WO2019038364A2

WO2019038364A2 - Method and system to drain a liquid gas transfer hose

Info

Publication number: WO2019038364A2
Application number: PCT/EP2018/072744
Authority: WO
Inventors: Patrick Englebert
Original assignee: Englemer BVBA
Current assignee: Englemer BVBA
Priority date: 2017-08-23
Filing date: 2018-08-23
Publication date: 2019-02-28
Anticipated expiration: 2020-02-23
Also published as: WO2019038364A3

Abstract

A liquid gas transfer and draining system for use in a method to transfer liquid gas and to drain the transfer hose that has been used in the transfer of liquid gas. A purge gas feed assembly is brought in communication with the upstream portion and the downstream portion of the transfer hose. A drain hose is inserted into the transfer hose such that the inlet of said drain hose is provided at the bottom bend of the U-shape of the transfer hose.

Description

METHOD AND SYSTEM TO DRAIN A LIQUID GAS TRANSFER HOSE The present invention relates to the field of transportation of liquid gas, more specifically to draining a transfer hose used to transfer liquid gas from one storage to another one.

Natural gas as well as petroleum gas are used as an energy supply. These gases are generally liquefied for long-distance transportation, e.g. transportation from a storage facility near the extraction location to a storage facility near end users. Liquefaction of substances that are gases at ambient conditions is achieved through cooling, thereby obtaining liquid (or liquefied) gasses, e.g. liquid natural gas (LNG) or liquid petroleum gas (LPG). Long-distance transportation often takes place by a ship, such as an LNG carrier, which typically comprises a number of tanks in which the liquid gas is stored. The liquid gas has to be transferred to and from this ship, whereby transfer can take place either to or from a fixed storage facility or to or from another ship, e.g. a vessel configured for regasification of the liquid gas. The latter is known as a ship-to-ship transfer.

Ship-to-ship transfers of liquid gas, but also transfers from a ship to a fixed storage facility, are performed using one or more cryogenic transfer hoses, which often provide thermal isolation of the liquid gas, by connecting each transfer hose at its inlet to a supply tubular element, e.g. a supply tube, on the liquid gas supplying entity, e.g. on the one ship, and at its outlet to a reception tubular element, e.g. a reception tube, on the liquid gas receiving entity, e.g. on the other ship. The liquid gas transfer hoses are often fairly long and flexible, to allow relative movements, e.g. primarily in vertical direction, e.g. heaving, of the ship or ships.

In the transfer of liquid gas, these transfer hoses are often hanging in a U-shape, such as for example shown in Figure 16 of US8864420. In this U-shaped state the transfer hose comprises a bottom bend, an upstream portion upstream of the bottom bend and a downstream portion downstream of the bottom bend. If the supply and reception tubular elements are located at different heights, said upstream portion and downstream portion may differ in length, e.g. there may be a long upstream portion and a short downstream portion. During loading or unloading of a ship the bend may find itself at different locations along the length of the hose due to the effective draft of the ship(s) changing. In present day practice liquid gas transfer hoses are employed with significant inner diameters, e.g. of 8 inches, 10 inches, 12 inches or even up to 16 inches inner diameter. For instance the companies like Gutteling, Trelleborg, Nexans, Brugg, Technip, manufacture liquid transfer hoses, e.g. for LNG transfer.

When the liquid gas transfer is stopped, e.g. because the supply storage has been emptied, liquid gas remains in the transfer hose, at least in the bottom bend, a lower portion of the upstream portion, and a lower portion of the downstream portion thereof. This liquid gas has to be removed prior to disconnecting the transfer hose, as exposing the liquid gas to ambient air causes e.g. rapid evaporation of the liquid gas, which is hazardous, e.g. as this poses an explosion risk. Also liquid gas could spill from the disconnected hose and instantaneously freeze components that come into contact with the gas, thereby, for example, such hull components losing their structural strength and/or functionality. This is also not acceptable.

A known method to partially remove the liquid gas from the transfer hose after the transfer has been stopped is to feed a pressurized purge gas, e.g. nitrogen, to the transfer hose at the upstream portion. This purge gas then pushes part of the liquid gas to the downstream portion of the transfer hose, and further into the reception tubular element. This known method has the disadvantage that not all liquid gas can be removed. To remove the remaining liquid gas, a prior art approach requires the remainder of the liquid gas to be evaporated. As cryogenic transfer hoses often have excellent insulating properties, evaporation is a slow process. The evaporation rate is then in practice accelerated by using fire hoses and spraying large amounts of water onto the outside of the transfer hose, as is shown in https://www.youtube.com/watch?v=W5RDB5 RKj4 . However, it may take several hours to evaporate the remaining liquid gas. The evaporation thus increases the transfer time, thereby increasing the total transfer and transportation time of the liquid gas, which adds to the costs of transport and transfer of liquid gasses. The present invention aims to provide a method to drain a liquid gas transfer hose in a manner that is faster and easier to perform and control than the current evaporation method.

To this end the present invention proposes a method according to claim 1 . The transfer hose is connected to the supply tubular element and reception tubular element using a connection mechanism. Commonly the ends of the transfer hose have a rigid end fitting with a flange with bolt holes to be connected to another flange via bolts. The connection(s) may include an emergency release device as is known in the art.

The transfer hose may comprise rigid end fittings at one or both of its ends near the inlet and/or outlet. These rigid end fittings may in embodiments have a length in the longitudinal direction of up to two times the diameter each. The end fittings may each include a flange.

Preferably, the source of pressurized purge gas is a source of pressurized nitrogen gas. However, also other purge gases for this purpose are possible, provided that they do not liquefy when in contact with the liquid gas remaining in the transfer hose upon stopping of the transfer, e.g. liquid natural gas, and that they are inert, that is, they do not react with the liquid gas, e.g. liquid natural gas.

