Hazard Identification of Ammonia FSS for Ammonia Fuelled Ammonia Carrier

Article information

J. Ocean Eng. Technol. 2024;38(6):402-413
Publication date (electronic) : 2024 December 6
doi : https://doi.org/10.26748/KSOE.2024.078
1Researcher, Offshore Industries R&BD Center, Korea Research Institute of Ships & Ocean Engineering, Geoje, Korea
2Senior Researcher, Offshore Industries R&BD Center, Korea Research Institute of Ships & Ocean Engineering, Geoje, Korea
3Principal Engineer, Offshore Industries R&BD Center, Korea Research Institute of Ships & Ocean Engineering, Geoje, Korea
4Principal Researcher, Offshore Industries R&BD Center, Korea Research Institute of Ships & Ocean Engineering, Geoje, Korea
Corresponding author Youngkyun Seo: +82-55-639-2419, ykseo@kriso.re.kr
Received 2024 September 30; Revised 2024 October 22; Accepted 2024 October 23.

Abstract

Ammonia is a zero-carbon fuel that has attracted considerable interest. The compound has high volumetric energy density and is easy to store and transport. Despite this, a proper study is necessary to ensure safety because ammonia fuel will likely be applied first to ammonia carriers. In this study, hazard identification (HAZID) was performed to identify the risk of the ammonia fuel supply system and preventive/mitigation measures were suggested to minimize the risk. The analyzed system scope was the ammonia fuel supply system from a fuel service tank on the deck to the front of the engine. The nodes with the most scenarios were the fuel service tank and the fuel supply line. The main factors included internal factors, such as design defects, malfunctions, and operational errors, and external factors, such as impact, thermal stress, hogging, and sagging. Recommendations are provided to reduce the risk of accident scenarios, including safety devices/alarm devices in process systems, system layout configurations, and heat and gas dispersion analysis. The results are expected to help predict/minimize damage regarding ammonia fuel supply system design, operational safety, and potential risks.

1. Introduction

Ships emit various pollutants, such as nitrogen oxides, sulfur oxides, particulate matter, and carbon dioxide. Among them, CO2 emissions from ships account for approximately 2.5% of global emissions. The International Maritime Organization (IMO) adopted initial greenhouse gas (GHG) strategies that specified GHG reduction goals and measures in 2018 to reduce GHG emissions (Ye et al., 2022). These initial strategies aimed to reduce GHG emissions by at least 50% compared to the 2008 levels by 2050 and ultimately to net zero. The initial strategies included short-term (2018–2023), mid-term (2023–2030), and long-term (2023–2030) measures. The short-term measures involve technical/operational energy efficiency measures and speed reduction regulations for new and existing ships. The mid-to-long-term measures involve technical measures that regulate the overall GHG emissions by forcing operational efficiency, market-based measures that forcibly increase the price of fossil fuels or impose a levy on GHG emissions, and technology/market combination measures that combine the two measures (Chircop, 2019). The 80th meeting of the Marine Environment Protection Committee strengthened the regulations on GHG emissions further by adopting strategies for net-zero GHG emissions by 2050 (Zhang et al., 2024).

With strengthened regulations on GHG emissions, the shipping industry is accelerating the introduction of zero-carbon fuels, such as hydrogen and ammonia. Ammonia has been considered a fuel for large ships because of its high storage efficiency compared to hydrogen and the fuel supply and demand benefit. According to Valera-Medina et al. (2018), the storage cost of ammonia was more than three times lower than that of hydrogen. Ammonia has already secured the technology and infrastructure required for the production and transport of fuel (Ishaq and Crawford, 2024). Nevertheless, caution is needed when handling ammonia because it is toxic and corrosive (Lan and Tao, 2014). Ammonia-fueled ships have been developed worldwide. The core of technology development is the ammonia engine and fuel supply system (FSS). MAN Energy Solutions, a German ship engine maker, succeeded in a combustion test of an ammonia engine in 2023 (MAN Energy Solutions, 2023).

The company also set the basic concept of ammonia FSS to be similar to that of the LPG low-flashpoint fuel supply system (LFSS) and added an ammonia catch system to treat ammonia that is inevitably released. WinGD, a Swiss ship engine maker, revealed its plan to supply ammonia engines starting in 2025. Alfa Laval, a Swedish marine equipment company, announced it would supply an ammonia FSS for engine testing (Alfa Laval, 2023). Hyundai Heavy Industries (HHI) developed an ammonia FSS equipped with a dual leakage prevention gas treatment system. The FSS can remove the nitrogen oxides in the ammonia engine exhaust gas using the ammonia released from it (HHI, 2021). Japan Engine Corporation conducted ammonia fuel tests under various conditions. Mitsubishi Shipbuilding developed and supplied ammonia FSS for large and low-speed two-stroke ship engines (Mitsubishi, 2023).

