\mathrm{P}=\mathrm{W}.\mathrm{F}\times \mathrm{E}\mathrm{R}\mathrm{D}\mathrm{o}$$

(10)

4.2. Event Sequence of the Human Corrective Measures of the Hydrogen Bunkering Process

• Replace the hose assembly.
• Properly label the inert gas line and hoses.
• Activate the emergency shutdown system (ESD).
• Identify and repair the source of the leak.
• Replace faulty lighting, gauges, and indicators.
• Determine the maximum filling limit of the tank.
• vii. Complete a planning stage checklist.

Figure 4 provides a simplified but essential framework showing that human reliability in hydrogen bunkering depends not just on task execution, but on the ability to

Detect deviations → Evaluate them → Respond appropriately.

This sequence feeds into broader human reliability analysis (HRA) and supports the development of risk mitigation strategies and corrective procedures in hydrogen-fueled maritime systems, giving room for more inputs to enhance safety.

Table 3. Hierarchical corrective task analysis for the hydrogen bunkering operation.

Task Number	Corrective Goal Intended	Task Step/Activity
0.1.1	Replace the hose assembly	Stop the H2 transfer immediately and activate the ESD.
0.1.2		Ensure to isolate the ruptured hose from the supply source.
0.1.3		Vent the residual H2 from the ruptured hose to a safe location or flare system.
0.1.4		Replace with a spare hose that has been tested and inspected.
0.1.5		Ensure all connections and resume the H2 transfer.
0.2.1	Properly label the inert gas line and hoses	Clearly mark the lines and hoses as INERT GAS with a contrasting colour and suitable size.
0.2.2		Colour-code the inert gas lines and hoses according to the defined system.
0.2.3		Ensure that hoses and gas lines have compatible couplings distinct from the H2 couplings.
0.2.4		Test inert gas lines and hoses regularly for leaks and contamination.
0.3.1	Activate the emergency shutdown system (ESD)	Press the ESD push button placed in strategic places.
0.3.2		Ensure the manual activation of the ESD.
0.3.3		Ensure that the automatic activation closes the transfer valves and pumps, releases the ERC, and opens the vent valves.
0.4.1	Identify and repair the source of the leak	Monitor for gas leakage using appropriate detection systems—pressure sensors and gas detectors.
0.4.2		Ensure stoppage of the whole transfer process and initiate repair following safety protocols and emergency procedures.
0.5.1	Replace faulty lighting, gauges, and indicators	Ensure replacement before the start of bunkering.
0.5.2		Replace using appropriate tools and spares.
0.5.3		Ensure that the new components are compatible and functional.
0.6.1	Determine the maximum filling limit of the tank	Ensure the maximum allowable liquid volume that the tank may be loaded with.
0.6.2		Ensure appropriate loading density at the loading temperature and reference temperature.
0.6.3		Monitor the maximum filling limit using appropriate instruments: pressure gauge, level gauge, etc.
0.7.1	Complete a planning stage checklist	Ensure to complete the checklist when placing a bunker order.
0.7.2		Include all necessary information about the bunker and safety procedures.

is developed as a goal-oriented safety table that outlines procedural steps aimed at improving human reliability in hydrogen bunkering operations. It is specifically structured to link corrective human actions with their corresponding cognitive activities, such as attention, perception, decision-making, and memory recall. This approach helps identify how humans respond during abnormal or uncertain conditions and what mental functions are activated to carry out corrective tasks. Ultimately, this table serves not only as a procedural guide but also as a human factor tool to enhance situational awareness.

Table 4. Common performance conditions of the human corrective actions in the hydrogen bunkering operation.

CPC	Evaluation of the CPC of the Hydrogen Bunkering Operation (Corrective Actions)	CPC and Performance Reliability
Adequacy of the organization	Efficient	Not significant
Adequacy of MMI and operational support	Adequate	Not significant
Working conditions	Compatible	Not significant
Availability of procedures/plans	Acceptable	Improved
Number of simultaneous goals	Matching current capacity	Not significant
Available time	Adequate	Improved
Time of day (circadian rhythm); daytime	Adjusted	Not significant
Adequacy of training and experience	Adequate, limited experience	Reduced
Crew collaboration quality	Very efficient	Improved

explains the influence of the common performance conditions (CPCs) on human performance in the response actions during the bunkering operation of hydrogen. The adequate management of the CPCs is pivotal in minimizing risks and will give room for improvement. Considering human corrective response actions, Table 4 presents the evaluation of the common performance conditions (CPCs) in relation to the corrective actions during the hydrogen bunkering operations. The CPC ratings were estimated based on expert judgements. The gathering of information through expert judgements was through a series of structured workshops, seminars, and semi-structured interviews with a panel of eight experts (five of them as maritime professionals and three others as HRA specialists). The process followed CREAM guidelines, where each CPC was rated (efficient, adequate, acceptable) and the impact on human performance reliability was interpreted—not significant, improved, or reduced.

