Safety device for an ammonia tank on board a ship

Abstract

A safety device for an ammonia tank on board a ship with a hull, the safety device being characterized in that there are at least two separate pipelines, arranged for ammonia gas, each comprising an inlet connected to the ammonia tank and each comprising a first hull outlet arranged below a waterline on the hull, such that the hull outlets, in any loading condition of the ship, at least open below the waterline, into the surrounding seawater outside the hull, and wherein each pipeline further comprises at least one respective safety valve arranged in the vicinity of the inlets and wherein each safety valve is arranged to change from a closed to an open position at a defined overpressure in the ammonia tank, such that in a fully or partially open position of the safety valves, the ammonia gas will be led from the ammonia tank via the pipelines and out via the first hull outlets to the surrounding seawater around the hull and dissolved into aqueous ammonia, such that ammonia gas is not released into the atmosphere around the ship.

Description

[0001] Title: Safety device for an ammonia tank on board a ship

[0002] Technical field

[0003] The present invention relates to a safety device for an ammonia tank on board a ship.

[0004] Background of the invention

[0005] Internationally, solutions are being developed to reduce the amount of greenhouse gases emitted into the atmosphere. The Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO) has adopted the "IMO Initial Strategy for Greenhouse Gas Emission Reduction" and will work to reduce greenhouse gas emissions from the world's ships in the future. To meet the IMO's emission reduction targets, ammonia as a fuel has been identified as one of the most promising solutions, as ammonia can be produced and burned without emitting large amounts of greenhouse gases. When ammonia is to be used on ships, it requires a strong focus on risk-reducing measures to deal with the particular challenge of ammonia's toxicity.

[0006] Description of the prior art

[0007] Ammonia is transported and used on a large scale internationally but has been little used as a fuel in the past. There has been a significant increase in projects worldwide where ammonia is proposed as a fuel on ships to reduce greenhouse gas emissions.

[0008] In particular, solutions that ensure that pressure relief from ammonia tanks does not expose people to toxic gases make the use of ammonia as a fuel on ships particularly challenging. Ventilation inlets and outlets to living spaces on board ships must be secured so that toxic gases that are released cannot enter where people are. Today's established solution has initially been based on having large distances from the emission point to ventilation inlets, outlets and other openings in the ship. Such distances can be demanding to safely achieve without installing very high ammonia discharge masts. These masts often limit the ship's operations, for example when laying at a quay where cranes are used or sailing under bridges. Purpose of the present invention

[0009] The present invention generally aims to solve at least one, but preferably several of the problems that exist with prior art.

[0010] More specifically, it has been an object of the invention to solve the challenge of installing an ammonia discharge mast, which handles toxic ammonia gas from the pressure relief valves of the ammonia tank, on ships.

[0011] The object of the invention is instead to lead the ammonia gas from the pressure relief valves into the sea, where the gas is dissolved in the seawater, thereby eliminating the need for an ammonia discharge mast, which leads the toxic gas from the pressure relief valves of the ammonia tank to the atmosphere.

[0012] The invention

[0013] These objects are fulfilled by a safety device as defined in the independent claims 1 and 24. Further embodiments of the safety device are set forth in the dependent claims 2-23.

[0014] Accordingly, there is provided a safety device for an ammonia tank on board a ship with a hull, wherein the safety device is characterized in that there are at least two separate pipelines arranged for ammonia gas, each comprising an inlet connected to the ammonia tank, and each comprising a first hull outlet arranged below a waterline on the hull, such that the hull outlets, in any load condition of the ship, at least open below the waterline, into the surrounding seawater outside the hull, and wherein each pipeline further comprises at least one respective safety valve arranged in the vicinity of the inlets and wherein each safety valve is arranged to change from a closed to an open position at a defined overpressure in the ammonia tank, such that in a fully or partially open position of the safety valves, the ammonia gas will be led from the ammonia tank, via the pipelines, and out via the first hull outlets to the surrounding seawater around the hull and dissolved into aqueous ammonia, such that ammonia gas is not released into the atmosphere around the ship.

[0015] There will always be a risk of ammonia gas being released into the atmosphere around the ship via a discharge mast, because even if the discharge mast has an outlet far away from the ship, the wind direction can lead the ammonia gas back to the people on board the ship. There is therefore a significantly lower risk in releasing the ammonia gas into the sea around the ship. Ammonia is readily soluble in water (NH3(aq)) called ammonium hydroxide. By leading the ammonia gas from the ammonia tank out through the hull below the waterline, the ammonia gas will mix with the seawater and a saturated water solution at 25 °C contains approx. 31 % ammonia.