Various classification societies published regulations and guidelines for using ammonia as a ship fuel. The published rules and guidelines commonly presented key design considerations based on the International Code of Safety for Ships using gases or other low-flash point fuels (IGF code). The IGF code is the international standard for ships that use gases or other low-flash point fuels and provides essential criteria for arrangement, installation, and control to minimize the risks for the crew and environment. Each classification considered the characteristics of ammonia (toxicity and corrosiveness) and presented detailed safety considerations. Bureau Veritas (BV) enacted temporary rules for ammonia in 2021 and published a revised edition in September 2024. The company set the allowable ammonia exposure concentration and the concentration at which the water mist system operates to treat ammonia to 30 ppm and required at least 30 times of ventilation per hour for the ventilation system capacity in the space with the ammonia exposure risk (BV, 2024). The Korean Register (KR) published a guide for ammonia-fueled ships in 2021. It also published a revised edition in June 2023, which included standard concentrations, toxic areas, safety measures, and gas treatment systems. It set the allowable ammonia exposure concentration to 25 ppm, which is lower than BV, and the upper exposure limit concentration at which the ammonia treatment system operates to 300 ppm. It requires a ventilation system with a capacity that is at least 30 times ventilation per hour (KR, 2023). ClassNK added ammonia fuel to the guidelines on ships that use low-flash point fuels in September 2021, with a revised edition published in June 2022. It set the allowable ammonia exposure concentration for sounding an alarm to 25 ppm and the concentration at which the master valve and double block and bleed (DBB) valve are blocked to 300 ppm. It requires a ventilation system with a capacity of at least 30 times ventilation per hour in the space where gas can accumulate and at least 45 times per hour for areas where ammonia-related equipment is installed and people can enter during operation (ClassNK, 2021). The American Bureau of Shipping (ABS) published a guide for ammonia-fueled ships in 2021. It also published a Requirement in September 2023 by adding essential items for issuing a classification society certificate. It limits the ammonia concentration before being released into the atmosphere through the vent mast and vent riser to 25 ppm and requires a ventilation system with a capacity that is at least 30 times ventilation per hour (ABS, 2023). Det Norske Veritas (DNV) published revised rules in October 2023 by adding requirements, such as atmospheric emission limits, diffusion analysis for emergency scenarios, ammonia leakage-related systems, and fire safety, to the rules published in 2021. It set the ammonia concentration released into the atmosphere to 300 ppm and the ammonia concentration in ventilated space at which a water mist system automatically operates to 350 ppm. Moreover, the ventilation system must operate at least 30 times per hour in the fuel preparation room and have sufficient space to handle fuel (DNV, 2023).

Various studies have also been conducted to ensure the safety of ammonia-fueled ships. In Japan, hazard identification (HAZID) was performed to propose the risk of ammonia-fueled ships. Fuel leaks and the loss of equipment control signals were estimated to be the most significant risk factors, but they need to be examined at the ship design, arrangement, and operation stages. Research was also conducted on the risks that may occur when fuel is supplied to a ship during the bunkering process. Surbana Jurong, Singapore’s state-owned consulting firm, and Singapore Maritime Academy (SMA), a college, conducted research on ammonia ship-to-ship (STS) bunkering concept design and HAZID/hazard and operability study (HAZOP)/ quantitative risk assessment (QRA) (DNV, 2022). Duong et al. (2023) analyzed a diffusion analysis software program using FLACS to compare the safety zones for leakage accidents during the NH3 and liquefied natural gas (LNG) STS bunkering processes. NH3 has a wider diffusion range than LNG when leaked under the same conditions because of its wider explosion range and toxicity. NH3 at − 33°C (1 bar) lasts longer in the diffusion area than LNG at −163°C (1 bar) because of the weak convection phenomenon caused by the insignificant temperature difference from the atmosphere. Ng et al. (2023) analyzed the effects of operational and meteorological conditions on atmospheric diffusion in the event of an NH3 STS bunkering leakage accident using Phast software. They mentioned semi-refrigerated (SR), non-refrigerated (NR), and fully refrigerated (FR) types as tank storage conditions and reported that FR is safer than SR and NR. They recommended that the flow rate should be distributed and transported using multiple hoses because the accident area increases in the event of an accident as the bunkering flow rate increases. Kim et al. (2022) analyzed various accident scenarios using the Phast software to determine safety zones during the truck-to-ship (TTS) bunkering of ammonia-fueled ships. They proposed population-dependent analysis (PDA) to consider the effect of population density on the level of damage. The hazard range increased as the leak hole size increased, and the hazard radius was presented within 10, 57, and 373 m in the event of one accident in 20,000, 100,000, and 200,000 years.

The engine room of a ship is a dangerous zone that contains all three elements of fire, i.e., oxygen, heat (ignition source), and fuel. Research has been actively conducted on the fire risk of the engine room. Pomonis et al. (2022) conducted a risk assessment for engine room fire scenarios when ammonia fuel was used compared to conventional fuels (LNG/marine diesel oil (MDO)) using PyroSim, a fire simulation software program. They reported that ammonia has less equipment damage and a longer fire evacuation time because of the low flame temperature compared to conventional fuels, but the risk from its toxicity in the event of direct leakage is relatively high. Yadav and Jeong (2022) analyzed the risks of fuel leaks inside the engine room of ammonia carriers using a Solidworks flow simulation. They reported that the results differed according to the leakage direction (transverse, vertical, and longitudinal) when the fuel leak from pipes began. The fuel leak in the longitudinal direction exhibited the highest risk as it spread within 30 seconds and reached the range set for alarms. The range was not reached in the transverse and vertical directions, but evacuation in less than two minutes was recommended.

Various studies have been conducted to determine the toxicity and fire risks of ammonia FSS and fuel, but no study has presented a risk assessment and measures to prevent and mitigate the risk for FSS, a key system of ammonia-fueled ships. The application of ammonia fuel to ships requires an integrated examination and analysis, including FSS. This paper presents preventive/mitigation measures to minimize the risk by performing HAZID for ammonia FSS. The contents of this paper are as follows. The concepts of ammonia carriers and FSS are proposed in Chapter 2, and the risk assessment methodology is described in Chapter 3. Each result and discussion are presented in Chapters 4 and 5. Finally, conclusions are drawn in Chapter 6.

