An inflatable bladder, a system comprising the bladder, and a method for bringing the bladder into and out of a vessel

Abstract

An inflatable bladder (3) for facilitating purging of a vessel (1), a system comprising the bladder, and a method using the bladder (3), wherein the inflatable bladder having an inside and outside, and an opening comprising a stem (31) for communicating a fluid into and out of the bladder The inflatable bladder (3) comprises at least one line (10) having at least one first end portion (101) and a second end portion (102) opposite the at least one first end portion (101), wherein the at least one first end portion (101) of the line (10) is secured to an inside of the inflatable bladder (3) at a location not forming part of the stem (31), and wherein the line has a length allowing the second end portion (102) of the line (10) to extend beyond an inlet of the stem (31) of the inflatable bladder (3) when fully inflated.

Description

[0001] AN INFLATABLE BLADDER, A SYSTEM COMPRISING THE BLADDER, AND A METHOD FOR

[0002] BRINGING THE BLADDER INTO AND OUT OF A VESSEL

[0003] The present invention is related to an inflatable bladder for facilitating purging of a vessel, a system comprising the bladder, and a method for bringing the bladder into and out of a vessel. More specifically the invention is related to a bladder and a system for use in a purging operation of a vessel that might periodically require gas freeing. By the term purging is meant replacing a first gas within a vessel with a second gas.

[0004] The vessel may be a transport container for gas on board a gas tanker or other transport facilities like train, lorry etc., or it might be a process tank or pressure vessel where the problem of displacement of dissimilar vapours is a challenge. Such a process tank or pressure vessel may for example be biogas reactors or other, normally gas filled containers, which sometimes needs gas freeing.

[0005] The publication EP2914893 Bl discloses a method and an apparatus for facilitating purging of a vessel. The apparatus is operatively connected to a vessel, and comprises an inflatable bellow or bladder being connected to a conduit for communicating a fluid between a fluid source into or out of the bladder. The apparatus comprises a fluid tight compartment for initially housing the bladder, a closable sealing means for selectively bringing the compartment in fluid communication with the internal of the vessel via an aperture in a portion of the vessel, and means for bringing the bladder into and out of the vessel. By inflating the bladder within the vessel, a gas between the inside of the vessel and the outside of the bladder will gradually be displaced, so that a volume between the bladder and the internal of the vessel is reduced, thereby facilitating purging of the vessel. However, there are issues related to the deployment and more particularly the withdrawal of the bladder from the vessel where some improvements with respect to the overall operability and the maintenance of the bladder's gas tight integrity throughout the whole operation of deployment and withdrawal.

[0006] With respect to the method and apparatus disclosed in EP2914893 Bl a particular issue which sometimes may cause an operational delay, is related to the stem or neck of the bladder through which a first gas (typically nitrogen) used to displace a second gas from the subject vessel. The operational delay may typically arise when the gas within the bladder flows rapidly out through the stem of the bladder when the bladder is retrieved from the vessel as the vessel is being refilled with a gas. The rapid exhaustion of the gas through the stem is prone to provide a corresponding pressure drop may cause the stem to collapse, only to re-open as the driving pressure exceeds the pressure in the compartment into which the bellow exhausts itself. This is akin to the phenomenon observed when releasing a party ballon to exhaust its air-filled interior though the filling nozzle, giving a characteristic sound.

[0007] In the operational case of the bladder, the rapid succession of open and collapse, may in some cases harm the integrity of the bladder such that damage may occur, or in some other cases, the bladder may end up blocking itself from exhaustion of the gas therefrom.

[0008] There is therefore a need for an improved bladder, apparatus, and method for purging a vessel.

[0009] The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

[0010] The object is achieved through features, which are specified in the description below and in the claims that follow.

[0011] The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

[0012] In a first aspect the invention there is provided an inflatable bladder for facilitating purg- ing of a vessel, the inflatable bladder having an inside and outside, and an opening comprising a stem or neck for communicating a fluid into and out of the bladder.

[0013] The inflatable bladder comprises at least one line having at least one first end portion and a second end portion opposite the at least one first end portion, wherein the at least one first end portion of the line is secured to the inside of the inflatable bladder at a location not forming part of the stem. The line has a length allowing the second end portion of the line to extend beyond an inlet of the stem of the inflatable bladder when fully inflated.

[0014] By securing the first end of the line to an inside of the inflatable bladder at a location not forming part of the stem, a body of the bladder may be pulled past the stem of bladder when being pulled out of a vessel. In one embodiment, the at least one line is secured to the inside of the bladder at a portion being opposite the stem. For a vessel wherein a bladder according to the invention has been inserted via an opening in a top portion of the vessel, the line may for example be secured to one or more portions forming a bottom part of the bladder when being inflated. Thus, when pulling the line or lines, the bladder may be pulled out of the vessel in an inside-out manner.

[0015] It is an advantage if the bladder is made from a lightweight and flexible material. A low weight of the bladder facilitates handling of the bladder prior to and after use. A flexible material is preferred with respect to adapting to any protrusions or recesses within the vessel receiving the bladder.