[0016] There is also provided a method for securing an ammonia tank in the event of an internal unwanted overpressure in the ammonia tank, comprising the following steps: a) providing a safety device according to one of the appended claims 1 -22, b) increasing the internal pressure in the ammonia tank to a level higher than the defined overpressure of the safety valves, c) opening the safety valves completely or partially, d) directing the ammonia gas from the ammonia tank via the pipelines, from the inlets to the hull outlets, and out below the waterline of the hull, so that the ammonia gas flows out into the surrounding seawater around the hull and dissolves into aqueous ammonia. This in order to avoid ammonia gas being released into the atmosphere around the ship.

[0017] The design pressure for the ammonia tank(s) is higher than the opening pressure of the safety valves connected to the tank, however, the opening pressure will be higher than the back pressure from the seawater, both dynamic and static, so that when the safety valves are fully or partially opened, the ammonia gas will be forced out through the hull outlets and mixed with the surrounding seawater.

[0018] Dissolving the ammonia gas in the surrounding seawater will prevent ammonia gas from penetrating into living spaces and creating life-threatening situations on board the ship, because even if the ammonia gas is discharged through a discharge mast, adverse weather conditions may lead the gas back to the ship.

[0019] Description of embodiments of the invention

[0020] In one embodiment of the invention, each of the at least two separate pipelines’ (5a, 5b) respective first hull outlets (5.2a, 5.2b) are arranged at a distance greater than or equal to the width of the hull (B) divided by two (B / 2) from each other and open into the surrounding water around the hull (3).

[0021] This has an advantage in the event of a grounding or collision, etc., where one of the hull outlets is no longer operational. By having them separately in two different watertight compartments, it will increase the probability that at least one of the outlets is operational after an incident. In another embodiment of the invention, the at least two separate pipelines’ respective first hull outlets are arranged on opposite sides of the hull.

[0022] The advantage of having them on opposite sides of the hull is that if there is more marine fouling on one side than the other, or if the ship is lying with one side against the quay, or against another type of obstacle, the ammonia gas will exit via the other pipeline on the other side.

[0023] In one embodiment of the invention, the defined overpressure in barg is in a range from 4 barg to 12 barg, in a more preferred range from 5 barg to 10 barg and in an even more preferred range from 6 barg to 8 barg.

[0024] The ammonia tank must be relieved in instances of overpressure, and the overpressure is determined by the design pressure of the tank. The advantage of having defined overpressure pressures that are in the range from 4-12 barg is that it is not desirable to design the tank with too high a pressure, as it becomes too expensive to produce, and another advantage is that the ammonia gas at 4 barg maintains a temperature above 0 °C.

[0025] Another advantage of having the defined overpressure in the range of 4-10 barg is that the pressure range is higher than the static and dynamic backpressure for the discharge of ammonia into seawater.

[0026] In one embodiment of the invention, the ammonia tank is arranged inside the lower part of the hull, so that the ammonia tank is completely or partially below the waterline of the hull at any normal load condition of the ship.

[0027] Normal load condition can be defined here as the load conditions for which the ship is designed, and an abnormal load condition is in case of damage, grounding, etc. The advantage of having a tank in the lower part of the hull is stability. Having a large tank on deck will provide a higher center of gravity for the ship.

[0028] In one embodiment of the invention, the at least two separate pipelines are further comprised with each of their respective gooseneck, which extends in a loop after the safety valves and at least above the waterline of the hull before the hull outlets. This is an advantage if the ammonia tank is arranged in the lower part of the hull, so that the seawater is not led back to the ammonia tank via the pipelines. By arranging the pipelines with a loop above the waterline, preferably also above the main deck, there will be no risk of the seawater being led in the pipelines back to the ammonia tank, as long as the ship has a normal load condition.

[0029] In one embodiment of the invention, each of the at least two separate pipelines are split or branched after the safety valves with each having its own respective branch pipe going to each of its own respective second hull outlet which at least opens out below the waterline into the surrounding seawater outside the hull.

[0030] Having two separate hull outlets connected to each pipeline will provide better redundancy and reduce the risk of blockage in the outlets.

[0031] In one embodiment of the invention, the other hull outlets are arranged in a different position than the first hull outlets on the hull.

[0032] It is an advantage to have the first and second hull outlets located in different positions, with regard to collision, grounding, marine fouling, lying at berth, etc.

[0033] In one embodiment of the invention, the first hull outlets are arranged in the bottom of the hull and the second hull outlets are located in the sides of the hull.

