Internal combustion engine

Abstract

An internal combustion engine (200) comprises a first ammonia fuel supply system (31) and a second Diesel fuel supply system (151). A fuel purge system (32) is used for purging the first fuel supply system using a first fluid nitrogen. An injector cooling system (34) is used for, when the engine runs on the second fuel, cooling the first injector (3) using a second fluid water. The second fluid is supplied to the first injector (3) via the first fuel supply system (31). A fuel valve unit (33) connects and disconnects the engine from the first fuel supply system, the fuel purge system, and the injector cooling system. The engine is configured to, after the first fuel supply system is filled with the second fluid by means of the injector cooling system, • remove the second fluid from the first fuel supply sys- tern, and store the removed second fluid, • purge the first fuel supply system with a third fluid, and • remove the third fluid from the first fuel supply system, in particular by means of the first fluid.

Description

[0001] PWIND071WO / ll . 11 . 2025 1 2025129078

[0002] Internal Combustion Engine

[0003] Technical Field

[0004] The present invention is directed to an internal combustion engine having at least one cylinder and to a method for operating such an internal combustion engine . Further aspects relate to a computer program product and a computer-readable medium for implementing such a method .

[0005] Background Art

[0006] Large engines , which can be configured as two-stroke or four- stroke engines - for example , as longitudinally scavenged two- stroke large engines or two-stroke cross-head engines — are often used as drive units for ships , particularly large ships and vessels for the transport of goods , or in stationary operations such as driving large generators for generating electrical energy . The engines usually run for considerable periods in continuous operation, which places high demands on operational safety and availability . As a consequence , particularly long maintenance intervals , low wear, and economical handling of the operating materials are central criteria for the operator .

[0007] Large engines typically have cylinders with an inner diameter (bore ) of at least 200 mm . Nowadays , large engines with a bore of up to 980 mm or even more are used . Within the framework of this application, the term " large engine" designates an internal combustion engine with a bore of the cylinder ( s ) that is at least 200 mm and preferably at least 300 mm . Engine speed is preferably below 800 RPM, especially for four-stroke engines , and more preferably below 200 RPM for two-stroke engines , which indicates the designation of low-speed engines . PWIND071WO / ll.11.2025 2 2025129078

[0008] Large engines are classically configured as large diesel engines, which are operated with heavy fuel oil. The engine can be a diesel or a gas engine, a dual-fuel or a multi-fuel engine. Under the aspects of economic and efficient operation, compliance with exhaust-gas limit values, sustainability, reduction of CO2emissions, and the availability of resources, alternatives to heavy fuel oil are now also being sought for large engines. In this respect, both liquid fuels — i.e., fuels that are introduced into the combustion chamber in the liquid state— and gaseous fuels — i.e., fuels that are introduced into the combustion chamber in the gaseous state — are used.

[0009] Examples of liquid fuels as known alternatives to heavy fuel oil are other heavy hydrocarbons, which are particularly left over as residues from oil refining; alcohols, in particular methanol or ethanol; ammonia; gasoline; diesel; or also emulsions or suspensions such as slurries. Biological fuels, such as oil made from algae or seaweed, HVO (hydro-treated vegetable oil) , and FAME (fatty acid methyl ester) based fuels are also possible. For example, it is known to use emulsions known as MSAR (Multiphase Superfine Atomized Residue) as fuel. As gaseous fuels, natural gases such as LNG (liquefied natural gas) , liquefied gases such as LPG (liquefied petroleum gas) , natural gas (NG) , petrol gas (PG) , ethane, or hydrogen are known. Further possible fuels comprise LBG (liquefied biogas) , hydrogen, ammonia, and synthetic fuels from CO2(e.g., made by Power-To-Gas or Power-To- Liquid processes) .

[0010] In particular, large engines are also known which can be operated with at least two or even more different fuels, whereby the engine is operated either with one fuel or with the other fuel depending on the operating situation or environment. It is also PWIND071WO / ll.11.2025 3 2025129078 known to concurrently inject the two different fuels into the combustion chamber of the cylinder.

[0011] Large engines that can be operated with two or more different fuels are referred to as dual-fuel or multi-fuel large engines. Depending on the fuels, these engines may be operated in a liquid mode, in which a liquid fuel is introduced into the cylinder for combustion, and / or in a gas mode, in which a gas is introduced into the cylinder as fuel.

[0012] Large engines, which can be operated with at least two or even more different liquid or gaseous fuels, are often operated in different operating modes depending on the fuel currently in use. In the operating mode often referred to as diesel operation, the combustion of the fuel generally takes place according to the principle of compression ignition or self-ignition of the fuel. In the mode often referred to as Otto operation, combustion takes place by induced ignition. This induced ignition can take place, for example, by an electrical spark (e.g., with a spark plug) or by the self-ignition of a small injected amount of fuel (pilot fuel) , which then causes the induced ignition of another fuel. The small amount of fuel intended for self-ignition is directly inserted into the combustion chamber or injected into a pre-chamber connected to the combustion chamber. Forced ignition can thus be achieved by use of a pre-chamber, a spark plug, and / or a pilot fuel. The process of induced ignition by self-ignition of a small amount of a liquid or another selfigniting fuel is sometimes referred to as pilot injection. Furthermore, mixed forms using both Otto and diesel operation are also known.

[0013] In particular, in view of attempts to reduce greenhouse gas emissions, the reduction of CO2production, and sustainability PWIND071WO / ll.11.2025 4 2025129078 goals, a reduction in the use of fossil fuels is strived for. Thus, alternatives are investigated to at least reduce or even completely avoid the use of fossil fuels in large engines. Even if this is still a long way off, a partial replacement of fossil fuels by renewable fuels is considered a significant success.

[0014] One alternative to fossil fuel is, for example, methanol or ammonia. However, such renewable fuels can cause corrosion problems in the fuel distribution and injection system, in particular during standstill of the engine, when the stagnant methanol can corrosively attack the pipes or other components of the fuel injection system. Furthermore, there is the risk that these fuels escape from the engine — e.g., as vapor— into the space which is accessible to engine maintenance or operating personnel. This constitutes a health hazard requiring comprehensive mitigation measures.

[0015] The escaping of gaseous fuel into the atmosphere are usually referred to as fuel slip or fugitive emissions. When methanol or ammonia is used as a fuel in a large engine, most of the methanol or ammonia is consumed in the combustion process. However, some of the fuel remains unburned and may escape into the atmosphere — e.g., by passing through the exhaust gas system of the large engine (slip) . All upstream losses are summarized as fugitive emissions. Methanol or ammonia is hazardous for the environment as well as for humans and animals. Therefore, great efforts are made to reduce the fuel slip occurring in large engines, such as those used for ship propulsion.

[0016] The present invention is in particular related to combustion engines which use ammonia as a (main) fuel. PWIND071WO / ll.11.2025 5 2025129078

[0017] Ammonia-fuelled ships are increasingly being developed and built, or engines adapted to be driven by ammonia-fuel, following a 2018 International Maritime Organisation commitment to cut International shipping's greenhouse gas emissions.

[0018] Ammonia is a synthetic product obtained from fossil fuels, biomass, or renewable sources (wind, solar, hydro, or thermal) , and when generated by renewable sources, ammonia will have virtually no carbon footprint or emit any CO2, SOX, particulate matter, or unburned hydrocarbons when combusted.

[0019] When the fuel is ammonia, it is desirable to minimise emissions of ammonia gas because ammonia is hazardous and has a pungent smell. This is particularly relevant for crew safety, and when an engine stops and / or when a change to conventional (backup) fuel takes place and / or in occurrence of an unexpected event. Therefore, it is known to purge the engine and pipings, typically with an inert gas, such as nitrogen.

[0020] Purging of ammonia is needed to enable maintenance during stops and, in general, to prevent appearance of ammonia in the engine room due to leakages.

[0021] The risk of events like ammonia leakage into the engine room or alike is thus minimized. Such leaks may cause the engine to trip during operations, and an unplanned engine stop may have very series consequences, e.g. in the harbour or port and / or during re-fuelling .

[0022] When ammonia is purged, a corrosion attack on the engine materials may be avoided during durable backup fuel operation or during a stand-still. PWIND071WO / ll . 11 . 2025 6 2025129078

[0023] Accumulation of fuel vapours up to the f lammable / combustible range in the air compartments / pockets may be avoided .

[0024] PCT / EP2024 / 074000 discloses an internal combustion engine with a fuel purge system and an inj ector cooling system . It does not disclose the preparation of the engine for maintenance , though .

[0025] Disclosure of the Invention

[0026] It is an obj ective of the present invention to at least in part prevent the drawbacks of the prior art and in particular to create an internal combustion engine and a method for preparing such an internal combustion engine for maintenance , which allow a safer and more ef fective operation .

[0027] This obj ective is achieved by an internal combustion engine , a method for preparing such an internal combustion engine for maintenance and a computer program product according to the independent claims .

[0028] According to a first aspect of the invention, an internal combustion engine has at least one cylinder with an inner diameter of at least 200 mm . The engine comprises a first fuel supply system for supplying a first fuel , in particular ammonia, to the engine . The first fuel supply system comprises at least one first inj ector for each cylinder . Thus , the first fuel can be inj ected into the cylinder when the engine runs on the first fuel .

[0029] The engine further comprises a second fuel supply system for supplying a second fuel , in particular Diesel , to the engine . The second fuel supply system comprises at least one second inj ector for each cylinder . Thus , the second fuel can be inj ected into the cylinder when the engine runs on the second fuel . PWIND071WO / ll.11.2025 7 2025129078

[0030] The engine further comprises a fuel purge system for purging the first fuel supply system including the first injector using a first fluid, in particular a gas like, e.g. nitrogen or an inert gas, and / or a third fluid, such as freshwater. Thus, the first fuel supply system can be purged of the first fuel when, e.g., the engine operation is switched to the second fuel or operation is stopped for the purpose of maintenance.

[0031] Within this context "freshwater" means water uncontaminated with the first fuel, for example ammonia.

[0032] Further, the engine comprises an injector cooling system for, when the engine runs on the second fuel, cooling the first injector using a second fluid such as water, and / or a third fluid, such as freshwater. Hereby, the second fluid and / or the third fluid is supplied to the first injector via the first fuel supply system.

[0033] Whereas the second fluid, for example water, may be allowed to contain up to 10% (m / m) of the first fuel, for example ammonia, the third fluid, for example freshwater, preferably is practically free of the first fuel. Hence, the third fluid typically is used for cooling only after the fuel system has been purged, for example with an inert gas, or after the second fluid has been removed from the cooling system.

[0034] Preferably, the injector cooling system comprises a cooling circuit, wherein the second fluid and / or the third fluid is reused to cool the first injector.

[0035] The engine further comprises a fuel valve unit for connecting and disconnecting the engine from the first fuel supply system (e.g. when switching to second fuel operation) , for connecting PWIND071WO / ll.11.2025 8 2025129078 and disconnecting the fuel purge system (e.g. for purging) , and for connecting and disconnecting the injector cooling system (e.g. as long as the engine is running on the second fuel) .

[0036] Within this context "connecting the engine to the first fuel supply system" means, that at least one fuel valve is opened, such that the first fuel may be guided to the at least one first injector from a fuel tank. Analogously, "disconnecting the engine to the first fuel supply system" means, that at least one fuel valve is closed, such that no first fuel is guided to the at least one first injector.

[0037] Within this context "connecting and disconnecting the fuel purge system" means opening and closing at least purge valve, such that the supply of a first or third fluid to the first fuel supply system is allowed or restricted.

[0038] Within this context "connecting and disconnecting the injector cooling system" means opening and closing at least cooling valve, such that the supply of second fluid to the first injector is allowed or restricted.

[0039] According to the invention, the engine is configured to, in particular but not necessarily in the mentioned order, after the first fuel supply system is filled with the second fluid by means of the injector cooling system, apply the following step.

[0040] The second fluid (e.g. ammonia contaminated water) is removed from the first fuel supply system. This is in particular achieved by means of the first fluid, e.g. nitrogen, but can also be achieved by a third fluid, such as freshwater. Then, the removed second fluid (e.g. ammonia contaminated water) may be PWIND071WO / ll.11.2025 9 2025129078 stored, e.g. in a wastewater tank, eventually as a mixture with the first or the third fluid.

[0041] The first fuel supply system may be purged with a first fluid (e.g. nitrogen) or a third fluid (e.g. freshwater) , preferably after the second fluid has been removed.

[0042] Additionally or alternatively, the engine may be configured to purge the first fuel supply system with a first fluid (e.g. nitrogen) or a third fluid (e.g. freshwater) before the second fluid is applied for cooling.

[0043] Eventually, the third fluid (e.g. fresh water) may be removed from the first fuel supply system. This may in particular be achieved by means of the first fluid (e.g. nitrogen) . The first fuel supply system then is clean and empty and can be opened for the purpose of maintenance.

[0044] When operating on the first fuel has ended, the first fuel supply system may still contain residuals of the first fuel. These residuals regularly contaminate the second fluid which is supplied by the injector cooling system to cool the first fuel supply system.