A purge gas feed assembly can be configured in several ways. It may for instance have a feed line in a T-shape, with a single line section that extends from the source of pressurized purge gas, via a valve associated with the purge gas source, for example a pressure control valve, and then splits to create a line section that ends in the first end and a line section that ends in the second end. It may for instance also comprise two line sections, of which one extends from the pressurized purge gas source to the first end, and another one that extends from the pressurized purge gas source to the second end. Other arrangements are also possible, like two separate purge gas supply systems, one on each side (supply and reception), provided the same pressure is delivered by both systems. The latter is for example contemplated when ships are relative far apart from one another during transfer. The first and second ends of the purge gas feed line may be connected to the respective inlet and outlet of flexible transfer hose, preferably via an intermediate fitting, wherein preferably one intermediate fitting is mounted between the supply tubular element outlet and the inlet of the transfer hose and another intermediate fitting is mounted between the outlet of the transfer hose and the inlet of the supply tubular element, so that the source of pressurized purge gas is in direct communication with both the inlet and the outlet of the transfer hose.

However, the purge gas feed line(s) may also be connected to the supply tubular element and reception tubular element so that purge gas from the purge gas feed line is provided to the transfer hose via the supply tubular element and reception tubular element. The latter version may require some adaptation of existing, possibly certified, equipment, whereas the provision of intermediate fittings does not require (major) adaptation of existing equipment. In another embodiment the end fitting of the inlet and/or of the outlet end of the transfer hose could be adapted to connect thereto the purge gas feed line. This, however, requires adaptation of well proven and certified transfer hoses and may therefore be less attractive than the other proposals above.

The connection of the purge gas feed line to the supply tubular element or more

downstream to an intermediate fitting or a transfer hose end fitting is to be provided downstream of a first valve, so that purge gas from the pressurized purge gas source can be provided to the transfer hose when the first valve is closed and the transfer has stopped.

Similarly, the connection of the purge gas feed line to the reception tubular element or more upstream to an intermediate fitting or a transfer hose end fitting is to be provided upstream of a second valve, so that gas can be provided from the pressurized gas source to the transfer hose when the second valve is closed and the transfer has stopped.

A third valve is preferably provided in proximity of the first end of the purge gas feed line and the fourth valve is provided in proximity of the second end of the purge gas feed line. This allows to control the flow at the first and second ends of the purge supply line, e.g. to avoid ingress of liquid gas during the transfer process.

In order to insert the drain hose into the transfer hose, it has a diameter smaller than that of the inner diameter of the transfer hose. The outer diameter of the drain hose may for instance be smaller than half of the inner diameter of the transfer hose, smaller than a third of the inner diameter of the transfer hose, or smaller than one fourth of the inner diameter of the transfer hose.

The drain hose is inserted into the transfer hose over such a length thereof that the inlet of the drain hose is located at the bottom bend of the U-shape of the transfer hose, so that substantially all liquid gas trapped in the transfer hose can be drained through the drain hose.

The drain hose may have a nozzle at the inlet, e.g. streamlined, e.g. bulbous, to enhance insertion of the drain hose into the transfer hose.

The drain hose may extend with its insertion portion within said transfer hose along the downstream portion thereof to the outlet of the transfer hose. The drain hose may however also extend with its insertion portion within said transfer hose along the upstream portion from the inlet thereof.

As is preferred, use is made of a drain hose insertion fitting, which is to be mounted at one of the inlet or the outlet of the transfer hose, so either between the outlet of the supply tubular element and the inlet of the transfer hose or between the outlet of the transfer hose and the inlet of the reception tubular fitting depending on whether one desires to place the drain hose in the upstream portion or the downstream portion of the transfer hose. As is preferred the drain hose insertion fitting is provided with a valved drain hose insertion port, e.g. a lateral port connecting at an angle, e.g. at an incline, to a straight main passage of the fitting. Other designs of the fitting are also possible, e.g. with the fitting having an S- shaped passage for the liquid gas and the insertion port being aligned with the part of the passage that adjoins the transfer hose, e.g. the port being axially aligned with the axis of the transfer hose end adjoining the insertion fitting.

As is preferred the drain hose insertion port comprises two valves in series, e.g. two ball valves, providing a secure valving when transfer of gas takes place through the hose and thus through the already installed drain hose insertion fitting.

In an embodiment the purge gas feed line connects to the drain hose insertion fitting, e.g. to location between the two valves of the drain hose insertion port.

It will be appreciated that the mentioned insertion fitting can be integrated with the supply tubular element, e.g. permanently secured thereto, or with the reception tubular element, or with an end of the transfer hose, or the mentioned intermediate fitting, e.g. permanently secured thereto.

The drain hose is to be inserted into the desired portion of the transfer hose after the transfer of liquid gas via the transfer hose has been stopped, and both the first and second valves have been closed to isolate remaining liquid gas in the transfer hose.

The drain hose is expected to first drain nearly all of the liquid gas from the hose. When the transfer hose has almost or has been fully drained, some pressurized gas in gaseous form, e.g. purge gas and/or evaporated liquid gas originally trapped in the transfer hose, may also flow through the drain hose. Liquid gas or, at a later stage, gas in gaseous form, emerging from the drain hose may be handled in various manners.

In an embodiment the drain hose is connected, or connectable (e.g. via a valved manifold) to an existing vapour duct, e.g. as often present on gas transport ships.

In an embodiment the drain hose is connected, or connectable (e.g. via a valved manifold) to a vaporizer device to vaporize the liquid gas, which vapour is then handled, e.g. fed to a vapour duct.

In an embodiment the drain hose is connected, or connectable, (e.g. via a valved manifold) to a storage tank or an existing branch on the supply or reception system

The drain hose may also be extended through an insertion port provided in the end fitting at the inlet or at the outlet of the transfer hose.