[0034] Arranging the first and second hull outlets in the bottom and in the hull sides provide even better redundancy with regard to collision, grounding, marine fouling, lying at berth, etc. In a further embodiment of the invention, the first hull outlets are arranged on each side of the bottom of the hull and the second hull outlets are arranged on each side of the hull, typically on the starboard and port sides.

[0035] In one embodiment of the invention, the branch pipes are arranged after the goosenecks and extend to each respective second hull outlet.

[0036] It is advantageous to have the branch pipes after the goosenecks to avoid backflow of seawater into the ammonia tank from the other hull outlets.

[0037] In an embodiment of the invention wherein the at least two separate pipelines further comprise each a respective drain pot comprising at least each a respective drain valve arranged at a point after the safety valves on the two separate pipelines before the gooseneck.

[0038] Condensation may occur inside the pipelines, and if the pipelines are arranged with a gooseneck, the condensation can be collected before the gooseneck as a water trap. It is therefore an advantage to be able to collect and drain out condensation water, or other fluid, from a drain pot. In a further embodiment of the invention, the drain pot is arranged with an instrument for motorization and / or warning if it should fill with fluid.

[0039] In an embodiment of the invention where the drain pots are drained to a separate collection tank, drainage tank, on board, so that drained, potentially ammonia- containing, water from the at least two separate pipelines can be treated before it is led overboard or delivered for treatment on shore.

[0040] It is not desirable to lead ammonia-containing water directly to a bilge well on board or directly overboard, so it is an advantage to collect it in a tank, so that the water can either be treated or delivered.

[0041] In an embodiment of the invention, the at least two separate pipelines further comprise a purging arrangement (compressor, compressed air, etc.) arranged after the safety valves and / or before the branch pipes, arranged to blow compressed air, or non-flammable gas (inert gas) through the pipelines and / or branch pipes.

[0042] It is advantageous to purge the lines, whether only to check the flow rate, or to completely empty the pipelines of ammonia gas.

[0043] In a further embodiment of the invention, the purging arrangement purges at predetermined time intervals through the pipelines and / or through the branch pipes after the safety valves and out through the hull outlets, so that the pipelines and / or branch pipes are checked for flow rate and reduced for marine fouling.

[0044] It may be advantageous to check flow rate at given intervals, because then a blockage may be detected. It is also advantageous to purge to prevent or remove marine fouling. In one embodiment of the invention, the at least two separate pipelines further comprise each respective pressure sensor connected to the pipelines after the safety valves before the outlets, so that the pressure in the pipelines can be monitored and logged when purging the pipelines.

[0045] Monitoring the back pressure in the pipelines when purging provides data indicating a change, so that a possible blockage of marine fouling can be predicted and prevented before it occurs.

[0046] In one embodiment of the invention, the pipelines further comprise each respective hatch arranged after the safety valves and which is arranged to be able to carry out mechanical cleaning of the pipelines and / or branch pipes.

[0047] It is an advantage to mechanically clean the pipes of marine fouling or other foreign bodies. For example, when there is an indication of increased pressure in connection with purging the pipes, the pipeline can be cleaned via access from the hatches.

[0048] In one embodiment of the invention, the first hull outlets and / or the second hull outlets have passages in the hull in the vicinity of a propeller, so that the ammonia gas discharged from the hull outlets is forced further away from the hull by means of the propeller water.

[0049] This is an advantage for supplying seawater so that the ammonia gas is quickly mixed with large quantities of seawater and a thinner mixture is formed that is less harmful to the living organisms in the sea. By using the propeller water, the ammonia gas will be mixed out in large quantities of seawater.

[0050] In one embodiment of the invention, a propeller is a tunnel thruster or a propulsion propeller or an azimuth propeller or the like.

[0051] It is an advantage that the propeller used to push seawater or drive the ammonia gas further in the seawater is large, the more seawater that flows past the hull outlets and mixes with the ammonia gas that comes out, the better.

[0052] In an embodiment of the invention where the pipelines and / or branch pipes are further comprised at least one circulation pump connected near the outlets, to maintain a continuous or semi-continuous circulation of fluid through the hull outlets to maintain an open flow path and reduce marine fouling.

[0053] Circulating water, with or without chemicals, in a closed or open system with a circulation pump, can be an advantage with regard to marine fouling.

[0054] In an embodiment of the invention, each of the hull outlets is comprised with its respective hull valve so that the hull outlets can be closed off or blinded if there is a break in one or more of the pipelines and / or branch pipes.