[0045] For example, in case of maintenance, it has to be taken care that any residuals of the first fuel are removed from the first fuel supply system. The first fuel supply system may be purged before cooling, such that the second fluid remains uncontaminated. Preferably, the second fluid, which may be contaminated, is removed by the first fluid or by the third fluid after cooling. This ensures, that there are no first fuel residuals remaining in the first fuel supply system, when maintenance begins . PWIND071WO / ll.11.2025 10 2025129078

[0046] In a final step, an e.g. liquid second or third fluid may be purged with an e.g. gaseous first fluid, such that the first fuel supply system is clean and empty.

[0047] According to a second aspect of the invention, a method for preparing an internal combustion engine as described above with regard to the first aspect of the invention comprises the steps of, in particular but not necessarily in the mentioned order:

[0048] - Removing the second fluid (e.g. ammonia contaminated water) from the first fuel supply system. This is in particular achieved by means of the first fluid, e.g. nitrogen. Then, the removed second fluid (e.g. ammonia contaminated water) is stored, e.g. in a wastewater tank. Alternatively, the second fluid can be removed using a third fluid, for example freshwater.

[0049] - Purging the first fuel supply system with a third fluid (e.g. fresh water) .

[0050] - Removing the third fluid (e.g. fresh water) from the first fuel supply system. This is in particular achieved by means of the first fluid (e.g. nitrogen) .

[0051] According to a third aspect of the invention, a computer program product comprises instructions to cause an engine control unit of an internal combustion engine according to the first aspect of the invention to execute the steps of a method according to the second aspect of the invention when the program is executed on the engine control unit.

[0052] A computer-readable medium can store such a computer program product . PWIND071WO / ll . 11 . 2025 11 2025129078

[0053] Brief Description of the Drawings

[0054] The invention will be better understood and obj ects other than those set forth above will become apparent when consideration is given to the following detailed description thereof . Such description makes reference to the annexed drawings , wherein :

[0055] Figure 1 shows a schematic representation of a first embodiment of a large engine 200 according to the invention;

[0056] Figure 2 shows a schematic representation of a system arrangement with a second embodiment of a large engine 200 according to the invention;

[0057] Figure 3 shows a schematic representation of an ammonia inj ector cooling water system of the second embodiment of a large engine 200 ;

[0058] Figure 4 shows operating modes for the X-DF-A- 1 . 0 engines .

[0059] Modes for Carrying Out the Invention

[0060] Fig . 1 shows a schematic representation of an embodiment of a large engine 200 . In Fig . 1 , only one of the cylinders 110 of the large engine 200 is shown . Usually, the large engine 200 comprises a plurality of cylinders 110 , for example at least four and up to twelve cylinders 110 or even more . The term " large engine" refers to internal combustion engines that are typically used as drive units for ships or in stationary operations , such as driving large generators for generating electrical energy . Typically, the cylinders 110 of a large engine 200 each have an inner diameter (bore ) of at least about 200 mm . Large engines 200 are known in various configurations , for example as two-stroke engines or four-stroke engines .

[0061] In the following description, reference is made by way of example to a large engine 200 configured as a longitudinally scavenged two-stroke large engine having a plurality of cylinders PWIND071WO / ll.11.2025 12 2025129078

[0062] 110. Each cylinder 110 has a combustion chamber 100. Furthermore, in each cylinder 110, a piston 120 is arranged for reciprocating movement between a top dead center and a bottom dead center .

[0063] The term "longitudinally scavenged" means that the scavenging or charging air is introduced into the cylinder 110 in the area of the lower end, and an exhaust valve 130 is arranged in or at the cylinder cover 2 located at the upper end of the cylinder 110.

[0064] In particular, reference is made to a large longitudinally scavenged two-stroke engine that can be operated with different fuels, namely with a first fuel and with a second fuel. Preferably, the large engine 200 is configured as a large diesel engine. The term "large diesel engine" refers to engines that can be operated at least in diesel operation. In particular, the term "large diesel engine" also comprises large engines 200 that can be operated in another mode, e.g., Otto operation, in addition to diesel operation.

[0065] According to a preferred configuration, the large engine 200 can be operated with ammonia as a first fuel and with a self-igniting and liquid second fuel. For this, the engine comprises a first fuel supply system 31 and a second fuel supply system 151. Usually, liquid fuel— such as heavy fuel oil (HFO) , marine diesel oil (MDO) , or marine gas oil (MGO)— is injected directly into the combustion chamber 100 at a suitable time and ignites there according to the diesel principle of self-ignition. For injecting the second fuel into the combustion chamber 100, each cylinder comprises a second fuel injector 150, which is different from the first fuel injector 3. Thus, each cylinder 110 comprises at least one, but preferably a plurality of, first fuel injectors 3 PWIND071WO / ll.11.2025 13 2025129078 for injecting the first fuel, as well as at least one, but preferably a plurality of, second fuel injectors 150 for injecting the second fuel.

[0066] The first fuel, which is injected with the fuel injector 3 into the combustion chamber 100, is, for example, a fuel for Otto operation, i.e., with induced ignition of the fuel. The first fuel can be injected into the combustion chamber 100 where it is ignited according to the Otto principle. This induced ignition is usually caused by introducing a small amount of self-igniting second fuel (e.g., diesel or heavy fuel oil) into the combustion chamber 100 or into a pre-chamber at a suitable moment, which second fuel then ignites itself and causes the induced ignition of the first fuel in the combustion chamber 100.

[0067] Introducing a small amount of a self-igniting liquid second fuel into the combustion chamber 100 or into at least one pre-chamber for the induced ignition of the first fuel is also referred to as pilot ignition. Beside a diesel oil it is also possible to use a gas or an alcohol such as methanol as pilot fluid for the pilot ignition.

[0068] In other embodiments, the induced ignition is achieved by way of spark ignition, laser pulse, or any other means suited for igniting the fuel in the combustion chamber 100.

[0069] In the following description, reference is made to a preferred embodiment in which the first fuel is ammonia, and the second fuel is a Diesel fuel for self-ignition, for example HFO, MDO, or MGO. Regarding the first fuel, it is preferred that the operation with the first fuel is an operation according to the Otto principle . PWIND071WO / ll . 11 . 2025 14 2025129078

[0070] Furthermore , the large diesel engine 200 can be operated in a mixed mode , in which both the first fuel and the second fuel are inj ected into the combustion chamber 100 of the cylinder 110 . In the mixed mode , both the combustion of the first fuel and the combustion of the second fuel contribute to the generation of torque .

[0071] In the embodiment described here , the large engine is configured as a longitudinally scavenged dual- fuel two-stroke large diesel engine , which can be operated with ammonia as the first fuel and / or with a diesel fuel as the second fuel .

[0072] The dual- fuel large diesel engine has a plurality of cylinders 110 . In each cylinder 110 , the piston 120 is connected in a manner known per se to a crosshead 122 via a piston rod 121 . The crosshead 122 is connected to a crankshaft 170 via a push rod or connecting rod 123 , so that the movement of the piston 120 is transmitted via the piston rod 121 , the crosshead 122 , and the connecting rod 123 to the crankshaft 170 to rotate it . The upper side of the piston 120 , together with the cylinder cover 2 , delimits the combustion chamber 100 into which the first fuel and / or the second fuel is introduced .

[0073] The structure and individual components of a large diesel engine 200 — such as the inj ection system for the fuels , the gas exchange system, the exhaust system, the turbocharger system for the supply of scavenging or charging air, as well as the monitoring and control system — are suf ficiently known to those skilled in the art for both two-stroke and four-stroke engine designs and therefore need no further explanation here .

[0074] In the embodiment of a longitudinally scavenged two-stroke large diesel engine 200 , scavenging air slots 115 are usually provided PWIND071WO / ll . 11 . 2025 15 2025129078 in the lower region of each cylinder 110 or cylinder liner .

[0075] These slots are periodically closed and opened by the movement of the piston 120 in the cylinder 110 , allowing the scavenging air provided by the turbocharger under charging pressure to flow into the cylinder 110 through the scavenging air slots 115 when they are open . In the cylinder cover 2 , the usually centrally arranged exhaust valve 130 is provided, through which the exhaust gases can be discharged from the cylinder 110 into the exhaust system after the combustion process . The exhaust system guides at least a part of the exhaust gases to a turbine of the turbocharger, whose compressor provides the scavenging air— also referred to as charging air — in a scavenge air receiver under scavenge air pressure . The scavenge air receiver is in fluid communication with the scavenging air slots 115 of the cylinders

[0076] 110 .

[0077] Each cylinder 110 comprises at least one first fuel inj ector 3 for inj ecting the first fuel into the combustion chamber 100 of the cylinder 110 . Preferably, the cylinder 110 comprises a plurality of first fuel inj ectors 3 , for example two or three first fuel inj ectors 3 , for uni formly distributing the first fuel in the combustion chamber 100 . In the embodiment of the large engine 200 described here , preferably exactly three first fuel inj ectors 3 are provided ( only one first fuel inj ector 3 is shown in the schematic representation of Fig . 1 ) . Each first fuel inj ector 3 is arranged in the cylinder cover 2 of the cylinder 110 . The cylinder cover 2 comprises an inner surface for delimiting the combustion chamber 100 and an inj ector bore (not shown in the figure ) extending through the cylinder cover 2 and opening into the inner surface . The inj ector bore is configured to receive the first fuel inj ector 3 . Preferably, the first fuel inj ectors 3 are arranged in the cylinder cover 2 near the exhaust valve 130 . PWIND071WO / ll.11.2025 16 2025129078

[0078] Each cylinder 110 further comprises at least one second fuel injector 150 for injecting the second fuel into the combustion chamber 100 of the cylinder 110. Preferably, the cylinder 110 comprises a plurality of second fuel injectors 150, for example two or three second fuel injectors 150, for uniformly distributing the second fuel in the combustion chamber 100. Each second fuel injector 150 is arranged in the cylinder cover 2 of the cylinder 110 in a manner known in the art. Preferably, the second fuel injectors 150 are arranged in the cylinder cover 2 near the exhaust valve 130.

[0079] Nowadays, a large diesel engine or a large engine 200 in general is operated in a fully electronically controlled manner. An engine control unit 180 operates and controls all functions of the large engine 200 — for example, the operation of the exhaust valves 130 for the gas exchange, the injection process for the fuels, and the pilot injection timing (when pilot injection is required)— by way of electric or electronic signals and commands. In addition, the engine control unit 180 receives information from several detectors, sensors, or measuring devices.

[0080] It is noted that the invention is not restricted to this specific type of a longitudinally scavenged two-stroke large engine 200, which can be operated with the first fuel and / or with the second fuel. The large engine can also be any other type of large engine.

[0081] The engine comprises a fuel purge system 32 for purging the first fuel supply system 31 using a first fluid, i.e. nitrogen. Further, the engine comprises an injector cooling system 34 for, when the engine runs on the second fuel, cooling the first injector 3 using a second fluid, i.e. water, wherein the second fluid is supplied to the first injector 3 via the first fuel supply system 31. A fuel valve unit 33 connects and disconnects PWIND071WO / ll . 11 . 2025 17 2025129078 the engine from the first fuel supply system 31 , connects and disconnects the fuel purge system 32 , and connects and disconnects the inj ector cooling system 34 . The engine 200 preferably is configured to , after the first fuel supply system 31 including the first inj ector 3 is filled with the second fluid (water ) by means of the inj ector cooling system 34 ,

[0082] - remove the second fluid ( contaminated water ) from the first fuel supply system 31 , in particular by means of the first fluid (nitrogen) that is used in the fuel purge system 32 , and store the removed second fluid,

[0083] - purge the first fuel supply system 31 with a third fluid ( fresh water ) , and

[0084] - remove the third fluid from the first fuel supply system 31 , in particular by means of the first fluid (nitrogen) .

[0085] Figure 2 shows a schematic representation of a system arrangement with a second embodiment of a large engine 200 according to the invention, which is similar to the first embodiment as shown in figure 1 .

[0086] The system arrangement with engine 200 can be roughly divided into di f ferent parts : the engine room 410 , the fuel venting unit 420 , the fuel preparation space 430 , the fuel processing space 440 and the fuel hold space 450 .

[0087] The internal combustion engine 200 comprises at least one cylinder 110 with an inner diameter of at least 200 mm, typically arranged in an engine room 410 .

[0088] The engine comprises a first fuel supply system 31 for supplying a first fuel to the engine including at least one first inj ector 3 ( see figure 1 ) for each cylinder . PWIND071WO / ll . 11 . 2025 18 2025129078

[0089] In this embodiment the first fuel supply system 31 is an ammonia fuel supply system, which is fluidly connectable to an ammonia storage tank 311 . Between the ammonia storage tank 311 and the first fuel supply system 31 , ammonia may be prepared and guided through a flow meter 312 , a pre- filter system 313 , a heat exchanger 314 , a high-pressure pump 315 and a high-pressure filter 316 .

[0090] The internal combustion engine 200 further comprises a second fuel supply system 151 ( see figure 1 ) not shown in figure 2 .

[0091] A main fuel supply valve 317 is arranged in a fuel supply line 318 , which fluidly connects the at least one first inj ector 3 ( see figure 1 ) with the ammonia storage tank 311 . The main fuel supply valve 317 belongs to the fuel valve unit 33 ( see figure 1 ) for connecting the engine to the first fuel supply system 31 and disconnecting and for disconnecting the engine form the first fuel supply system 31 .