In an embodiment the insertion portion of the drain hose extends within the transfer hose along the downstream portion thereof to said end fitting. Similarly, said drain hose may extend through the end fitting at the inlet of the transfer hose, so that the insertion portion of the drain hose extends within the transfer hose along the upstream portion thereof to said end fitting.

The drain hose may be inserted into the transfer hose before connecting the transfer hose and before the start of the transfer of liquid gas through the transfer hose. As in this arrangement the drain hose occupies part of the diameter of the transfer hose and influences the flow of liquid gas there through, this is less preferred. More preferable is the insertion of the drain hose at a later stage, in particular after the transfer has been stopped and preferably both the first and second valve have been closed. A practical reason to insert the drain hose only after stopping the liquid gas transfer is that the location of the bottom bend of the drain hose is likely to change during the liquid gas transfer, for instance when liquid gas is transferred from one ship, that then becomes lighter and as a result floats higher upon the water, while the liquid gas receiving ship attains a lower position in the water.

The drain hose, after draining has been completed, is preferably removed while the transfer hose is still connected to supply tubular element and to the reception tubular element. During transfer of liquid gas via the transfer hose both the first and second valve are open. Any valves of an already connected purge gas feed line, e.g. the third and fourth valve of the purge gas feed line, are closed. If the drain hose has already been inserted, the drain hose valve will be closed.

The transfer may stop when all liquid gas has flown through the outlet of the supply tubular element, that is, when the storage, e.g. tank or container, connected to the supply tubular element has been fully emptied. However, it may also be that the storage connected to the supply tubular element has only been partially emptied. In either case liquid gas will generally be trapped in the transfer hose, at least in the U-shaped bend thereof.

The gas is preferably drained by opening both the third and fourth valves so as to bring the source of pressurized gas, e.g. nitrogen, in communication with both the inlet and the outlet of the transfer hose. The draining, once the drain hose has been properly inserted to the bend in the hose, is effected by opening the drain hose valve.

Now draining of the transfer hose through the application of pressurized gas both at the upstream portion and downstream portion is performed.

The method and system to drain a transfer hose used in transfer of liquid gas may be used in conjunction with the transfer from a supply tubular element provided on a first ship to a reception tubular element on a second ship, e.g. in a side-by-side arrangement. The transfer is then a ship-to-ship transfer. Such ship-to-ship transfer may for instance take place near an offshore extraction site, after transportation over sea to a market for end users, e.g. to a regasification vessel, or outside a port to lighten a transportation vessel. For example ship- to-ship transfer may be done between a floating liquefaction plant, e.g. the Prelude vessel, and a shuttle gas tanker. Also a situation of bunkering, wherein a supply tanker ship supplies liquid gas to another, e.g. larger, ship is contemplated.

The method and system may however be used also in conjunction with the transfer from a ship to a fixed storage facility, e.g. a shore terminal, or between two fixed storage facilities. One can also envisage transfer between a vehicle and some other facility.

The present invention also comprises a liquid gas transfer and draining system according to claim 1 1 . The liquid gas transfer and draining system is envisaged for use in a method comprising the steps of:

- connecting the transfer hose with its inlet to the outlet of the supply tubular element and with its outlet to the inlet of the reception tubular element,

- transferring liquid gas from the supply tubular element through the transfer hose to the reception tubular element, said transfer including opening the first valve and the second valve,

- stopping the transfer including closing the first valve and the second valve,

- inserting the inlet and insertion portion of the drain hose into the transfer hose, so that the inlet of the drain hose is located at the bottom bend of the transfer hose,

- bringing the purge gas feed assembly in communication with the upstream portion and the downstream portion of the transfer hose,

- draining liquid gas trapped in the transfer hose via the drain hose, e.g. including opening a drain hose valve, so as to allow draining of liquid gas through the drain hose, wherein said pressurized purge gas enters the transfer hose both at the upstream portion and at the downstream portion thereof so as to force the trapped liquid into the drain hose.

When the transfer hose has been drained, and in practice vapor formed by evaporating gas has been purged as well, it may be disconnected from the supply tubular element and/or reception tubular element, e.g. with prior removal of the drain hose from the transfer hose.

The present invention also comprises a liquid gas transfer and draining assembly. Said assembly comprising a transfer hose, a drain hose and a purge gas feed assembly. Said transfer hose and drain hose are configured for transfer of liquid gas.

The transfer hose has an inlet and an outlet. Said transfer hose moreover may comprise both at its inlet and outlet a rigid end fitting for connecting to tubular elements. Said transfer hose hangs during transfer in a U-shape having a bottom bend, an upstream portion upstream of said bottom bend and a downstream portion downstream of said bottom bend.

A purge gas feed line can be connected to a source of pressurized purge gas, e.g. of nitrogen gas. The purge gas feed line has a first end that can, directly or via an intermediate fitting, be connected to the rigid end fitting at the inlet of the transfer hose and a second end that can be connected, directly or via an intermediate fitting, to the rigid end fitting at the outlet of the transfer hose. The purge gas feed line may also comprises one or more valves to control a flow of pressurized gas from said source. The present invention also relates to a liquid gas transfer and draining system for use in a method to transfer liquid gas and to drain the transfer hose that has been used in said transfer of liquid gas. A purge gas feed assembly is brought in communication with the upstream portion and the downstream portion of the transfer hose. A drain hose is insertable into the transfer hose such that the inlet of said drain hose is provided at the bottom bend of the U-shape of the transfer hose. The invention also relates to the use of this system in the transfer of liquid gas and the later draining of the transfer hose.

Instead of a single drain hose a group or a bundle of multiple drain hoses, e.g. helically wound drain hoses, can be used.