• Considering the CPCs in Table 2 and Figure 5:
• ∑reduced = 1 ∑Not significant = 5 ∑Improved = 3 = (1, 5, 3).
• Figure 5 clearly indicates the tactical mode.

Figure 5 shows the CPC profiles of (1, 5, 3). As per Hollnagel’s model, this maps to tactical control mode. The CPC combination clearly corresponds to the “tactical mode”, where actions are primarily goal-oriented and responsive. There is some planning but not full strategic foresight due to one reduced CPC. Tactical mode is characterized by targeted, responsive behaviour, which is common in complex but semi-stable operations like hydrogen bunkering, where some uncertainties exist, but most performance conditions are acceptable or improved.

Figure 5. Relations between CPC score and control modes (Hollnagel, 1998 [6]).

Figure 5. Relations between CPC score and control modes (Hollnagel, 1998 [6]).

Table 5. Reliability interval (probability of action failure) of the corrective actions in the hydrogen bunkering operation.

Control Modes	Reliability Interval (Probability of Action Failure)
Strategic	0.000005 < p < 0.01
Tactical	0.001 < p < 0.1 (1, 5, 3)
Opportunistic	0.01 < p < 0.5
Scrambled	0.1 < p < 1.0

shows the control modes of the human operator and the probability interval of the bunkering of hydrogen and the reliability interval. It better explains human decision-making and the execution of safe operations. The control modes—ranging from strategic to opportunistic—represent the levels of human cognitive control and adaptability under varying conditions of certainty and time pressure. By mapping these modes to reliability data, the table offers a deeper understanding of how human decision-making evolves in response to operational demands, equipment conditions, and the presence of uncertainties.

Table 6. Applying the extended CREAM to produce specific action failure probabilities.

Task Number	Corrective Goal Intended	Task Step	Cognitive Activities
0.1.1	Replace the hose assembly	Stop the hydrogen transfer immediately and activate the ESD	Execute
0.1.2		Ensure to isolate the ruptured hose from the supply source	Coordinate
0.1.3		Vent the residual hydrogen from the ruptured hose to a safe location or flare system	Execute
0.1.4		Replace with a spare hose that has been tested and inspected	Execute
0.1.5		Ensure all connections and resume the hydrogen transfer	Execute
0.2.1	Properly label the inert gas line and hoses	Clearly mark the lines and hoses as INERT GAS with a contrasting colour and suitable size	Plan
0.2.2		Colour-code the inert gas lines and hoses according to the defined system	Execute
0.2.3		Ensure that hoses and gas lines have compatible couplings distinct from the hydrogen couplings	Verify
0.2.4		Test inert gas lines and hoses regularly for leaks and contamination	Monitor
0.3.1	Activate the emergency shutdown system (ESD)	Press the ESD push button placed in strategic places	Execute
0.3.2		Ensure the manual activation of the ESD	Verify
0.3.3		Ensure that the automatic activation closes the transfer valves and pumps, releases the ERC, and opens the vent valves	Verify
0.4.1	Identify and repair the source of the leak	Monitor for gas leakage using appropriate detection systems—pressure sensors and gas detectors	Monitor
0.4.2		Ensure stoppage of the whole transfer process and initiate repair following safety protocols and emergency procedures	Verify
0.5.1	Replace faulty lighting, gauges, and indicators	Ensure replacement before the start of bunkering	Verify
0.5.2		Replace using appropriate tools and spares	Execute
0.5.3		Ensure that the new components are compatible and functional	Verify
0.6.1	Determine the maximum filling limit of the tank	Ensure the maximum allowable liquid volume that the tank may be loaded with	Evaluate
0.6.2		Ensure appropriate loading density at the loading temperature and reference temperature	Evaluate
0.6.3		Monitor the maximum filling limit using appropriate instruments: pressure gauge, level gauge, etc.	Monitor
0.7.1	Complete a planning stage checklist	Ensure to complete the checklist when placing a bunker order	Verify
0.7.2		Include all necessary information about the bunker and safety procedures	Execute

clearly identifies the cognitive activities involved in the hydrogen bunkering operation that are essential for enhancing safety and reduction in errors. Execution, as a cognitive activity, appears to be the most demanding in the bunkering operation, being more dependent on paying attention, working memory, and motor planning. This also demonstrates the carrying out of the planned steps to complete a task.

Table 7. Cognitive demand table of the corrective actions in the hydrogen bunkering operation.

