The Technical Field of the Invention

The invention relates to mechanical and fluid technologies for completely emptying residuals in the cargo tanks after completion of an emptying sequence. More particularly, the invention relates to a system and a method for emptying a liquid containing cargo tank, comprising a closable room or volume arranged below and in liquid communication with a cargo tank through closable opening; a supply line for supply of a pressurized gas to the closable room; an outlet line for emptying the liquid from the closable room; and a sealing body associated with an actuator for moving the sealing body into sealing contact with the communicating opening between the closable room and the cargo tank, the actuator being powered by the pressurized gas. Background for the invention

For existing chemical cargo tanker ^' s pumping systems, there are challenges related to the complete removal of remaining residuals after ended conventional pumping and stripping sequences of the tanks. The remaining residuals represent a part of the actual shipped cargo, and for some types of cargo, there will be an important economic benefit to deliver all the shipped liquids. This is difficult, and not possible or adequate for most tankers with today ^' s conventional tank stripping arrangement.

Current tank set up design arrangement for most installations is not capable of complete emptying all residuals in the tanks. State of the art for emptying and recover residuals from a cargo tank will not give satisfying results.

Chemical cargo tank vessels carry different types of cargo, and it is important to secure that tanks are sufficiently cleaned and all remaining cargo and washing water are removed before new cargo is loaded.

The fully removal of remaining residuals for today's tanks are done manually by ship crew. This can be an unsafe solution seen from an HSE point of view. For many of the different shipped cargos, the content can be dangerous and represent a high risk for explosion or toxicity, which restricts the possibility to enter cargo tanks.

Normal remaining quantity of cargo in the cargo tanks at completed discharge sequence for existing systems can vary from 25 to 250 L, depending on pump type, tank design and condition of pump and stripping systems. In addition to the cargo, there will be the same amount of washing water collected in the tanks after ended washing sequences. Removal of remaining cargo and washing water will have to take place. The crew of the ship often perform this job manually, which demands unnecessary time and labour.

Cargo lines, depending of design/layout, are emptied completely by use of pressurized nitrogen or air at ended stripping sequence.

Remaining cargo in the cargo pipe from the pumps are emptied through the stripping pipe by adding pressurized inert gas through the cargo pipe purging valve while pump is running. The cargo discharge valve is closed during the stripping sequence and the pump is continuously running to maintain backpressure for the cargo pipe from the pump while nitrogen is pushing the liquid column down to the assembly point for the cargo and stripping pipe. When the stripping sequence of cargo is completed, remaining residual liquids will be remained in the pump suction well.

The liquid can, for designs as explained further below, be removed by vacuum stripping systems. The efficiency for vacuum systems is normally poor, and the designs are limited concerning density and viscosity for cargos and lifting heights.

WO 84/01 138 discloses a stripping system for a cargo tank, comprising an auxiliary tank located at a level near the bottom of the cargo tank whose cargo is to be discharged. Moreover, the system consists of a vacuum source connected to the auxiliary tank to produce a partial vacuum in said tank relative to the cargo pressure and a valve permitting the cargo to flow from the cargo tank into the auxiliary tank at said partial vacuum. The system also includes a discharge line for carrying the cargo away from the auxiliary tank with an associated valve, and a pressure source connected to the tank, thereby permitting the contents of the auxiliary tank to be forced out through the discharge line. The auxiliary tank is an integral part of the discharge pump that is submersible into the cargo tank via a deck hatch.

WO 97/06050 discloses a cargo discharging pump submersible in the cargo of a cargo tank of a ship via a well at the bottom of the cargo tank. A stripping pipe runs from the discharge side of the pump to a delivery location via upper deck of the ship. The pump has an impeller which is equipped with opposite pairs of locally defined blades, which are disposed downstream just within the pump inlet, the stripping pipe being equipped with pressure medium at a first, lower level and communicate with a pressure medium and/or vacuum source at least at a second, higher lying level of the stripping pipe.

GB 2 130 303 relates to a stripper for tank holds of a vessel. The stripper is arranged to operate without pumps. The stripper consists of a drain sump having a discharge line and an inlet for inflow from the cargo hold. A compressed air line extends into the drain sump. The inlet can be closed by a float element by floatation, when there is sufficient liquid to fill the sump, and by the pressure of compressed air being supplied to the sump, via the pipe when there is only sufficient liquid to fill the drain sump partly. The float has a blind bore afforded by a tube, which bore receive loosely the outlet end part of the line so that the part and the tube operate the closable valve.