[0055] This is an advantage in the event of a collision or grounding, where the pipeline and / or branch pipes are damaged.

[0056] In one embodiment of the invention, the pipelines are each equipped with a respective ammonia gas sensor after each respective safety valve to detect involuntary ammonia gas release in the event of a leak from the ammonia tank through the safety valves.

[0057] This is an advantage to verify that the safety valve is tight but also an advantage if one is to perform mechanical cleaning through the hatch to know that the pipe is free of ammonia gas.

[0058] In one embodiment of the invention, each of the first outlets is connected to a respective ejector that is arranged to suck ammonia gas from the pipelines and mix the ammonia gas with an ejector water flow that is passed on to the surrounding water around the hull.

[0059] This is an advantage when there is little excess pressure left in the pipe, as it will form a suction effect in the pipelines that helps to extract the ammonia gas. In addition, it will be an advantage to mix the ammonia gas with the propellant medium, which in this scenario is seawater, so that the ammonia gas is mixed to form thin aqueous ammonia.

[0060] In one embodiment of the invention, the respective ejector has an ejector water flow, propellant medium, from a fire pump that is powered via an emergency power panel on board the ship. In one embodiment of the invention, each of the hull outlets is arranged with a dispenser that distributes the ammonia gas in the water so that the dissolution rate from ammonia gas to aqueous ammonia is increased.

[0061] The advantage of a dispenser is that it will disperse the gas into the water in a better way than a hull outlet.

[0062] In an embodiment of the invention where the ship is no longer located with surrounding seawater that can receive ammonia gas in the event of overpressure in the tank, the safety device or ammonia tank must be connected to a temporary discharge point or to a pipeline that leads the ammonia gas further down to below the sea surface. Optionally, the pipelines can be connected to an additional pipeline to the safety device, so that the ammonia gas in the event of overpressure is directed to a sufficient amount of water, typically a large ballast tank or the like.

[0063] In one embodiment, there may be two or more ammonia tanks on board a ship.

[0064] In one embodiment, two or more ammonia tanks may be connected together via one or more pipes, so that the ammonia can either flow freely between the ammonia tanks or be pumped to and from the ammonia tanks.

[0065] In one embodiment, two or more ammonia tanks may be connected together via one or more pipes, and the safety device may have one inlet in each of the tanks, as shown in Figure 12.

[0066] The example is given for a specific embodiment, and the invention is not limited thereto, but also encompasses modifications and variations within the scope of the claims set forth below after the reference table.

[0067] Brief description of the figures

[0068] Preferred embodiments of the invention will be discussed in more detail below with reference to the accompanying figures, where:

[0069] Figure 1 shows a simple profile drawing of a transverse section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b.

[0070] Figure 2 shows a simple profile drawing of a longitudinal section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b. Figure 3 shows a simple profile drawing of a transverse section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b and each has its respective branch pipe 5.3a and 5.3b.

[0071] Figure 4 shows a simple profile drawing of a longitudinal section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b and each has its respective branch pipe 5.3a and 5.3b.

[0072] Figure 5 shows a simple profile drawing of a transverse section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b and each has its respective gooseneck 7a and 7b.

[0073] Figure 6 shows a simple profile drawing of a longitudinal section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b and each has its respective gooseneck 7a and 7b.

[0074] Figure 7 shows a simple profile drawing of a transverse section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b and each has its respective gooseneck 7a and 7b followed by each respective branch pipe 5.3a and 5.3b.

[0075] Figure 8 shows a simple profile drawing of a longitudinal section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b and each has its respective gooseneck 7a and 7b followed by each respective branch pipe 5.3a and 5.3b.

[0076] Figure 9 shows a simple profile drawing of a longitudinal section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b and each of which has its respective gooseneck 7a and 7b followed by each of its respective branch pipes 5.3a and 5.3b where all the hull outlets 5.2a, 5.2b, 5.4a and 5.4b are arranged with hull valves 13a, 13b, 13c and 13d.

[0077] Figure 10 shows a simple profile drawing of a transverse section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b comprising ejectors 14a, 14b.

[0078] Figure 11 shows a simple profile drawing of a transverse section of a ship and an ammonia tank (NH3 Tank), which has two separate pipelines 5a and 5b comprising dispensers 15a, 15b.

[0079] Figure 12 shows a simple profile drawing of a longitudinal section of a ship comprising two ammonia tanks (NH3 tanks), which are connected in series with a crossover 18, so that the ammonia can be moved between the tanks. Detailed description of the figures

[0080] Figures 1 -12 show an embodiment of a safety device for an ammonia tank on board a ship according to the present invention.