Task	Task Step	Cognitive Activity	Observation	Interpretation	Planning	Execution
0.1.1	Stop the hydrogen transfer immediately and activate the ESD	Execute				√
0.1.2	Ensure to isolate the ruptured hose from the supply source	Coordinate			√
0.1.3	Vent the residual hydrogen from the ruptured hose to a safe location or flare system	Execute				√
0.1.4	Replace with a spare hose that has been tested and inspected	Execute				√
0.1.5	Ensure all connections and resume the hydrogen transfer	Execute				√
0.2.1	Clearly mark the lines and hoses as INERT GAS with a contrasting colour and suitable size	Plan			√
0.2.2	Colour-code the inert gas lines and hoses according to the defined system	Execute				√
0.2.3	Ensure that hoses and gas lines have compatible couplings distinct from the hydrogen couplings	Verify	√
0.2.4	Test inert gas lines and hoses regularly for leaks and contamination	Monitor	√
0.3.1	Press the ESD push button placed in strategic places	Execute				√
0.3.2	Ensure the manual activation of the ESD	Verify	√
0.3.3	Ensure that the automatic activation closes the transfer valves and pumps, releases the ERC, and opens the vent valves	Verify	√
0.4.1	Monitor for gas leakage using appropriate detection systems—pressure sensors and gas detectors	Monitor	√
0.4.2	Ensure stoppage of the whole transfer process and initiate repair following safety protocols and emergency procedures	Verify	√
0.5.1	Ensure replacement before the start of bunkering	Verify	√
0.5.2	Replace using appropriate tools and spares	Execute				√
0.5.3	Ensure that the new components are compatible and functional	Verify	√
0.6.1	Ensure the maximum allowable liquid volume that the tank may be loaded with	Evaluate			√
0.6.2	Ensure appropriate loading density at the loading temperature and reference temperature	Evaluate			√
0.6.3	Monitor the maximum filling limit using appropriate instruments: pressure gauge, level gauge, etc.	Monitor	√
0.7.1	Ensure to complete the checklist when placing a bunker order	Verify	√
0.7.2	Include all necessary information about the bunker and safety procedures	Execute				√

identifies the relationship between the cognitive activities and four cognitive processes, such as observation, interpretation, planning, and execution. This can also be used as a training tool. The table outlines the cognitive workload required of the operator during human corrective actions in hydrogen bunkering operations. It establishes a clear relationship between key cognitive activities and the four fundamental cognitive processes: observation, interpretation, planning, and execution. These processes collectively determine how effectively an operator perceives, understands, responds to, and manages unexpected events or operational uncertainties. By mapping each corrective task to its associated cognitive demands, the table provides insight into the mental load and decision-making complexity involved in critical safety functions.

Table 8. Credible corrective failure modes in the hydrogen bunkering operation.

Task Number	Cognitive Activity	Observation			Interpretation			Planning		Execution
		O1	O2	O3	I1	I2	I3	P1	P2	E1	E2	E3	E4	E5
0.1.1	Execute										√
0.1.2	Coordinate								√
0.1.3	Execute									√
0.1.4	Execute											√
0.1.5	Execute									√
0.2.1	Plan								√
0.2.2	Execute											√
0.2.3	Verify		√
0.2.4	Monitor			√
0.3.1	Execute											√
0.3.2	Verify					√
0.3.3	Verify			√
0.4.1	Monitor			√
0.4.2	Verify	√
0.5.1	Verify		√
0.5.2	Execute											√
0.5.3	Verify					√
0.6.1	Evaluate						√
0.6.2	Evaluate					√
0.6.3	Monitor			√
0.7.1	Verify		√
0.7.2	Execute													√

presents a pathway linking cognitive activities to potential operator error modes during hydrogen bunkering operations. By tracing how failures in observation, interpretation, planning, or execution can lead to specific error modes, the table provides a structured view of how cognitive breakdowns manifest in operational tasks.

Identifying these failure modes offers a proactive approach to error management, enabling targeted interventions such as task redesign, procedure revision, or enhanced training.

Table 9. Couplings between CPCs and cognitive processes with error mode and nominal CFP.