Vacuum stripping arrangement is an optional stripping method, which can be used for smaller size chemical cargo tankers carrying low viscosity cargos. Vacuum stripping system is mainly used to remove washing water after tank cleaning. Use of vacuum systems for removing residual cargo is an option, but there are several uncertain issues and challenges related to the method. Vacuum stripping

arrangement is installed on few vessels due to its need for high capacity of purging medium and if s uncertain ability to collect cargo with high viscosity index, high density and for tank applications with a tank height above certain critical limits for vacuum lifting.

Some challenges related to vacuum as stripping method are:

• The ejector system's ability to create a sufficient vacuum for removal of cargo.

• Vacuum stripping has a limitation for lifting capacity, which is directly

dependent of tank height and cargo density.

• Consumption of a large amount of nitrogen to empty the cargo pipe, followed by driving the ejector system and again emptying the cargo pipe after collecting residuals from the pump suction well.

• A large number of operations for the stripping sequence cause a greater

consumption of operation time, which results in increased time at terminals. This might also result in less cargo operations per year.

· The potential for fluids to boil due to decreased pressure when exposed to vacuum.

Summary of the Invention

The invention relates to all types of cargo; from a cargo tanker vessel and floating storage and production units - shipping and offshore, in order to empty the tanks completely after completing the use of conventional pump and stripping process, thus enabling complete emptying of residuals in cargo tanks.

The invention is based on the principles of gravity filling and evacuation by pressurization of cargo from a closable and sealed volume. The idea is to use inert gas pressure for driving the cargo to the top. For enabling this, the tank has to be equipped with a closable volume with an automatic closing and sealing mechanism.

An object of the invention is to provide a simple, improved and more efficient method and device for completely emptying a cargo tank. Another object of the invention is to provide an emptying method and a device that are less dependent on manual cleaning or washing operations,

Another object of the present invention is to provide an improved and more efficient emptying method and device.

Yet another object of the present invention is to provide a method and a device where the liquid to be emptied or evacuated is pressed out of the system by a high pressure.

Another object of the present invention is to provide a method and a device that in a controlled and effective manner may seal the closable room from the cargo tank, securing that the entire pressure delivered from a pressure source is used for closing the opening between the closable room or volume and the cargo tank.

Yet another object of the present invention is to provide a method and a device that prevent pressurized gas to enter the closable room or volume until the opening or aperture between the cargo tank and the closable room is sealed and closed in pressure tight manner.

Still another object of the invention is to provide a method and system that do not allow evacuation of liquid until the chamber is completely sealed and closed.

Another object of the present invention is to arrive at an alternative method and system for closing the closable room or volume.

Moreover, yet another object of the invention is to provide an alternative closing and opening solution for closing and opening the closable room or volume and also to prevent pressurized gas from entering into the closable room or volume until the closable room or volume is sealed from a cargo tank.

Yet another object is that the system may be provided with a self-forcing seal plug which will obtain an even larger sealing force by the pressure from the CCCV due to surface ratio from the engagement by the actuator volume.

Yet another object of the present invention is to provide a method and a device securing that sufficient force is applied to the seal or device for closing the aperture or opening between the cargo tank and the closable room or volume, before pressurized fluid is allowed to enter the closed or sealed closable room or volume for driving residual liquid out of the closable room or volume.

A purpose of the invention is to make a system for emptying a liquid containing cargo tank that avoids the problems of earlier known solutions, this purpose is achieved by the help of the system and method according to independent claims 1 and 5, together with their dependent claims. The objects of the present invention are achieved by a solution as defined by the appended independent claims. Alternatives, embodiments and options are defined by the dependent claims.

According to the invention, it is provided a system for emptying a liquid containing cargo tank, comprising a closable volume arranged below and in liquid communication with a cargo tank through closable opening ; a supply line for supply of a pressurized gas to the closable volume; an outlet line for emptying the liquid from the closable volume; and a sealing body associated with an actuator for moving the sealing body into sealing contact with the opening, the actuator being powered by the pressurized gas, The actuator is in the form of a piston and a cylinder, and that the cylinder is provided with a flow restrictor and an closable orifice in fluid communication with the closable volume, and being configured to remain closed until the piston has brought the sealing body in sealing contact with the opening.