2. System Description

2.1 Target Ship: Ammonia Carrier

An 84K ammonia carrier was selected as the target ship of this study. The technology to use ammonia as ship fuel has been developed, increasing expectations for demand and transport. The initial application of ammonia fuel to ammonia carriers is highly likely because the operational efficiency of ships is improved when the cargo is used as fuel, as in the case of LPG carriers.

Table 1 lists the basic specifications of the target ship along with engine specifications. Type C tanks are commonly applied to small and medium-sized ships, but type A was applied to the target ship, which is a large ship with a cargo capacity of 84,000 m3, to transport a large amount of ammonia at atmospheric pressure. An ammonia engine under development by MAN Energy Solutions is scheduled to be mounted on the carrier.

Principal dimensions of 84K ammonia carrier

Fig. 1 presents a schematic diagram of the ammonia carrier. Some fuel from the cargo tank is transported to the fuel service tank. The transported ammonia meets the temperature and pressure conditions required by the engine through the FSS and supplies it into the engine through the fuel valve train (F.V.T).

Fig. 1.

System configuration of ammonia carrier

2.2 Ammonia Fuel Supply System

Fig. 2 presents the process flow diagram (PFD) of the configuration of the FSS of the ammonia carrier. The ammonia loaded in the fuel service tank is supplied to the engine through the F.V.T after meeting the operating conditions through pressure and temperature control and glycol–water systems. Not all of the supplied fuel is consumed in the ammonia engine. Some of it is sent to the pressure and temperature control system through the recirculation system.

Fig. 2.

Process flow diagram (PFD) of fuel supply system

2.2.1 Fuel service tank

The fuel service tank serves as a buffer that temporarily stores the fuel from the cargo tank. It receives the fuel every one to three days and is located on the top deck of the ship. A type C tank with high resistance to internal pressure is used for the fuel service tank. The boil-off gas (BOG) generated by external heat inflow was accumulated in the tank or treated through the reliquefaction system installed in the ship.

2.2.2 Fuel pressure & temperature control system

The pressure and temperature control system controls the fuel to the temperature and pressure required by the engine. Its main equipment includes pumps to increase the pressure to the level required by the engine and a heat exchanger to adjust the temperature to the required level. The pumps increase the pressure of the fuel in two stages (low pressure and high pressure), and the temperature of the fuel is controlled through heat exchange with glycol–water in the heat exchanger. The pressure and temperature conditions required by the ammonia engine are approximately 80 bar and 25 to 45 °C.

2.2.3 Glycol–water system

Glycol–water, a mixture of ethylene glycol and water, is commonly used as a heat exchange medium because it can prevent freezing. The glycol–water system adjusts the temperature of the fuel to supply it in the range required by the engine. The glycol–water system consists of an expansion tank, a pump, and heat exchangers (a heater and a cooler). The glycol–water temperature is controlled as it passes through the heater and cooler. The glycol–water temperature is increased through heat exchange with the steam in the heater and decreased through heat exchange with seawater in the cooler.

2.2.4 Recirculation system

The recirculation system supplies the fuel returned from the engine to the pressure and temperature control system after separating the oil and gas mixed with the fuel. It consists of an oil separator to separate oil and a vapor–liquid separator to separate gas from the fuel. It sends the fuel returned from the engine to the inlet of the high-pressure pump after the separation process because the failure to remove oil and gas from the returned fuel can lead to equipment damage.

2.2.5 F.V.T

The F.V.T performs a stable fuel supply into the engine and blocks the supply in an emergency. It has two skids: a supply valve train and a return valve train. In general, the fuel of the process line is cut off through the double block and bleed valve.

3. Methodology of Hazard Identification

A risk assessment is a method of identifying and evaluating potential hazards that may occur in a system. It aims to prevent accidents by removing hazards and performing necessary measures. Risk assessment methods can be divided mainly into quantitative and qualitative assessment methods. Quantitative assessment methods include QRA/toxicological risk assessment (TRA), and qualitative assessment methods include failure mode and effects analysis (FMEA), HAZID, and HAZOP. QRA, a method of determining the impact on the risk of the system, is used in process design, safety, inspection, maintenance, planning, and operational management (Acikalin, 2009). TRA, a method of evaluating the risk related to exposure to potentially hazardous substances, is used to evaluate the toxicological risks in the early stages of the system (Torres and Bobst, 2015).

FMEA, a methodology for identifying the results caused by the errors of components and determining the importance of each error mode regarding the system performance, is used in the safety and reliability analysis and design stages. HAZID, a qualitative analysis method, is performed using a brainstorming technique that involves experts from various fields to identify risks (Kim, 2022). HAZOP is a technique to analyze and evaluate hazards systematically in the design review process and risks for operability (Siddiqui et al., 2014).

The study was conducted based on HAZID, which can identify existing risks at the initial design stage and assess all potential hazards inside the ship through brainstorming. HAZID is performed based on the procedure shown in Fig. 3 and is described below (KRISO, 2021).

Fig. 3.

Hazard identification flow chart

3.1 HAZID Procedure

3.1.1 Identification of HAZID nodes

The target system was divided into nodes to examine its hazards. The size and number of nodes vary depending on the complexity of the process and the discretion of the risk assessment team.

