WO2013068561A1

WO2013068561A1 - Offshore lng flushing station

Info

Publication number: WO2013068561A1
Application number: PCT/EP2012/072323
Authority: WO
Inventors: Jean-Robert Fournier; Jean-Damien René ROLLIER; Pieter ADAMS; Laurent Le Touze
Original assignee: Single Buoy Moorings Inc.
Priority date: 2011-11-10
Filing date: 2012-11-09
Publication date: 2013-05-16

Abstract

A flushing station for a liquefied gas transfer line docking, coupling and draining system, is arranged for connection with a gas transfer line and includes a receiving space for a liquefied gas transfer line connector and a guiding system for guiding the transfer line to/from the receiving space. The receiving space includes - a structural connector clamping/locking system for clamping/locking of the transfer line connector in the receiving space; - a de-icing utility arranged for removal of ice from the liquefied gas transfer line connector and/or the structural connector clamping/locking system; - a coupling for the liquefied gas transfer line connector with a locking device and a valve arrangement for closing and opening the transfer line at the coupling's location; - an inerting system for coupling to the transfer line connector inbetween valves of the valve arrangement and for removing air and liquid from the space inbetween the valves.

Description

OFFSHORE LNG FLUSHING STATION

Field of the invention

The invention relates to a liquefied gas transfer line draining and flushing systems.

The invention also relates to a docking station for a liquefied gas transfer line connector installed on a floating structure lying at the sea surface and comprising processing units for liquefied gas to be transferred between the floating structure and a floating tanker via at least one transfer line that extends from the floating structure to the floating tanker to carry liquefied gas from one to the other.

Background of the invention

A typical drainage system for a liquefied gas transfer line is described in patent application WO2007108705. In this application a drainage system is disclosed which comprises hydraulic isolation valves closing off the fluid connection between the two offshore structures between which fluid is exchanged. There is also a nitrogen tank connected to the fluid connection for injecting nitrogen into the fluid connection through an injection channel. Flow of nitrogen through the injection channel can be controlled by means of a valve. A waste accumulator is connected to the fluid connection for collecting fluid and nitrogen pressed out of the fluid connection through an exhaust channel due to the nitrogen injection. The channel between the fluid connection and the waste accumulator may be closed by means of a valve.

WO2005043032 discloses that when unloading is substantially complete, nitrogen gas may be used to force LNG from the unloading arms back into the carrier and into the storage tanks via drain lines. In one embodiment according to this application, a piping layout may be sloped to allow LNG to drain into the storage tanks without the use of a drain drum while in another embodiment, one or more unloading arms may be purged with nitrogen after unloading liquefied natural gas from a carrier. Drainage of the system may be by gravity controlled flow back into the tank. Residual pressure within the system may at least partially assist the gravity controlled flow back to the tanks.

The prior art drainage principle is thus basically defined by: Isolating a pipe segment, between an outlet valve and an inlet valve;

Opening the outlet valve to a disposal tank, and

Opening the inlet valve for connecting to a purging medium tank. The purging medium is typically gas such as gaseous nitrogen, which is known for its use to purge LNG systems to avoid remaining liquid/solid particles in the process network.

A disadvantage of the prior art solutions is the liquefied gas transfer line connector during the flushing and draining of the transfer line may be damaged. In fact, upon exposing the transfer line to liquefied gas the transfer line and its components become cold and covered by ice. The handling of the cold fluid connector is made challenging as the system is covered with ice and kept cold by the liquefied gas contained in the offloading lines. The ice trapped, especially the ice trapped in the seal assembly where the transfer line is coupled to the floating structure for example in the volume between the seal and the actual ball valve, can potentially damage the valve sealing in the seal assembly of the fluid connector. Further, none of the prior art drainage systems avoids occurrence of high gas velocity in the transfer line once the high pressure gas flow has managed to remove the liquid slug in the transfer line.