[0092] The internal combustion engine 200 further comprises a fuel purge system 32 for purging the first fuel supply system 31 using a first fluid, in this case nitrogen . The fuel purge system 32 comprises an inert gas supply system 321 .

[0093] An inert gas valve 322 arranged in an inert gas line 323 also belongs to the fuel valve unit 33 ( see figure 1 ) . In case the inert gas valve 322 is open, nitrogen is supplied from the inert gas supply system 321 to the first fuel supply system 31 and the fuel purge system 32 is "connected" . I f the inert gas valve 322 is closed, no nitrogen may be guided to the first fuel supply system 31 and the fuel purge system 32 is "disconnected" . PWIND071WO / ll.11.2025 19 2025129078

[0094] The internal combustion engine 200 further comprises an injector cooling system 34. The injector cooling system 34 comprises a cooling circuit 341 only partially shown in the figure. The part not shown in this figure, which is the ammonia injector cooling water system 345, is shown in more detail in figure 3.

[0095] For example, when the engine runs on the second fuel, the first injector 3 (see figure 1) is cooled using a second fluid, wherein the second fluid is supplied to the first injector 3 (see figure 1) via the first fuel supply system 31.

[0096] The second fluid may be guided through the fuel supply line 318 to the first injector 3 (see figure 1) and through an ammonia purging pipe 342 away from the first injector 3 (see figure 1) .

[0097] A cooling fluid supply valve 343 as well as a cooling circuit valve 344 also belong to the fuel valve unit 33 (see figure 1) . In case the cooling fluid supply valve 343 and the cooling circuit valve 344 are open, second fluid, e.g. water, may circulate through the first fuel supply system 31 and the injector cooling system 34 is "connected".

[0098] In case the cooling fluid supply valve 343 and the cooling circuit valve 344 are closed, no circulation of second fluid is possible and the injector cooling system 34 is "disconnected".

[0099] Via the cooling fluid supply valve 343 also freshwater may be supplied to the the first fuel supply system 31. Contaminated second fluid may be washed out of the first fuel supply system 31, e.g. for preparing maintenance.

[0100] An inert gas supplied from the inert gas supply system 321 to the fuel supply system 31 may be used for purging the first fuel PWIND071WO / ll . 11 . 2025 20 2025129078 supply system 31 before cooling . Purged gaseous ammonia may be guided through the ammonia purging pipe 342 and, i f the gaseous purge valve 351 is open, into an ammonia vapour processing system 352 .

[0101] A liquid, such as water, supplied to the first fuel supply system 31 may be used for purging the first fuel supply system 31 before cooling . Purged liquid ammonia or diluted ammonia may be guided through the ammonia purging pipe 342 and, i f the liquid purge valve 353 is open, into a catch tank 354 .

[0102] The interstitial space of the double walled pipes 361 of the first fuel supply system 31 and the ammonia purging pipe 342 may be vented by a ventilation system 362 , for removing leaked fuel .

[0103] Figure 3 shows a schematic representation of an ammonia inj ector cooling water system 345 of the second embodiment of a large engine 200 .

[0104] The ammonia inj ector cooling water system 345 comprises an interface 346a, 346b for establishing a fluid connection on the one hand to the fuel supply line 318 ( see figure 2 ) and on the other hand to the ammonia purging pipe 342 ( see figure 2 ) .

[0105] Cooling water may be guided from a cooling water buf fer tank 347 via interface 346a to the fuel supply line 318 ( see figure 2 ) and further to the first inj ector 3 ( see figure 1 ) . Downstream the first inj ector 3 , the cooling water is guided via the ammonia purging pipe 342 ( see figure 2 ) to the interface 346b and back to the cooling water buf fer tank 347 . Thus , the cooling water is circulated . PWIND071WO / ll . 11 . 2025 21 2025129078

[0106] The ammonia inj ector cooling water system 345 comprises a heat exchanger 348 to provide a cooling temperature . The ammonia inj ector cooling water system 345 also comprises a cooling water pump 349 .

[0107] Cooling water may be provided to the cooling water buf fer tank 347 from a cooling water storage tank 340 .

[0108] As the cooling water may be contaminated by first fuel , in this case ammonia, the cooling water buf fer tank 347 may be released into an ammonia wastewater tank 355 .

[0109] Gaseous ammonia evaporating from the cooling water may be released into the environment E or into the ammonia vapour processing system 352 .

[0110] The ammonia inj ector cooling water system 345 and eventually the whole cooling circuit 341 ( see figure 2 ) may be purged by introducing an inert gas from the inert gas supply system 321 or by introducing freshwater from a cooling water storage tank 340 .

[0111] Figure 4 shows operating modes for the X-DF-A- 1 . 0 engines as explained further below .

[0112] In the document "CONCEPT GUIDANCE for X-DF-A" as of November 22 , 2024 , further advantageous embodiments as well as applications of the invention are described . The content of the document is essentially reproduced below . PWIND071WO / ll . 11 . 2025 22 2025129078

[0113] Purpose of this Concept Guidance for the X-DF-A engine

[0114] The purpose of the Concept Guidance for the X-DF-A engine is to introduce ammonia as a fuel for marine application with the related implication on the system design. This document covers a wide range of information, such as the characteristics of ammonia as a fuel, the related risks of fire and explosion, as well as toxicity for humans and environment. The engine design criteria are under WinGD responsibility, while the design requirements for the external supply system are mentioned for reference only and are not binding.

[0115] Characteristics of ammonia as a fuel

[0116] Introduction

[0117] Ammonia (NHs) is a colourless, toxic gas at ambient temperature and pressure. It has a pungent smell and lower density compared to air. To be in liquid state, it needs either to be cooled down at -33°C at atmospheric pressure or pressurised to the corresponding saturation pressure at ambient temperature.

[0118] Ammonia has a carbon- and sulphur-free molecular composition. Burning of NHs creates minimal CO2 and SOx emissions due to pilot fuel requirements. Emissions of air pollutants related to carbon (black carbon or soot, unburnt hydrocarbons (HC), methane slip and carbon monoxide (CO)) are nearly eliminated. Therefore, it is an attractive fuel for marine applications towards lower carbon emissions as required by the International Marine Organization’s (IMO) CO2 and Greenhouse Gas (GHG) targets for 2030 and 2050. In addition, since ammonia is sulphur free, the sulphur content limits established by Regulation 14 of MARPOL Annex VI, are completely met when using ammonia as a fuel.

[0119] Generally, ammonia is produced via the Haber-Bosch synthesis process from hydrogen and nitrogen. While the nitrogen comes from air separation, different sources can be used to produce hydrogen. Based on the sources used to produce hydrogen, ammonia can be classified as “grey", “blue" and “green". Large-scale industrial productions of ammonia are based mainly on fossil fuel feedstock for “grey" and “blue" ammonia production which still produces CO2 as residual product of the synthesis process. However, ammonia has the potential to become completely “green" when it is produced by using hydrogen obtained from using renewal energy sources (e.g. hydrogen is obtained by electrolysis of water, and the electricity used in the process is obtained by only renewable energy sources). A gradual decarbonisation is possible by increasing the amount of “green" ammonia production and use.

[0120] The WinGD X-DF-A is a dual-fuel engine which injects ammonia into the engine. For this engine, liquid injection is under development. This engine utilises the diesel combustion principle, ensuringemission optimised combustion.

[0121] The WinGD X-DF-A engines meet IMO Tier II NOx emission levels in both ammonia mode and diesel mode. The engines also meet IMO Tier III NOx levels in both modes through exhaust gas aftertreatment (e.g. Selective Catalytic Reduction (SCR)).

[0122] This document is based on the “International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code)" and “International Code of Safety for Ship Using Gases or Other Low-flash-point Fuels (IGF Code)" as well as on the available classification society rules at the time of the document release. This document is for application of X-DF-A engines on any vessel type, i.e. it is valid for both Ammonia carriers as well as Ammonia fuelled non-gas carriers. PWIND071WO / ll . 11 . 2025 23 2025129078

[0123] Ammonia properties

[0124] The following Table 0-1 provides the required ammonia specifications at the engine inlet

[0125] Table 0-1: Specifications of ammonia bunker limits

[0126] ("(Suitable method must be applied and reported.

[0127] The following values are only for guidance. Project-specific values must be considered.

[0128] Table 0-2: Comparison of energy properties for ammonia and marine gas oil

[0129] (*> storage condition -33°C and 1 bar(a)

[0130] (**) condition 25°C and 1 bar(a)

[0131] Safety Considerations

[0132] Using ammonia as a fuel adds some additional challenges during the design phase of the vessel, engines and related systems. Fuel containment, distribution and supply systems can be based on existing technologies, but still risk assessment must be performed to confirm that the risks from ammonia fuel affecting persons on board, environment and ship structural strength or integrity are addressed. The risk assessment must be carried out using acceptable and recognized risk analysis techniques, taking into consideration the IGF code and corresponding class rules for ammonia.

[0133] In a liquid state, ammonia is not flammable and cannot ignite. However, it vaporizes rapidly. The main safety concern is its toxicity. For these reasons, duringthe design phase the following must be considered: PWIND071WO / ll . 11 . 2025 24 2025129078

[0134] • segregation

[0135] • double barriers arrangements

[0136] • leakage detection

[0137] • automatic isolation of leakages.

[0138] Fire or explosion

[0139] Ammonia is a flammable gas with narrow flammability range. Its flammable range in dry air is between 14% (vol) and 27% (vol). It has a flashpoint of 132°C and an auto ignition temperature of 651°C. Therefore, the risk of fire caused by ammonia is lower compared to other fuels due to its higher Lower Explosion Limit (LEL). However, when ammonia is stored in a liquid phase under pressure, the Boiling Liquid-Expanding Vapours Explosions (BLEVEs) are a hazard often associated with ammonia. BLEVE can occur when ammonia is stored in a pressurised tank above its boiling point. The liquid can begin to boil and expand if the tank fails and is exposed to ambient pressure. This can result in tank explosions.

[0140] Fire prevention

[0141] Ammonia fire and explosion prevention is achieved by reducing potential ignition sources to a minimum, controlling the storage conditions of ammonia, using certified safe type electrical equipment suitable for hazardous zones.

[0142] Reduction of potential ignition sources to a minimum

[0143] Ammonia burns with difficulty in open air and generally needs a supporting flame to keep burning. Even if risk of ammonia fire is lower compared to other fuels, it can still occur in case particular conditions are met. In addition to pure ammonia fires, the fire risks of ammonia are higher when ammonia is mixed with other fuels and lubricating oils because of increased flammable properties of ammonia. Such fuel mixtures can have a much broader explosive range. Ammonia fires and explosions can be prevented by reduction of potential ignition source to a minimum where ammonia can be present.

[0144] Control of ammonia storage conditions

[0145] Ammonia can react with halogens, interhalogens and oxidizers and can cause violent reactions or explosions. Therefore, ammonia must be stored in temperature-controlled tank(s), well-ventilated location, and separate from oxidizing gases and acids. Dilution can be utilized in order not to reach ammonia flammability range.

[0146] Certified safe type electrical equipment

[0147] Electrical equipment cannot be installed in hazardous areas, unless it is essential for operational purposes. To facilitate the selection and design of appropriate electrical equipment and installations, hazardous containment areas are classified into zones 0, 1 and 2 based on the associated risk of explosion. All hazardous areas must always be inaccessible to passengers and unauthorised crew.

[0148] According to the IGF code (Part A-l, 12.5), the hazardous area zones are classified as following:

[0149] Hazardous area zone 0 includes, but is not limited to, the following areas:

[0150] • interiors of ammonia tanks

[0151] • pipework for pressure relief or other venting systems for fuel tanks

[0152] • pipes and equipment containing ammonia.

[0153] Hazardous area zone 1 includes the following areas:

[0154] • tank connection space

[0155] • fuel preparation rooms PWIND071WO / ll . 11 . 2025 25 2025129078 fuel storage hold space and inter-barrier spaces cofferdams enclosed or semi-enclosed spaces where ammonia leakages can occur.

[0156] Hazardous area zone 2 includes, but is not limited to, the following areas:

[0157] • areas within 1.5 m surrounding open or semi-enclosed spaces of zone 1

[0158] • space containing bolted hatch to tank connection space.

[0159] Fire detection

[0160] Standard fire detection devices can be applied for ammonia fuelled installations.

[0161] Fire control

[0162] The United States National Centre for Biotechnology Information (NCBI) recommends dry chemicals or CO2 for fire extinguishment in case of small fires, and water spray, fog or foam fire extinguishment systems in case of large ammonia fires. It is important to carefully handle the contaminated waters to prevent environmental effects.

[0163] Ammonia detection

[0164] The four most common types of fixed sensors used to detect ammonia vapour are reported below.

[0165] Infrared sensors

[0166] Infrared sensors measure gas as a function of the absorbance of infrared light. Ammonia has a usable absorbance peak at a wavelength of about 1.53 pm. Absorbance at this wavelength is proportional to the concentration of ammonia present in the sensing chamber of the sensor. The benefit of infrared technology for ammonia detection is long-term sensor stability, resulting in limited requirement for calibration. Infrared detectors have a wide dynamic range and are not degraded or consumed by exposure to high concentrations of ammonia. The limitations are the physical size of the detector, need to protect the detector against potential effects of fluctuating temperature and humidity, and higher cost compared to other detector types.