3.1.2 Node briefing

The nodes used for risk assessment and the operating procedure were explained to the members participating in risk assessment. The members were composed of experts related to the target system, and HAZID was performed using brainstorming to identify potential risks. Table 2 lists the expert group.

Member of HAZID expertise team

3.1.3 Identification of hazards and hazardous events

Through drawings and information documents, hazards are identified by determining if certain situations and equipment may cause risks.

3.1.4 Identification of causes & consequences

All potential causes for each identified accident and the magnitude of damage in terms of people, assets, and the environment were considered. Double jeopardy, which applies two independent events simultaneously, was not considered.

3.1.5 Identification of preventive and mitigating safeguards

This study examined whether the safeguards considered were designed to prevent accidents or reduce the magnitude of damage.

3.1.6 Risk ranking

A risk assessment was performed by combining the frequency of accidents and the magnitude of damage using the matrix technique. The matrix technique was derived numerically, and it can determine the priorities of risks.

3.1.7 Identification of recommendations

Further recommendations were identified by judging the devices and recommendations reflected in the current system to minimize and prevent risks and considering the risk ranking.

3.2 Risk Ranking

The risk ranking was calculated by identifying the hazards of the system and determining the frequency of the risk and the magnitude of the damage. The risk ranking for each identified accident scenario was determined (Table 5) considering the likelihood rating listed in Table 3 and the consequence rating shown in Table 4. The matrix consisted of seven likelihoods and five consequences, making it possible to estimate the risk with 35 measures through combinations according to Eq. (1).

(1) Risk(R)=Likelihood(L)×Consequency(C)

Risk matrix (LR, 2016)

Likelihood rating (LR, 2016)

Consequence rating

Frequency ratings can be distinguished for each scenario, and the likelihood ratings were assigned based on the criteria shown in Table 3. The magnitude of damage was calculated according to the five ratings distinguished in Table 4, and damage influence levels for people, assets, and the environment were considered.

Based on the risk matrix, the risks mentioned in Table 5 were classified according to the frequency of accidents and the magnitude of damage.

  • - Low risk (green): It is considered acceptable and requires no additional preventive or mitigation measures.

  • - Medium risk (yellow): The risk must be reduced in the applicable range, and mitigation measures must be implemented.

  • - High risk (red): The risk is unacceptable, and mitigation measures must be implemented to reduce it below the medium level.

4. Results

Fig. 4 shows the six nodes of ammonia carrier FSS. The node range was set from the fuel service tank installed on the top deck to F.V.T in front of the engine, including the fuel supply line.

Fig. 4.

Node of ammonia carrier PFD

A risk assessment was conducted on the FSS of the ammonia-fueled ship. The assessment results are presented, considering existing safeguards and measures for additional risks. The system and each processing device were examined based on Fig. 4, and the possible causes and results were examined by producing nodes based on the core system of the target ship. The organized HAZID team identified 129 accident scenarios. Four accident scenarios were classified as low risk, and 125 accident scenarios as medium risk. Table 6 lists the risk rating distribution by the node for the target ship. Approximately 38% of the identified accident scenarios are concentrated at node 4.

Number of risk scenarios and risk rating

4.1. Node 1: Ammonia Filling Lines for Fuel Service Tank

At node 1 (filling lines), approximately 10% of all accident scenarios are concentrated. In the case of the risks mentioned in Table 7, Risk 12 or higher was mentioned. The main hazard was ammonia leakage from the flanges, fittings, and valves connected to piping. The causes were the internal and external factors. The internal factors included a failure to produce them according to the code and design standards, operation that exceeds the design conditions, and material defects. The external factors included thermal stress, external impacts, and hogging/sagging. The resulting ammonia leakage may lead to human casualties and hull damage. In addition, failure to perform pipeline purging after charging the fuel service tank can lead to leakage into the atmosphere and accidents caused by the pressure increased by heat intrusion into piping.

Part of node 1 HAZID worksheet result

4.2 Node 2: Fuel Service Tank

At node 2 (fuel service tank), approximately 22% of all accident scenarios are concentrated. The accident scenarios of Table 8 mentioned a Risk of 12 or higher. The main hazard is overfilling the fuel service tank located on the deck. Such an event may occur due to operator errors, tank level meter errors, cases in which the tank is not produced according to the code and design rules, or it is operated in excess of the design conditions. This may lead to ammonia leakage to the vent mast connected to the tank. The same situation can occur if leakage occurs in the flanges, fittings, and valves connected to the piping as with node 1 and if ammonia remains in the piping. This is a hazard because a cargo handling crane is installed on the top deck to move equipment. Leakage occurs in some cases due to operator error and crane defects. While the aforementioned hazards are internal factors, weather conditions, which are external environments, are also risk factors. The resulting hull damage and ammonia leakage can lead to human casualties.

Part of node 2 HAZID worksheet result

4.3 Node 3: Ammonia Fuel Lines between Fuel Service Tank and Fuel Preparation Room

Ammonia fuel lines corresponding to node 3 represented 12% of all accident scenarios. Table 9 lists the cases of Risk 12 or higher. The main hazard was found to be ammonia leakage related to flanges, valves, and fittings, which are the joints connected to piping, as with nodes 1 and 2. The causes include failure to produce them according to the code and design standards, excessive operating conditions, material defects, external impacts, thermal stress, vibration, and hogging/sagging. The resulting ammonia leakage may lead to the risk of injury and the corrosion of hull materials. Failure to remove the remaining ammonia from piping in the stop or shutdown process during FSS operation may also act as a risk factor.