Known draining systems for liquefied gas transfer lines are gravity controlled draining systems, using line pressurization and sudden opening of the transfer line releasing pressure and progressing boil off of the remaining fluid within the transfer line. Using a draining system with line pressurization and sudden opening the transfer line is feasible when no draining port exist at a lowest point of the transfer line, and the line is closed at both extremities, pressurized with appropriate gas, one of the extremities being suddenly opened to release the pressurized gas. In such a way, a part of the released gas will also carry a portion of the remaining liquid. The progressive boil-off of the remaining liquid in the transfer line using simply heat ingress from the ambient temperature is a slow-going process. The boil-off can be accelerated with a flow of hot gas until line is emptied. In the prior art systems large variations of the pressure inside the line can damage the line. The prior art system is equipped with dedicated relief arrangements. It has to be understood that the term "liquefied gas" as used here refers to liquefied gas in general not only to low temperature liquefied gas such as liquefied petroleum gas (LPG) or liquefied carbon dioxide, but also to cryogenic fluids such as LNG or others.

Summary of the Invention

The object of the present invention is to provide a flushing station for a liquefied gas transfer line docking, coupling and draining system, the flushing station being arranged for connecting to a transfer line , and comprising:

a receiving space for the liquefied gas transfer line connector;

a guiding system for guiding the transfer line to/from the receiving space

the receiving space comprising:

- a structural connector clamping/locking system for clamping/locking of the transfer line connector in the receiving space;

- - a de-icing utility such as a sea/fresh water systems nozzle tied-up to sea/fresh water systems, arranged for removal of ice from the liquefied gas transfer line connector and/or the structural connector clamping/locking system;

- a coupling for the liquefied gas transfer line connector with a locking device and a valve arrangement or closing and opening of the transfer line at the location of the coupling

- an inerting system for coupling to the transfer line connector in-between the valves of the valve arrangement and arranged to remove air and liquid from the space between the valves in the connector

The solution proposed in the present invention enables a liquefied gas transfer line draining and flushing system which is safe with a simplified procedure.

In a first aspect, the invention proposes a system enabling to flush and drain liquefied gas transfer lines offshore without damaging the cold fluid connector, with an active drainage system that can avoid high gas velocity in the transfer line if needed or requested. The connector damage if any is related to handling aspects, not draining or flushing issues.

In a further aspect, the invention concerns an arrangement of the liquefied gas transfer line storage support structure that enables a transfer line self drainage.

In a third aspect, the invention deals with a simplified drainage system that allows to simplify the sequence of events after an emergency disconnection of a transfer line full of cold liquefied product such as cryogenic product by using less or simpler process steps. After an emergency disconnection, when using an horizontal axis storage reel, steps required are to reel-in, de-ice, dock-in, remove gas and liquid from the line segment between valves, drain it partially by gravity, flow-in high velocity gas into the segment and finally inert the line segment with nitrogen.

Alternatively, steps required can be to reel-in, reel-out, dock-in, remove gas and liquid from the segment of the line between valves, drain a final segment by gravity, and finally inert with nitrogen. It reduces the equipment requirements (vaporizers no longer needed for this operation), improves safety of operations by avoiding pressurizing the transfer line and reduces the duration of operations.

According to an embodiment of the present invention, the use of a vertical axis storage system allows proceeding after an emergency disconnection in a simpler manner with only the steps to reel-in, de-ice, dock-in, remove gas and liquid from the segment of the transfer line between valves, drain it substantially totally by gravity, and finally inert with nitrogen.

Moreover, the present invention has an advantage in that the control on velocity and pressure is improved as the draining system can be operated with a steady flow / operating set point. In fact, the draining system according to the present invention is a draining system that is arranged to avoid high gas velocity.

Further the present invention provides a docking station for a liquefied gas transfer line connector installed on a floating structure lying at the sea surface and comprising processing units for liquefied gas to be transferred between the floating structure and a floating tanker via at least one transfer line that extends from the said floating structure to the said floating tanker to carry liquefied gas from one to the other wherein the docking station is integrated into a flushing station as mentioned above. An advantage of the present invention is that the receiving space of the docking station is integrated into a pivoting platform mounted on the structural support structure which is part of the floating vessel.

According to the present invention the gas transfer line can be a cryogenic transfer line such as a composite cryogenic hose or a cryogenic hose in hose and the connector can be a connector comprising a fluid flow connector combined with a structural disconnectable load diverter, diverting the loads and moments created by the transfer line, away from the valves and the fluid flow connector.

Moreover, the present invention provides an offshore cryogenic offloading system that lies in a sea having a sea surface and a sea floor, wherein cryogenic fluid is transferred between two floating units comprising:

a floating structure that lies at the sea surface and comprises processing units,

a floating tanker that lies at the sea surface and transports the cryogenic fluids from one location to another,

at least one cryogenic transfer line that extends from the said floating structure to the said floating tanker to carry cryogenic fluids from one to the other;

at least one vapor return line that extends from the said floating structure to the said floating tanker to carry the boil-off vapor from the floating tanker to the floating structure in normal operations,

wherein the floating unit is provided with a flushing station as mentioned above.