Task Number	Cognitive Activity	COCOM Function	Error Mode	Nominal CFP
0.1.1	Execute	Execution	E2: Action at wrong time	3.0E−3
0.1.2	Coordinate	Planning	P2: Inadequate plan	1.0E−2
0.1.3	Execute	Execution	E1: Action of wrong type	3.0E−3
0.1.4	Execute	Execution	E3: Action on wrong object	5.0E−4
0.1.5	Execute	Execution	E1: Action of wrong type	3.0E−3
0.2.1	Plan	Planning	P2: Inadequate plan	1.0E−2
0.2.2	Execute	Execution	E3: Action on wrong object	5.0E−4
0.2.3	Verify	Observation	O2: Wrong identification	7.0E−2
0.2.4	Monitor	Observation	O3: Observation not made	7.0E−2
0.3.1	Execute	Execution	E3: Action on wrong object	5.0E−4
0.3.2	Verify	Interpretation	I2: Decision error	1.0E−2
0.3.3	Verify	Observation	O3: Observation not made	7.0E−2
0.4.1	Monitor	Observation	O3: Observation not made	7.0E−2
0.4.2	Verify	Observation	O1: Wrong object observed	1.0E−3
0.5.1	Verify	Observation	O2: Wrong identification	7.0E−2
0.5.2	Execute	Execution	E3: Action on wrong object	5.0E−4
0.5.3	Verify	Interpretation	I2: Decision error	1.0E−2
0.6.1	Evaluate	Interpretation	I3: Delayed interpretation	1.0E−2
0.6.2	Evaluate	Interpretation	I2: Decision error	1.0E−2
0.6.3	Monitor	Observation	O3: Observation not made	7.0E−2
0.7.1	Verify	Observation	O2: Wrong identification	7.0E−2
0.7.2	Execute	Execution	E5: Missed action	3.0E−2

explains the relationship between common performance conditions (CPCs), cognitive processes, error modes, and nominal cognitive failure probabilities. This describes how each cognitive process is associated with a specific error mode and how internal and external factors influence human performance in the hydrogen bunkering process.

Table 10. Assessment of the effects of CPCs on cognitive function corrective failures (Task 1).

CPC	Level	T0.1.1	T0.1.2	T0.1.3	T0.1.4	T0.1.5
		E2	P2	E1	E3	E1
Adequacy of the organization	Efficient	1.0	1.0	1.0	1.0	1.0
Adequacy of MMI and operational support	Adequate	1.0	1.0	1.0	1.0	1.0
Working conditions	Compatible	1.0	1.0	1.0	1.0	1.0
Availability of procedures/plans	Acceptable	1.0	1.0	1.0	1.0	1.0
Number of simultaneous goals	Matching current capacity	1.0	1.0	1.0	1.0	1.0
Available time	Adequate	0.5	0.5	0.5	0.5	0.5
Time of day (circadian rhythm); day time	Adjusted	1.0	1.0	1.0	1.0	1.0
Adequacy of training and experience	Adequate, limited experience	1.0	1.0	1.0	1.0	1.0
Crew collaboration quality	Very efficient	0.5	0.5	0.5	0.5	0.5
Total influence of CPC		0.25	0.25	0.25	0.25	0.25

,

Table 11. Assessment of the effects of CPCs on cognitive function corrective failures (Task 2).

CPC	Level	T0.1.1	T0.1.2	T0.1.3	T0.1.4
		P2	E3	O2	O3
Adequacy of the organization	Efficient	1.0	1.0	1.0	1.0
Adequacy of MMI and operational support	Adequate	1.0	1.0	1.0	1.0
Working conditions	Compatible	1.0	1.0	1.0	1.0
Availability of procedures/plans	Acceptable	1.0	1.0	1.0	1.0
Number of simultaneous goals	Matching current capacity	1.0	1.0	1.0	1.0
Available time	Adequate	0.5	0.5	0.5	0.5
Time of day (circadian rhythm); day time	Adjusted	1.0	1.0	1.0	1.0
Adequacy of training and experience	Adequate, limited experience	1.0	1.0	1.0	1.0
Crew collaboration quality	Very efficient	0.5	0.5	0.5	0.5
Total influence of CPC		0.25	0.25	0.25	0.25

,

Table 12. Assessment of the effects of CPCs on cognitive function corrective failures (Task 3).

CPC	Level	T 0.3.1	T 0.3.2	T 0.3.4
		E3	I2	O3
Adequacy of the organization	Efficient	1.0	1.0	1.0
Adequacy of MMI and operational support	Adequate	1.0	1.0	1.0
Working conditions	Compatible	1.0	1.0	1.0
Availability of procedures/plans	Acceptable	1.0	1.0	1.0
Number of simultaneous goals	Matching current capacity	1.0	1.0	1.0
Available time	Adequate	0.5	0.5	0.5
Time of day (circadian rhythm); day time	Adjusted	1.0	1.0	1.0
Adequacy of training and experience	Adequate, limited experience	1.0	1.0	1.0
Crew collaboration quality	Very efficient	0.5	0.5	0.5
Total influence of CPC		0.25	0.25	0.25

,

Table 13. Assessment of the effects of CPCs on cognitive function corrective failures (Task 4).