Part of node 3 HAZID worksheet result

4.4 Node 4: Fuel Preparation Room

At node 4 (fuel preparation room), approximately 38% of all accident scenarios are concentrated. The risks listed in Table 10 represent cases of Risk 12 or higher. The main hazard was found to be ammonia leakage from equipment, piping, valves, and fittings caused by internal defects (material defects/corrosion and design/production/ installation defects), abnormal operation exceeding design conditions, and external heat and vibration. As with node 3, failure to remove the remaining ammonia from piping in the event of system shutdown increases the possibility of leakage due to the overpressure caused by external heat intrusion. The main equipment and fluids for operating the equipment inside the fuel preparation room are presented. Among them, steam with high-temperature and high-pressure conditions can leak at the major connections due to design, fabrication, and installation faults or abnormal operating conditions, causing injuries.

Part of node 4 HAZID worksheet result

4.5 Node 5: Ammonia Fuel Lines between Fuel preparation Room and Engine Room

Regarding fuel lines between the fuel preparation room and engine room, which correspond to node 5, 13% of all accident scenarios were concentrated. As mentioned in Table 11, the main hazard was ammonia leakage from the flanges, valves, fittings, and joints connected to piping, where leakage can commonly occur as with the fuel lines of the aforementioned nodes. Various causes exist, and ammonia can leak due to design and fabrication faults and excessive operation, external impacts, thermal stress, vibration, hogging, and sagging. Failure to remove the remaining ammonia from piping in the event of an FSS stop or shutdown also acts as a risk factor.

Part of node 5 HAZID worksheet result

4.6 Node 6: Fuel Valve Train

Node 6, which is the fuel valve train between the preparation room and the engine room, represents 5% of all accident scenarios. The risk mentioned in Table 12 is ammonia leakage from the valves, fittings, and flanges connected to the fuel line. The risk can be caused by design, fabrication, and installation faults, as well as excessive operating conditions and material defects. Caution is needed because ammonia leakage can cause injuries or deaths.

Part of node 6 HAZID worksheet result

4.7 Recommendation

Recommendations were added when existing safeguards were insufficient at the acceptable level, or additional measures were required through risk assessment. Consequently, 22 recommendations were derived for FSS. A medium risk was determined when the risk level was calculated considering the existing safeguards alone. When additional preventive/mitigation measures were applied to minimize the medium risk, the risk level was reduced to low risk for five out of 22 scenarios. Additional safeguards, system configuration modification, and design/analysis were derived as recommendations.

4.7.1 Additional safeguards recommendation

Despite the presence of preventive and mitigation measures against hazardous events, additional safeguards to the system were derived as recommendations to improve the safety level. Additional safeguards and tank warning devices (alarms) were required to prevent fuel leakage.

  • - Reliquefaction system safeguards in preparation for the carryover scenario

  • - Vent mast safeguards in preparation for tank overfilling

  • - Safeguards to prevent damage to the tank substructure

  • - Additional safeguards to minimize fuel leakage through the vent mast

  • - Additional safeguards for the cargo hose handling crane

  • - Safety valves to reduce the pressure inside fuel lines

  • - Alarm function against the low water level in the fuel service tank

  • - Installation of warning and alarm devices against the low water level in the glycol–water tank

  • - Method to detect ammonia heat exchanger leakage

4.7.2 System design recommendation

Ammonia, a highly corrosive substance, has a high diffusion rate. Therefore, design must be performed that considers potential hazardous events to prevent leakage.

  • - Minimizing the number of flanges in the fuel system and flange shield

  • - Location of the fuel service tank in consideration of the radius of the cargo hose handling crane

  • - Pump type to prevent ammonia leakage

  • - Materials that consider the corrosiveness of ammonia

4.7.3 Additional analysis recommendation

Environmental factors change when ships are docked or sailing, affecting the system operation. In the case of the ammonia engine, liquid ammonia is supplied, and problems with performance occur if it is supplied together with gas. Owing to these problems, the need for thermal analysis of the ammonia supply line and ammonia gas treatment diffusion analysis considering leakage was mentioned.

  • - Ammonia fuel line thermal stress analysis

  • - Temperature analysis for fuel lines from the fuel preparation room to the engine

  • - Vibration analysis for fuel lines to the engine

  • - Diffusion analysis for leakage from the fuel preparation room

  • - Gas dispersion for the vent mast

5. Discussion

In this study, a risk assessment was conducted using the HAZID technique for the FSS of a next-generation zero-carbon, ammonia-carrier-based ammonia-fueled ship. This study assessed the risk of FSS, eliminated potential risks, and presented measures for safety. Major accident scenarios were derived and analyzed to ensure the safety of the system. In addition, various possible risks were investigated, and related safety measures were proposed. After distinguishing the main nodes of the system, 129 accident scenarios were derived, and 32 dangerous accidents were identified. Possible accident scenarios, causes, and results were investigated by analyzing the hazards. The main conclusions were as follows.

  • (1) Approximately 38% of all accident scenarios were concentrated in the fuel preparation room, which produces pressure and temperature conditions to supply ammonia into the engine. All were evaluated as medium risk except for some with low risk.

  • (2) In the case of the fuel service tank that represented approximately 22% of all accident scenarios, fuel leakage through damage to the tank was evaluated as high risk because the tank was loaded with ammonia.