In an aspect the present invention provides a liquefied gas transfer line draining and flushing system wherein the outlet of the transfer line is combined to a dedicated pressure regulation equipment/valve or a stream flow control equipment/valve during the draining so as to better control velocity and pressure.

In an aspect the present invention provides a liquefied gas transfer line draining and flushing system wherein the transfer line is drained by reeling and unreeling on the transfer line storage structure. In an aspect the present invention provides a liquefied gas transfer line draining and flushing system wherein the transfer line storage structure has a vertical rotation axis.

In an aspect the present invention provides a liquefied gas transfer line draining and flushing system wherein the transfer line storage structure is fixed and provided with means having capabilities to roll on and roll-off the transfer line.

Brief description of the drawings:

The invention will be further described below in connection with exemplary embodiments with reference to the accompanying drawings, wherein

FIGs. l a and lb show different possible configurations of the disposition of a remaining liquid and gas within the transfer line.

FIG. 2 shows a side view of the aft of a floating LNG vessel comprising a liquefied gas flushing station according to an embodiment of the present invention.

FIG. 3 shows an aft view of the floating LNG vessel part shown in FIG. 2.

FIG. 4 shows a section view of the liquefied gas flushing station according to an embodiment of the present invention.

FIG. 5 shows a top view of the rotating arm integrating the liquefied gas flushing station in a working position and in a storage position. Description of embodiments

FIGs. la and lb show different possible configurations of the disposition of the remaining liquid within the transfer line. FIG. la shows a slug within the transfer line. A slug consists of a gas pocket 20 and a liquid slug 21. Slug flow can pose serious problems to the design and operation of two-phase flow systems such as a transfer line for a liquefied gas. Large and fluctuating rates of gas and liquid can severely reduce the production and in the worst case shut down or damage of topside equipment like separator vessels and compressors. Removal of slugs within transfer lines is therefore very important. However when draining a transfer line comprising slugs, high pressure gas flow is required to push the liquid slug in the line. As a result, when the slug has disappeared, the high pressure gas flow required suddenly causes a high gas velocity in the transfer line as shown in FIG. lb when all the liquid has been pushed onto the transfer line walls 22.

The draining system according to the present invention is a draining system that is arranged to avoid high gas velocity by using of a dedicated pressure regulation equipment/valve or a stream flow control equipment/valve at the outlet of the line during the draining. In the present invention, the control on velocity and pressure is improved as the draining of the transfer line is operated with a steady flow / operating set point.

In fact, when liquid is present in the transfer line while draining is carried out, the inlet pressure pushes the liquid through the draining pressure regulation equipment/valve or a stream flow control equipment/valve and when the liquid has disappeared the flow velocity is limited by the valve cracking pressure. The latter solution is preferred when gravity controlled draining is not possible.

Usually gravity controlled draining is done with a vertical hose or loading arm, gravity being used to drain the transfer line with a lower point of the transfer line being equipped with a draining port or valve.

Draining by gravity is usually performed to purge the liquid from a lower end of a flexible hose section which end is equipped with a draining port and corresponding valve arrangement.

During gravity controlled draining, the liquid volume drained from the transfer line volume is usually compensated by gas. Entering pressurized gas at the top of the transfer line may also improve the draining rate.

According to the present invention, combining a transfer line stored on a reel having a vertical axis or several transfer lines each stored on a reel having a vertical axis, stacked one onto the other, with liquefied gas flushing stations as described below renders possible to benefit from more deck space, easy handling of a flushing procedure with a minimum risk of damaging the transfer line and the transfer line connector.

An additional embodiment of a liquefied gas transfer line draining and flushing system which is safe with a simplified procedure according to the present invention is a "screw" draining by reeling and unreeling the transfer line on the storage reel so that on one end of the transfer line any liquid inside the hose is screw drained to the evacuation means which are arranged for removal of the liquid and gas, for example to be manifolded to drain tanks or vapor recovery systems, or separation tanks, etc, for further processing.