[0081] In Figure 1 we see a cross-section of the ship 4 with the hull 3, where it is indicated where the waterline 8 stands on the hull 3. The figure shows an embodiment where the ammonia tank 2 is arranged in the lower part of the hull 3 and where the inlets 5.1 a, 5.1 b are arranged in the upper part of the ammonia tank 2. We see from the Figure that the pipelines 5a, 5b are separate and that they each comprise their respective safety valve 6a, 6b close to the inlets 5.1 a, 5.1 b to the ammonia tank 2. The pipelines 5a, 5b lead further down to the bottom of the hull 3 and to the first hull outlets 5.2a, 5.2b, so that an ammonia gas that is released from the ammonia tank 2 and out through the inlets 5.1 a, 5.2a past the safety valves 6a, 6b is guided by the pipelines 5a, 5b to the hull outlets 5.2a, 5.2b to the surrounding seawater. The same principle is illustrated by Figure 2, only that it is a profile drawing of a longitudinal section. Figure 2 shows two separate pipelines 5a and 5b, now respectively with pipe runs such that pipeline 5a runs aft of the ammonia tank and pipeline 5b is ahead of the ammonia tank and each down to its respective hull valve 5.2a, 5.2b. Figures 1 and 2 also show the waterlines 8. Figure 1 shows the width B of the hull 3.

[0082] In Figures 3 and 4 we see an embodiment with branch pipes 5.3a, 5.3b, or branch pipes, so that the pipelines 5a, 5b are divided after the safety valves, but before the hull outlets 5.2a, 5.2b. Figure 3 shows the design in a cross-section, where we see that the branch pipes 5.3a, 5.3b are connected to the pipelines 5a, 5b after the safety valves 6a, 6b and go to each hull side (port and starboard) and each respective second hull outlet 5.4a, 5.4b in the hull sides on each side of the ship. The figure also shows that the pipeline 5a, 5b, after the branch pipes 5.3a, 5.3b, goes to the bottom of the hull, separated from each other, and to each respective first hull outlet 5.2a, 5.2b on each side in the bottom of the hull 3. Figure 8 also shows where the waterline 8 is on the hull and that all the hull outlets lie below the waterline 8. Figure 4 shows the longitudinal profile of the ship 4, with the same principle as in Figure 3, but now the pipelines 5a, 5b are separated fore and aft of the ammonia tank 2. The branch pipes 5.3a, 5.3b are connected to the pipelines 5a, 5b after the safety valves 6a, 6b, but before the first hull outlets 5.2a, 5.2b. The branch pipes 5.3a, 5.3b are led to the second hull outlets 5.4a, 5.4b which have a passage in the hull 3 at a different location than the first hull outlets 5.2a, 5.2b. Figures 3 and 4 also show the water lines 8 and that the ammonia tank 2 is located below the water line 8.

[0083] Figures 5 and 6 show an embodiment where a gooseneck (loop) is arranged after the safety valves 6a, 6b and before the first hull outlets 5.2s, 5.2b on the pipelines 5a, 5b from the ammonia tank 2. Figure 5 shows an embodiment where the ammonia tank 2 is arranged in the lower part of the hull 3 and where the inlets 5.1a, 5.1 b are arranged in the upper part of the ammonia tank 2. We see from the Figure that the pipelines 5a, 5b are separate and that they each comprise their respective safety valve 6a, 6b close to the inlets 5.1 a, 5.1 b to the ammonia tank 2. The pipelines 5a, 5b lead on to the goosenecks 7a, 7b and further down to the bottom of the hull 3 and to the first hull outlets 5.2a, 5.2b, so that an ammonia gas that is released from the ammonia tank 2 and out through the inlets 5.1 a, 5.2a past the safety valves 6a, 6b is led by the pipelines 5a, 5b through the goosenecks 7a, 7b and further to the hull outlets 5.2a, 5.2b out into the surrounding seawater. The same principle is shown by Figure 6 only that it is a profile drawing of a longitudinal section. Figure 6 shows two separate pipelines 5a and 5b, now respectively with pipe runs such that pipeline 5a runs aft of the ammonia tank and pipeline 5b runs ahead of the ammonia tank and each with its respective gooseneck 7a, 7b and down to its respective hull valve 5.2a, 5.2b. The figures show the waterline 8 and that both first hull outlets 5.2a, 5.2b are arranged below the waterline 8.