  • (3) The leakage of ammonia, which is the primary fuel, through the defects of equipment/piping connections or the external environment was the leading risk, and detection systems and diffusion analysis were presented as recommendations.

  • In the risk assessment results, 22 recommendations were presented for additional safeguards, system layout considerations, and additional risk-related analysis. The risk level was reduced to a low risk when some additional recommendations were considered.

6. Conclusions

Understanding the risk and safety requirements and identifying mitigation measures are important. This study conducted a risk assessment on ammonia-fueled ships and a fuel supply system (FSS) under research and development. Hazard identification (HAZID) analysis was conducted to identify the main hazards, and related safety measures were proposed. Ammonia leakage in the system was identified as one of the risks that can seriously affect operation. Most of the risks could be identified from FSS and the fuel service tank, and they were evaluated as a medium risk. The need to identify hazardous areas is increasing, and recommendations, such as diffusion analysis, were presented to minimize the potential exposure risk.

The risk assessment results of this study are expected to help predict/minimize the damage that can be caused by the occurrence of abnormal scenarios during the design of ammonia-fueled ships. It is essential to understand risk and safety requirements for introducing new fuels. The main point is identifying and minimizing the risks in advance by assessing them and implementing mitigation measures.

Notes

No potential conflict of interest relevant to this article was reported.

This research was supported by Korea Research Institute of Ships and Ocean engineering a grant from Endowment Project of “Development of Evaluation Model for Hydrogen Offshore Supply Chain and Test Technologies for Hydrogen Equipment” funded by Ministry of Oceans and Fisheries (2520000285).

References

ABS. 2023. Requirements for Ammonia Fueled Vessels ABS.
Acikalin A. 2009;Integration of safety management effectiveness into QRA calculations. Process Safety Progress 28(4):331–337. https://doi.org/10.1002/prs.10323.
Laval Alfa. 2023. WinGD partners with Alfa Laval to advance the development of ammonia-powered engines [Press release]. https://www.alfalaval.com/media/news/2023/wingd-partners-with-alfa-laval-to-advance-the-development-of-ammonia-powered-engines/.
Bureau Veritas (BV). 2024;Ammonia-Fuelled Ships – Tentative Rules (NR-671 R02).
Chircop A. 2019;The IMO initial strategy for the reduction of GHGs from international shipping: A commentary. The International Journal of Marine and Coastal Law 34(3):482–512. https://doi.org/10.1163/15718085-13431093.
Class N. K. 2021. Guidelines for Ships Using Ammonia as Fuels (Ed. 1.1) (Methyl/EthylAlcohol/LPG/Ammonia) Nippon Kaiji Kyokai, Technical Solution Department. https://www.classnk.or.jp/account/en/Rules_Guidance/ssl/guidelines.aspx.
DNV. 2022. DNV selected to lead pioneering ammonia bunkering safety study in Singapore News From DNV. https://www.dnv.com/news/dnv-selected-to-lead-pioneering-ammonia-bunkering-safety-study-in-singapore-216787.
DNV. 2023;Part 6 Additional class notations - Chapter 2 Propulsion, power generation and auxiliary systems Rules for Classification https://www.scribd.com/document/750856348/DNV-RU-SHIP-Pt-6-Ch-2.
Duong P. A, Ryu B. R, Jung J, Kang H. 2023;Comparative analysis on vapor cloud dispersion between LNG/liquid NH3 leakage on the ship to ship bunkering for establishing safety zones. Journal of Loss Prevention in the Process Industries 85:105167. https://doi.org/10.1016/j.jlp.2023.105167.
HHI. 2021. Hyundai Heavy Industries Group to accelerate commercialization of ammonia fuelled ship [Press release]. https://www.hhi.co.kr/Public/pub01_2?page=1&ndate=2021-09-04&bidx=2866&seek=&SearchName=.
Ishaq H, Crawford C. 2024;Review and evaluation of sustainable ammonia production, storage and utilization. Energy Conversion and Management 300:117869. https://doi.org/10.1016/j.enconman.2023.117869.
Kim I. S, Jeong B. U, Song M. K, Nam D. 2022;Determination of bunkering safety zones for ammonia-fueled ship. Journal of Advanced Marine Engineering and Technology 46(5):261–269. https://doi.org/10.5916/jamet.2022.46.5.261.
Kim S. H. 2022;A review of HAZID/Bowtie methodology and its improvement. Journal of the Society of Naval Architects of Korea 59(3):164–172. https://doi.org/10.3744/SNAK.2022.59.3.164.
Korea Register (KR). 2023. Guidelines for ships using ammonia as fuels
KRISO. 2021. Development of ammonia fuel supply system HAZID study for ammonia fuel supply system
Lan R, Tao S. 2014;Ammonia as a suitable fuel for fuel cells. Frontiers in Energy Research 2:35. https://doi.org/10.3389/fenrg.2014.00035.
LR. 2016. ShipRight Design and Construction, Additional Design Procedures: Risk Based Designs (RBD) p. 16. Lloyd’s Register of Shipping.
Energy Solutions MA. N. 2023. July. 13. Ground breaking First Ammonia Engine Test Completed [Press release]. https://www.man-es.com/company/press-releases/press-details/2023/07/13/groundbreaking-first-ammonia-engine-test-completed.
Mitsubishi. 2023. May. 24. Mitsubishi shipbuilding completes delivery of ammonia fuel supply system for large, low-speed two stroke marine engines [Press Information]. Mitsubishi Heavy Industries. https://www.mhi.com/news/23052401.html.
Ng C. K. L, Liu M, Lam J. S. L, Yang M. 2023;Accidental release of ammonia during ammonia bunkering: Dispersion behaviour under the influence of operational and weather conditions in Singapore. Journal of Hazardous Materials 452:131281. https://doi.org/10.1016/j.jhazmat.2023.131281.
Pomonis T, Jeong B, Kuo C. 2022;Engine room fire safety evaluation of ammonia as marine fuel. Journal of International Maritime Safety, Environmental Affairs, and Shipping 6(1):67–90. https://doi.org/10.1080/25725084.2021.2015867.
Siddiqui D. N, Nandan A, Sharma M, Srivastava A. 2014;Risk management techniques HAZOP and HAZID study. International Kournal on Occupationl Health & Safety, Fire Environment – Allied Science 1(1):5–8.
Torres J. A, Bobst S, eds. 2015. Toxicological risk assessment for beginners p. 1160–1166. Springer. https://doi.org/10.1007/978-3-319-12751-4.
Valera-Medina A, Xiao H, Owen-Jones M, David W. I, Bowen P. J. 2018;Ammonia for power. Progress in Energy and combustion science 69:63–02.
Yadav A, Jeong B. 2022;Safety evaluation of using ammonia as marine fuel by analysing gas dispersion in a ship engine room using CFD. Journal of international maritime safety, environmental affairs, and shipping 6(2–3):99–116. https://doi.org/10.1080/25725084.2022.2083295.
Ye M, Sharp P, Brandon N, Kucernak A. 2022;System-level comparison of ammonia, compressed and liquid hydrogen as fuels for polymer electrolyte fuel cell powered shipping. International Journal of Hydrogen Energy 47(13):8565–8584. https://doi.org/10.1016/j.ijhydene.2021.12.164.
Zhang C, Zhu J, Guo H, Xue S, Wang X, Wang Z, Chen T, Yang L, Zeng X, Su P. 2024;Technical requirements for 2023 IMO GHG strategy. Sustainability 16(7):2766. https://doi.org/10.3390/su16072766.