[0167] Chemosorption sensors

[0168] Chemosorption sensors consist of a metal oxide semiconductor on a sintered alumina ceramic support contained within a flame arrestor. In clean air the electrical conductivity is low. Oxidation of the measured gas on the sensing element increases its conductivity. An electrical circuit is used to convert the change in conductivity to an output signal which corresponds to the gas concentration. The benefits of chemosorption sensors are their long operational life and low cost. However, since the sensors are not specifically designed to ammonia, false alarms can be triggered by interfering contaminants.

[0169] Electrochemical sensors

[0170] The gas detection technique is very straightforward in concept. Gas that enters the sensor undergoes an electrochemical reaction that causes a change in the electrical output of the sensor. The difference in the electrical output is proportional to the amount of gas present. Electrochemical sensors are designed to minimise the effects of interferingcontaminants, makingthe readings as specific as possible for the gas being measured. The positive benefits for this type of sensor are the specificity to ammonia, low cross sensitivity to other interfering contaminants, low ppm range resolution as well as cold temperature performance down to -40° C. The limit is that the lifetime of this type of sensors is based on the “ppm" exposure. Once the “ppm hour" exposure life of the sensor is exceeded, it is no longer capable of detecting gas and needs to be replaced. Therefore, this type of sensor is recommended to PWIND071WO / ll . 11 . 2025 26 2025129078 be used where the ambient background concentration of ammonia is sufficiently low to allow a reasonable operational life of the device.

[0171] Charge carrier injection sensors

[0172] Charge carrier injection (Cl) sensors depend on the adsorption of ammonia by “charge carrier" molecules in a solid-state substrate. By absorbing ammonia, the charge carriers are “injected" into the sensor element, causing a change in resistance that is proportional to the concentration of ammonia present. The substrate materials are selected to maximise the sensor sensitivity to ammonia while minimising the effects of interfering contaminants. The benefits of Cl sensors are wide detection range, stability and long lifetime. Cl sensors are not affected by humidity and severe temperature.

[0173] Impact on health

[0174] Ammonia is toxic to humans. The odour threshold for ammonia is very low, from 5 ppm concentration it can be detected by most people, and this does not constitute a health risk.

[0175] Based on Acute Exposure Guideline Levels (AEGL) for airborne chemicals defined by the US Environmental Protection Agency (EPA), the limits to ammonia exposure can be identified, as shown in the Table 2-1:

[0176] Table 0-1: EPA Acute Exposure Guideline Levels (Source: EPA, 2016)

[0177] AEGL 1: Notable discomfort, irritation or certain asymptomatic non-sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.

[0178] AEGL 2: Irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape

[0179] AEGL 3: Life-threatening health effects or death

[0180] Toxic exposure can occur by inhalation (breathing in vapour), dermal or eye contact with ammonia vapour or liquid.

[0181] PWIND071WO / ll . 11 . 2025 27 2025129078

[0182] Table 0-2: Exposure guidance (Source: Karabeyoglu A, Brian E., 2012)

[0183] Because of its toxicity, the direct release of ammonia to open air must be limited to the lowest practicable level. Direct venting of ammonia to the atmosphere is not permitted in normal condition. Venting of ammonia for control of pressure in the storage tanks is not permitted. It is only allowed in case of failure conditions.

[0184] NOTE: For this guideline, ammonia Permissible Exposure Limit (PEL) means a concentration 30 ppm ammonia vapours in air, corresponding to the Acute Exposure Guideline Level 1 (AEGL-1) given by USEPA (see Table 0-1).

[0185] Toxic area zones

[0186] The conducted analysis demonstrates that the main safety concern in relation to ammonia is associated with its toxicity and gas-dispersion properties. Toxicity adds complexity to the ship design, and toxic areas must be defined.

[0187] In addition to hazardous areas classification, toxic areas must be classified to identify areas or spaces in which a toxic atmosphere is present or can be expected to be present. Therefore, appropriate safeguards must be implemented and access to such areas must be restricted.

[0188] Toxic areas must be classified into different zones based upon the frequency of the occurrence and duration of toxic atmosphere, as follows:

[0189] • Zone A: an area in which toxic atmosphere is present continuously or for long periods or frequently

[0190] • Zone B: an area in which toxic atmosphere is not likely to occur during normal operation but, if it does occur, will persist for a short period only.

[0191] Ammonia detection against toxicity

[0192] The same ammonia detector types, as mentioned in section “Ammonia detection", can be applied for toxicity detection but calibrated according to the ammonia concentration within the PEL range.

[0193] Inhalation

[0194] Ammonia can be very toxic, and inhalation can cause severe symptoms according to the exposure time and concentrations, as defined in Table 0-1. In case of inhalation of ammonia vapours, the individual must be moved to an area with fresh air. Supplemental oxygen with assisted ventilation can be PWIND071WO / ll . 11 . 2025 28 2025129078 also required. Symptoms can develop hours after exposure and are made worse by physical effort. Severe short-term exposure can cause long-term damage.

[0195] Ingestion

[0196] Not a relevant route of exposure because at ambient temperature and pressure ammonia is in gaseous state.

[0197] Skin contact

[0198] In case of contact with skin, it is recommended to immediately use an emergency shower and flush the exposed area with ample amounts of lukewarm water for at least 15 minutes. Note that ammonia can freeze the exposed clothing and the skin below it and this can result in extensive skin damage. Contaminated clothing and shoes must be removed and washed before reuse. Medical attention is required.

[0199] Eye contact

[0200] In case of contact with eyes, the gas irritates or burns the eyes. Permanent damage including blindness can result. It is recommended to immediately flush the eyes with ample amounts of lukewarm water for at least 20 minutes. Medical attention is required.

[0201] Environmental impact

[0202] Ammonia is classified as toxic to aquatic life with long lasting effects. The permissible discharge limit is defined as the maximum concentration of ammonia in the effluents. This limit depends on the international or local regulation limits. Normally, effluents containing liquid or dissolved ammonia are not to be discharged overboard.

[0203] Material compatibility

[0204] Ammonia is corrosive to a wide variety of metals, such as copper, zinc or copper-based alloys. Steel, stainless steel and some non-ferrous metals, such as aluminium- or nickel-based alloys, are compatible with ammonia. However, carbon steels are known to be prone to stress corrosion cracking. The susceptibility of carbon steels stress corrosion cracking increases with higher strength steels, particularly in situations with high residual or applied stresses. The risk of stress corrosion cracking can be mitigated by using minor amounts of water in ammonia of approximately 0.2%.

[0205] Polymers used, e.g. in sealings exhibit a varying degree of compatibility with ammonia.

[0206] All the components of the Fuel Supply System, including the Ammonia Injector Cooling Water System (AICWS), must be made of stain less steel (SUS 304L or 316L grades). The engine ammonia fuel piping system applies SUS 316L quality.

[0207] For further information on material selection for the ammonia supply system, see Table 0-5.

[0208] Spill prevention and handling

[0209] For ammonia fuelled vessels, an exhaustive risk assessment must be performed to consider all the hazards associated with physical layout, operation, process and maintenance, with regard to any foreseeable failure. The analysis must ensure that risks are ALARP (As Low AS Reasonably Practicable). Risks which cannot be eliminated must be mitigated. PWIND071WO / ll . 11 . 2025 29 2025129078

[0210] The risk assessment must consider the possible liquid and gaseous ammonia fuel leakages and spills and their related consequences during the ship operations (e.g. during bunkering). It is important to consider the following aspects:

[0211] • accumulation of ammonia vapours in spaces containing a potential source of ammonia release and their spreading over the ship spaces through non-gastight openings

[0212] • spreading of ammonia vapours from the vent mast outlet on open decks and their possible recirculation to accommodation through openings and ventilation inlets

[0213] • formation of ammonia vapour cloud

[0214] • heat release in case of ammonia dissolution in water

[0215] • draining of hold space in case of type A tank failure.

[0216] The risk assessment must cover at least the following aspects:

[0217] • design and arrangement of bunkering station

[0218] • design and arrangement of contaminated water holding tank

[0219] • materials of machinery, equipment and components

[0220] • protection of single walled piping outside of machinery spaces

[0221] • toxic area zones

[0222] • spaces, systems and equipment requiring gas detection

[0223] • gas detector locations

[0224] • emergency ventilation rates

[0225] • dispersion of emergency toxic releases to atmosphere

[0226] • control, alarm and safety instruments for other essential equipment

[0227] • additional control, alarm and safety requirements, apart from the mentioned

[0228] • Engine Safety Concept.

[0229] The systems must be designed to detect leakages of gases and liquids from the fuel system and automatically isolate any leakages to limit the amount of ammonia release. For spillages handling, drip trays must be provided where leakages are expected (e.g. bunkering connection, flanges).

[0230] Each drip tray must be:

[0231] • made of suitable material to hold spills

[0232] • fitted with a drain valve to enable drain

[0233] • of sufficient size and capacity to handle reasonably foreseeable spills and to collect water from any water spry located above it.

[0234] Mechanical spray shielding must be arranged around potential leakage points from the ammonia system.

[0235] In addition to all design and operation preventive measures, suitable Personal Protective Equipment (PPE) must be available for all people working with ammonia to eliminate the residual risks.

[0236] The PPE must include, but not be limited to:

[0237] • large aprons

[0238] • special gloves with longsleeves

[0239] • suitable footwear

[0240] • coveralls of chemical-resistant material

[0241] • tight-fitting goggles or face shields. PWIND071WO / ll . 11 . 2025 30 2025129078

[0242] The protective clothing and equipment must cover all skin so that no part of the body is unprotected. Respiratory and eye protection for evacuation purposes must be available for everyone onboard.

[0243] To entry and work in a gas-filled space, self-contained positive pressure air-breathing apparatus incor- poratingfull face mask must be available.

[0244] Engine Design Criteria

[0245] Operating modes, see fig. 4

[0246] The engine is designed for continuous service on ammonia and diesel. Depending on the selected option, different operating modes are available within specific engine power ranges.

[0247] The following list includes the operating modes available for the ammonia engine:

[0248] • ammonia mode

[0249] • diesel mode.

[0250] Changeover between the operating modes:

[0251] • transfer (automatically active for changeover to, or between, modes with ammonia operation)

[0252] • ammonia trip (immediate action, always available while a mode with ammonia operation is selected).

[0253] Injection concept

[0254] Main fuel injection

[0255] Considering the ignition proprieties of ammonia, a high-pressure injection system is applied. This enables optimum combustion process.

[0256] The system comprises:

[0257] • ammonia supply pipes

[0258] • ammonia injectors.

[0259] Ammonia supply pipes

[0260] Ammonia is supplied to the engine inlet at 85 bar(g). If a fuel rail is provided in a fuel box, no doublewall pipes are required because the fuel box fulfils the second barrier function.

[0261] Ammonia injection system

[0262] Actuation oil supply unit provides actuation oil to the ammonia pressure amplified integrated on the injectors. This allows to build up the injection pressure.

[0263] Ammonia injectors

[0264] Spring-loaded injectors dedicated to ammonia are located on the cylinder cover.

[0265] Ammonia injectors sealing concept

[0266] Ammonia is separated from the actuation oil by sealings and sealing chambers.

[0267] Pilot fuel injection

[0268] Pilot fuel injection is provided by main diesel injectors. PWIND071WO / ll . 11 . 2025 31 2025129078

[0269] Double-barrier concept for ammonia

[0270] The ammonia storage and supply system must be arranged in a way that any ammonia release and consequences thereof are minimised. Therefore, a double-barrier concept is applied for pipingsystem. In this concept, the piping system is protected by a gas- and liquid-tight outer pipe or duct.

[0271] A failure of one barrier must not lead to a leak from the piping system into the surrounding area. This prevents danger to the persons on board, to the environment and to the ship.

[0272] The annular space between the inner and outer pipe must have mechanical ventilation of extraction type with a minimum capacity of 30 air changes per hour, and be ventilated to the open air, after passing a gas detector. The double-wall enclosure must be connected to a suitable drainage tank allowing the collection and detection of any possible leakage.

[0273] Inerting of the annular space can be accepted as an alternative to ventilation. Suitable alarms must be provided to indicate a loss of inert gas pressure between the pipes.

[0274] Ammonia fuel system arrangement

[0275] System arrangement, see fig. 2

[0276] The ammonia fuel system arrangement comprises the following:

[0277] • ammonia bunkering station and storage tan k(s)

[0278] • ammonia Fuel Supply System (FSS)

[0279] • Fuel Valve Unit (FVU)

[0280] • ammonia pipingsystem

[0281] • venting system, including Ammonia Vapour Processing System (AVPS)

[0282] • inert gas supply system

[0283] • Ammonia Injector Cooling Water System (AICWS), including low-salinity water supply.