[0084] Figures 7 and 8 show an embodiment of a combination of the preceding Figures 1 -6. Figures 7 and 8 show an embodiment in which a gooseneck (loop) is arranged after the safety valves 6a, 6b and then branch pipes 5.3a, 5.3b before the first hull outlets 5.2s, 5.2b on the pipelines 5a, 5b from the ammonia tank 2.

[0085] Figure 9 shows an embodiment where the pipelines 5a, 5b from the ammonia tank 2 comprise;

[0086] - each respective hatch 17a, 17b,

[0087] - each respective gooseneck 7a, 7b, comprising each respective pressure sensor 11 a, 11 b and each respective ammonia sensor 12a, 12b,

[0088] - each respective drain pot 9a, 9b, comprising each respective drain pot 9.1a, 9.1 b and each respective gooseneck 7a, 7b,

[0089] - each respective branch pipe 5.3a, 5.3b, comprising each respective hull valve 13c, 13d and each respective second hull outlet 5.4a, 5.4b, - each respective hull valve 13a, 13b and each respective second hull outlet 5.2a, 5.2b, and a drainage tank, collection tank, 10 to which each of the drainage pipes 9.2a, 9.2b leads. Furthermore, Figure 9 also shows a purging arrangement 16 which is connected to the pipelines immediately after the safety valves 6a, 6b, to purge the pipelines 5a, 5b, and the branch pipes 5.3a, 5.3b, and out through the hull outlets 5.2a, 5.2b, 5.4a and 5.4b. The hatches 17a, 17b, are arranged after the safety valves 6a, 6b on each respective pipeline 5a, 5b, and can be opened when necessary for cleaning the insides of the pipelines 5a, 5b and the branch pipes 5.3a, 5.3b.

[0090] The figure also shows the waterline 8 and how the hull outlets 5.2a, 5.2b, 5.4a, 5.4b are arranged separately from each other below the waterline 8 on the hull 3, and how the goosenecks 7a, 7b are arranged to extend above the waterline 8.

[0091] Figure 10 shows a cross-section of the ship 4 with the hull 3, where it is indicated where the waterline 8 is on the hull 3. The figure shows an embodiment where the ammonia tank 2 is arranged in the lower part of the hull 3 and where the inlets 5.1a,

[0092] 5.1 b are arranged in the upper part of the ammonia tank 2. We see from the figure that the pipelines 5a, 5b are separate and that they each include their respective safety valves 6a, 6b close to the inlets 5.1 a, 5.1 b to the ammonia tank 2. The pipelines 5a, 5b lead further down to the bottom of the hull 3 and to each respective ejector 14a, 14b before the first hull outlets 5.2a, 5.2b, so that an ammonia gas that is released from the ammonia tank 2 and out through the inlets 5.1a, 5.2a past the safety valves 6a, 6b is led by the pipelines 5a, 5b before being mixed with the ejector water flow, the propellant, and led out via the hull outlets 5.2a, 5.2b to the surrounding seawater.

[0093] Figure 11 shows a cross-section of the ship 4 with the hull 3, where it is indicated where the waterline 8 is on the hull 3. The figure shows an embodiment where the ammonia tank 2 is arranged in the lower part of the hull 3 and where the inlets 5.1a,

[0094] 5.1 b are arranged in the upper part of the ammonia tank 2. We see from the figure that the pipelines 5a, 5b are separate and that they each include their respective safety valve 6a, 6b close to the inlets 5.1 a, 5.1 b to the ammonia tank 2. The pipelines 5a, 5b lead further down to the bottom of the hull 3 and to the first hull outlets 5.2a, 5.2b which are arranged with dispensers 15a, 15b, so that an ammonia gas that is released from the ammonia tank 2 and out through the inlets 5.1a, 5.2a past the safety valves 6a, 6b is led by the pipelines 5a, 5b to the hull outlets 5.2a, 5.2b provided with dispensers 15a, 15b which increase the mixing rate of the ammonia gas with the surrounding seawater.

[0095] Figure 12 shows a longitudinal profile of the ship 4, where the pipelines 5a, 5b are connected to each part of an ammonia tank 2 which are connected together in series and communicate with each other via a crossover 18. The figure shows that the connected pipeline 5a is connected to the ammonia tank 2 aft and pipeline 5b is connected to the forward ammonia tank 2. Both pipelines 5a, 5b each comprise their respective safety valve 6a, 6b and each their first hull outlet 5.2a, 5.2b.