Article information Continued

Fig. 1.

System configuration of ammonia carrier

Fig. 2.

Process flow diagram (PFD) of fuel supply system

Fig. 3.

Hazard identification flow chart

Fig. 4.

Node of ammonia carrier PFD

Table 1.

Principal dimensions of 84K ammonia carrier

Item Particular Description
Ship dimension Length over all (L.O.A) 226 m
Length between perpendicular (L.B.P) 216.0 m
Breadth (MLD) 38.0 m
Depth (MLD) 24.2 m
Design draft (MLD) 11.2 m
Scantling draft (MLD) 11.2 m

Cargo design Cargo tank type IMO Type A
Cargo capacity 84,000 m3
Cargo design condition 0.25 barg, −45 °C

Main engine Engine type Two-stroke ammonia fuelled engine

Table 2.

Member of HAZID expertise team

Job title Role/Expertise Company
Principal engineer HAZID facilitator/Risk assessment Classification
Principal engineer Observer/Process design Shipyard
Specialist Plan approval Classification
Specialist Plan approval Classification
Technical director Subject matter expert Engineering cooperative
Principal researcher Risk assessment Research institute
Principal researcher Operation Research institute
Senior researcher Fuel supply system design Research institute
Senior researcher Fuel supply system design Research institute
Senior manager Main engine Engine maker
Researcher Fuel supply system design Research institute
Researcher Fuel supply system design Research institute
Researcher Risk assessment Research institute

Table 3.

Likelihood rating (LR, 2016)

Rating Likelihood Ship years Ship/Fleet lives World fleet lives
L7 ≤100 to 10−1 Extremely likely 10 - -
L6 ≤10−1 to 10−2 Very likely < 10 to 100 - -
L5 ≤10−2 to 10−3 Likely < 100 to 1,000 4 to 40 -
L4 ≤10−3 to 10−4 Unlikely < 1,000 to10,000 < 40 to 400 0.167
L3 ≤10−4 to 10−5 Very unlikely < 10,000 to 100,000 < 400 to 4,000 < 0.167 to 1.67
L2 ≤10−5 to 10−6 Extremely unlikely < 100,000 to 1,000,000 < 4,000 to 40,000 < 1.67 to 16.67
L1 ≤10−6 Remote < 1,000,000 < 40,000 < 16.67

Table 4.

Consequence rating

Rating Consequence

People (LR, 2016) Asset Environment
C5 11 + fatalities Extensive damage or total loss (> USD 10,000,000) Massive damage over large area
C4 2–10 fatalities Severe vessel damage (USD 1,000,000–10,000,000) Significant spill response required
C3 Single fatality or multiple major injuries Non-severe vessel damage (USD 100,000–1,000,000) Spill response required
C2 Major injury Minor (local equipment) damage (USD 10,000–100,000) Non-compliance
C1 Minor injury Slight damage (< USD 10,000) Minor on-site impact

Table 5.

Risk matrix (LR, 2016)

Risk matrix Consequence

C1 C2 C3 C4 C5
Likelihood L7 M H H H H
L6 M H H H H
L5 M M H H H
L4 L M M H H
L3 L L M M H
L2 L L M M H
L1 L L L M M

Table 6.