The flow restrictor may comprise a check valve configured to be closed until the sealing body has lifted to a sealing contact with the opening, whereupon the check valve is opened to allow pressurized gas to enter the closable volume.

Moreover, according to the invention it is also provided a method for emptying a liquid containing cargo tank, comprising a closable volume or room arranged below and in liquid communication with a cargo tank through closable opening, where undrained cargo upon completed emptying process from the cargo tank will flow into the closable room; supplying pressurized gas through a gas supply line to the closable room or volume; emptying cargo from the closable volume through an outlet line; while sealing the opening by moving a sealing body into sealing contact with the opening, the motion of the sealing body being provided by the pressurized gas supplied through the supply line. Pressurized gas is prevented from being supplied to the closable volume or room until a sealing contact between the sealing body and the opening is provided, whereupon liquid in the closable volume is forced out of the closable volume by the pressurized gas.

According to one embodiment, the emptying of the cargo tank may be provided in successive steps, where the closable volume is more or less completely filled, whereupon the sealing body closes the opening by powering an actuator with the pressurized gas, whereupon the liquid in the closable volume is emptied, whereupon the sealing body once more is retracted by the actuator to an open position, allowing liquid cargo to flow into the closable volume, whereupon the emptying sequence is repeated until all liquid cargo is drained out of the tank and the closable volume. The present invention solves the problems of the prior art as it has the possibility to completely remove all remaining cargo, after completion of normal pumping and stripping sequences, in a safe and effective way, nearly independent of viscosity and density of the shipped cargos, and nearly independent of tank heights and size for cargo tanks. The invention also enables complete emptying of washing water from cargo tanks without any need for manual removal from the tank. This is not possible in a good way with existing inventions, due to excessive time

consumption and limitation for cargo tank heights. (Vacuum systems are normally limited to maximum 10 meters lifting height depending on cargo density).

The invention comprises use of a Closable Cargo Collector Volume (hereby referred to as CCCV). CCCV means a small pressure tank volume for collection of cargo. Further, the volume is being pressurized by gas to force the cargo out through a stripping pipe further to the cargo pipe on the outside of the tank.

The CCCV, which may have any form, volume or shape suited for the purpose, will be integrated below the suction well of the cargo tanks and gives the unique possibility to have all cargo collected by gravity and forced out by use of pressurized gas.

The benefit with this invention is the innovative use of a minor space in the ballast tank area of the vessels, which gives a greater collective volume for residual cargo. When this open volume is turned into a closable volume by use of the remote closable inlet valve, it gives a benefit that no other stripping systems have taken into use as of today.

The solution according to the invention will be located in the ballast tanks below the cargo tank floor, and below the cargo pump in each of the respective cargo tanks and form an extension of the pump's suction well. The solution

according to the invention will be installed into the existing double bottom tank below pumps suction well, and take a minor part of the volume in the ballast tank.

Installation of the system is available for both new vessels and as an upgrade for existing operating vessels. The arrangement of the invention includes a new customized pump suction well for maintaining the function for both the pump system and the new CCCV arrangement for completely emptying the cargo tank.

The principle of the invention is to push the remaining cargo in the suction well through a pipe to the cargo pipes on ship deck by applying pressurized inert gas to a closable cargo collector volume (CCCV) arranged below the existing suction well. The remaining cargo will first drain to the pump suction well from the sloped cargo tank floor. Since the CCCV according to the invention is below the suction well, all cargo will drain into the CCCV. Pressurized gas is applied through a gas inlet pipe to pressurize the actuator volume inside the CCCV. Pressurized gas will be taken from the existing systems on board the vessel and connected to the CCCV by tubing. The seal plug moves upwards and seals and closes the CCCV. The CCCV is then pressurized from gas pressure coming through an orifice in the actuator volume. Cargo is being forced through a cargo outlet pipe located in the lowest point in the tank.

According to the invention a system to pressurize, a closable volume below and in relation to a chemical cargo tank or another cargo tank is provided, intended to build up a differential pressure to the environment in order to force out any residual cargo from the cargo tank, drained into the closable volume through a valve.

The system may be provided with a self-forcing seal plug which will obtain an even larger sealing force by the pressure from the cargo collector volume due to surface ration from the engagement by the actuator volume.

The system according to the present invention provides a regulation system with a closable orifice and a flow restrictor that ensures the piston to actuate and seal/isolate the CCCV fully from the environment prior to pressurizing the CCCV, with the same source of pressure.