[0096] Reference Table

Claims

CLAIMS1 . A safety device (1 ) for an ammonia tank (2) on board a ship (4) with a hull (3), wherein the safety device (1 ) comprises:- at least two separate pipelines (5a, 5b... ) arranged for ammonia gas, each comprising an inlet (5.1a, 5.1 b... ) connected to the ammonia tank (2), and each comprising a first hull outlet (5.2a, 5.2b... ) arranged below a waterline (8) on the hull (3), such that the hull outlets (5.2a, 5.2b ... ), in any loading condition of the ship (4) at least open below the waterline (8), into the surrounding seawater outside the hull (4), and- wherein each pipeline (5a, 5b... ) further comprises at least one respective safety valve (6a, 6b... ) arranged in the vicinity of the inlets (5.1a, 5.1b... ) and wherein each safety valve (6a, 6b... ) is configured to change from the closed to the open position at a defined overpressure (barg) in the ammonia tank (2), so that in a fully or partially open position of the safety valves (6a, 6b... ) the ammonia gas is led from the ammonia tank (2) via the pipelines (5a, 5b... ) and out via the first hull outlets (5.2a, 5.2b... ) into the surrounding seawater around the hull (3) and dissolved into aqueous ammonia, so that ammonia gas is not released to the atmosphere around the ship (4).

2. The safety device (1 ) according to claim 1 , wherein each of the at least two separate pipelines’ (5a, 5b) respective first hull outlets (5.2a, 5.2b... ) are arranged at a distance greater than or equal to the width (B) of the hull divided by two (B / 2) from each other and open into the surrounding water around the hull (3).

3. The safety device (1) according to claim 1 or 2, wherein the defined overpressure in barg is in a range from 2 barg to 10 barg, in a more preferred range from 3 barg to 8 barg and in an even more preferred range from 4 barg to 6 barg.

4. The safety device (1) according to any one of the preceding claims, wherein the ammonia tank (2) is arranged inside the lower part of the hull (3), such that the ammonia tank (2) is wholly or partly below the waterline (8) around the hull (3) at any normal loading condition of the ship (4).

5. The safety device (1) according to any one of the preceding claims, wherein the at least two separate pipelines (5a, 5b... ) further each comprise a respectivegooseneck (7a, 7b... ), which extends in a loop after the safety valves (6a, 6b... ) and at least above the waterline (8) of the hull (3) before the hull outlets (5.2a, 5.2b... ).

6. The safety device (1) according to any one of the preceding claims, wherein each of the at least two separate pipelines (5a, 5b... ) is split (branched) after the safety valves (6a, 6b) with each respective branch pipe (5.3a, 5.3b... ) to each respective second hull outlet (5.4a, 5.4b) which at least opens below the waterline (8) into the surrounding seawater outside the hull (4).

7. The safety device (1) according to claim 6, wherein the second hull outlets (5.4a, 5.4b... ) are arranged in a different position than the first hull outlets (5.2a, 5.2b) on the hull (4).

8. The safety device (1) according to claim 6 or 7, wherein the first hull outlets (5.2a, 5.2b... ) are located in the bottom of the hull (4) and wherein the second hull outlets (5.4a, 5.4b) are located in the sides of the hull (4).

9. The safety device (1) according to any one of claims 6-8, wherein the branch pipes (5.3a, 5.3b... ) are arranged after the goosenecks (7a, 7b... ) and extend to their respective second hull outlets (5.4a, 5,4b... ).

10. The safety device (1 ) according to any one of claims 4-9, wherein the at least two separate pipelines (5a, 5b... ) further comprise each respective drain pot (9a, 9b ...) comprising at least each respective drain valve (9.1a, 9.1 b... ) arranged at a point after the safety valves (6a, 6b... ) on the two separate pipelines (5a, 5b... ) before the gooseneck (7a, 7b... ).11 . The safety device (1 ) according to claim 8, wherein the drain pots (9a, 9b) are drained to a separate collection tank, drain tank, (10) on board, so that drained ammonia-containing water from the at least two separate pipelines (5a, 5b... ) can be treated before being led overboard or being delivered for treatment on shore.

12. The safety device (1 ) according to any one of the preceding claims, wherein the at least two separate pipelines (5a, 5b... ) further comprise a purging arrangement (16) arranged after the safety valves (6a, 6b... ) and / or before the branch pipes (5.3a, 5.3b), which blows compressed air, or non-flammable gas (inert gas).

13. The safety device (1 ) according to claim 12, wherein the purging arrangement (16) at predetermined time intervals purges through the pipelines (5a, 5b... ) and / or branch pipes (5.3a, 5.3b) after the safety valves (6a, 6b ..) and out through the hull outlets (5.2a, 5.2b, 5.4a, 5.4b... ), so that the pipelines (5a, 5b... ) and / or branch pipes (5.3a, 5.3b) are checked for flow and reduced for marine fouling.