An inerting inlet may be provided on the connector at the other end of the transfer line in order to prevent the liquid being moved from creating a vacuum or vacuum like phenomena inside the hose. Such an arrangement for a draining system simplifies the sequence of events after an emergency disconnection of a hose full of cold liquefied product such as cryogenic product. In the event of a quick reconnection being needed and a wish to transfer only inerted lines, the inerting operation can be significantly speeded up. Liquid is usually drained back to storage tanks using natural gas let in at the inerting inlet to avoid vacuum.

FIG. 2 shows a side view of the aft of a floating LNG vessel 1 comprising a docking station or receptacle 8 for a liquefied gas transfer line connector installed on a floating structure 1 lying at the sea surface. Further the floating LNG vessel comprises processing units for liquefied gas to be transferred between the floating structure and a floating tanker via at least one transfer line 3 that extends from the floating structure 1 to the floating tanker to carry liquefied gas from one to the other wherein the docking station or receptacle is integrated into a liquefied gas flushing station which comprises: a receiving space for the liquefied gas transfer line connector;

a guiding system for guiding the transfer line to/from the receiving space

the receiving space comprising:

a structural connector clamping/locking system for clamping/locking of the transfer line in the receiving space;

a de-icing utility such as a sea/fresh water systems nozzle tied-up to sea/fresh water systems, arranged for removal of ice from the liquefied gas transfer line connector and/or the structural connector clamping/locking system

a coupling for the liquefied gas transfer line connector with a locking device and a valve arrangement for closing and opening of the transfer line at the location of the coupling an inerting system for coupling to the transfer line connector in-between the valves of the valve arrangement and arranged to remove air and liquid from the space between the valves in the connector. In FIG. 2 the liquefied gas flushing station 2 is shown in a working position i.e. outboarding from the aft of the vessel. The liquefied gas flushing station 2 receives the connector (not shown) of one transfer line 3 which is stored on a reel 4. In this particular embodiment, the reel has a horizontal axis 5, but a reel having a vertical axis or several reels having each a vertical axis stacked one onto the other could also have been a possibility.

FIG. 3 shows an aft view of the floating LNG vessel part shown in FIG. 2. In this figure it appears clearly that there is one flushing station (2a, 2b and 2c) per transfer line (3a, 3b and 3c). Guiding and support means 6 ensure the transfer line connector is well received and supported in the receptacle 8 of the flushing station.

FIG. 4 shows a section view of the liquefied gas flushing station 2 according to an embodiment of the present invention. In this figure it is clearly shown that the transfer line connector 7 is received in the receptacle 8 and clamped to it via a clamping and locking device 9. The fluid connector 7 is also connected to a fluid swivel path 10 linking the transfer line 3 to evacuation means 1 1 arranged for flushing remaining fluids from the transfer line e.g. to a drain or cargo tank.

According to the embodiment shown in FIG. 4 the receptacle 8 is integrated into a pivoting platform 12 mounted on a structural support structure 13 which is part of the floating vessel 1. The pivotable platform 12 enables to bring the receptacle 8 to the transfer line connector 7 which is more convenient than bringing the transfer line connector to the receptacle as the flexibility of a (low temperature) liquefied gas transfer line may be far less than the flexibility of an oil transfer line (usually at about ambient temperature). In addition, having a pivoting or retractable platform allows clearance between the transfer lines. Further, a connector for a liquefied gas transfer line is also bigger than for an oil transfer line and thus, limiting its displacement is advantageous.

The flushing station also includes (not shown) a de-icing utility, a coupling for the fluid connector with a locking device and a valve arrangement and an inerting system to remove air from the space between the valves in the fluid connector. The de-icing utility is arranged for de-icing the arrangement of the fluid connector and the receptacle, such that the fluid connector is removable from the receptacle without obstacle from ice.

In the embodiment shown, the liquefied fluid connector can be a connector of the type as described in patent application WO2011026951 filed by Applicant, i.e. a connector comprising a fluid flow connector combined with a structural disconnectable load diverter, which is arranged for diverting loads and moments created by the transfer line, away from the valves and the fluid flow connector.

The flushing station hence comprises a structural receiving space as the receptacle 8 for the structural connector part and a receiving space for the fluid connector part of the line transfer connector.

This receiving space for the fluid connector part comprises a locking device and a valve arrangement as well as a quick connect disconnect coupling (QCDC) and optionally an Emergency Release System (ERS).

In use, the handling of the cold fluid connector is made challenging as the system is covered with ice and kept cold by the liquefied gas contained in the offloading transfer lines. The ice trapped in the seal assembly can potentially damage the valves of the fluid connector part.