[0016] For further facilitating handling of the bladder and protecting the bladder prior to use, the bladder may be arranged in a cartridge having a first end portion and a second end portion opposite the first end portion. The cartridge may have a form of a sleeve. Preferably, a perimeter portion of the stem of the bladder is secured to a perimeter portion of the cartridge. By securing a stem of the bladder to a sleeve shaped cartridge, the stem is prevented from collapsing which would result in at least reducing fluid communication through the stem. In a position of use of the cartridge, the second end portion is closer to a vessel than the first end portion of the bladder.

[0017] The second end portion of the cartridge may be provided with a breakable sealing for temporarily keeping the inflatable bladder within the cartridge. In one embodiment, the first end portion of the cartridge is provided with a releasable lid for preventing the bladder from being inadvertently released from the cartridge during transport and handling prior to use.

[0018] In a second aspect of the invention, there is provided a system for handling an inflatable bladder according to the first aspect of the invention in connection with purging of a vessel, the system comprising:

[0019] - a compartment configured for operatively connecting the inflatable bladder to an inlet of a vessel to be purged, the compartment comprising: at least one first portion and a second portion, the second portion configured for fluid tight connection to an inlet of a vessel to be purged, the at least one first portion of the compartment being movable with respect to the second portion of the compartment between an open position for allowing access to an inside of the compartment, and a closed position wherein the at least one first portion is sealingly connected to the second portion; a valve for controlling fluid communication between the compartment and a vessel to be purged, wherein the valve in an open position is configured for allowing passage of the bladder; a retrieval mechanism for receiving the second end portion of the at least one line of the bladder; and

[0020] - a conduit for communicating a fluid into and out of the compartment, wherein the conduit is provided with a conduit valve for controlling fluid communication into and out of the compartment.

[0021] A purpose of the at least one first portion of the compartment being movable with respect to the second end portion of the compartment is to allow access to the internal of the compartment when connecting the bladder to the system and removing the bladder from the compartment after completion of a purging process.

[0022] A purpose of the retrieval mechanism is to pull the at least one line and thereby the bladder out of a vessel after completion of a purging process.

[0023] The second end portion of the compartment may be movable on a guide. A guide is ad- vantageous over for example an external retrieval mechanism in that it may facilitate exact position of the first portion of the compartment when moved towards the second portion to provide a sealed connection therebetween.

[0024] The system may comprise the bladder according to the first aspect of the invention, and wherein a portion of the stem of the bladder is operatively connected to the second end portion of the compartment. However, in an embodiment wherein the bladder is arranged in a cartridge wherein a perimeter portion of the stem of the bladder is secured to a perimeter portion of the cartridge, the cartridge is operatively connected to the second end portion of the cartridge. In such an embodiment the stem of the bladder is indirectly secured to the second end portion of the cartridge.

[0025] In one embodiment, the system forms part of a vessel to be purged. This means that the system is secured to the vessel when the vessel is moved from one location to another location. An advantage of this embodiment is that a purging process can commence once the vessel has arrived at a desired destination, or once the bladder has been arranged within the compartment at the desired destination. In an alternative embodiment, the system forms part of a stationary facility and is configured for temporary connection to a vessel during a purging process. An advantage of this is that the system is not connected to the vessel while being moved from one location to another location. A system forming part of a stationary facility is of particular interest for a vessel being moved on road or rail but may also be relevant for a vessel being transported on sea.

[0026] The system may comprise at least two compartments wherein each compartment comprising a bladder, wherein each compartment being connected to a respective inlet of a vessel.

[0027] The system may comprise at least two vessels arranged in series, wherein each vessel comprises at least one compartment comprising a bladder. In such as system, the vessels are preferably configured for controllable fluid communication therebetween, and the compartments are preferably configured for fluid communication therebetween.

[0028] In a third aspect of the invention, there is provided a method for bringing an inflatable bladder into and out of a vessel, wherein the method comprising: a) providing an inflatable bladder according to the first aspect of the invention; b) securing a portion of the at least one line extending beyond the inlet of the stem of the bladder to an object outside the vessel; c) bringing a portion of the bladder into the vessel via an inlet of the vessel and performing intended activity by the bladder; d) activating a pulling force to the at least one line and bringing the first end portion of the at least one line secured to the inside of the bladder out of the vessel; and e) pulling the remaining portion of the bladder out of the vessel.

[0029] The remaining portion of the bladder is thus pulled out of the vessel via the stem.

[0030] Step a) of the method may further comprise arranging the bladder within a compartment configured for being sealingly connected to the inlet of the vessel.

[0031] Step b) may further comprise securing the at least one second end portion of the line to a retrieval mechanism. In an embodiment wherein the bladder is arranged within a compartment configured for being sealingly connected to the aperture of the vessel, the retrieval mechanism is preferably arranged within the compartment.