Number of risk scenarios and risk rating

No. Node name Risk rating

Low Medium High
1 Ammonia filling lines for fuel service tank 0 13 0
2 Fuel service tank 0 29 0
3 Ammonia fuel lines between fuel service tank and fuel preparation room 0 15 0
4 Fuel preparation room 4 45 0
5 Ammonia fuel lines between fuel preparation room and engine room 0 17 0
6 Fuel valve train 0 6 0

Table 7.

Part of node 1 HAZID worksheet result

Hazardous event Cause Consequence Frequency rating Consequence rating Risk rating
Ammonia leakage from the equipment, piping, fitting, valve, or flange connection Design, fabrication, installation and testing according to applicable codes and standards Potential for injury or fatality due to exposure to ammonia C3 L4 M
Abnormal operation exceeding design conditions C3 L4 M
Material defect/corrosion Potential for damage to hull structure exposed to low temperature and corrosive ammonia C3 L4 M
External impact C2 L4 M
Thermal stress C3 L4 M
Hogging/sagging of hull structure C3 L4 M

Trapped ammonia in the isolated segment Lack of drain after ammonia filling operation for the fuel service tank Potential for injury or fatality due to exposure to ammonia C3 L4 M

Table 8.

Part of node 2 HAZID worksheet result

Hazardous event Cause Consequence Frequency rating Consequence rating Risk rating
Overfilling of the fuel service tank Operator error Potential for ammonia liquid release from the vent mast C3 L4 M
Fault in the level transmitter for the fuel service tank Potential for injury or fatality due to exposure to ammonia C3 L4 M

Ammonia leakage from the equipment, piping, fitting, valve, or flange connection Design, fabrication, installation, and testing according to applicable codes and standards C3 L4 M
Abnormal operation exceeding design conditions Potential for injury or fatality due to exposure to ammonia. C3 L4 M
Material defect/corrosion Potential for damage to hull structure exposed to low temperature and corrosive ammonia C3 L4 M
External impact C2 L4 M
Thermal stress C3 L4 M
Hogging/sagging of hull structure C3 L4 M

Dropped object from the cargo hose handling crane Operator error Potential for damage to the fuel service tank or associated piping C3 L4 M
Mechanical fault in the cargo hose handling crane Potential for injury or fatality due to exposure to ammonia C3 L4 M
Green sea Bad weather condition Potential for damage to hull structure exposed to low temperature and corrosive ammonia C3 L4 M

Table 9.

Part of node 3 HAZID worksheet result

Hazardous event Cause Consequence Frequency rating Consequence rating Risk rating
Ammonia leakage from the equipment, piping, fitting, valve, or flange connection Design, fabrication or installation fault Potential for injury or fatality due to exposure to ammonia C3 L4 M
Abnormal operation exceeding design conditions C3 L4 M
Material defect/corrosion Potential for damage to hull structure exposed to low temperature and corrosive ammonia C3 L4 M
Thermal stress C3 L4 M
Vibration C3 L4 M

Trapped ammonia in the isolated segment Lack of drain after ammonia FSS shutdown/stop Potential for injury or fatality due to exposure to ammonia C3 L4 M

Steam leakage from the equipment, piping, fitting, valve, or flange connection Design, fabrication or installation fault Potential for injury due to exposure to high temperature steam C3 L4 M
Abnormal operation exceeding design conditions
Material defect/corrosion

Table 10.

Part of node 4 HAZID worksheet result

Hazardous event Cause Consequence Frequency rating Consequence rating Risk rating
Ammonia leakage from the equipment, piping, fitting, valve, or flange connection Design, fabrication or installation fault Potential for injury or fatality due to exposure to ammonia C3 L4 M
Abnormal operation exceeding design conditions C3 L4 M
Material defect/corrosion Potential for damage to hull structure exposed to low temperature and corrosive ammonia C3 L4 M
Thermal stress C3 L4 M
Vibration C3 L4 M

Trapped ammonia in the isolated segment Lack of drain after ammonia FSS shutdown/stop Potential for injury or fatality due to exposure to ammonia C3 L4 M

Steam leakage from the equipment, piping, fitting, valve, or flange connection Design, fabrication or installation fault Potential for injury due to exposure to high temperature steam. C3 L4 M
Abnormal operation exceeding design conditions
C3 L4 M
Material defect/corrosion C3 L4 M

Table 11.

Part of node 5 HAZID worksheet result

Hazardous event Cause Consequence Frequency rating Consequence rating Risk rating
Ammonia leakage from the equipment, piping, fitting, valve, or flange connection Design, fabrication or installation fault Potential for injury or fatality due to exposure to ammonia C3 L4 M
Abnormal operation exceeding design conditions C3 L4 M
Material defect/corrosion Potential for damage to hull structure exposed to low temperature and corrosive ammonia C3 L4 M
External impact C3 L4 M
Thermal stress C3 L4 M
Vibration C3 L4 M
Hogging/sagging of hull structure C3 L4 M

Trapped ammonia in the isolated segment Lack of drain after ammonia FSS shutdown/stop Potential for injury or fatality due to exposure to ammonia. C3 L4 M

Table 12.

Part of node 6 HAZID worksheet result

Hazardous event Cause Consequence Frequency rating Consequence rating Risk rating
Ammonia leakage from the equipment, piping, fitting, valve or flange connection Design, fabrication or installation fault Potential for injury or fatality exposure to ammonia. due to C3 L4 M
Abnormal operation exceeding design conditions C3 L4 M
C3 L4 M
Malfunction/system failure
Material defect/corrosion C3 L4 M