[0284] Bunkering station

[0285] Ammonia is transferred on board the vessel through a bunkeringstation. The recommended location for this station is on the open deck because there is natural ventilation. Ammonia bunkering station must be of enclosed or semi-enclosed type and must be subject to special consideration within the risk assessment. It must be designed in such a way to minimise the vapour accumulation and to avoid the gas release to the atmosphere during bunkering operations. This station must be designed with two means of escape as widely separated as possible. One of them must open outwards and give direct access to the open deck. Where direct access to the open deck is not practicable, an airlock must be provided. Access doors or hatches to bunkering station must be gastight towards other enclosed spaces in the ship and adjacent open areas. The bunkeringstation must be provided with ventilation of a mechanical extraction type. In addition, it must be located at a certain distance from air intakes, accommodation openings and machinery spaces. The bunkering lines cannot be led through accommodations. In case of passage in enclosed spaces, a second barrier for the bunkering line must be considered (e.g. double-wall pipe or ducts). To prevent ammonia contamination, filters must be considered on the bunkering lines. All the bunker hoses on board must be suitable for ammonia. The bunkering manifold must be designed to withstand the external loads during bunkering. The connections at the bunkering station must be of a dry-disconnect type. The couplings must be of a standard type. A manually operated stop valve and a remotely operated shutdown valve must be arranged in series and as close as possible to the connection point. Otherwise, a combined manually operated and remote shutdown valve can be used. Remote control must be possible from the bunkering control station. PWIND071WO / ll . 11 . 2025 32 2025129078

[0286] Table 0-1: Proposal of design parameters for the ammonia bunkering station

[0287] <*> This represents the recommended closing time from trigger of the alarm till full closure of the valve. Longer time based on pressure surge consideration can be acceptable. The closing time must also be sufficient to prevent overfilling of the storage tank when automatic shutdown is initiated by the tank high level alarm.

[0288] Ammonia leakages detection system must be provided in the bunkering station. A water mist system (water screen) must be provided on the outside of all the access doors to bunkering station. This must be manually operable from the outside of the compartment and automatically in the event of gas detection or emergency shutdown. Remote control of the pumps supplying water to the water mist system must be possible from a remote and safe location. Bunkering station must also be monitored by direct line of sight or Closed-Circuit Television (CCTV).

[0289] Bunkering lines must be arranged to be self-draining to the storage tank(s). Different arrangements can de selected in case the bunkering station is lower than the storage tank(s). The bunkering lines must be designed for inerting and gas freeing. In case two bunkering connections (e.g. one for each side of a ship) with a common bunkering line are available on board, a suitable segregation arrangement must be provided.

[0290] For safety purposes, drip trays must be provided below the bunkering connections to collect and direct any spillage to a dedicated drain tank.

[0291] Ammonia storage tank(s)

[0292] From the bunkeringstation ammonia is transferred to the ammonia storage tank(s).

[0293] Given that the Lower Heating Value (LHV) of ammonia is lower compared to MGO, larger quantities of ammonia are required compared to MGO for the same energy content. Ammonia requires about 2.8 times more storage tank volume than MGO.

[0294] Table 0-2: Design parameters for ammonia storage and service tanks

[0295] From storage tank and catch tank, liquid ammonia is delivered via the Low-Pressure (LP) supply side and the High-Pressure (HP) pump to the engine. PWIND071WO / ll . 11 . 2025 33 2025129078

[0296] The following requirements must be considered for the ammonia storage tanks:

[0297] • Tanks must be protected against mechanical damages which can occur duringship operation.

[0298] • Tanks must be protected against external damages which can occur in case of collision or grounding.

[0299] • Tanks connections must be located above the highest liquid level in the tank. Connection below the liquid level can be accepted for tank(s) of type C.

[0300] • Ammonia tank inlet and outlet valves must be provided. It is recommended to place these valves as close as possible to the tanks.

[0301] • Possible vacuum in the ammonia tank must be taken into account.

[0302] • Tanks must not be vented directly to the atmosphere during normal operation. Venting of fuel vapour for controlling the tank pressure is not allowed, except for emergency situations.

[0303] • Filling levels must be monitored.

[0304] • Ammonia storage tank(s) relief valve(s) must open only in case of overpressure resultingfrom fire in the vicinity of the tank.

[0305] • The Maximum Allowable Working Pressure (MAWP) of the fuel tank must not exceed 90% of the Maximum Allowable Relief Valve Setting (MARVS).

[0306] • Except for fully pressurised type C tank(s), ammonia tanks must be provided with a vapour return line. Alternative design to control pressure in the tank during bunkering can be considered.

[0307] Different types of storage tank(s) can be used for ammonia such as:

[0308] • independent (types A, B and C)

[0309] • integral (membrane type)

[0310] • portable (independent tank of type C).

[0311] Depending on the selected type, a secondary barrier can be required, as mentioned in the Table 0-3: Secondary barriers requirements for storage tank(s)Table 0-3.

[0312] Table 0-3: Secondary barriers requirements for storage tank(s)

[0313] Except for fully pressurised type C tank(s), the pressure and temperature in the storage tank(s) must always be kept within the design range by means of different methods. The following methods are recommended by the classification societies:

[0314] • liquified ammonia fuel cooling

[0315] • reliquefication of vapour

[0316] • thermal oxidation of vapour

[0317] • energy consumption by the ship (engine, gas turbines, boilers etc.)

[0318] • pressure accumulation

[0319] • dissolution of vapours in water.

[0320] For redundancy, except for fully pressurised type C tanks, always at least two methods must be selected. Independently of the selected method, the maximum tank pressure must always be maintained PWIND071WO / ll . 11 . 2025 34 2025129078 below the set pressure of the pressure relief valve for a period of 15-21 days (based on administra- tion / classification society rules), assuming the tank is full.

[0321] Independent and integral tanks(s)

[0322] Independent tanks are self-supporting and not integrated in the ship structures. They can be classified as A, B and C types.

[0323] Integral tanks are part of the ship structure and stressed in the same manner and by the same loads as the adjacent hull structure.

[0324] The different types of independent and integral tanks are defined below:

[0325] Type A: Tanks at (or near) atmospheric pressure and refrigerated to temperature of -33°C (fully refrigerated tank). Design vapour pressure must be less than 0.7 bar(g).

[0326] For type A tanks there are following additional requirements:

[0327] • The secondary barrier must be designed to contain possible ammonia leakages for a period of 15 days.

[0328] • In case the second barrier is provided by the ship hull, it must be built with suitable material to withstand -33 °C.

[0329] • The ammonia hold space must be provided with drainage system for liquid ammonia handling in case of spillages or tank rupture.

[0330] • The ammonia hold space must be inerted with inert gas provided by inert gas system.

[0331] Type B: Tanks designed using model tests, refined analytical tools and analysis methods to determine stress levels, fatigue life and crack propagation characteristics. Where such tanks are primarily constructed of plane surfaces (prismatic tanks), the design vapour pressure must be less than 0.7 bar(g).

[0332] Type C: Tanks under pressure at ambient temperature (fully pressurised tank) or tanks under pressure lower than the vapour pressure at ambient temperature (semi-pressurised tank).

[0333] For type C tanks there are following additional requirements:

[0334] • The design pressure of a fully pressurised tank type C must not be less than the ammonia vapour pressure at the maximum ambient temperature expected in service. This temperature must be minimum 45°C (for marine applications).

[0335] • Fuel storage hold spaces act as a secondary barrier if the tank is located below open desks and the fuel storage bulkheads are at least 900 mm away from the outer shell of the tank.

[0336] Integral Tanks: Integral type tanks, such as a membrane tank, are built into the hull as part of the vessel structure. Integrated tanks are low-pressure tanks, designed for pressure less than 0.7 bar(g).

[0337] Furthermore, depending on the tanks position, additional requirements can follow. For instance, if the tank is located on open deck, the tank must be protected against mechanical damage and surrounded by coamings. Water spray system for emergency cooling must also be provided, as well as drip trays for spillage collection. If the tanks are located below open decks, tank connections, valves and flanges must be in a tank connection space (see section “Ammonia hold space"). The ammonia hold space must be separated from the machinery space of category A by a cofferdam of at least 900 mm. PWIND071WO / ll . 11 . 2025 35 2025129078

[0338] Portable tank(s)

[0339] Portable tanks are independent tanks which can be easily loaded and unloaded from the vessel and connected and disconnected from the ship systems. Portable tanks must be certified by the classification society and comply with requirements for type C tanks.

[0340] Portable tanks must have an equivalent safety as permanent fuel tanks. For portable tanks, following additional requirements must be considered:

[0341] • Tanks can be located either on the open decks or in ammonia hold space.

[0342] • Tanks must be secured to the ship structure.

[0343] • The influence of the portable tanks on the ship stability must be considered.

[0344] • Connections to the ship fuel piping systems must be made with approved flexible hoses suitable for ammonia.

[0345] • Pressure relief system of portable tanks must be connected to the venting system.

[0346] • Control and monitoring systems for portable tanks must be integrated in the ship control and monitoringsystem.

[0347] • Access to all tanks connection must be ensured for inspection purpose.

[0348] In addition, the portable tanks connected to the ship Fuel Supply System (FSS) must be designed so that they can be isolated at any time without affecting any of the other tanks.

[0349] NOTE: Portable tanks must be certified by the classification society and comply with the type C tanks requirements

[0350] Ammonia hold space

[0351] The ammonia hold space is the area enclosed by the ship structure in which ammonia storage system is located.

[0352] This space acts as a full or partial second barrier and must be inerted with inert gas. Alternatively, in case it acts as a partial second barrier, the space can be filled with air. If this space surrounds type C tanks, it can be inerted with dry air. Access to fuel storage hold space must be arranged as a bolted hatch, unless this access is independent and direct to open decks. The ammonia storage hold space cannot be used for other purposes.

[0353] Tank connection space

[0354] All tank connections, fittings, flanges and tank valves must be enclosed in a gas tight space, unless the tank connections are on open deck. The space must be able to safely collect leakage from the tank connections.

[0355] The tank connection space must be separated from the machinery space of category A. Separation of this space from other high fire risk spaces must be considered. This space must be ventilated to open deck. Suitable material must be selected to withstand lowest temperature which can occur in case of a spillage. The space entrance must be designed according to the classification society rules. Water screen must be provided at the entrance.

[0356] NOTE: The above-mentioned requirements are not applicable for gas-carrier ships which follow the IGC code. PWIND071WO / ll . 11 . 2025 36 2025129078

[0357] Ammonia piping

[0358] The ammonia piping must be designed to minimise risks associated to any possible leakage in the system. Therefore, the ammonia piping must be always enclosed in a gastight secondary barrier with exception for the following spaces:

[0359] • ammonia hold space (for all tanks type except C type)

[0360] • tank connections space

[0361] • fuel preparation space

[0362] • bunkering stations

[0363] • on open decks (for piping containingammonia for short period)

[0364] • in case of full-welded vent piping (if passing through ventilated spaces).

[0365] In addition, the following requirements must be considered:

[0366] • Fuel piping systems must be designed in such a way that the systems can be emptied, purged and inerted.

[0367] • Ammonia pipes must be located at least 800 mm from the ship side.

[0368] • Ammonia pipes (especially on open decks and ro-ro spaces) must be protected against mechanical damages.

[0369] • Ammonia piping must not be directed through accommodation spaces, service spaces, as well as electrical equipment rooms.

[0370] • Fuel piping and vent lines must not be routed through the tanks.

[0371] • Any valve on the piping system, required to isolate ammonia supply system in case of leakages, must be remotely operated from safe locations.

[0372] • The piping must be designed to deal with possible icing of component due to low temperature in the ammonia storage tank. Low-temperature piping must be insulated from the adjacent structure.

[0373] • Fuel piping must be capable of absorb! ng thermal expansion or contraction caused by extreme temperature. Provision must be considered to protect piping from stress and fatigue.

[0374] • All the piping segments which must be isolated while fully filled with liquid ammonia must be equipped with a pressure relief valve. The vent line from these valves must be directed to the AVPS.

[0375] Depending on the ammonia state (liquid or gaseous) the following additional requirement must be considered:

[0376] • If the piping system is designed for liquid ammonia, design pressure above the vapour pressure of ammonia at 45 °C must be considered (18 bar(a)). It is done to prevent venting of ammonia.

[0377] • If the pipingsystem is designed for gaseous ammonia, the fuel line must be sufficiently heated with heat trace.

[0378] • The pipingsystem must include the pipingfor ammonia recovery system. PWIND071WO / ll . 11 . 2025 37 2025129078

[0379] Table 0-4: Design parameters for the ammonia inner pipe of supply system (at the engine inlet)

[0380] Table 0-5: Material recommendation for ammonia supply system piping

[0381] The material is selected based on sufficient corrosion resistance, required strength, temperature frac- ture toughness, stress, as well as fatigue resistance. These recommendations are valid for inner and outer piping. The engine ammonia fuel pipingsystem applies 316L quality.

[0382] For the design of single wall piping or the inner pipe of double-wall piping, the minimum wall thickness for steel pipes can be calculated using the following formula:

[0383] (to + b + c)

[0384] (11 - — 100J

[0385] Equation 0-1: Wall thickness calculation for steel pipes where:

[0386] • t[mm] represents minimum wall thickness for steel pipes at the deign pressure

[0387] • t0[mm] represents theoretical thickness for steel pipes at the deign pressure • b[mm] represents bending allowance

[0388] • c[mm] represents corrosion allowance. This value is equal to 0 for ammonia piping.