The drain hose may have a heating system, e.g. to provide heat in order to keep the drain hose flexible for insertion and/or withdrawal, and/or to have the capability for evaporation of liquid gas when desired.

The heating system of the drain hose may comprises one or more channels of the drain hose through which a heating medium is to be circulated, e.g. heated liquid or a heated gas.

The drain hose may be provided with one or more temperature sensors, e.g. at or near the inlet thereof, and/or distributed over the length of the drain hose, e.g. on an exterior of the drain hose. These one or more temperature sensors are adapted to sense the temperature at one or more locations. For example the temperature measured is indicative of the draining being completed, e.g. as the sensor in the bottom of the bend is no longer submerged in liquid gas. The one or more temperature sensors may be used to sense the level of liquid gas still present in the transfer hose during the draining process, e.g. as an indication of the progress of the draining. In another embodiment, or in combination herewith, the drain hose may be provided with one or more optical sensors that detect whether the sensor is submerged in liquid gas or finds itself above the level of the liquid gas in the drain hose during the draining process. The output of one or more sensors provided on the drain hose may be forwarded, e.g. optical, to a controller and/or display device. For example the controller is linked to the drain valve.

The transfer hose may be provided with a guide member for the insertable drain hose, for example a strip, along which the drain hose slides during insertion and withdrawal. The guide member can be fastened to the wall of the transfer hose, e.g. integrated therewith if the transfer hose is made dedicated to the combination with an insertable drain hose. For example the transfer hose is provided with a drain hose guide duct acting as guide member for the insertable drain hose, e.g. the guide duct being perforated so that liquid gas can enter into the guide duct, e.g. at least in a region where the bend is expected, and then into the drain hose. The drain hose may be slided along the one or more guide members in view of positioning an inlet of the drain hose at the bend of the transfer hose.

The insertion fitting may be provided with a curved guide for the insertable drain hose, e.g. said curved guide being movable between a retracted position, not obstructing the flow of liquid gas through the fitting, and a deployed position wherein the curved guide assists the bending of the drain hose.

In an embodiment the insertion of the drain hose is done via an insertion port, e.g. of an insertion fitting, that is aligned with the axis of inlet or the outlet of the transfer hose, so that the drain hose can basically be inserted without the need for a major bending of the drain hose near the insertion location.

The system may comprises a drain hose inserter device adapted to engage on the drain hose and to exert a force thereon to insert the drain hose into the transfer hose, for example the inserter device having one or more rollers or tracks engaging on the exterior of the drain hose and driven by a drive, e.g. a manually power drive or a motorized drive.

In an embodiment two transfer hoses are arranged in parallel, connected at their inlets and their outlets via a Y-fitting to one supply tubular element and one reception tubular element. In this case one can envisage a drain hose and related equipment as described herein for each transfer hose, with the draining of the two hoses being done simultaneously via two drain hoses. For example on Y-fitting is provided with two drain hose insertion ports or the like as described herein, with two drain hoses being provided to allow for draining of both transfer hoses simultaneously.

In an embodiment the system further comprises at least one ship, e.g. in ship to shore transfer, or a first ship and a second ship in ship-to-ship transfer.

The present invention also relates to a drain hose and drain hose insertion fitting for use in the draining of a liquid gas transfer hose. A further aspect of the present invention relates to a method and system to transfer liquid gas and to drain a transfer hose that has been used in the transfer of liquid gas. Herein use is made of a liquid gas transfer and draining system comprising a supply tubular element, a reception tubular element, a transfer hose, wherein the supply tubular element, reception tubular element, transfer hose and drain hose being configured for transfer of liquid gas, wherein the supply tubular element has a first valve and the reception tubular element has a second valve, wherein the transfer hose has an inlet and an outlet, said transfer hose connectable at its inlet to said outlet of the supply tubular element and connectable at its outlet to said inlet of the reception tubular element, said transfer hose when connected to said supply tubular element and said reception tubular element hanging in a U-shape and having a bottom bend, an upstream portion upstream of said bottom bend, and a

downstream portion downstream of said bottom bend, wherein the system further comprises a purge gas feed assembly with a source of pressurized purge gas, e.g. nitrogen gas, that is brought in communication with the transfer hose. Herein the method and system involves the use and provision of one or more temperature sensors that are introduced into the transfer hose, preferably at least one temperature sensor at the bottom bend, wherein the output of said one or more temperature sensors is, for example, used as an indication of the draining of the hose being completed and/or the progress of the draining. The method and system may comprises one or more features as discussed herein, e.g. the use of drain hose, e.g. a drain hose provided with one or more of said temperature sensors.

The invention also relates to the combination of a liquid gas transfer hose, a drain hose, and a purge gas feed assembly including a source of pressurized purge gas, as described herein.

The invention will now be discussed with reference to the drawings. In the drawings:

Figure 1 shows a schematic view of an embodiment of a prior art liquid transfer via flexible hose,

Figure 2 shows a schematic view of an exemplary embodiment of the liquid gas transfer and draining system according to the invention during transfer of liquid gas,

Figure 3 shows the system of figure 2 once liquid gas transfer has been stopped and the inventive draining of the transfer hose is effected,

Figure 4 shows an embodiment of a drain hose insertion fitting and a drain hose inserter device,

Fig. 5 illustrates schematically the transfer of liquid gas using so-called Y-pieces and parallel transfer hoses. With reference to the figures 2, 3, 4 and 5 embodiments and optional features of the liquid gas transfer and draining system and the liquid gas transfer and draining assembly according to the invention will be described. First, with reference to figure 1 , a well-known prior art arrangement for liquid gas transfer via a transfer hose will be described.

In the figures the same or similar components have been denoted with the same reference numerals. All figures are schematic and not to scale.