CPC	Level	T 0.4.1	T 0.4.2
		O3	O1
Adequacy of the organization	Efficient	1.0	1.0
Adequacy of MMI and operational support	Adequate	1.0	1.0
Working conditions	Compatible	1.0	1.0
Availability of procedures/plans	Acceptable	1.0	1.0
Number of simultaneous goals	Matching current capacity	1.0	1.0
Available time	Adequate	0.5	0.5
Time of day (circadian rhythm); day time	Adjusted	1.0	1.0
Adequacy of training and experience	Adequate, limited experience	1.0	1.0
Crew collaboration quality	Very efficient	0.5	0.5
Total influence of CPC		0.25	0.25

,

Table 14. Assessment of the effects of CPCs on cognitive function corrective failures (Task 5).

CPC	Level	T 0.5.1	T 0.5.2	T 0.5.3
		O2	E3	I2
Adequacy of the organization	Efficient	1.0	1.0	1.0
Adequacy of MMI and operational support	Adequate	1.0	1.0	1.0
Working conditions	Compatible	1.0	1.0	1.0
Availability of procedures/plans	Acceptable	1.0	1.0	1.0
Number of simultaneous goals	Matching current capacity	1.0	1.0	1.0
Available time	Adequate	0.5	0.5	0.5
Time of day (circadian rhythm); day time	Adjusted	1.0	1.0	1.0
Adequacy of training and experience	Adequate, limited experience	1.0	1.0	1.0
Crew collaboration quality	Very efficient	0.5	0.5	0.5
Total influence of CPC		0.25	0.25	0.25

,

Table 15. Assessment of the effects of CPCs on cognitive function corrective failures (Task 6).

CPC	Level	T 0.6.1	T 0.6.2	T 0.6.3	T 0.6.4
		E2	P2	E1	E3
Adequacy of the organization	Efficient	1.0	1.0	1.0	1.0
Adequacy of MMI and operational support	Adequate	1.0	1.0	1.0	1.0
Working conditions	Compatible	1.0	1.0	1.0	1.0
Availability of procedures/plans	Acceptable	1.0	1.0	1.0	1.0
Number of simultaneous goals	Matching current capacity	1.0	1.0	1.0	1.0
Available time	Adequate	0.5	0.5	0.5	0.5
Time of day (circadian rhythm); day time	Adjusted	1.0	1.0	1.0	1.0
Adequacy of training and experience	Adequate, limited experience	1.0	1.0	1.0	1.0
Crew collaboration quality	Very efficient	0.5	0.5	0.5	0.5
Total influence of CPC		0.25	0.25	0.25	0.25

and

Table 16. Assessment of the effects of CPCs on cognitive function corrective failures (Task 7).

CPC	Level	T 0.7.1	T 0.7.2
		O2	E5
Adequacy of the organization	Efficient	1.0	1.0
Adequacy of MMI and operational support	Adequate	1.0	1.0
Working conditions	Compatible	1.0	1.0
Availability of procedures/plans	Acceptable	1.0	1.0
Number of simultaneous goals	Matching current capacity	1.0	1.0
Available time	Adequate	0.5	0.5
Time of day (circadian rhythm); day time	Adjusted	1.0	1.0
Adequacy of training and experience	Adequate, limited experience	1.0	1.0
Crew collaboration quality	Very efficient	0.5	0.5
Total influence of CPC		0.25	0.25

show the assessment of the common performance conditions on the cognitive functions of human corrective actions in the bunkering operation. The assessment is to enhance decision-making and problem-solving in the process.

Table 17. CFP of individual task steps.