[0389] • a[%] represents negative manufacturing tolerance for thickness. This value is equal to 12.5.

[0390] 1If only ambient air suction for the ventilation supply is applied.

[0391] 2If there is the possibility to supply dry air as ventilation air, to avoid condensation within the annular space in case the ammonia temperature drops below the ambient air temperature. PWIND071WO / ll . 11 . 2025 38 2025129078

[0392] Theoretical thickness t0can be calculated using the fol lowing formula:

[0393] Equation 0-2: Theoretical wall thickness calculation for steel pipes where:

[0394] • P[MPa] represents maximum system design pressure defined in Table 0-4

[0395] • D [mm] represents the outside pipe diameter

[0396] N R R

[0397] • AT — r] represents allowable stress defined as the lower value between — and —

[0398] • represents specified minimum tensile strength at ambient temperature

[0399] • represents specified minimum yield stress at ambient temperature

[0400] • e represents non-dimensional efficiency factor equal to 1.

[0401] Bending allowance b can be calculated using the following formula:

[0402] Equation 0-3: Bending allowance where:

[0403] • r[mm] represents the radius of the bend

[0404] Ammonia supply pumps

[0405] The ammonia storage and supply system include the following pumps:

[0406] • Low-Pressure (LP) ammonia supply pumps

[0407] • High-Pressure (HP) ammonia supply pumps.

[0408] LP pumps can be located adjacent to the ammonia storage tank or can be of submerged type. HP pumps must be located downstream the connection of the catch tank return line.

[0409] These pumps must be designed to ensure the ammonia is delivered at the engine inlet at 85 bar(g) with a tolerance + / - 2 bar. LP and HP ammonia supply pumps are controlled based on the signals from the Engine Control System (ECS).

[0410] All pumps in ammonia storage and supply system must be protected against dry running. Therefore, a flow switch is recommended at each pump outlet. In addition, if the pumps can develop pressure exceeding the system design pressure, the pumps must be provided with a pressure relief valve. This valve must relieve the pressure to the suction side of the pump.

[0411] Heat exchanger and filters

[0412] To ensure ammonia is supplied to the engine inlet at proper temperature, a heat exchanger is required. This heat exchanger can be located up- or downstream the HP pump. The location upstream the HP PWIND071WO / ll . 11 . 2025 39 2025129078 pump is recommended due to lower operating pressure. The temperature sensor must be placed downstream the HP pump to measure the resulting temperature including the pump heating effect.

[0413] Table 0-6: Design parameters for the heat exchanger

[0414] When the system temperature is below the low-temperature shutdown value, ammonia supply to the engine must be stopped.

[0415] A filter of duplex type is recommended to be provided in the ammonia supply system. The filter must be provided with a differential pressure display and alarm signal.

[0416] Table 0-7: Design parameters for the ammonia duplex filter

[0417] Fuel valve unit

[0418] The Fuel Valve Unit (FVU) is the interface between the engine and the auxiliary systems. The purposes of this unit are to isolate the engine from the ammonia supply system, to connect the inert gas supply system, to connect the injector cooling water system, as well as to divert the flow during purging procedure.

[0419] The FVU is normally located in a dedicated area outside the machinery space. This area can be accessed after the ammonia supply system is shut down and after gas freeing of the area.

[0420] The main components of the FVU include the following:

[0421] • A manually operated stop valve(s) and an automatically operated master fuel valve(s) coupled in series or a combined manually and automatically operated master fuel valve(s) installed on the main ammonia supply line to each consumer. These valves must be placed outside the machinery space in which ammonia fuelled machinery is located and as close as possible to the ammonia fuel preparation equipment.

[0422] • Two shut-off valves in series with a venting valve in between with a double-block-and-bleed function, installed on the main ammonia supply line to each consumer.

[0423] • A manual shutdown valve, installed on the main ammonia supply line to each consumer for maintenance purposes. This must be installed upstream of the double-block-and-bleed valve.

[0424] • If the master fuel valve is in an enclosed space, such as a fuel preparation room, this space must be protected against fuel leakage by another automatic shutdown valve arranged for closure in case ammonia is detected within the enclosed space or in case of loss of ventilation

[0425] 3If only ambient air suction for the ventilation supply is applied.

[0426] 4If there is the possibility to supply dry air as ventilation air, to avoid condensation within the annular space in case the ammonia temperature drops below the ambient air temperature. PWIND071WO / ll . 11 . 2025 40 2025129078 in the duct of the double-wall fuel pipe. That additional automatic shutdown valve can be the fuel tank outlet valve.

[0427] Two shut-off valves in series with a venting valve in between with a double-block-and-bleed function, installed on the AICWS inlet and outlet connections.

[0428] NOTE: All valves in the ammonia supply system must be remotely controlled, if they are not easily accessible.

[0429] The final layout of the FVU can vary depending on ammonia FSS design and engine requirements.

[0430] The number of valves can be reduced by combiningseveral functions in a single valve depending on different class requirements

[0431] Fuel preparation space

[0432] The fuel preparation space is a dedicated area containing equipment for ammonia preparation purposes. Such equipment can include:

[0433] • fuel pumps

[0434] • FVU

[0435] • compressors

[0436] • vaporisers

[0437] • heat exchangers and filters.

[0438] The design of this space must follow the IGF code requirements together with additional requirements defined by the relevant classification society.

[0439] In general, this space must be provided with independent ventilation of underpressure type and must be arranged to safely contain and manage leakage in the foreseeable worst-case scenario. The area cannot be located adjacent to the machinery space of category A or any other high-risk area, therefore, a segregation must be foreseen. Access from open deck is preferable. If this is not possible, access via air lock must be foreseen.

[0440] Inert gas supply system

[0441] Purpose of inert gas system

[0442] The purpose of the inert gas supply system is to provide inert gas (e.g. N2) to the ammonia storage and supply system for inerting and purging procedures. Inert gas is also used for the following:

[0443] • to remove the injector cooling water from the ammonia injectors during the changeover procedure

[0444] • to purge the liquid ammonia

[0445] • to purge ammonia vapour, in case the injector cooling water is not available

[0446] • to test pressure (e.g. FSS components, annular space).

[0447] The inert gas supply must be always available while running the engine in ammonia mode, i.e. a sufficient inert gas storage capacity is required. PWIND071WO / ll . 11 . 2025 41 2025129078

[0448] Table 0-8: Design parameters for the inert gas supply system

[0449] Inerting and purging procedure

[0450] The purging procedure can be performed on the engine, the ammonia FSS, the bunkering and storage system, and different system components to remove ammonia from ammonia fuel system.

[0451] Liquid ammonia in the main engine is purged by inert gas (e.g. nitrogen). Once the liquid ammonia is removed, the AICWS is activated, and the engine is ready to start in diesel mode. The purging procedure is carried out through different connections to the inert gas supply system. The inerting procedure is used to eliminate the possibility of any flammable mixture being present in the ammonia storage and supply system. This is achieved by utilising an inert gas which must be permanently available on board. Normally, N2 is used as inert gas and provided by means of a nitrogen generator. Two shut-off valves in series with a venting valve in between, providing a double-block-and-bleed function, must be installed on nitrogen supply system. In addition, a non-return valve must be installed. This valve can have a combined shut-off functionality. This prevents any return of flammable liquid and vapour to inert gas system.

[0452] After maintenance on ammonia fuel system, a tightness test must be performed. It consists of pressurisingcomponents (up to maximum operational pressure) to verify that the components are correctly assembled (see section “Pressure testing concept"). This test can be performed with inert gas or with any other alternative method.

[0453] Ammonia injector cooling water system, see fig. 3

[0454] The ammonia injector cooling water unit comprises the ammonia injector cooling water buffer tank with a heat exchanger (cooling element) which can be installed internally or externally to the buffer tank and an ammonia injector cooling water supply pump. Together with the interface valves, piping system and the Fuel Injection System (FIS), it forms the Ammonia Injector Cooling Water System (AICWS). PWIND071WO / ll . 11 . 2025 42 2025129078

[0455] Purpose of ammonia injector cooling water system

[0456] The main purpose of the AICWS is to cool the ammonia injectors when the engine is running on diesel mode. When the engine is running in diesel mode, the ammonia injector cooling water circulates from the ammonia injector cooling water buffer tank to the ammonia injectors and back to the ammonia injector cooling water buffer tank in a closed loop.

[0457] In addition, injector cooling water is used in the purging procedure to remove the vapour after the liquid purging.

[0458] Design parameters for ammonia injector cooling water system

[0459] Table 0-9: Ammonia injector cooling water system parameters

[0460] Refilling system of ammonia injector cooling water buffer tank

[0461] The main cooling medium is fresh water, with low-salinity, from the on-board fresh-water generator. The injector cooling water must be replaced when the ammonia contamination in the buffer tank reaches 10%. Venting system

[0462] During normal operation, including fuel change-over and engine stop, direct venting of ammonia to the atmosphere is not permitted. Therefore, a fixed venting system must be arranged to collect the vapours generated from failure conditions, from tank safety valves, from valves with double-block-and- bleed function, as well as other pressure relief valves available in the ammonia supply system.

[0463] 5System volume is defined as the engine volume plus the piping volume from the FVU to the engine plus the piping volume from the engine to the FVU. PWIND071WO / ll . 11 . 2025 43 2025129078

[0464] For the tank ventingsystem the main components which must be considered are vents, pressure relief valves, stop valves, as well as vacuum relief valves (if the tank can be subject to external pressure above the tank design pressure).

[0465] NOTE: Pressure relief valve must be connected to the highest part of the liquified fuel tank.

[0466] Any ammonia vapour release to the atmosphere must be done via a vent mast which is designed for venting:

[0467] • processed vapours (comingfrom AVPS)

[0468] • vapours generated from failure conditions

[0469] • vapours from tank safety valves in case of fire.

[0470] The ammonia vapour release to atmosphere must not exceed the PEL at any location where passengers or crew members can be present. The vent mast must be located at B / 3 or 6 m height (whichever is higher) above the main deck, walking ways and working areas, and at B or 25 m height (whichever is less) from any air intake or accommodations.

[0471] NOTE: Ammonia vapour within enclosed spaces can also be absorbed by water mist system (see section “Ammonia injector cooling water system").

[0472] Ammonia vapour processing system

[0473] The AVPS is designed to collect and treat ammonia vapours from the engine as well as from the ammonia fuel storage and supply system, including bleed lines which can include water vapour from the AICWS. The AVPS must be designed with a capacity which enables the reduction of ammonia vapour concentration below the PEL (30 ppm) in case the ammonia vapours are released for a longer period. After the treatment, the ammonia vapours are directed to the vent mast.

[0474] Different technologies can be selected for the AVPS, as reported below.

[0475] Diffusion tank

[0476] This type of technology consists of a diffusion tank filled with water. The ammonia vapours coming from the ventingsystem are directed to this tank. The pipingsystem directs the ammonia to the tank bottom at maximum 10 m from the maximum liquid level. The tank capacity must consider the amount of water and ammonia without overflowing at a defined temperature (since solubility of ammonia can vary with temperature).

[0477] The following requirements must be considered for the diffusion tank:

[0478] • A vent pipe with an installed ammonia sensor must be provided and connected to the vent mast.

[0479] • A level indicator on the tank, for low- and high-level alarm, must be provided.

[0480] • Discharge connection for contaminated water must be provided.

[0481] • Overboard discharge under the water level is also possible in accordance with local regulations.

[0482] Scrubber

[0483] This type of technology consists of a closed-loop scrubber to reduce ammonia concentration in case of ammonia vapour release. PWIND071WO / ll . 11 . 2025 44 2025129078

[0484] Combustion unit

[0485] The ammonia vapours are burned. Pilot fuel is used to initiate and sustain ammonia combustion. The ammonia combustion units must be designed to immediately operate in case of ammonia release (e.g. from safety valve or venting system). Therefore, a buffer tank must be provided. In addition, a phase separator (knockout drum) must be provided to separate the liquid and gaseous state to prevent ammonia droplets to enter the combustion unit before being evaporated.

[0486] Dilution system

[0487] This system can be applied for failure mode handling and must be designed to provide sufficient dilution of effluents containing gaseous ammonia by mixing them with fresh air or by increasing the ventilation rate. The dilution rate must be sufficient to reduce the ammonia release below the PEL at any location where passengers or crew members can be present.

[0488] In addition to different technologies availablefor AVPS, in general, water mist system can also be used to absorb ammonia release. This system must be installed in the areas where ammonia release can occur (e.g. piping and components, bunkering station connection). The system must be activated automatically when ammonia concentration exceeds 30 ppm. Manual activation must be also possible locally or from the engine control room.

[0489] Ventilation system

[0490] A separate ventilation system for hazardous spaces is required to avoid any ammonia vapour accumulation. This system is of a mechanical extraction type with independent fans. It must be kept separated from non-hazardous space ventilation system.

[0491] The following requirements must be considered:

[0492] • During normal operation, the ventilation must ensure at least 30 air changes per hour.

[0493] • The ventilation system must ensure proper ventilation in the lower and higher points of the hazardous space and must always be active during ammonia operations.