The system is configured so that the design of main system may be fully removable for easy service access.

The system according to the invention may be based on automatic operated mechanism with few remote operations.

The system according to the invention may be used for all types of cargo tanker vessels and floating storage and production units (shipping and offshore).

Moreover, the system may be driven from the gas source and the existing compression aggregate of the tank vessel.

From an environmental point of view, this new invention will reduce the quantity of waste residuals. This also means a reduced need for washing water to clean the tanks and following reduced amount of delivered waste to cargo terminals at completion of a cargo operation. If one single washing sequence may be avoided, it means that the generated waste volume will be noticeably reduced, saving both cost and environmental consequences.

The following advantages may be obtained with the solution according to the present invention:

• Few operations: open/closing of few valves; purging valve and stripping valve for few repeated sequences, enabling completely removal of remaining cargo or washing water. • Good service ability, as all the vital parts are removable along with top plate of the invention.

• No need for unnecessary tank entries.

• Important contribution to HSE perspectives on board operating vessels.

· Small probability for making mistakes during operations.

• All handling of cargo liquid are made inside closed volumes, which restricts

physical contact for operators

• Great reduction in usage of purging medium compared with comparative

systems.

· Operation time compared to other systems is shorter since the invention is based on the closable volume principle.

The orifice that is discussed is a closable opening for fluid communication between the gas pressure through the actuator and into the CCCV. The orifice may consist of a check valve of a certain type that can be interchangeable and set to a certain crack pressure for regulation purposes for when the gas pressure can be let into the CCCV from the actuator that is to actuate in advance.

A check valve is a valve that normally allows fluid to flow through it in only one direction. An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. This cracking pressure can be set to different pressure by use of different springs.

There is discussed a flow restrictor 5 in conjunction with the orifice. A flow restrictor is referred to as e.g. a nozzle that represent a resistance or a loss of pressure while fluid flows through it. This is interchangeable and is for regulation purposes as well. In the description of the drawings both, the closable orifice and check valve is discussed as one term with pos 12.

The pressurized gas that is discussed for driving the actuator and for pressurizing the CCCV is referred to, but not limited to any inert gas. The gas can be air as well.

Short Description of the Drawings

An embodiment of the present invention shall now be described in closer details, referring to the attached drawings, wherein:

Figure 1 is a view of a typical conventional state of the art vacuum stripping arrangement;

Figure 2 and 2a disclose an illustration where the invention is located in a tank vessel, where Figure 2a shows in enlarged format the lower end of the stripping arrangement according to the present invention, showing a pump in a pump suction well provided with the present invention integrated below the pump suction well;

Figure 3 shows in enlarged scale and more detailed the general arrangement of an embodiment of the invention;

Figure 4 shows schematically a principle drawing of an arrangement of the invention installed in a cargo tanker vessel;

Figure 5 shows a step by step illustration of the invention in operation for emptying residuals from a cargo tanks;

Figure 6 shows schematically an alternative arrangement of the invention installed in a cargo vessel;

Figure 7 shows schematically a second alternative arrangement of the invention arranged in a cargo tank vessel; and

Figure 8 shows schematically in an enlarged scale an embodiment of the system for closing and opening the fluid communication between the cargo tank and the closable room or volume and the arrangement for venting pressurized fluid into the closed closable room or volume, once the fluid communication between the cargo tank and the closable room is closed.

Detailed Description of Embodiment in Drawings

The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the emptying cargo tanks on board a tank vessel. However, the embodiments to be discussed next are not limited to such type of use, but to any type of or systems of emptying a tank more or less completely.

Reference throughout the specification to "one embodiment" or "an embody- ment" means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more

embodiments.

Figure 1 is a view of a typical conventional state of the art vacuum stripping arrangement, disclosing only the system as such. As shown a cargo pump 14 is arranged in association with a pump suction well 15. The pump 14 is in fluid communication with the cargo pipe 16 connected to a manifold (not shown). The stripping system comprises an ejector 17; a vacuum suction valve 18; a vacuum stripping valve 19; and a stripping valve 20, all associated with a pipe system.

Figure 2 and 2a disclose an illustration where the invention is located in a tank

22 in a vessel 21 , where Figure 2a shows in enlarged format the lower end of one of the stripping arrangement according to the present invention, showing a pump 14 in a pump suction well 15 provided with the present invention integrated below the pump suction well 15.