The liquid transfer system comprises a supply tubular element 2, a reception tubular element 3, and a flexible transfer hose 4.

In the embodiment shown in figure 1 , the flexible transfer hose 4 is at its inlet 41 connected to the outlet 22 of the supply tubular element 2 and is it its outlet 42 connected to the inlet 32 of the reception tubular element 3. For example, as common, the inlet 41 is formed by an inlet end fitting 46 of the hose, e.g. a flanged end fitting to be bolted onto a flange of the element 2. For example, as is common, the outlet 42 is formed by an outlet end fitting 47 of the hose 4, e.g. a flanged end fitting to be bolted onto a flange of the element 3.

The supply tubular element 2 comprises a first valve 21 near its outlet 22.

The reception tubular element 3 comprises a second valve 31 near its inlet 32. The transfer hose 4 is configured for transfer of liquid gas, e.g. a multilayer composite hose,

The hose 4 is suspended between the supply tubular element 2 and reception tubular element 3 and at least part of it hangs in a U-shape. Said U-shape comprises a bottom bend 43, an upstream portion 44 upstream of said bottom bend and a downstream portion 45 downstream of said bottom bend.

The wording inlets, outlets, upstream and downstream portion indicate that the flow of liquid gas during transfer is from the supply tubular element 2 through the transfer hose 4 to the reception tubular element 3.

A source of pressurized purge gas 51 is provided, e.g. filled with nitrogen. The source 51 is connectable via a valve 54 to the inlet or the outlet of the hose 4. As explained herein, liquid gas transfer is effected by installing the hose 4 and then opening both the first and second valves 21 , 31 so that liquid gas flows through the hose 4. Once transfer is completed a purging process is carried out. In the prior art approach this involves: A first phase where fire hoses are used to spray water onto the exterior of the hose 4 in order to (slowly) evaporate the liquid gas in the hose 4, with for example the second valve 32 being opened so that the vapour is discharged from the hose 4, for example to be collected in a tubular of the system downstream of valve 32,

a second phase to purge remaining vapour from the hose, performed by flushing

pressurized purge gas, e.g. nitrogen, into the hose from one end and collecting the mixture of vapour and nitrogen or the like at the other end until the concentration of liquid gas vapour in the hose is low enough for safe disconnection of the hose 4.

In practical embodiments the first phase may take about one hour, with the second phase taking 2 - 3 hours, so a total time of 3 - 4 hours, is not uncommon.

Now, with reference to figures 2, 3, 4 and 5, embodiments of the innovative approach will be discussed.

The liquid gas transfer and draining system 1 comprises the supply tubular element 2, the reception tubular element 3, the flexible transfer hose 4.

Also now provision is made for a purge gas feed line 5 and a flexible drain hose 6.

In the embodiment shown in figure 2, 3 , the flexible transfer hose 4 is at its inlet 41 connected to the outlet 22 of the supply tubular element 2 and is it its outlet 42 connected to the inlet 32 of the reception tubular element 3.

The supply tubular element 2 comprises the first valve 21 near its outlet 22. The reception tubular element 3 comprises the second valve 31 near its inlet 32.

The transfer hose 4 is suspended between the supply tubular element 2 and reception tubular element 3 so that a part thereof has a U-shape. Said U-shape comprises a bottom bend 43, an upstream portion 44 upstream of said bottom bend and a downstream portion 45 downstream of said bottom bend. The wording inlets, outlets, upstream and downstream portion indicate that the flow of liquid gas during transfer is from the supply tubular element 2 through the transfer hose 4 to the reception tubular element 3. In the present embodiment the transfer hose moreover comprises rigid end fittings 46, 47 at the inlet 41 and outlet 42 of the transfer hose.

The purge gas feed line 5 is connected to the source of pressurized purge gas 51 , e.g. of nitrogen gas.

The purge gas feed line 5 has a first end 52 in communication with the upstream portion 44 of the transfer hose 4 and a second end 53 in communication with the downstream portion 45 of the transfer hose 4. In the present embodiment the purge gas feed line 5 moreover comprises a third valve 54 provided near the first end 52 of the purge gas feed line, and a fourth valve 55 near the second end 53 thereof.

As is preferred use is made of an intermediate purge gas feed line connection fitting 60, here between the outlet 22 of the tubular element 2 and in inlet end fitting 46 of the hose 4. The line 5 connects, via third valve 54, to a port of this fitting 60. As mentioned herein alternative designs allow for the purge gas feed line 5 to connect to the tubular element 2, downstream of first valve 21 , or to the fitting 46. As is preferred, use is made of a drain hose insertion fitting 70, which is here mounted at the outlet end fitting 47 of the transfer hose 4, so between the outlet of the transfer hose and the inlet of the reception tubular fitting.

As is preferred the drain hose insertion fitting 70, shown in figure 4 in some more detail, is provided with a valved drain hose insertion port 71 .

As is preferred the drain hose insertion port 71 comprises two valves 73, 74 in series, here, two ball valves, providing a secure valving when transfer of liquid gas takes place through the hose 4 and thus through the already installed drain hose insertion fitting 70. As shown here the second end of the purge gas feed line 5 connects, via the fifth valve 81 , to the drain hose insertion fitting, in more detail to the drain hose insertion port 71 . This is done to avoid a vapor leak out of the hose 4 via the port 71 . The flexible drain hose 6 has an inlet 61 and downstream thereof an insertion portion 62 that is configured to be inserted into the hose 4 via the fitting 70. Downstream thereof the drain hose 6 has an external portion 63 that does not enter into the fitting 70 and connects via a drain hose valve 64 to some discharge assembly, of which embodiments are discussed herein.