[0032] Step c) may comprise inflating the bladder by introducing a pressurized gas into a spaced defined by the first portion and the second portion of the compartment to urge a portion of the bladder from the compartment into the vessel to displace at least a portion of a fluid being between an internal surface of the vessel and the outside of the bladder. By introducing a pressurized gas into a spaced defined by the first portion and the second portion of the compartment, no gas supplying lines is in direct contact with the stem of the bladder. A risk of damaging any part of the bladder is thereby substantially eliminated.

[0033] In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

[0034] Fig. 1 shows a side elevation of a vessel provided with an external compartment arranged on top of the vessel and in connection with an inlet of the vessel; Fig. 2 shows the vessel in fig. 1, wherein a bladder and a retrieval mechanism are housed within the compartment;

[0035] Fig. 3 shows the compartment in fig, 2 wherein a top portion of the compartment has been released from a bottom portion and raised to an elevated position;

[0036] Fig. 4 shows the vessel in fig. 2, wherein a portion of the bladder has been released from the compartment, and wherein the bladder is partially inflated within the vessel, and wherein a line extends from a portion of the bladder and is operatively connected to a retrieval device;

[0037] Fig. 5 shows the vessel in fig. 4, wherein a bladder has been fully inflated, and wherein a first end portion of the line comprises several lines;

[0038] Fig. 6 shows a vessel wherein a fully inflated bladder comprises several lines;

[0039] Fig. 7 shows the vessel in fig. 4 wherein the bladder is partially deflated and in the process of being withdrawn from the vessel;

[0040] Figs. 8a-8b show two embodiments of a cartridge housing a bladder in packed position;

[0041] Fig. 9a shows view A-A of the cartridge in fig. 8a, wherein the cartridge comprises a protrusion for facilitating correct orientation of the bladder within the compartment;

[0042] Fig. 9b shows cartridge in fig. 9a seen from view B-B in fig. 8a;

[0043] Fig. 9c shows view A-A of the cartridge in fig. 8b, wherein the cartridge comprises a protrusion for facilitating correct orientation of the bladder within the compartment;

[0044] Fig. 9d shows the cartridge in fig. 9c seen from view B-B in fig. 8b;

[0045] Figs. 10a-10d show examples of the cartridge comprising a bladder, and various methods by which the cartridge could be supported inside the compartment to ensure that the filling stem is kept open and ensure gas tightness between the compartment and the vessel; Fig. 11a shows an example of how the cartridge is securing a bladder stem support to the inside of the compartment, and wherein a second end portion of a line is operatively connected to a retrieval mechanism;

[0046] Fig, 11 b illustrates the bladder in fig. 11a after a bottom sealing of the cartridge has been ruptured and a portion of the bladder has been released from the cartridge;

[0047] Fig. 12 shows and example a compartment arranged in a co-linear fashion with a vessel to reduce a headroom above the vessel;

[0048] Fig. 13 shows the compartment in figure 12 after the first portion of the compartment has been moved along its axis to give access to the bladder arranged in a cartridge;

[0049] Fig. 14 shows a vessel comprising internal structures, wherein the vessel comprises a plurality of compartments and bladders that are in the process of being inflated between the internal structures to occupy substantially the entire volume within the vessel; and

[0050] Figs. 15a-15e show in smaller scale a process of inserting and retrieval of a bladder into and out of a vessel; and

[0051] Figs. 16A-16C show steps of sequential loading of multiple vessels arranged in series.

[0052] Any positional indications refer to the position shown in the figures.

[0053] In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons, some elements may in some of the figures be with-out reference numerals.

[0054] A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

[0055] In the figures, reference number 1 denotes a vessel for being purged by means of an inflatable bladder 3 according to the first aspect of the invention. The inflatable bladder 3 has an inside and an outside, and an opening comprising a stem 31 or neck for communi- eating a fluid into and out of the bladder. A body of the bladder 3 has similarities with the bladder disclosed in EP2914893B1. However, the bladder 3 according to the invention comprises at least one line 10 having at least one first end portion 101 and a second end portion 102opposite the at least one first end portion 101 as illustrated in figures 4 to 7. The at least one first end portion 101 of the line 10 is secured to an inside of the inflatable bladder 3. The line 10 has a length allowing the second end portion 102 of the line to extend beyond the stem 31 of the inflatable bladder 3 when fully inflated.

[0056] In the embodiments shown in figures 5 and 6, the line 10 (or lines) is secured to the inside of the bladder 3 at a portion that in a position of use within a vessel 1 is opposite an inlet 9 of the vessel 1.

[0057] In fig. 4, the first end portion 101 of the line 10 is secured to the inside of the bladder 3 in a single point of contact, while in fig. 5 the line 10 is secured to the inside of the bladder in a plurality of contact points (three shown).