Reference is made to Figure 3. As shown, all the main components of present invention are assembled to the top plate 10 attached to the CCCV 1 with a wing nut 1 1 . The top plate 10 and the wing nut 1 1 are equipped with O-rings 8 for sealing purposes. The inlet 3 and outlet 4 -pipe are assembled, both below and above the top plate 10, with fittings and flanges for easy assembly/disassembly. The pipe extension will be fitted and routed on the side of the cargo tank reaching through to deck. This design allows easy service access to the CCCV 1 and components assembled to the top plate. Removal of parts for relocation to a workshop for service will be easy. The CCCV 1 will be welded in relation to the pump suction well. One side of the CCCV will face towards ballast tank. The sealing piston top 2 will be made of chemical resistant high shore elastomer that seals towards the tank top 10.

All material selection will take antistatic electricity into consideration. The check valve in the orifice 12 can be set to any crack pressure ensuring that the piston will move and seal of the CCCV 1 prior to any gas pressure will be allowed to flow through the orifice and into the CCCV 1 . Both the flow restrictor 5 and check valve 12 will be interchangeable and will be adjusted to provide a certain resistance for the gas ensuring that the configuration is that the piston moves and seals the CCCV 1 prior to any gas flow through the orifice into the CCCV 1 . The check valve 12 will as well prevent cargo from entering inside the piston arrangement 9 when the system is not in operation. The nozzle 5 is a flow restrictor, which will help to regulate that the piston will lift up and ensuring the sealing plug (2) to keep being in sealing position during the emptying of the CCCV 1 process. Bracket 6 for guiding of the piston 2 is fitted to the top plate 10 for easy access and service providing full disassembly possibility. Spring for piston return 7 will force the piston back to rest position (open position) when sequence is completed. The spring (7) is fitted to supplement the gravity force on the piston 2 for conquer the friction force between the dynamic seals 13 for ensuring open position while not in operation. There will be installed suitable seals 8 between the CCCV 1 and the actuator volume 9. This is in order to prevent cargo from entering the actuator volume 9. Gas pressure enters the actuator volume 9, forcing the piston to upper position due to increased pressure in the actuator volume 9. This will isolate the collector volume CCCV 1 . Following gas will flow through an orifice through a flow restrictor 5 and a check valve 12 to build up pressure in the CCCV 1 .

Reference is made to Figures 3 to 5 showing the principle of the invention and the various operational steps taken for emptying a tank completely.

Figure 4 shows schematically a principle drawing of an arrangement of the invention installed in a cargo tank 22 of a cargo tank vessel 21 . As shown the cargo is pumped from the cargo tank 22 through a pipe line 16 to a manifold (not shown) by means of a pump15, arranged in association with a pump suction well 15. The cargo outlet line 16 to the manifold is provided with a valve 23.

Moreover, as indicated in Figure 4, compressed gas is delivered from a compressor 24 through a gas pipe 25 to an actuator volume 26, the gas pipe 25 being provided with a valve 27 and marked with a broken line. From the actuator volume 26 gas under pressure is delivered to one side of a piston in a piston/cylinder unit 28 for opening/closing the valve 2 and to the CCCV through the orifice 5 and the check valve 12 into the CCCV.

After a conventional pumping and stripping operation for a cargo tank is completed, the residual cargo located in the pump suction well C for the cargo tank will be drained into the CCCV 1 (see Figure 5A). For figure 5 the dashed black arrow illustrates gas pressure in a direction while the grey arrow illustrates cargo flow in a direction. The small white arrow illustrates the sealing piston's movement for open/close the CCCV. Pressurized inert gas will be applied to the inlet pipe 3. The actuator volume 9 will be pressurized and the piston will move the seal plug 2 upwards for closing off the cargo collector volume 1 . Gas will then start to flow through the flow restrictor and orifice 5, further through the check valve 12, and finally out to the CCCV 1 . The orifice 5 represents a particularly resistance and ensures that the piston 2 moves and seals prior to the gas pressure build-up in the CCCV 1 . As the pressure increases in the CCCV, the cargo, which represents a higher density than the inert gas will be forced into the cargo outlet pipe 4, (see Figure 5B). The check valve 5 prevents in addition cargo to leak inside the actuator volume 9 when the system is not pressurized. The operation continues until all residual cargo in the cargo collector volume 1 is forced out through the cargo outlet pipe 4. Completion of this cargo stripping sequence can e.g. be detected by noise change from free flow of gas in the cargo pipe, or by minor pressure fluctuation, vibration due to gas/liquid mixture passing inside the pipe at the final phase of purging out residuals, or by other suitable detection methods, (see Figure 5C).