Task	Task Activity	Error Mode	Nominal CFP	Weighting Factor	Adjusted CFP (HEPs)
0.1.1	Stop the hydrogen transfer immediately and activate the ESD	E2: Action at wrong time	3.0E−3	0.25	7.5E−4
0.1.2	Ensure to isolate the ruptured hose from the supply source	P2: Inadequate plan	1.0E−2	0.25	2.5E−3
0.1.3	Vent the residual LNG from the ruptured hose to a safe location or flare system	E1: Action of wrong type	3.0E−3	0.25	7.5E−4
0.1.4	Replace with a spare hose that has been tested and inspected	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.1.5	Ensure all connections and resume the LNG transfer	E1: Action of wrong type	3.0E−3	0.25	7.5E−4
0.2.1	Clearly mark the lines and hoses as INERT GAS with a contrasting colour and suitable size	P2: Inadequate plan	1.0E−2	0.25	2.5E−3
0.2.2	Colour-code the inert gas lines and hoses according to the defined system	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.2.3	Ensure that the hose and gas lines have compatible couplings distinct from the LNG couplings	O2: Wrong identification	7.0E−2	0.25	1.75E−2
0.2.4	Test inert gas lines and hoses regularly for leaks and contamination	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.3.1	Press the ESD push button placed in strategic places	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.3.2	Ensure the manual activation of the ESD	I2: Decision error	1.0E−2	0.25	2.5E−3
0.3.3	Ensure that the automatic activation closes the transfer valves and pumps, releases the ERC, and opens the vent valves	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.4.1	Monitor for gas leakage using appropriate detection systems—pressure sensors and gas detectors	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.4.2	Ensure stoppage of the whole transfer process and initiate repair following safety protocols and emergency procedures	O1: Wrong object observed	1.0E−3	0.25	2.5E−4
0.5.1	Ensure replacement before the start of bunkering	O2: Wrong identification	7.0E−2	0.25	1.75E−2
0.5.2	Replace using appropriate tools and spares	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.5.3	Ensure that the new components are compatible and functional	I2: Decision error	1.0E−2	0.25	2.5E−3
0.6.1	Ensure the maximum allowable liquid volume that the tank may be loaded with	I3: Delayed interpretation	1.0E−2	0.25	2.5E−3
0.6.2	Ensure appropriate loading density at the loading temperature and reference temperature	I2: Decision error	1.0E−2	0.25	2.5E−3
0.6.3	Monitor the maximum filling limit using appropriate instruments: pressure gauge, level gauge, etc.	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.7.1	Ensure to complete the checklist when placing a bunker order	O2: Wrong identification	7.0E−2	0.25	1.75E−2
0.7.2	Include all necessary information about the bunker and safety procedures	E5: Missed action	3.0E−2	0.25	7.5E−4

and

Table 18. CFP of individual task steps.

Task No	Task Activity	Error Mode	Nominal CFP	Weighting Factor	Adjusted CFP (HEPs)
0.1.1	Stop the hydrogen transfer immediately and activate the ESD	E2: Action at wrong time	3.0E−3	0.25	7.5E−4
0.1.2	Ensure to isolate the ruptured hose from the supply source	P2: Inadequate plan	1.0E−2	0.25	2.5E−3
0.1.3	Vent the residual LNG from the ruptured hose to a safe location or flare system	E1: Action of wrong type	3.0E−3	0.25	7.5E−4
0.1.4	Replace with a spare hose that has been tested and inspected	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.1.5	Ensure all connections and resume the LNG transfer	E1: Action of wrong type	3.0E−3	0.25	7.5E−4
0.2.1	Clearly mark the lines and hoses as INERT GAS with a contrasting colour and suitable size	P2: Inadequate plan	1.0E−2	0.25	2.5E−3
0.2.2	Colour-code the inert gas lines and hoses according to the defined system	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.2.3	Ensure that the hose and gas lines have compatible couplings distinct from the LNG couplings	O2: Wrong identification	7.0E−2	0.25	1.75E−2
0.2.4	Test inert gas lines and hoses regularly for leaks and contamination	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.3.1	Press the ESD push button placed in strategic places	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.3.2	Ensure the manual activation of the ESD	I2: Decision error	1.0E−2	0.25	2.5E−3
0.3.3	Ensure that the automatic activation closes the transfer valves and pumps, releases the ERC, and opens the vent valves	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.4.1	Monitor for gas leakage using appropriate detection systems—pressure sensors and gas detectors	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.4.2	Ensure stoppage of the whole transfer process and initiate repair following safety protocols and emergency procedures	O1: Wrong object observed	1.0E−3	0.25	2.5E−4
0.5.1	Ensure replacement before the start of bunkering	O2: Wrong identification	7.0E−2	0.25	1.75E−2
0.5.2	Replace using appropriate tools and spares	E3: Action on wrong object	5.0E−4	0.25	1.25E−4
0.5.3	Ensure that the new components are compatible and functional	I2: Decision error	1.0E−2	0.25	2.5E−3
0.6.1	Ensure the maximum allowable liquid volume that the tank may be loaded with	I3: Delayed interpretation	1.0E−2	0.25	2.5E−3
0.6.2	Ensure appropriate loading density at the loading temperature and reference temperature	I2: Decision error	1.0E−2	0.25	2.5E−3
0.6.3	Monitor the maximum filling limit using appropriate instruments: pressure gauge, level gauge, etc.	O3: Observation not made	7.0E−2	0.25	1.75E−2
0.7.1	Ensure to complete the checklist when placing a bunker order	O2: Wrong identification	7.0E−2	0.25	1.75E−2
0.7.2	Include all necessary information about the bunker and safety procedures	E5: Missed action	3.0E−2	0.25	7.5E−3

show an adjusted CFP which is obtained from a combination of nominal CFP and the weighting factor. The weighting factor is the total influence of the common performance conditions (CPCs) on the operation of hydrogen bunkering. The weighting factor is the total multiplication of the values of the cognitive values of the task steps.