[0058] Turning now to figures 1 and 2 illustrating a side elevation of a vessel 1 provided with a system comprising an external compartment 5, 5'arranged on top of the vessel 1 and in connection with an opening or inlet 9 in the vessel 3. The compartment comprises a first portion 5 and a second portion 5'. The second portion 5' is secured to the inlet 9 of the vessel 1 in a fluid tight manner. The vessel 1 is further provided with common tubing 4, 4' for communicating a fluid into and out of the vessel 1. The tubing 4' (illustrated with dotted lines in some, but not all, of the figures) extends along an inside portion of the vessel 1.

[0059] The first portion 5 of the compartment is movable with respect to the second portion 5' of the compartment between an open position for allowing access to an inside of the compartment (as illustrated in fig. 3), and a closed position wherein the at least one first portion 5 is sea lingly connected to the second portion 5' (as illustrated in figures 1 and 2). A sealing 5” is illustrated by a dotted line in figures 1 and 2.

[0060] A valve 7 forming part of the system is arranged in connecting with the inlet 9 of the vessel 1. The valve 7 is illustrated in a closed position in fig. 1, and in an open position in fig. 2.

[0061] The system further comprises a retrieval mechanism 51 comprising a spool, and a conduit 57', 57 for communicating a fluid into and out of the compartment 5, 5', respectively, as indicated by arrows. Each conduit 57, 57' is provided with a valve (not shown) for controlling fluid communication through the conduits 57, 57'.

[0062] In fig. 2, a bladder 3 is arranged within the compartment 5, 5' and supported by the second portion 5. A second end portion 102 of the line 10 of the bladder 3 is operatively connected to the retrieval mechanism 51.

[0063] Fig. 3 illustrates the system and bladder in fig. 2, wherein the first portion 5 of the compartment has been disconnected from the second portion 5' of the compartment to make access to facilitate installing the bladder 3 within the second portion 5'. The first portion 5 of the compartment may be lifted by an external hosting apparatus, or it may be movable on a guide (not shown) known per se.

[0064] To facilitate handling of the bladder 3 and protect the bladder prior to being arranging within the compartment 5, 5' as illustrated in fig. 2 and 3, the bladder is in figures 8a-llb. arranged in a cartridge 11 having a first end portion and a second end portion opposite the first end portion. The cartridge 11 may have any suitable form, for example a square form as illustrated in figures 9a and 9b, a circular form as illustrated in figures 9c and 9d, a not shown non-circular form, or polygonal form.

[0065] The cartridge 11 comprises in the embodiment shown, an orientation means 11', here in the form of a protrusion, for mating with a complementary orientation means (not shown) arranged in the second portion 5' of the compartment.

[0066] Independent of the form of the cartridge 11, the second end portion of the cartridge 11 is provided with a breakable sealing 3' for temporarily keeping the inflatable bladder 3 within the cartridge 11. The breakable sealing 3' is configured to break when being subject to a force above a predetermined level. The force may be provided by means of a fluid pressure applied in the compartment 5, 5' and exerts a pressure towards the bladder 3 when being within the cartridge 11. In connection with testing of prototypes of the cartridge 11, the breakable sealing 3' was made from a perforated polyethylene sheet. The bladder 3 may also be made from a polyethylene sheet or any other suitable material.

[0067] Fig. 11a shows details of the bladder 3 in a packed condition inside the cartridge 11 where the bottom breakable seal 3' is intact and the line 10 is connected to the retrieval mechanism 51. Fig. lib illustrates a situation where the bladder 3 is deployed into the not shown vessel 1 below. The stem 31 of the bladder 3 protrudes into the cartridge 11, which is supported inside a suitable mating surface in the not shown compartment 5. The line 10 is shown hanging between the retrieval mechanism 51 and the bottom of the bladder 3. From the bottom of cartridge 11 hangs a ruptured section of the breakable sealing 3'.

[0068] Figure 12 shows a variant of the compartment 5, 5' where it is located colinearly with that of the vessel 1 it serves as opposed to being fitted perpendicular (or close to perpendicular) on figures 1-11. The purpose of this arrangement is to minimise the required headroom for the certain application such as rail and road haulage along with certain inland waterway barges, where the tunnels and bridges may represent a limitation on headroom.

[0069] As for the vertical arrangement shown in figures 1-llb, the compartment comprises as disclosed above at least two portions 5, 5' (two shown) with a sealing 5”, wherein the first portion 5 may be moved along a not shown guide to secure unobstructed access to the cartridge 11 containing the bladder 3 by also making guide roller 51' and retrieval mechanism 51 movable along not shown guides.

[0070] Fig. 13 shows the colinearly located compartment in fig. 12, wherein the first portion 5 is slid along a not shown mechanism to an open position. In a similar fashion, the retrieval mechanism 51 and the guide roller 51' may be moved in a similar manner as indicated by the arrows along a not shown mechanisms of known type. Once the first portion 5 of the compartment is slid open and the retrieval mechanism 51 and guide roller 51' are slid aside, the cartridgell may be replaced as necessary. Figure 14 shows a plurality of bladders as will be required in a vessel where there are internal structures 12 such as slosh bulkheads etc. or other compelling reasons why a plurality of bladders is a better solution than single bladder.