When gas pressure in the inlet port for inert gas 3 is released, the piston returns by the force of the spring 7 and ensures that the sealing plug (2) will open for refill of cargo from the suction well into the CCCV 1 , (see Figure 5D -5F). This sequence will be repeated for as many times as required for emptying all cargo in the pump suction well.

Figure 6 shows schematically an alternative arrangement of the invention installed in a cargo vessel. The CCCV 1 is closed from the cargo tank 22 by a remotely operated valve 33 actuated by an independent line 32 by either gas, hydraulic fluid or an electric activated solenoid valve (Figure 6 only illustrates schematically the principle of a gas actuated remotely valve) The CCCV (1 ) is filled with cargo when the valve 33 is open. When the valve 33 is remotely closed, an independent supply line 25for gas will pressurize the CCCV 1 by opening valve 27, that results in that the residual cargo will be forced out through the cargo outlet pipe 4. The remotely activated valve 33 is opened/closed respectively by operating valve 29 and 30 for applying pressure through either pressure line 31 or 32, connected to the CCCV isolation valve 33. An open valve 29 feeds gas pressure in pressure line 31 and will open valve 33 given that valves 27 and 30 are closed. An open valve 30 feeds gas pressure in pressure line 32 and will close valve 33, given that valves 27 and 29 are closed.

When all cargo is forced out from the CCCV 1 , the remotely activated valve 33 can be opened for re-fill of the CCCV 1 and the cycle can be repeated until all residual cargo in the tank 22 is emptiedFigure 7 shows schematically a second alternative arrangement of the invention arranged in a cargo tank vessel 21 . Gas pressure is applied through a gas supply line 25 to the actuator volume 34 in the CCCV 1 . The actuator 34, which is in form of a piston and cylinder, moves upwards and seals and closes the CCCV 1 by a sealing plug 2. When the sealing plug 2 is in sealing contact with the CCCV opening, the cylinder allows gas pressure to flow into the CCCV 1 through an orifice and a check valve 12, that is in fluid communication with the

CCCV 1 , in the cylinder wall. The piston inside the cylinder 34 function as a valve for suppling gas pressure to the CCCV 1 and is configured to ensuring that the CCCV 1 will be completely closed before any gas pressure can be applied to the CCCV 1 . The piston 34 has a spring return 7 that ensures the piston to go to rest position once the gas supply line is closed. This also allows cargo to be re-filled to the CCCV 1 and the operation can be repeated until all residual cargo is emptied. The system may be provided with a self-forcing seal plug 2 which will obtain an even larger sealing force by the pressure from the CCCV 1 due to surface ration from the engagement by the actuator volume.

Figure 8 shows schematically in an enlarged scale an embodiment of the system for closing and opening the fluid communication 34 between the cargo tank 22 and the CCCV 1 and the arrangement for supplying pressurized gas into the closed closable room or volume, once the fluid communication between the cargo tank 22 and the CCCV 1 is closed, gas is applied through a gas inlet pipe 25 to pressurize the actuator volume 9 inside the CCCV 1 . The actuator 34 is in the form of a piston and a cylinder, and the cylinder is provided with a closable orifice 12 in the cylinder wall that is in fluid communication with the CCCV 1 , the orifice 12 is being configured to be closed until the piston 34 has brought the sealing body 2 in sealing contact with the opening. Pressurized gas will be taken from the existing systems on board the vessel and connected to the CCCV 1 by tubing. The sealing plug 2 on the actuator piston 34 moves upwards and seals and closes the CCCV opening. The CCCV 1 is then pressurized from gas pressure coming through an orifice 12 in the actuator volume 9, which is in fluid communication with the actuator 34. The actuator 34 configuration will as well ensure that the piston 34 will keep sealing although gas pressure is released through the orifice 12. The check valve 12 will as well prevent cargo from entering inside the piston arrangement 34 when the system is not in operation. The system may be provided with a self-forcing seal plug which will obtain an even larger sealing force by the pressure from the CCCV 1 due to surface ration from the engagement by the actuator volume. The piston has a spring return 7 that ensures the piston to go to rest position once the gas supply line is closed. This also allows cargo to be re-filled to the CCCV 1 and the operation can be repeated until all residual cargo is emptied