The de-icing device (not shown) allows safe operation of the cold fluid connector to create a tight fluid path and purge the offloading transfer line.

This system allows increasing the safety of operations and speeding up the offloading operation sequence. Additionally, draining the liquefied gas transfer lines to a drain tank, away from the transfer lines such as cryogenic transfer hose and valves such as ball valves located in the fluid connector and in the flushing station avoids any ice contamination entering the storage and processing facilities.

FIG. 5 shows a top view of the rotating arm integrating the liquefied gas flushing station according to an embodiment of the present invention in working position A and in storage position B.

In working position A the connector 7 is fixed to the receptacle 8 and the flushing station is outboarding from the aft of the vessel 1. The pivoting platform 12 is pivoted in such a position so that the receptacle is placed just below the connector of the transfer line when stored on the reel, its connection end placed in the guiding and support means in order to flush and drain the transfer line. In a storage position B, the pivoting platform is retracting inwards the aft of the vessel to be located within a dedicated space within the vessel (see reference number 15 in FIG. 3).

In a particular embodiment of FIG.5, the pivoting angle between the working position A and the storage position B is approximately 110°.

In all embodiments described it could be advantageous to have a motorized transfer line reel storage.

In order to simplify the reel structure, improve the safety, ease the maintenance, the manufacture and installation of the transfer line storage structure, the motorized transfer line reel storage could be fixed to the vessel and provided with means having capabilities to roll on and roll-off the transfer line such that the hoses can be dealt with individually. The transfer lines are stored on circular horizontal racks that allow for the entire hose string length to be stored onboard on one or several levels. Each level has its own drive mechanism for roll on and roll-off capabilities such that the hoses can be dealt with individually. Obviously hose synchronization is also possible as is the possibility of counter rotating each level with respect to the next. Each horizontal rack consists of a roller support structure (or slide or storing tray) supported at the outer radius by supporting structures. It is onto these rollers, trays, slides or displacing means that the hose string is stored. Tracks and or rollers (or conveyor belts) can be powered individually to drive the hose onto the rack. Another method is to use a rack and pinion drive on the outer perimeter of the rack. Yet another method could use wheels, tracks or belts that directly contact the hose and drive it along. These would be spaced as dictated by for example friction requirements.

A combination of any of these can also be used to limit loads on the hoses, act as a brake, or to accommodate hose accessories such as floatation aids, ballast or spoolpieces or other hose accessories.

The reel end of the hose can be connected to rigid piping or flexible hoses or a hybrid thereof in order to radially transfer the product to the center of the circular rack, where a swivel system will transfer the product to the other piping system, cargo tank, or other processing facility. This radial piping system can also be used as driver arm for the hose roll on system, with the driver system being integrated into the swivel stack.

In case of rigid radial piping, a double swivel can be included in order to accommodate the rotation that will be needed to absorb the height difference when more than one turn is needed to store the hose string, and the subsequent length will be stored above or below the first one. This is for a circular arrangement. An arrangement that maintains a single length radial pipe can also be accommodated by designing the inner radius rollers/guides to spiral inwards as the level difference raises and the vertical displacement rotates following a set radius. A single swivel solution can then be considered.

In case of a flexible solution, the extra length needed to follow the spiral track path can be included in the design.

In either case, the storing ring can be angled such as to ensure that liquids will always collect at the lower end, and any gasses will collect at the upper end. Thus allowing for natural draining of any fluids should it be required. In case of cryogenic fluids, the accumulated liquids will then evaporate in a relatively controlled manner as the natural angle of the system will keep the evaporation area relatively small. Any remaining cryogenic fluids can then be evaporated by purging from the lowest collection point with hot gas that will bubble up along the spiral.

Any maintenance or change-out can be undertaken from the inside using templates or jigs on e.g. a forklif to hold hoses in position whilst splitting the flanges. Access can be from above using overhead cranes as well. When positioning the system slightly inboard, a straight ramp can be used to perform inspection and maintenance tasks on the hoses, in combination or not with driving system described above, or mechanical hose immobilization devices. Examples are hose change-out, and floatation aids change- out.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

Claims

1. A flushing station for a liquefied gas transfer line docking, coupling and draining system, the flushing station being arranged for connection with a gas transfer line and comprising:

a receiving space for the liquefied gas transfer line connector

a guiding system for guiding the transfer line to/from the receiving space the receiving space comprising:

- a de-icing utility such as a sea/fresh water systems nozzle tied-up to sea/fresh water systems, arranged for removal of ice from the liquefied gas transfer line connector and/or the structural connector clamping/locking system;

- a coupling for the liquefied gas transfer line connector with a locking device and a valve arrangement for closing and opening the transfer line at the location of the coupling;

- an inerting system for coupling to the transfer line connector in-between the valves of the valve arrangement and arranged to remove air and liquid from the space between the valves in the connector.