Figure 2 shows the situation during liquid gas transfer via the hose 4. As preferred, the drain hose 6 is now fully external of the path through which the liquid gas travels from element 2 to element 3. Once the liquid transfer has been completed both the first valve 21 and the second valve 32 are closed, thus trapping a substantial volume of liquid gas in the hose 4.

Now the drain hose is inserted and the situation shown in figure 3 is obtained. This entails e.g. first opening the valves 73, 74 whilst at the same time allowing nitrogen to flood the port 71 of the fitting 70 via the opened valve 81 from the source 51 . In embodiments a sealing member, e.g. expandable, can be provided in or on the port 71 as shown in figure 4 so as the close the annulus between the drain hose 6 and the port 71 . For example the nitrogen injection is downstream of such seal. Once the drain hose 6 has been properly inserted, the third valve 54 and fourth valve 55 are also opened so that the liquid gas in the hose is pressurized by the gas from source 51 at both the inlet and the outlet of the hose 4.

Proper insertion preferably entails that the inlet 61 of the drain hose 6 is at the bottom 43 of the bend in the hose 4. This location can be easily recognized, e.g. by having indicia representing intervals of length on the hose so that one can see how far the bend is removed from the fitting 70. Also indicia representing length or a insertion length

measurement device can be provided to detect the actual insertion length of the drain hose 6.

So, once properly inserted, the inlet 61 and the insertion portion 62 are inserted within the transfer hose 4 with the inlet at the bottom bend 43 thereof. The insertion portion 62 extends in the present embodiment along the downstream portion of the transfer hose to the rigid end fitting 47 at the outlet 42 thereof. The transfer hose 6 then extends through the fitting 70. The remaining external portion 63 is thus outside of the fitting, e.g. in a loop of variable length so as to allow for insertion into the hose 4. At the end of this loop the drain hose valve 64 is mounted.

It is envisaged that draining the hose in this manner is a matter of minutes. During this brief time span very little evaporation of liquid gas has taken place, also because only the interfaces with the gas volume filled by source 51 at both ends of the hose 4 are available for evaporation.

It is expected that at the end of the draining of nearly all of the content from the hose, only a little residual cold gas vapour remains at the bottom of the bend, that is then purged by gentle gas pressure from source 51 via the hose 6. It is expected that as this vapour has hardly been warmed up, e.g. to about—140 to -120 Celsius, this vapour is heavier than the nitrogen from source 51 and will thus remain at the bottom of the bend and enter the inlet 61 of the hose 6. Thus the purging of this last bit of gas is expected to take far less time than the second phase of the prior art approach described above. The discharged liquid gas, and any residual vapour, emerging from the drain hose 6 as the valve 64 is opened can be handled in various manners.

In one embodiment the drain hose 6 connects to an ambient vaporizer device which is heated by ambient air so not needing any heat source to effect vaporization. These vaporizers are known components and can be installed in close vicinity of the location of the one or more tubular elements at the supply or reception side of the system. The outlet of such a vaporize device, or any other vaporizer device, may be connected to a vapour manifold. Such a vapour manifold is commonly standard in combination with one or more transfer hose arrangements in order to transfer vapour.

In another embodiment the drain hose 6 could connect to a liquid drain tube, e.g. to a storage tank, so avoiding the need for a vaporizer.

The figure 4 shows an embodiment of a drain hose insertion fitting 70 and a drain hose inserter device 77. In the embodiment shown the drain hose inserter device 77 comprises driven tracks engaging on the drain hose 6 and adapted to push the drain hose 6 into the transfer hose and to pull the drain hose from the transfer hose. The device 77 can comprise one or more motors and/or be manually powered.

In the embodiment shown the port 71 is at an incline relative to the straight passage for the liquid gas through the fitting 70.

The port 71 has multiple valves 73, 74 in series.

It is illustrated that the port 71 may have, upstream of the one or more valves 73, 74 thereof, a docking space 76 for at least a frontal section of the drain hose 6, so that drain hose is already properly aligned with the port 71 ahead of the use of this equipment, e.g. even ahead of the start of the liquid gas transfer so that the draining capability is readily operable when needed. This docking space 76 and/or other parts of the fitting 70 may be provided with a heating system, e.g. to avoid icing of the port 71 , space 76, and/or keep the hose 6 flexible.

The port 71 may be provided with one or more sealing device 78 that seal the annulus between the drain hose 6 and the port 71 , e.g. inflatable sealing devices.

Figure 5 illustrates a liquid gas transfer arrangement wherein so-called Y-fittings are employed as well as parallel transfer hoses 4 connected between said Y- fittings. The figure 5 serves to illustrate an embodiment of implementing the present invention in such a transfer arrangement.

As can be seen two transfer hoses 4 are arranged in parallel, connected at their inlets and their outlets via a Y-fittings 90, 91 to one supply tubular element 2 via valve 21 and to one reception tubular element 3 via valve 31 .

The Y-fittings 90, 91 for example have a central port of 16 inches diameter, to connect to respective tubular elements 2, 3 of the same diameter, whereas the transfer hoses each have an 8 inches diameter, so the other ports of each Y-fitting having an 8 inch diameter. Here two drain insertion fittings 70a, b are provided, each mounted between a respective port of Y-fitting 91 and the end of a respective transfer hose 4. The purge gas supply comprises source 51 , valves 54, 55, 56, and supply line 5 as discussed herein before. So simultaneous drainage of the liquid gas which remained in the transfer hoses can be performed via drain hoses, not shown. Each drain hose is inserted via its respective insertion fitting 70a, 70b.

In an alternative, not shown, the purge gas line 5 connects to the one or more Y-fittings directly.