[0494] • Ventilation outlets from hazardous spaces must be located at a proper distance from nearest air intake, air outlet, from opening to other enclosed spaces as well as from decks and gangways, accordingto the classification society requirements.

[0495] • Ventilation outlets from hazardous spaces can be grouped together.

[0496] Back flow prevention device must be considered for ventilation outlets.

[0497] In case ammonia vapour concentration at the ventilation outlet of the enclosed spaces exceeds 30 ppm, different actions are possible:

[0498] • stop the ventilation system and activate the water mist system

[0499] • direct ventilation outlets to the AVPS

[0500] • increase the ventilation rate to achieve ammonia vapour concentration below the LEL at the ventilation outlet. PWIND071WO / ll . 11 . 2025 45 2025129078

[0501] The annular space of the double-wall piping is also equipped with a mechanical ventilation of under pressure type (see section “Double-barrier concept for ammonia"). The ventilation system must ensure an extraction capacity of at least 30 air changes per hour. In case ammonia vapour concentration in the annular space exceeds the defined trigger values, different actions must be initiated, accordingto the classification society requirements.

[0502] Annular space purging

[0503] To purge the annular space in case a leakage is detected, please refer to section “Leakage detection", a purging arrangement is applied. The purging arrangement enables handling the leakage as described in section “Leakage handling".

[0504] Exhaust gas system

[0505] Some requirements must be followed for the design of the exhaust gas system as following:

[0506] • The system must be designed to prevent any accumulation of unburnt fuel.

[0507] • Pressure relief valves must be considered.

[0508] • The explosion ventingsystem outlet must be in an area where people can normally be present.

[0509] • Separate exhaust system must be considered for any other engine.

[0510] • The ammonia concentration in the exhaust gas must not present a significant health hazard.

[0511] Fire system provisions

[0512] The following design requirements must be considered for ammonia fire protection system:

[0513] • The fuel preparation space must be classified as a machinery space of category A.

[0514] • The boundaries of the fuel preparation space towards other machinery spaces of category A, control stations and cargo areas must be at least of A-60 type.

[0515] • Boundaries of A-60 type must also be considered for accommodations (up to the navigation bridge), service spaces, control spaces, machinery spaces and escape routes which are adjacent to ammonia tanks on open decks.

[0516] • The ammonia storage hold space must be separated by a cofferdam of at least 900 mm with insulation of at least A-60 type from the machinery space of category A. For type C tanks, the fuel storage hold space is considered as a cofferdam.

[0517] • The bunkering station must also use insulation of A-60 type except for spaces with little fire risk where the standard insulation can be used.

[0518] • Fire protection of fuel pipes led through ro-ro spaces must be subject to specific consideration of classification society.

[0519] • Ammonia tanks on open decks must be provided with a fixed water mist fire system. This system must be designed with an application rate of 10 ( / min) / m2for horizontal surfaces and 4 ( / min) / m2for vertical surfaces. This system can be part of the main fire system.

[0520] • The fixed water mist fire system must be divided at least into two sections which can be operated independently.

[0521] • Remote control of pumps and valves must be possible from safe locations.

[0522] • The bunkeringstation must be provided with a fixed installed dry chemical powder extinguishingsystem with a capacity of 3.5 kg / s for a minimum of 45-second-discharge. In addition, a dry chemical powder extinguisher of about 5 kg (or equivalent) must be located near the entrance of the bunkering station.

[0523] • Fuel preparation space and tank connection spaces arranged with motors for submerged pumps must be protected by a fixed fire-fighting system.

[0524] • Approved automatic fail-safe fire dampers must be fitted in the ventilation trunk for tank connection space and fuel preparation room. PWIND071WO / ll . 11 . 2025 46 2025129078

[0525] Fixed fire detection and fire alarm system must be provided for all compartments containing ammonia FSS.

[0526] Ammonia bilge system

[0527] Following requirements must be considered for the bilge system:

[0528] • Bilge system serving hazardous spaces must be segregated from other bilge systems and must be designed to discharge to designed shore reception facilities.

[0529] • Bilge wells must be designed in such a way to contain any foreseeable leakage.

[0530] • When a second barrier is required for storage tank(s), suitable arrangement to bilge system must be provided.

[0531] • Bilge system sections must be designed to fulfil the required drainage capacity in spaces where water mist system is installed.

[0532] • Bilge water holding tanks and drain tanks, which can contain dissolved ammonia, must be located outside the machinery spaces. These tanks must be vented to the AVPS or vent mast and must be provided with a vapour detector in the vent pipe.

[0533] • Bilge water holding tanks and drain tanks, which can contain dissolved ammonia, must be protected by cofferdams.

[0534] • Effluents, containing dissolved ammonia below the permissible limit, can be discharged overboard below the water line, in accordance with local regulations.

[0535] Control, monitoring and safety system

[0536] The safety functions of the ammonia storage and supply system must be arranged in a dedicated control, monitoring and safety system that is independent from the fuel control system. Control and monitoring instruments must be provided to prevent unacceptable loss of power in case of a single failure of the ammonia storage and supply system.

[0537] This system must be arranged to automatically isolate the ammonia storage and supply system upon failure and / or fault conditions and it must be designed to restore the propulsion as soon as possible upon fuel safety action. Manual intervention for operators must be provided.

[0538] For the X-DF-A engines, each fuel type must be fitted with its own independent control, monitoring and safety system. The control, monitoring and safety system of other consumers must be kept independent.

[0539] Bunkering and ammonia tanks

[0540] To control overflow, each ammonia tank must be fitted with a level gauging device. In addition, visual and audible high-level liquid alarm must be provided. This alarm must be released when the tank is filled up to about 95% of the tank volume. In case of a high liquid level alarm, a shut-off valve is automatically activated to prevent excessive liquid pressure in the bunkering line, as well as to prevent the tank from becoming full.

[0541] Each fuel tank must be monitored for pressure and fitted with local indicating devices. The indicators must clearly mark the highest and lowest pressure permitted in the tank. High-pressure alarm and, if vacuum protection is required, low-pressure alarm must de activated before the safety valve set value is reached. Alarms must be heard on the bridge, in the control room and locally.

[0542] A local reading pressure gauge must be fitted between the stop valve and the shore connection at each bunkering line. Pressure gauges must also be fitted to fuel pump discharge lines and to the bunkering and vapour return lines. Each fuel pump discharge must be monitored for pressure. PWIND071WO / ll . 11 . 2025 47 2025129078

[0543] In case submerged fuel pump motors are installed in the tanks, liquid low-level must be monitored. In addition, each fuel tank must be provided with fuel temperature indicators in at least three locations, at the bottom and middle of the tank, as well as the top of the tank below the highest allowable liquid level. Fuel storage hold spaces and inter-barrier spaces, without open connection to the atmosphere, must be provided with pressure indication.

[0544] The bunkering station must be controlled from a safe remote location, where it is possible to control its level and to operate the remote-control valves. From this location, overfill alarms, tank pressure and temperature and automatic shutdown must also be visible. If the ventilation of the double-wall bunkering lines stops, an audible and visual alarm must be activated at the bunkering control location. If ammonia leakage is detected in the double-wall bunkering lines, an audible and visual alarm and emergency shutdown of the bunkering valve must automatically be activated.

[0545] Ammonia detection provisions

[0546] Ammonia detector sensors must be permanently installed in several locations according to the classification society requirements. The number of detectors and the limits of ammonia vapour concentration must be compliant with the classification society requirements and to the satisfaction of the administration.

[0547] There are following possible locations for ammonia detectors:

[0548] • tank(s) connection space

[0549] • annular spaces around ammonia piping

[0550] • ammonia preparation rooms

[0551] • hazardous areas containing potential sources of ammonia release

[0552] • machinery spaces containing ammonia equipment / piping and consumers

[0553] • air locks

[0554] • bunkering station

[0555] • vent pipes (e.g. from ammonia drain tank or from bilge water holding tanks)

[0556] • vent mast outlet

[0557] • ventilation outlets.

[0558] When ammonia tank(s) other than type C tanks are used, hold spaces and / or inter-barrier spaces must be provided with a permanently installed system of ammonia detection capable of measuring ammonia concentrations from 0% to 100% by volume.

[0559] The ammonia detectors must be installed at least to the ceiling and at the bottom of the concerned space. Additional ammonia detectors can be required dependingon the results of ammonia dispersion studies performed by the shipyard.

[0560] Fire detection provisions

[0561] Fire detection in machinery spaces must provide audible and visual alarms on the navigation bridge, the central control station (e.g. engine control room), as well as locally.

[0562] Ventilation provisions

[0563] Any loss of the required ventilation capacity must provide audible and visual alarms on the navigation bridge, the central control station (e.g. engine control room).

[0564] Bilge wells

[0565] Bilge wells must be provided with sensors to detect its levels, as well as with ammonia detector, according to the classification society requirements. Alarm must be given at high-level in bilge well. PWIND071WO / ll . 11 . 2025 48 2025129078

[0566] Alarms and safeguard settings

[0567] Different alarms and monitoring parameters for ammonia leakage detection are provided by the classification societies.

[0568] Ammonia fuel system operation

[0569] Normal operation

[0570] Transfer from diesel to ammonia mode

[0571] Engine start up in diesel mode

[0572] During the engine start-up in diesel mode, the engine and the connection piping from and to the FVU are normally filled with water. When the engine is ready to start in diesel mode, the injector cooling water system is activated, and water circulates in the fuel Injection system. Duringthis step, the water tank pressure is kept at 22 bar(g).

[0573] Functional test (optional)

[0574] This test can be performed at any time before the system is filled with ammonia (e.g. after long time of diesel operation without any valve movement). Inert gas at 30 bar(g) is used to pressurise the water in the injection system and the connection pipingfrom and to the FVU. Once the system is pressurised, inert gas supply is cut off and the return line is opened to the water tank to perform the pressure test. Different valves on the engine are tested in a specific sequence by differential pressure. During this test, as soon as the engine is ready for changeover to ammonia mode, the cooling water pump stops and the inert gas connection to the FVU is activated to pressurise the system.

[0575] Transfer from diesel mode to ammonia mode (if functional test is executed)

[0576] Upon competition of the functional test, the water from the engine is purged into the water buffer tank by means of inert gas (e.g. N2) at 30 bar. At the end of this step, the engine is ready to start ammonia mode.

[0577] Transfer from diesel mode to ammonia mode (if functional test is skipped)

[0578] At this stage, water is circulating in the injectors. When the engine is ready for changeover from diesel mode to ammonia mode, the water circulation is stopped. The water is purged into the water buffer tank by means of inert gas (e.g. N2) at 30 bar. At the end of this step, the engine is ready to start ammonia mode.

[0579] Transfer from ammonia mode to diesel mode

[0580] At the end of ammonia mode, the engine and the fuel supply system are filled with ammonia. The engine transfers to diesel mode while the ammonia system remains in ammonia stand-by and still supplies ammonia to the engine and ammonia circulates back to the FSS. If the stand-by stop exceeds a defined period of time, or if the engine is stopped by a shut-down, or if the engine stop is initiated by the safety system or operator, the liquid ammonia is purged to the catch tank and then the injector cooling water is activated. PWIND071WO / ll . 11 . 2025 2025129078

[0581] Trip from ammonia mode to diesel mode

[0582] When the engine trips to diesel mode, ammonia mode is stopped, the ammonia is purged out with inert gas (e.g. N2), followed by starting the injector cooling water system. The purging gas is released from the Ammonia Injector Cooling Water System (AICWS) buffer tank to the Ammonia Vapour Processing System (AVPS).

[0583] Ammonia mode

[0584] Ammonia FSS and engine filling

[0585] As the first step the ammonia injector cooling water is purged to the AICWS buffer tank. As the second step the ammonia FSS and the engine are filled with ammonia. The ammonia filling process starts against the back pressure of the catch tank. Liquid ammonia is transferred to the engine by the high- pressure pump, operating at minimum speed. An engine internal sequential filling procedure is carried out. The inert gas is pushed to the catch tank by liquid ammonia. Some ammonia recirculates to the catch tank till the return is cut-off and the pressure to the engine is build up to 85 bar(g).

[0586] Normal operation

[0587] During normal operation, the liquid ammonia is supplied to the engine by LP and HP pumps. Downstream the HP pump, excessive amount of liquid ammonia is recirculated back to the HP pump suction side to adapt the ammonia consumption. During normal operation, there is no recirculation from the engine to the catch tank.

[0588] Stand-by stop

[0589] Stand-by stop defines a temporary suspension of ammonia supply to the engine in a state of readiness (of the engine and FSS) to initiate ammonia mode. During this step, ammonia is still supplied to the engine but not injected. The system remains pressurised in stand-by while the engine continuous operation in diesel mode (including manoeuvringstop). To ensure cooling of the ammonia injectors, ammonia recirculates via the catch tank and the cooler. The ammonia flow rate is reduced.

[0590] Ammonia normal stop: liquid purging

[0591] Normal stop defines the end of ammonia mode. The end of ammonia mode is either requested by the operator or activated automatically. An automatic activation is triggered in the following cases:

[0592] • the engine is stopped and secured (e.g. during port stay)

[0593] • stand-by stop exceeds the project specifically defined maximum time

[0594] • ammonia trip is initiated by the safety system.