Table 19. Integrated CFP values with equipment reliability.

Task No	Task Activity	Adjusted (CFP)	Adjusted Equipment Failure Probability (EFP)	FFP	Final Probability (FP)
0.1.1 Replace the hose assembly.	Stop the hydrogen transfer immediately and activate the ESD	0.00075	ESD (0.00000699)	0.0007569848	0.9992430152
0.1.2	Ensure to isolate the ruptured hose from the supply source	0.0025	Gas detector (0.0000015)	0.0025014965	0.9974985038
0.1.3	Vent the residual hydrogen from the ruptured hose to a safe location or flare system	0.00075	Gas detector 0.0000015	0.0007514989	0.9992485011
0.1.4	Replace with a spare hose that has been tested and inspected	0.000125	Gas detector (0.0000015)	0.00012649981	0.9998735002
0.1.5	Ensure all connections and the hydrogen transfer operation are ready to start	0.00075	Multimeter or electrical testers (0.000025)	0.00077498125	0.9992250188
0.2.1 Properly label inert gas line and hoses	Clearly mark the lines and hoses as INERT GAS with a contrasting colour and suitable size	0.0025	Gas detector (0.0000015)	0.00250149625	0.9974985038
0.2.2	Colour-code the inert gas lines and hoses according to the defined system	0.000125	Gas detector (0.0000015)	0.00012649981	0.9998735002
0.2.3	Ensure that hoses and gas lines have compatible couplings distinct from the hydrogen couplings	0.0175	Couplings (0.000011)	0.0175108075	0.9824891925
0.2.4	Test inert gas lines and hoses regularly for leaks and contamination	0.0175	Portable gas detectors (0.0000015)	0.01750147375	0.9824985263
0.3.1 Activate the emergency shutdown system (ESD)	Press the ESD push button placed in strategic places	0.000125	ESD (0.00000699)	0.00013198913	0.9998680109
0.3.2	Ensure the manual activation of the ESD	0.0025	ESD (0.00000699)	0.00250697253	0.9974930275
0.3.3	Ensure that the automatic activation closes the transfer valves and pumps, releases the ERC, and opens the vent valves	0.0175	ESD (0.00000699)
0.4.1 Identify and repair the source of the leak	Monitor for gas leakage using appropriate detection systems—pressure sensors and gas detectors	0.0175	Gas detector (0.0000015)
0.4.2	Ensure stoppage of the whole transfer process and initiate repair following safety protocols and emergency procedures	0.00025	ESD (0.00000699)	0.00025698825	0.9997430117
0.5.1 Replace faulty lighting, gauges, and indicators	Ensure replacement before the start of bunkering	0.0175	Multimeter or electrical testers (0.000025)	0.0175245625	0.9824754375
0.5.2	Replace using appropriate tools and spares	0.000125	Multimeter or electrical testers (0.000025)	0.00014999688	0.9998500031
0.5.3	Ensure that the new components are compatible and functional	0.0025	Multimeter or electrical testers (0.000025)	0.0025249375	0.9974750625
0.6.1 Determine the maximum filling limit of the tank	Ensure the maximum allowable liquid volume that the tank may be loaded with	0.0025	Tank level gauges (0.00000015)	0.00250014963	0.9974998504
0.6.2	Ensure appropriate loading density at the loading temperature and reference temperature	0.0025	Tank level gauges (0.00000015)	0.00250014963	0.9974998504
0.6.3	Monitor the maximum filling limit using appropriate instruments: pressure gauge, level gauge, etc.	0.0175	Tank level gauges (0.00000015)	0.01750014738	0.9824998526
0.7.1 Complete a planning stage checklist	Ensure to complete the checklist when placing a bunker order	0.0175	VHF Radio (0.0000000045)	0.01750000442	0.9824999956
0.7.2	Include all necessary information about the bunker and safety procedures	0.0075	VHF Radio (0.0000000045)	0.007500004466	0.9924999955

shows the combined failure probability of the human corrective actions as a response to any unwanted situation in the bunkering operation of hydrogen. This combined probability study clearly considers both human and equipment reliability in the corrective actions of human response to unwanted situations. This combined study helps to enhance human probability by reducing human cognitive failure probability.