[0071] Fig. 15a illustrates an initial state of a single vessel containing a heel gas is illustrated as in figure 2 where the valve 7, for example a gate valve, separates the compartment 5, 5' from the vessel 1 with the bladder 3 packed in its cartridge 11 and connected by the line 10 to the retrieval mechanism 51.

[0072] Fig. 15b, illustrates a condition (as shown in fig. 4) where the bladder 3 has been released into vessel 1 and is being inflated with a first gas (e.g. nitrogen) such that the heel gas in the vessel 1 is gradually being displaced as from the vessel 1.

[0073] Fig. 15c illustrates a condition (as shown in fig 5) where the bladder 3 has been fully inflated such that all the heel gas has been displaced from the vessel 1.

[0074] Fig. 15d illustrates a condition (as shown in fig 8) where the bladder 3 is being deflated and extracted through its filling stem 31 and through the cartridge 11 onto the retrieval mechanism 51. This is done in conjunction with a new gas being introduced into the space between the bladder 3 exterior and vessel 1 interior.

[0075] Fig. 15e illustrates a condition where the bladder 3 has been fully extracted and wound onto the retrieval mechanism 51 in the form of a winch.

[0076] Turning now to figures 16A to 16C which illustrate four vessels arranged in series. Each vessel comprises a compartment comprising a bladder. The vessels are arranged in series and interconnected by means of conduits provided with valves. The compartments are also interconnected by means of a conduit so that fluid to allow fluid communication therebetween. In such an embodiment, the present invention may be used to expedite gas freeing / grade change with much less use of a first gas (e.g. nitrogen) and with neither loss of- / nor release of heel gas to the environment. A person skilled in the art will appreciate that the piping system as illustrated may be arranged in a more efficient manner dependent on the application and whether the vessels are co-located in a structure of a ship or tank- or vessel farm or simply as series of separate vessels such as a train of rail- cars. The illustrated piping arrangement is thus one way of organising the sequential plug ventilation of a plurality of vessels as shown.

[0077] Valves being in a closed condition are shown filled, while valves being in an open condition are shown un-filled.

[0078] Fluid flow between the vessels and out of and into the respective bladders of the vessels, is illustrated by means of arrows.

[0079] Fig. 16A illustrates an operational condition of an initial state SI where all the vessels are empty of liquid gas and only contains the heel from last liquid gas cargo and all valves are closed.

[0080] Fig. 16B shows operational conditions of state S2 throughout to state S6, where:

[0081] Vessel #1 is first from left, #2 is second, #3 is third and #4 is fourth vessel from left.

[0082] Similarly, compartment # 1 is first from left, #2 is second, #3 is third and #4 is fourth compartment from left.

[0083] For simplicity, the first gas (e.g. nitrogen) is only referred to as "nitrogen", the bladder 3 is only referred to as "bladder". Compartment 5, 5' is "compartment" and vessel 1 is simply referred to as "vessel".

[0084] The term "vessel communication" is to be construed as the conduit between the vessels containing the heel as opposed to "nitrogen communication", which describes the conduit between the bladders via the compartments.

[0085] The second state S2 is where nitrogen is released into the compartment such that the bladder inflates inside vessel #1. All vessels #2, #3 and #4 are in communication with each other such that the displaced heel is taken care of in a safe manner at the exit from vessel #4. The nitrogen communication between compartments #1 and #2 is closed.

[0086] The third state S3 is where the bladder inside vessel #1 is completely full of nitrogen. The vessel communication between vessel #1 and #2 is now closed, the vessel communication between vessels #2, #3, and #4 remain open to receipt at the exit from vessel #4. The fourth state S4 follows immediately the third state S3, where compartment #1 is set in communication with compartment #2. The inlet valve to vessel #1 is open such that a new heel gas may flow into vessel #1 to displace the nitrogen from the deflating bladder inside vessel #1. The displaced nitrogen from the bladder in vessel #1 is lead via compartment #1 to compartment #2 such that bladder inside vessel #2 inflates and displaces the heel gas from vessel #2 via vessel #3 to receipt at the exit from vessel #4.

[0087] The fifth state S5 is where the bladder from vessel #1 is completely deflated and retrieved from vessel #1. The closable sealing means have been closed between vessel #1 and compartment #1 as is the nitrogen communication between vessels #1 and #2. The vessels #2, #3, and #4 are in communication with each other such that the heel gas can exit at vessel #4.

[0088] The sixth state S6 follows immediately from the fifth state S5, where compartment #2 is set in communication with compartment #3. The inlet valves to vessels #1 and #2 are open such that a new heel gas may flow into vessel #2 via vessel #1 to displace the nitrogen from the deflating bladder inside vessel #2. The displaced nitrogen from the bladder in vessel #2 is lead via compartment #2 to compartment #3 such that bladder inside vessel #3 inflates and displaces the heel gas from vessel #3 via vessel #4 to receipt at the exit from vessel #4.