[0595] The liquid ammonia is sequentially purged from the engine to the catch tank. Inert gas at 30 bar(g) is supplied to the engine for the liquid purging.

[0596] Ammonia normal stop: evaporation (back-up)

[0597] This step is only required if the injector cooling water system cannot be activated. If this step is required, it follows the liquid purging and enables controlled vaporisation of remaining liquid ammonia in the system. The pressure is gradually reduced, and the system is depressurised to the AVPS, e.g. to an AVPS buffer tank. This step is finalised when the pressure in the system and AVPS are equalised.

[0598] Ammonia normal stop: vapour purging (back-up)

[0599] This step is part of the back-up solution and starts after the ammonia evaporation is completed. During the vapour purging, the remaining ammonia vapour is purged to the AVPS. During this step, inert gas PWIND071WO / ll . 11 . 2025 50 2025129078 is supplied at 5 bar(g). At the end of the vapour purging, the ammonia system is depressurised to atmospheric pressure.

[0600] Diesel mode

[0601] During diesel mode the injector cooling system is running. Water is supplied to the injectors by the AICWS via the FVU, while the engine is still running in diesel mode.

[0602] Leakage detection

[0603] Leakage detection on the engine including the interface to the FVU

[0604] Different types of sensors are used to detect an ammonia leakage. On engine side, ammonia liquid detectors are used to detect leakages of liquid ammonia. In addition, ammonia liquid detectors are placed at the lowest points of the supply and purging pipe interfaces.

[0605] A gas detector placed at the outlet of the double-wall pipe is also used for an early detection of any ammonia vapour to the annular space.

[0606] Minor leakage: ammonia vapour release

[0607] Minor ammonia vapour leakages are detected by the ammonia gas detector, placed at the end of the double-wall pipe of the ammonia purging line. In case an ammonia leakage is detected, the ventilation flow can either be directed to the AVPS or can be stopped until a safe release is possible.

[0608] Major leakage: liquid ammonia release

[0609] A major leak is given if the quantity of liquid ammonia is so significant that the liquid ammonia does not evaporate immediately. In this case, the annular space will begin to fill with liquid ammonia. This leak is detected by the Liquid Leakage Detectors (LLD). Upon detection of the liquid ammonia leak by the LLDs, an automatic purging procedure is initiated. The liquid ammonia will be removed sequentially by means of inert gas (e.g. N2) from the inner fuel piping and the annular space. Once the liquid ammonia is purged, vapour purging of the inner and outer pipe is initiated.

[0610] A possible purging procedure is described in WO 2025 / 061427 Al as filed on 28.08.2024.

[0611] Leakage detection in the FSS including the interface to the FVU

[0612] Ammonia leakage detection in the FSS, including the interface to the FVU, is performed by ammonia gas detectors in the fuel preparation space. In addition, supply pressure is monitored to detect any supply pressure loss due to ammonia leakage.

[0613] Leakage handling

[0614] Minor leakage without triggering the liquid leakage detector

[0615] If an ammonia leakage is detected by the ammonia gas detector, the ammonia system is purged ac- cordingto the emergency purging procedure as described in the "X-DF-A operating mode changeovers sequences".

[0616] Major leakage with triggering the liquid leakage detector

[0617] If an ammonia leakage is also detected by the liquid leakage detector, the ammonia system is purged according to the emergency purging procedure as described in the "X-DF-A operating mode changeovers sequences", followed by the annular space purging procedure as described in the "Leakage in the annular space of X-DF-A handling procedure". PWIND071WO / ll . 11 . 2025 51 2025129078

[0618] Maintenance work

[0619] Maintenance work on the engine including the interface to the FVU

[0620] When maintenance work on the engine is required, it is crucial to ensure that all ammonia pipes are purged and depressurised. This mitigates the risks associated with residual toxic ammonia as well as the risks of a pressurised system. The purging procedure for maintenance work involves the usage of inert gas, such as nitrogen, to effectively evacuate remaining water or ammonia from the engine internal pipes including the interface to the FVU.

[0621] Two specific conditions must be taken into consideration:

[0622] • purging procedure for maintenance work when the system is filled with water

[0623] • purging procedure for maintenance work when the system is filled with ammonia vapour (back-up).

[0624] Ammonia gas freeing

[0625] A prerequisite for any maintenance work is that the engine is stopped and secured against starting. In this condition, the engine is purged for stoppingand the injector cooling system is filled with water. In case the injector coolingwater system is not available, the ammonia vapour must be purged according to the back-up procedure as described in sections “Ammonia normal stop: evaporation (back-up)" and “Ammonia normal stop: vapour purging (back-up)".

[0626] Purging procedure for maintenance work when the system is filled with injector cooling water

[0627] When the maintenance work starts with the system filled with injector cooling water, the following steps must be followed prior to start of maintenance work:

[0628] • Removal of contaminated water. It is done by means of inert gas supply at 30 bar(g) to eliminate any contaminated water from the engine internal pipes. The high-pressure nitrogen evacuates contaminated water from the engine internal piping, including the interfaces to the FVU and purges this water to the AICWS.

[0629] • Depressurisation of the system to 4 bar(g). This is done via the AICWS buffer tank vent valve.

[0630] • Drainage of the AICWS buffer tank by one time the system volume. The water is drained to the wastewater tank.

[0631] • Depressurisation of the system to atmospheric pressure. A small pressure may remain as caused by the AVPS.

[0632] • Filling with freshwater. Once the system water is removed, the system is filled sequentially with clean freshwater. This step ensures that even traces of remaining system water, which can contain dissolved ammonia, are completely removed.

[0633] • Flushing the freshwater. The system is purged sequentially by using nitrogen at 5 bar(g) to evacuate the freshwater. The vent vale of the AICWS buffer tank is kept fully open during this procedure.

[0634] • Final depressurisation of the system. As a final step, the system must be completely depressurised, i.e. any remaining pressure, which may be caused by the ammonia vapour treatment system, must be released. For this, the FVU connection to the AVPS is used. The AVPS must vent the remaining ammonia-free nitrogen directly to the atmosphere without any back pressure of the treatment system.

[0635] Purging procedure for maintenance work when the system is filled with ammonia vapour (back-up)

[0636] If the AICWS is not available, it is recommended to make this system available and to start the maintenance procedure according to the description above in the “Purging procedure for maintenance work when the system is filled with injector cooling water". PWIND071WO / ll . 11 . 2025 52 2025129078

[0637] When the maintenance work needs to start anyway with the system filled with ammonia vapour, the following steps must be followed prior to start maintenance work:

[0638] • The ammonia vapour purging, as described in section “Ammonia normal stop: vapour purging (back-up)", is extended until the remaining ammonia vapour concentration in the pipingsystem is within the maximum acceptable concentration.

[0639] • The ammonia concentration can be measured at the measurement connection of the FVU.

[0640] A possible purging procedure is described in WO 2025 / 061427 Al as filed on 28.08.2024.

[0641] Pressure test after maintenance

[0642] Upon completion of maintenance work, a pressure test must be performed.

[0643] Maintenance work on the FSS including the interface to the FVU

[0644] The FSS purging, including the interface to the FVU, must follow the FSS maker’s design. WinGD provides a purging proposal.

[0645] Pressure testing concept

[0646] Three different types of tests are performed on the ammonia fuel system:

[0647] • commissioning leakage test

[0648] • leakage test after maintenance

[0649] • operational function test.

[0650] Maintenance concept

[0651] Purging is a safety procedure designed to evacuate ammonia from the engine and the system for maintenance work.

[0652] Specific requirements must be followed prior to start maintenance work. Upon completion of maintenance work, pressure testing is an activity which ensures safety conditions prior to start of ammonia mode.

[0653] This chapter presents an overview of purging procedure for:

[0654] • the ammonia Fuel Supply System (FSS), including the interface to the FVU

[0655] • the engine, including the interface to the FVU.

[0656] In addition, the chapter presents the pressure testing after maintenance work.

[0657] Ammonia purging and ammonia freeing for engine maintenance

[0658] The engine purging process involves the removal of ammonia from the engine, includingthe interface to the FVU.

[0659] Ammonia purging and ammonia freeing for FSS maintenance

[0660] The FSS purging process involves the removal of ammonia from the ammonia fuel supply pipingsystem, includingthe interface to the FVU. PWIND071WO / ll . 11 . 2025 53 2025129078

[0661] Pressure testing after engine maintenance

[0662] A pressure test is required after maintenance work on the ammonia system, particularly following maintenance activities on the FSS, the FVU or on the engine. This test is essential to confirm the tightness of the system and that the valves on the FVU are ope rati ng correctly. Emission Considerations

[0663] All X-DF-A engines are IMO Tier III compliant with an exhaust gas aftertreatment system. Selective Catalytic Reduction (SCR) system is an exhaust gas aftertreatment system which can be selected to reduce NOx emissions for compliance with Tier III NOx regulations in diesel mode and ammonia mode.

[0664] PWIND071WO / ll . 11 . 2025 54 2025129078

[0665] Note :

[0666] Any embodiments described with respect to the device shall similarly pertain to the method and the computer program product . Synergetic ef fects may arise from di f ferent combinations of the embodiments although they might not be described in detail .

[0667] While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims .

[0668] PWIND071WO / ll . 11 . 2025 59 2025129078

[0669] Reference numbers cylinder cover 2 first fuel inj ector 3 first fuel supply system 31 fuel purge system 32 inj ector cooling system 34 fuel valve unit 33 combustion chamber 100 cylinders 110 scavenging air slots 115 piston 120 piston rod 121 crosshead 122 connecting rod 123 exhaust valve 130 second fuel inj ector 150 second fuel supply system 151 crankshaft 170 engine control unit 180 ammonia storage tank 311 flow meter 312 pre- filter system 313 heat exchanger 314 high pressure pump 315 high pressure filter 316 main fuel supply valve 317 fuel supply line 318 inert gas supply system 321 inert gas valve 322 inert gas line 323 cooling water storage tank 340 cooling circuit 341 ammonia purging pipe 342 cooling fluid supply valve 343 cooling circuit valve 344 ammonia inj ector cooling water system 345 interface 346a, 346b cooling water buf fer tank 347 heat exchanger 348 cooling water pump 349 gaseous purge valve 351 ammonia vapour processing system 352 liquid purge valve 353 catch tank 354 ammonia wastewater tank 355 double walled pipes 361 ventilation system 362 large engine 200 PWIND071WO / ll . 11 . 2025 60 2025129078 engine room 410 fuel venting unit 420 fuel preparation space 430 fuel processing system 440 fuel hold space 450

Claims

PWIND071WO / ll.11.2025 55 2025129078Claims1. An internal combustion engine (200) , having at least one cylinder (110) with an inner diameter of at least 200 mm comprising- a first fuel supply system (31) for supplying a first fuel to the engine comprising at least one first injector (3) for each cylinder,- a second fuel supply system (151) for supplying a second fuel to the engine comprising at least one second injector (150) for each cylinder,- a fuel purge system (32) for purging the first fuel supply system (31) using a first fluid,- an injector cooling system (34) for, when the engine runs on the second fuel, cooling the first injector (3) using a second fluid, wherein the second fluid is supplied to the first injector (3) via the first fuel supply system (31) ,- a fuel valve unit (33) for connecting and disconnecting the engine (200) from the first fuel supply system (31) , for connecting and disconnecting the fuel purge system, and for connecting and disconnecting the injector cooling system, characterized in that the engine is configured to, after the first fuel supply system is filled with the second fluid by means of the injector cooling system,- remove the second fluid from the first fuel supply system, in particular by means of the first fluid, and collect the removed second fluid.

2. The internal combustion engine (200) of claim 1 configured toPWIND071WO / ll.11.2025 56 2025129078 purge the first fuel supply system with a third fluid.

3. The internal combustion engine (200) of claim 2 configured to- remove the third fluid from the first fuel supply system, in particular by means of the first fluid.

4. The internal combustion engine (200) of any one of the preceding claims wherein the first fuel is ammonia and / or wherein the second fuel is Diesel.

5. The internal combustion engine (200) of any one of the preceding claims wherein the first fluid comprises a gas, in particular nitrogen.

6. The internal combustion engine (200) of any one of the preceding claims wherein the second fluid comprises a liquid, in particular water or freshwater.

7. The internal combustion engine (200) of any one of the preceding claims, wherein the third fluid comprises a liquid, in particular water, advantageously freshwater.

8. A method for operating an internal combustion engine (200) of any one of the preceding claims, in particular for preparing the internal combustion engine (200) for maintenance, comprising a step of:- removing a second fluid from a first fuel supply system and collecting the removed second fluid,- and in particular wherein the step of removing the second fluid is carried out by means of a first fluid.

9. The method of claim 8 comprising a step of:PWIND071WO / ll.11.2025 57 2025129078- purging the first fuel supply system with a third fluid, in particular freshwater.

10. The method of claim 9 comprising a step of: - removing the third fluid from the first fuel supply system, in particular by means of the first fluid.

11. A computer program product comprising instructions to cause an engine control unit (180) of an internal combustion en- gine (200) of any one of the claims 1 to 7 to execute the steps of a method of claim any one of the claims 8 to 10 when the program is executed on the engine control unit (180) .

12. A computer-readable medium having stored thereon the computer program product of claim 11.

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