2. Docking station for a liquefied gas transfer line connector installed on a floating structure (1) lying at the sea surface and comprising processing units for liquefied gas to be transferred between the floating structure and a floating tanker via at least one transfer line that extends from the said floating structure to the said floating tanker to carry liquefied gas from one to the other characterized in that the docking station is integrated into a liquefied gas flushing station which comprises:

a receiving space for the liquefied gas transfer line connector;

a guiding system for guiding the transfer line to/from the receiving space, the receiving space comprising:

- a structural connector clamping/locking system for clamping/locking of the transfer line connector in the receiving space; - a de-icing utility such as a sea/fresh water systems nozzle tied-up to sea/fresh water systems, arranged for removal of ice from the liquefied gas transfer line connector and/or the structural connector clamping/locking system;

3. Docking station for a liquefied gas transfer line connector according to claim 2 wherein the receiving space (8) is integrated into a platform (12) mounted on the structural support structure (13) which is part of the floating vessel (1).

4. Docking station for a liquefied gas transfer line connector according to claim 3 wherein the platform (12) mounted on the structural support structure (13) is a pivoting platform.

5. Docking station for a liquefied gas transfer line connector according to any one of claims 2 - 4, wherein the liquefied gas transfer line is a composite cryogenic hose.

6. Docking station for a liquefied gas transfer line connector according to any one of claims 2 - 4, wherein the liquefied gas transfer line is a cryogenic hose in hose.

7. Docking station for a liquefied gas transfer line connector according to any one of claims 2 - 6, wherein the liquefied gas transfer line connector is a connector comprising a fluid flow connector combined with a structural disconnectable load diverter, arranged for diverting the loads and moments created by the transfer line, away from the valves and the fluid flow connector.

8. Offshore cryogenic offloading system that lies in a sea having a sea surface and a sea floor, wherein cryogenic fluid is transferred between two floating units comprising:

a floating structure that lies at the sea surface and comprises processing units; a floating tanker that lies at the sea surface and transports the cryogenic fluids from one location to another;

at least one cryogenic transfer line that extends from the said floating structure to the said floating tanker to carry cryogenic fluids from one to the other; at least one vapor return line that extends from the said floating structure to the said floating tanker to carry the boil-off vapor from the floating tanker to the floating structure in normal operations;

characterized in that the floating unit is provided with a docking station for a liquefied gas transfer line as defined in any one of the preceding claims 2 - 7.

9. Offshore cryogenic offloading system that lies in a sea having a sea surface and a sea floor, wherein cryogenic fluid is transferred between two floating units comprising:

a floating structure that lies at the sea surface and comprises processing units, a floating tanker that lies at the sea surface and transports the cryogenic fluids from one location to another;

characterized in that the floating unit is provided with a flushing station for a liquefied gas transfer line docking, coupling and draining system according to claim 1.

10. A liquefied gas transfer line draining and flushing system, wherein the transfer line is drained by reeling and unreeling on the transfer line storage structure.

1 1. A liquefied gas transfer line draining and flushing system according to claim 10, wherein the transfer line storage structure has a vertical rotation axis.

12. A liquefied gas transfer line draining and flushing system according to claim 10 or 11 , wherein the transfer line storage structure is fixed and provided with means having capabilities to roll-on and roll-off the transfer line.

13 A liquefied gas transfer line draining and flushing system according to any one of claims 10 - 12, wherein the outlet of the transfer line is combined to a dedicated pressure regulation equipment/valve or a stream flow control equipment/valve during the draining.

14. A flushing station according to claim 1 , provided with a liquefied gas transfer line draining and flushing system according to any one of the preceding claims 10 - 13.

15. A docking station according to any one of the preceding claims 2 - 7, provided with a liquefied gas transfer line draining and flushing system according to any one of the preceding claims 10 - 13.