[0089] Figure 16C shows operational conditions of a seventh state S7 throughout to an eleventh state Sil, where:

[0090] Vessel #1 is first from left, #2 is second, #3 is third and #4 is fourth vessel from left.

[0091] Similarly, compartment # 1 is first from left, #2 is second, #3 is third and #4 is fourth compartment from left.

[0092] For simplicity, the first gas (e.g. nitrogen) is only referred to as "nitrogen", the bladder 3 is only referred to as "bladder". Compartment 5,5' is "compartment" and vessel 1 is simply referred to as "vessel".

[0093] The term "vessel communication" is to be construed as the conduit between the vessels containing the heel as opposed to "nitrogen communication", which describes the conduit between the bladders via the compartments.

[0094] The seventh state S7 is where the bladder from vessel #2 is completely deflated and retrieved from vessel #2. The closable sealing means have been closed between vessel #2 and compartment #2 as is the nitrogen communication between vessels #2 and #3. Communication between vessels #1 and #2 is open and closed between vessels #2 and #3. The vessels #3 and #4 are in communication with each other such that the heel gas can exit at vessel #4.

[0095] The eight state S8 follows immediately from the seventh state S7, where compartment #3 is set in communication with compartment #4. The inlet valves to vessels #1, #2 and #3 are open such that a new heel gas may flow into vessel #3 via vessels #1 and #2 to displace the nitrogen from the deflating bladder inside vessel #3. The displaced nitrogen from the bladder in vessel #3 is lead via compartment #3 to compartment #4 such that bladder inside vessel #4 inflates and displaces the heel gas from vessel #4 to receipt at the exit from vessel #4.

[0096] The ninth state S9 is where the bladder from vessel #3 is completely deflated and retrieved from vessel #3. The closable sealing means have been closed between vessel #3 and compartment #3 as is the nitrogen communication between vessels #3 and #4. Communication between vessels #1, #2 and #3 is open and closed between vessels #3 and #4. The vessel #4 is open such that the last heel gas can exit at vessel #4.

[0097] The tenth state S10 follows immediately from state S9, where compartment #4 is open to atmosphere to let out the nitrogen. The inlet valves to vessels #1, #2, #3 and 4 are open such that a new heel gas may flow into vessel #4 via vessels #1, #2 and #3 to displace the nitrogen from the deflating bladder inside vessel #4. The valve leading from vessel 4 is now closed.

[0098] The eleventh state Sil follows completion of the exhaustion and retrieval of bladder from vessel #4 and all valves are now closed, and the vessels are ready to receive a new liquid cargo corresponding to the new heel in the vessels. From the disclosure herein, it should be clear that the present invention is related to the installation and retrieval of the bladder prior to and after its use, respectively, where good access is required to ensure correct installation for its subsequent automatic handling.

[0099] In an embodiment of the present invention it is illustrated how a line is connected to the interior of the bladder in the opposite end of the filling stem. In one embodiment the line extends from its connection point (or multiple such points) inside the bladder across the bladder and through the filling stem and beyond such that this line can be secured to a winch or similar spooling device to act as a bladder retrieval mechanism located outside the bladder and inside the compartment, where the entire bladder handling mechanism may be located.

[0100] Once the bladder(s) is(are) filled with the first gas (e.g. nitrogen) and the second gas is completely displaced from the vessel, a third gas may be introduced in the compartment leading to the displacement of the first gas from inside the bladder and through the filling stem and further via the compartment to a safe release point. At this stage, the retrieval mechanism to which the line is secured starts pulling the line carefully such that the bottom of the bladder (i.e. the opposite end of the filling stem) starts moving in the direction of the filling stem. In this manner, the bladder will eventually be extracted from the vessel through its own filing stem and onto the retrieval mechanism.

[0101] Whilst this procedure is not guaranteed to avoid all occurrences of successive col- lapse / open in places along the neck, it maintains the bladder material relatively taut such that no blockage is caused by crumpled parts of bladder blocking the exit (stem). In this manner blockage free extraction of the bladder is secured, and no damage will be sustained to the bladder during its extraction from the vessel.

[0102] In an embodiment of the present invention the retrieval mechanism is located inside a compartment, which may be selectively set in communication with the main vessel. This compartment comprises at least two parts, which may be separated in a controlled fashion such that free and unobstructed access to the bladder and its handling equipment is secured. Of these at least two parts forming the compartment, at least one part is opera- tionally secured to the main vessel via a closable sealing means.

[0103] According to the present invention, the bladder may typically be folded and packed inside a cartridge attached to the filling stem of the bladder. The cartridge inside which the bladder is packed may be of a more rigid construction than the bladder itself such that it, aside from functioning as a "mouthpiece" to ensure open access for gas flow into the bladder interior and protection of the bladder during shipment and handling, may be used to support and secure the bladder filling neck to the inside of the compartment from where the bladder is stored prior to its use.