14. The safety device (1 ) according to one of claims 12 or 13, wherein the at least two separate pipelines (5a, 5b... ) further each comprise a respective pressure sensor (11a, 11 b... ) connected to the pipelines (5a, 5b... ) after the safety valves (6a, 6b ..) before the outlets (5.2a, 5.2b, 5.4a, 5.4b... ), so that the pressure in the pipelines (5a, 5b... ) can be monitored and logged by purging the pipelines (5a, 5b... ).

15. The safety device (1 ) according to any one of the preceding claims, wherein the pipelines (5a, 5b... ) further comprise each respective hatch (17a, 17b... ) arranged after the safety valves (6a, 6b... ) and which is arranged to carry out mechanical cleaning of the pipelines (5a, 5b... ) and / or the branch pipes (5.3a, 5.3b).

16. The safety device (1 ) according to any one of the preceding claims, wherein the first hull outlets (5.2a, 5.2b... ) and / or the second hull outlets (5.4a, 5.4b... ) have passageways in the hull in the vicinity of a propeller, so that the ammonia gas discharged from the hull outlets (5.2a, 5.2b, 5.4a. 5.4b... ) is forced further away from the hull (3) by means of the propeller water.

17. The safety device (1 ) according to claim 16, wherein a propeller is a tunnel thruster or a propulsion propeller or an azimuth propeller or the like.

18. The safety device (1 ) according to any one of the preceding claims, wherein the pipelines (5a, 5b... ) and / or branch pipes (5.3a, 5.3b...) further comprise at least one circulation pump (17) connected in the vicinity of the outlets (5.2a, 5.2b... ), to maintain a continuous or semi-continuous circulation of fluid through the hull outlets (5.2a, 5.2b, 5.4a, 5.4b... ) to maintain an open flow path and reduce marine fouling.

19. The safety device (1 ) according to any one of the preceding claims, wherein each of the hull outlets (5.2a, 5.2b, 5.4a, 5.4b... ) comprises a respective hull valve (13a, 13b, 13c, 13d... ) such that the hull outlets (5.2a, 5.2b, 5.4a, 5.4b... ) can beclosed off or blinded in the event of a rupture in one or more of the pipelines (5a, 5b... ) and / or branch pipes (5.4a, 5.4b... ).

20. The safety device (1 ) according to any one of the preceding claims, wherein the pipelines (5a, 5b... ) are each arranged with a respective ammonia gas sensor (12a, 12b... ) after each respective safety valve (6a, 6b... ) to detect involuntary ammonia gas release in the event of a possible leak from the ammonia tank (2) through the safety valves (6a, 6b...).21 . The safety device (1 ) according to any one of the preceding claims, wherein each of the first outlets (5.2a, 5.2b, 5.4a, 5.4b... ) is connected to a respective ejector (14a, 14b, 14c, 14d... ) which is arranged to suck ammonia gas from the pipelines (5a, 5b, 5.4a, 5.4b... ) and mix the ammonia gas with an ejector water flow which is passed on to the surrounding water around the hull (4).

22. The safety device (1 ) according to claim 21 , wherein each respective ejector (14a, 14b, 14c, 14d... ) has an ejector water flow, driving medium, from a fire pump which is powered via an emergency power panel on board the ship (4).

23. The safety device (1 ) according to any one of the preceding claims, wherein each of the hull outlets (5.2a, 5.2b, 5.4a, 5.4b... ) is provided with a dispenser (15a, 15b, 15c, 15d... ) which distributes the ammonia gas into the water so that the dissolution rate from ammonia gas to aqueous ammonia is increased.

24. Method for securing an ammonia tank (2) in the event of an internal unwanted overpressure in the ammonia tank (2), comprising the following steps: a) providing a safety device (1 ) according to one of the preceding claims 1 -22, b) the internal pressure in the ammonia tank (2) is increased to a level higher than the defined overpressure (barg) of the safety valves (6a, 6b... ), c) the safety valves (6a, 6b... ) are opened completely or partially, d) the ammonia gas is led from the ammonia tank (2) via the pipelines (5a, 5b) from the inlets (5.1 a, 5.2a... ) to the hull outlets (5.2a, 5.3) below the waterline (8) of the hull (4) and flows out into the surrounding seawater around the hull (4) and is dissolved into aqueous ammonia, so that ammonia gas is not released into the atmosphere around the ship (4).

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