Claims

C L A I M S

1 . Method to transfer liquid gas and to drain a transfer hose (4) that has been used in said transfer of liquid gas (1 1 ), wherein use is made of a liquid gas transfer and draining system (1 ) comprising a supply tubular element (2), a reception tubular element (3), a transfer hose (4), a drain hose (6), said supply tubular element, reception tubular element, transfer hose and drain hose being configured for transfer of liquid gas, wherein said supply tubular element (2) has a first valve (21 ) and said reception tubular element (3) has a second valve (31 ), wherein said transfer hose (4) has an inlet (41 ) and an outlet (42), said transfer hose connectable at its inlet (41 ) to said outlet (22) of the supply tubular element (2) and connectable at its outlet (42) to said inlet (32) of the reception tubular element (3), said transfer hose (4) when connected to said supply tubular element (2) and said reception tubular element (3) hanging in a U-shape and having a bottom bend (43), an upstream portion (44) upstream of said bottom bend, and a downstream portion downstream (45) of said bottom bend, wherein the system further comprises a purge gas feed assembly (5) with a source of pressurized purge gas (51 ), e.g. nitrogen gas, that is brought in communication with the upstream portion (44) of said transfer hose (4) and with the downstream portion (45) of said transfer hose (4), wherein said drain hose (6) has an inlet (61 ), an insertion portion (62) downstream from said inlet and an external portion (63) downstream of said insertion portion, wherein the inlet (6) and insertion portion (61 ) of said drain hose (6) are insertable into the transfer hose (4) such that the inlet (61 ) of said drain hose (6) is located at the bottom bend (43) of the U-shape of the transfer hose, said drain hose (6) extending with its insertion portion (61 ) within said transfer hose (4) along the downstream or upstream portion thereof, said drain hose (6) extending with its external portion (63) outside of said transfer hose, said drain hose (6) having a drain hose valve (64), said method comprising the steps of: - connecting the transfer hose (4) with its inlet (41 ) to the outlet of the supply tubular element (2) and with its outlet (42) to the inlet of the reception tubular element (3),

- transferring liquid gas from the supply tubular element (2) through the transfer hose (4) to the reception tubular element (3), said transferring including opening the first valve (21 ) and the second valve (31 ),

- stopping the transfer of liquid gas including closing the first valve (21 ) and the second valve (31 ),

- inserting the inlet (61 ) and insertion portion (62) of the drain hose (6) into said transfer hose (4) and locating the inlet of said drain hose at the bottom bend (43) of the transfer hose,

- bringing the purge gas feed assembly (5,51 ) in communication with the upstream portion (44) and the downstream portion (45) of the transfer hose,

- draining liquid gas trapped in the transfer hose by opening the drain hose valve (64), so as to drain liquid gas from the transfer hose (4) through the drain hose (6), with pressurized purge gas from said purge gas source (51 ) entering the transfer hose (4) both at the upstream portion and at the downstream portion thereof so as to force the trapped liquid gas into the drain hose (6).

2. Method according to claim 1 , wherein said drain hose extends with its insertion portion (62) within said transfer hose along the downstream portion (45) thereof to the bottom bend (43) thereof, or

with its insertion portion within said transfer hose along the upstream portion (44) thereof to the bottom bend (43) thereof.

3. Method according to claim 1 or 2, wherein said purge gas feed assembly comprises a purge gas feed line (5) having a first end (52) that is brought in communication with the upstream portion (44) of said transfer hose (4) and a second end (53) that is brought in communication with the downstream portion (45) of said transfer hose (4), and wherein the purge gas feed line (5) comprises a third valve (54) to control flow of pressurized purge gas (51 ) at the first end of the purge gas feed line and a fourth valve (55) at the second end of the purge gas feed line.

4. Method according to one or more of the preceding claims, wherein at least the insertion portion (62) of the drain hose (6) has an outer diameter smaller than half the inner diameter of the transfer hose (4), e.g. the outer diameter of the drain hose is smaller than one fourth of the inner diameter of the transfer hose (4).

5. Method according to one or more of the preceding claims, wherein the supply tubular element (2) is provided on a first ship and the reception tubular element (3) on a second ship so that the transfer of liquid gas is ship-to-ship transfer of liquid gas.

6. Method according to one or more of the preceding claims, wherein the liquid gas that is transferred via the transfer hose (4) is liquid natural gas.

7. Method according to one or more of the preceding claims, wherein use is made of a drain hose insertion fitting (70), which is mounted at one of the inlet or the outlet of the transfer hose (4), which fitting (70) has a port (71 ) adapted for insertion of the drain hose (6) into the transfer hose (4), for example wherein the port (71 ) is embodied as a valved drain hose insertion port, e.g. comprising two valves (73,74) in series, e.g. two ball valves that are closed during the transfer of liquid gas through the transfer hose (4) and are opened to allow for entry of the drain hose (6) into the transfer hose (4).

8. Method according to claim 7, wherein purge gas feed assembly, e.g. a purge gas feed line (5) thereof, connects to the drain hose insertion fitting (70), e.g. to location between the two valves of the drain hose insertion port (71 ).

9. Method according to one or more of the preceding claims, wherein the drain hose (6) is provided with one or more temperature sensors, and wherein the method comprises, for example, using the output of said one or more temperature sensors as an indication of the draining of the hose (4) being completed and/or the progress of the draining.

10. Method according to one or more of the preceding claims, wherein the drain hose (6) is connected to a vaporizer device (80), e.g. an ambient vaporizer, and liquid gas removed from the transfer hose (4) via the drain hose (6) is vaporized, e.g. said vapor being fed to a vapor line onboard a ship.