[0104] The way the bladders is packed inside the cartridge has proved to be operationally advantageous with respect to how the bladder develops inside the vessel as it is filled with a gas such as nitrogen. The bladder will typically be made to fit inside the vessel such that its shape reflects the interior geometry of the vessel and where in the vessel the bladder is inserted (which may be the case for large ships (or large tanks) using multiple bladders per gas cargo tank). For this reason, the cartridge in which the bladder may be packed as it is delivered from the manufacturer will be marked according to what installation it belongs, what vessel, its individual installation location on the vessel itself and orientation of the cartridge inside the compartment.

[0105] To ensure correct orientation the cartridge may be fitted with some sort of "timing mark" or orientation means that may be in the form of a notch or protrusion on one of the supporting sides of the cartridge, which are meant to mate within a reciprocal shape to ensure correct orientation of the cartridge to its support receptacle in the lower end of the compartment. Although the cartridge may also be shaped to be asymmetric about its vertical axis to secure correct orientation, this may have an adverse effect on the bladder packaging efficiency inside the cartridge.

[0106] According to the present invention, the cartridge in which the bladder is packed may be fitted with a supporting surface to fit inside a mating surface on the compartment to secure a gas tight connection such that gas supplied into the bladder via the compartment does not slip past the filling stem and into the vessel into which the bladder is inflated. The supporting surface on the cartridge may be arranged in the form of a flange (or similar discontinuity) at the top such that the cartridge rests into a space below. Alternatively, the lower end of the cartridge (the one closest to the vessel) may be supported by a mating surface at the bottom of the cartridge such that the cartridge protrudes into a space above the mating surface in the compartment. Finally, the cartridge may be supported by a flange (or similar discontinuity) along any section of the cartridge's extension.

[0107] According to the present invention, the cartridge in which the bladder may be packed, may be provided with a breakable seal, which is designed to rupture upon a certain pressure differential between the vessel and the compartment. One embodiment of such breakable seal may be a polymer film, fixed across the entire lower part of the cartridge and fitted with perforations along the preferred lines of failure. The perforated lines may be in any arrangement across the lower cross section of the cartridge (below the bladder when it is in the packed form), which secures a free area through which the bladder may drop and subsequently develop.

[0108] In an embodiment, the cartridge will be supplied to the site of deployment such that it has a sealed, perforated bottom and a disposable top, which is removed upon insertion into the cartridge receptacle in the compartment. Once the disposable top is removed, a line (or multiple lines) for attachment to the bladder retrieval mechanism (typically a winch) is revealed. The bladder is principally ready for deployment once it has correctly inserted in its reciprocal support inside the compartment, the line(s) secured to the retrieval mechanism and the compartment is secured closed.

[0109] In an embodiment of the present invention where the bladder exceeds a certain weight (for example more than 10-20 kg), the retrieval mechanism may be used as handling mechanism of the bladder, which is packed in a cartridge, during its installation inside the compartment. In its simplest form, the handling system may be used to both lift and swing the cartridge from a location outside the compartment (e.g. a trolley) and lower it into the compartment at the correct location and orientation.

[0110] For smaller applications, where the packed bladder in its cartridge constitutes a weight less than a certain value (e.g. 10 kg or less), the bladder handling becomes much simpler. Such small applications lend themselves to different configurations such as horizontal arrangement where the cartridge is still placed overhead the sealable closing means but offset the handling mechanism such that the compartment may be arranged in with its axis parallel to the vessel served. This is useful for small scale transport applications where the headroom may be a limiting factor such as is the case for rail and road transport (bridge and tunnel restrictions) along with that of inland waterways, where low bridges may pose a similar restriction.

[0111] Disclosed herein is a method for handling and retrieval of the bladder into- and out of the compartment when this is opened for bladder replacement. Handling and retrieval of the bladder may be done by lifting the bladder from an area outside the bladder and into the compartment in way of the closable sealing means. Such lifting could be either by lifting and luffing in combination with slewing.

[0112] Disclosed herein is a method of releasing the bladder from its stored position into the vessel in which it shall be used comprises the following: Opening of closable sealing means between compartment and vessel served by bladder. Supply a first gas (e.g. nitrogen) into the compartment such that the load exerted upon the bladder from the fluid pressure in the compartment makes any perforated sheet of the cartridge open and thus releasing the packed bladder into the compartment where it will be inflated.

[0113] Disclosed herein is a method of extracting a bladder through its own stem by retrieving a line (or similar flexible connection) that may be connected to the bottom of the bladder such that the bladder is extracted from the vessel through its own filing stem or nozzle. The method of extraction is done in a careful manner to ensure that there always is sufficient replacement gas in the vessel to ensure that the pressure inside the vessel is always approximately the same as that of the bladders to ensure a steady flow of first gas from the bladder via the compartment to next use or atmosphere. This is achieved through the use known technology for monitoring fluid pressures, -temperatures, -volumes and extraction rate.