5. Discussion

5.1. Original Contribution of the Research Findings to the Industry

The scissor approach provides a valuable framework for understanding how equipment design can directly support and enhance human performance, particularly during corrective actions under conditions of uncertainty. In high-risk environments where time-sensitive decisions are required, well-designed equipment interfaces and systems can reduce cognitive load, minimize misidentification, and guide operators toward correct actions.

By modelling human reliability alongside equipment reliability, the scissor approach advocates for a mutually reinforcing relationship—where technological systems are tailored to human capabilities and limitations, and human actions are supported by intuitive, responsive, and fail-safe equipment. This integration is especially vital in hydrogen applications, where the novelty of the fuel, the risk of leakage, and the lack of operational familiarity can elevate the likelihood of both “action on wrong object” and “observation not made” error modes.

These insights support the need for human-centred design, proactive training, and operational procedures that embed human factor considerations into every layer of hydrogen bunkering system design and execution.

Further integrating the weighted factor indicates that if more proper human decisions are planned into any shipping operation, considering the better management of crew and equipment, human error can be drastically reduced. The final cognitive failure probability (FCFP) indicates a high reduction in cognitive failure with a high increase in reliability. The weighted factor can help to identify the most critical parameters that can influence reliability. How effectively the weighted factor is used will also determine how human error can be reduced, considering enhanced decision-making, improved risk assessment, focused training, and the design of the hydrogen bunkering process. In a nutshell, the weighted factor can only help to reduce human error if the factors are based on sound data and risk assessment that focus on areas of more likely human mistakes in the shipping operation.

5.2. Recommendations for Improving the Current Issue

The scissor approach, as an integrated concept of reliability study, has made promising attempts to enhance human reliability in the corrective response to the occurrence of uncertainties during the bunkering operation of hydrogen. The bunkering of hydrogen is still a very new interest; therefore, there is still a need to engage in in-depth study in areas of training personnel, risk assessment and mitigation, safety distances and hazard zones, storage systems and leak control, regulatory compliance, and more emergency response plans. If safety must be optimal, there is a need for collaboration among industry stakeholders, technology providers, regulators, and maritime training centres because hydrogen bunkering is an evolving field with great industrial interest.

5.3. Limitations of Current Research and Suggestions for Future Work

The hydrogen bunkering operation is a very new and evolving area in the maritime sector, so data collection is quite challenging due to limited information about the bunkering operation of hydrogen. However, there is significant momentum in the maritime industry in its use as a pivotal step in decarbonizing the industry, as the global maritime industry is aiming to cut down emissions and bring in sustainable development strategies. It is therefore greatly believed that as things continuously unfold in the use of hydrogen as an alternative fuel in shipping, more information will be available in areas of both human reliability assessment and equipment reliability study.

Another limitation is in decision-making on the CPCs. Subjectivity could not be totally ruled out in the hydrogen bunkering operation, being a very new area of knowledge. The human reliability aspect of this study marries the expertise of analysts using their experience on the operational task and perceptions to evaluate the likelihood of human error, which can be subjective. Employing decision-making models is the best way to help improve this process. These decision-making models also have their challenges; however, they can bring more in-depth knowledge in this respect.

6. Conclusions

Integrating equipment reliability into the cognitive failure probability values reduces the CFP error values, indicating the interest that reliable equipment in an industrial environment can enhance human reliability in carrying out any shipping operations, thereby reducing human errors. Every shipping operation either responds to uncertainties or is a functional interaction between the human element and equipment factor. Unwanted situations cannot be totally eradicated. However, human responses, if properly put in place, can bring a failed system to an operational state. Human corrective actions have played vital roles in restoring operations even during emergencies. During these corrective actions, however, human errors still remain hidden. Investigating human errors during these corrective actions and possible ways of enhancing the human response to incidents becomes an interest in maritime safety. The use of hydrogen as an alternative fuel in the shipping industry is a very novel interest that will involve a lot of uncertainties; therefore, preparation for any unwanted situation is a good direction to point at. Building a proper and adequate corrective goal will greatly enhance the hydrogen bunkering operation.

From the analysis, the most dominant human error modes identified during the human corrective response actions in the hydrogen bunkering operations are “action on wrong object” and “observation not made.” These errors typically arise under conditions of uncertainty, where time pressure, cognitive overload, or poor system design can impair human performance.

“Action on wrong object” involves executing the correct action on an incorrect system or component, often due to misidentification or interface confusion. “Observation not made” reflects a failure to detect critical cues or indicators, which can prevent timely and appropriate responses to developing hazards.

These findings highlight the need for enhanced human–machine interface design, improved procedural clarity, and targeted training that emphasizes situational awareness and decision-making under stress. Addressing these dominant error modes is essential to strengthening operational safety and human reliability in response to uncertainties in hydrogen bunkering environments.