1 1 . A liquid gas transfer and draining system (1 ) for use in a method to transfer liquid gas and to drain the transfer hose (4) that has been used in said transfer of liquid gas (1 1 ) , e.g. the method of any of claims 1 - 10, said system comprising:

- a liquid gas transfer hose (4),

- a drain hose (6), - a purge gas feed assembly including a source of pressurized purge gas (51 ), e.g. nitrogen gas, said transfer hose and drain hose being configured for transfer of liquid gas (1 1 ), wherein said transfer hose has an inlet (41 ) and an outlet (42), said transfer hose connectable at its inlet to an outlet (22) of a supply tubular element having a first valve (21 ), and connectable at its outlet (42) to an inlet (32) of a reception tubular element (3) having a second valve (31 ), said transfer hose when connected to said supply tubular element and reception tubular element hanging in a U-shape having a bottom bend (43), an upstream portion (44) upstream of said bottom bend and a downstream portion (45) downstream of said bottom bend, wherein said purge gas feed assembly is adapted to be brought in communication with the upstream portion of said transfer hose and to be brought in communication with the downstream portion of said transfer hose, wherein said drain hose (6) has an inlet (61 ), an insertion portion (62) downstream from said inlet (61 ) and external portion (63) downstream of said insertion portion, wherein the inlet and insertion portion of said drain hose are insertable into the transfer hose such that the inlet of said drain hose is provided at the bottom bend of the U-shape of the transfer hose, said drain hose extending with its insertion portion within said transfer hose along the downstream or upstream portion thereof, said drain hose extending with its external portion outside of said transfer hose, said drain hose being associated with a drain hose valve (64).

12. System according to claim 1 1 , wherein said purge gas feed assembly comprises a purge gas feed line (5) connectable or connected to said source of pressurized purge gas (51 ), e.g. nitrogen gas, and wherein said purge gas feed line has a first end (52) that can be brought in communication with the upstream portion of said transfer hose, said purge gas feed line having a second end (53) that can be brought in communication with the downstream portion of said transfer hose, and wherein the system comprises a third valve (54) and a fourth valve (55) adapted to control flow at said first end (52) and second end (53) of the purge gas feed line (5).

13. System according to claim 1 1 or 12, wherein at least the insertion portion (62) of the drain hose (6) has an outer diameter smaller than half the inner diameter of the transfer hose (4), e.g. the outer diameter of the drain hose is smaller than one fourth of the inner diameter of the transfer hose (4).

14. System according to one or more of the claims 1 1 - 13, wherein the supply tubular element (2) is provided on a first ship and the reception tubular element (3) on a second ship so that the transfer of liquid gas is ship-to-ship transfer of liquid gas.

15. System according to one or more of the claims 1 1 - 14, wherein the system comprises a drain hose insertion fitting (70), which is adapted to be mounted at one of the inlet or the outlet of the transfer hose (4), which fitting (70) has a port (71 ) adapted for insertion of the drain hose (6) into the transfer hose (4), for example wherein the port (71 ) is embodied as a valved drain hose insertion port, e.g. comprising two valves (73,74) in series, e.g. two ball valves, which valve or valves is/are closed during the transfer of liquid gas through the transfer hose (4) and are opened to allow for entry of the drain hose (6) into the transfer hose (4).

16. System according to claim 15, wherein the purge gas feed assembly, e.g. a purge gas feed line (5) thereof, is adapted to be connected to the drain hose insertion fitting (70), e.g. to location between the two valves of the drain hose insertion port (71 ).

17. System according to one or more of the preceding claims 1 1 - 16, wherein the drain hose (6) is provided with one or more temperature sensors.

18. System according to one or more of the claims 1 1 - 17, wherein the drain hose (6) is connected to a vaporizer device (80), e.g. an ambient vaporizer, allowing liquid gas removed from the transfer hose (4) via the drain hose (6) to be vaporized, e.g. said vapor being fed to a vapor line onboard a ship.

19. Use of a system according to one or more of the claims 1 1 - 18 in ship-to-ship transfer of liquid gas, wherein the supply tubular element (2) is provided on a first ship and the reception tubular element (3) on a second ship.

20. Use of a system according to one or more of the claims 1 1 - 18 in transfer of liquid natural gas.

21 . Use of a liquid gas drain hose (6) for draining liquid gas from a bottom bend of a transfer hose that has been used for transfer of liquid gas (1 1 ), wherein the liquid gas drain hose has an inlet and insertion portion of said drain hose is insertable, or has been inserted, into the transfer hose such that the inlet of said drain hose is provided at the bottom bend of the U-shape of the transfer hose. 21 . In combination:

- a transfer hose configured for transfer of liquid gas (1 1 ),

wherein said transfer hose has an inlet (41 ) and an outlet (42), said transfer hose during transfer of liquid gas hanging in a U-shape having a bottom bend (43), an upstream portion (44) upstream of said bottom bend and a downstream portion (45) downstream of said bottom bend,

- a liquid gas drain hose (6) having an inlet (61 ), an insertion portion downstream from said inlet (62) and external portion (63) downstream of said insertion portion, wherein the inlet and insertion portion of said drain hose are insertable into the transfer hose such that the inlet of said drain hose is provided at the bottom bend of the U-shape of the transfer hose, said drain hose extending with its insertion portion within said transfer hose along the downstream portion or upstream portion thereof, said drain hose extending with its external portion outside of said transfer hose.

22. A drain hose insertion fitting (70), which is configured to be mounted at one of the inlet or the outlet of the liquid gas transfer hose (4), which fitting (70) has a port (71 ) adapted for insertion of a drain hose (6) into the transfer hose (4), for example the port (71 ) being embodied as a valved drain hose insertion port, e.g. comprising two valves (73,74) in series, e.g. two ball valves that are closed during the transfer of liquid gas through the transfer hose (4) and are opened to allow for entry of the drain hose (6) into the transfer hose (4).

23. Method for draining a liquid gas transfer hose (4), wherein use is made of the combination of claim 21 and/or the drain hose insertion fitting of claim 22.