[0114] In one embodiment of the present invention, a method of reducing the overall first gas required to displace a larger aggregate volume in a plurality of vessels, is disclosed. This is attained through sequential gas displacement and -replacement of a series of vessels with an aggregate volume made up by a plurality of vessels such as may be the case on a train set, ship, or lorry with trailer.

[0115] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

C l a i m s1. An inflatable bladder (3) for facilitating purging of a vessel (1), the inflatable bladder (3) having an inside and outside, and an opening comprising a stem (31) for communicating a fluid into and out of the bladder (3), c h a r a c t e r i s e d i n that the inflatable bladder (3) comprises at least one line (10) having at least one first end portion (101) and a second end portion (102) opposite the at least one first end portion (101), wherein the at least one first end portion (101) of the line (10) is secured to the inside of the inflatable bladder (3) at a location not forming part of the stem (31), and wherein the line has a length allowing the second end portion (102) of the line (10) to extend beyond an inlet of the stem (31) of the inflatable bladder (3) when fully inflated.

2. The bladder (3) according to claim 1, wherein the at least one line (10) is secured to the inside of the bladder at a portion being opposite the stem (31).

3. The bladder (3) according to claim 1 or 2, wherein the bladder (3) is arranged in a cartridge (11) having a first end portion and a second end portion opposite the first end portion, wherein a perimeter portion of the stem (31) of the bladder (3) is secured to a perimeter portion of the cartridge.

4. The bladder (3) according to claim 3, wherein the second end portion of the cartridge (11) is provided with a breakable sealing (3') for temporarily keeping the inflatable bladder (3) within the cartridge (11).

5. A system for handling the inflatable bladder (3) according to any one of the preceding claims and an apparatus for handling an inflatable bladder in connection with purging of a vessel (1), the system comprising:- a compartment (5, 5') configured for operatively connecting the inflatable bladder (3) to an inlet (9) of a vessel (1) to be purged, the compartment comprising: at least one first portion (5) and a second portion (5'), the second portion configured for fluid tight connection to an inlet (9) of a vessel (1) to bepurged, the at least one first portion (5) of the compartment being movable with respect to the second portion (5') of the compartment between an open position for allowing access to an inside of the compartment, and a closed position wherein the at least one first portion (5) is sea lingly connected to the second portion (5'); a valve (7) for controlling fluid communication between the compartment (5, 5') and a vessel (1) to be purged, wherein the valve (7) in an open position is configured for allowing passage of the bladder (3); a retrieval mechanism (51) for connecting to the second end portion (102) of the at least one line (10) of the bladder (3); and a conduit (57, 57') for communicating a fluid into and out of the compartment, wherein the conduit is provided with a conduit valve for controlling fluid communication into and out of the compartment (5, 5') .

6. The system according to claim 5, wherein the second portion (5) of the compartment is movable on a guide.

7. The system according to claims 5 or 6, wherein the system comprises the inflatable bladder according to any one of claims 1 to 4, and wherein a portion of the stem (31) of the bladder (3) is operatively connected to the second portion (5') of the compartment.

8. The system according to claim 7, wherein the system forms part of a vessel (1) to be purged.

9. The system according to claim 7, wherein the system forms part of a stationary facility, and is configured for temporary connection to a vessel (1) to be purged.

10. The system according to any one of claims 5 to 9, wherein the system (1) comprises at least two compartments (5, 5') each compartment comprising a bladder (3), wherein each compartment being connected to a respective inlet (9) of a vessel (1).

11. The system according to any one of claims 5 to 10, wherein the system comprises at least two vessels arranged in series, wherein each vessel (1) comprises at least one compartment (5, 5') comprising a bladder (3).

12. A method for bringing an inflatable bladder (3) into and out of a vessel (1), c h a r a c t e r i s e d i n that the method comprising: a) providing an inflatable bladder (3) according to any one of claims 1-4; b) securing a portion of the at least one line (10) extending beyond the inlet of the stem (31) of the bladder (3) to an object outside the vessel (1); c) bringing a portion of the bladder (3) into the vessel via an inlet (9) of the vessel and performing intended activity by the bladder (3); d) activating a pulling force to the at least one line (10) and bringing the first end portion (101) of the at least one line (10) secured to the inside of the bladder (3) out of the vessel (1); and e) pulling the remaining portion of the bladder (3) out of the vessel (1).

13. The method according to claim 12, wherein step a) comprises arranging the bladder (3) within a compartment (5, 5') configured for being sealingly connected to the inlet (9) of the vessel (1).

14. The method according to claim 12 or 13, wherein step b) comprises securing the at least one second end portion (102) of the line (10) to a retrieval mechanism (51).

15. The method according to claim 13, wherein step c) comprises inflating the bladder (3) by introducing a pressurized gas into a space defined by the first portion (5) and the second portion (5') of the compartment to urge a portion of the bladder from the compartment into the vessel (1) to displace at least a portion of a fluid being between an internal surface of the vessel (1) and the outside of the bladder (3).

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