Patent Application
20180299071
The invention relates to the field of mechanical constructions used for storing and/or transporting fluids, and notably to constructions containing pipes requiring to be secured to supports, in particular in the case in which the pipe is arranged in the interior of a reservoir or of a tank and more specifically when said reservoir or said tank is likely to be subjected to wide variations in temperature in the course of its use.
In membrane tank technology, the internal surfaces of a supporting structure such as the internal hull of a ship having a double hull or a shore-based storage facility are covered with a multi-layer structure containing two fine sealing membranes alternated with two layers of thermal insulation, which serve both to limit the flow of heat through the tank wall and to support the fluid-tight membranes structurally.
In order to maximize the operating performance of a suchlike tank, it is desirable to optimize the useful storage volume that it is possible to load in the tank and to unload from the tank. However, the use of an unloading pump which sucks the liquid towards the top of the tank makes it necessary to maintain a certain liquid level in the bottom of the tank, as the suction element of the pump will otherwise enter into communication with the gaseous phase, which will deactivate and/or degrade the pump. Taking account of the specific circumstances which may arise during the operation of the tank, for example under the effect of sloshing of the load caused by wave action or by an earthquake, the necessary liquid level can be minimized only with difficulty.
Publication JP2001108198 envisages the provision of a localized depression in a bottom wall of a shore-based tank exhibiting reduced dimensions with respect to said bottom tank wall. A suchlike depression constitutes a buffer reservoir known as a sump, into which the pumping pipe discharges. More specifically, the pumping pipe is secured to a lateral wall of the tank such that its bottom end is inserted into the sump. The dimensions of the sump and the insertion of the end of the pumping pipe into the sump thus enable the quantity of liquid necessary for the effective functioning of the pump to be limited and optimizes the operating performance of the tank.
However, the lower end of the pumping pipe is left loose in the sump. As a result, this end of the pumping pipe is able to behave like a pendulum in the case of a heavy swell for a tank installed in a ship or else an earthquake in the case of a tank housed in a shore-based facility. Furthermore, this free end of the pumping pipe may exhibit undesirable and repetitive movements as a result of oscillations caused by the vibrations of the pump: suchlike behavior by the free end of the pumping pipe may cause premature wear of said pumping pipe and/or of the pump.
Similar problems are prone to arise in any pipe that is likely to be subjected to forces, notably vibratory loads, in the course of its utilization.
An underlying idea of the invention is to provide a device for securing a pipe in a housing, for example, such as a sump situated in a bottom wall of a fluid-tight and thermally insulating tank.
According to one embodiment, the invention provides a securing device for securing a pipe in a housing, the device containing:
Thanks to these characterizing features, it is possible to secure the free end of a pumping pipe in a tank housing. Furthermore, a suchlike securing device does not require the modification of the housing or a fixing passing through a wall of said housing. In addition, a suchlike securing device allows a pipe to be secured in housings exhibiting different dimensions and/or shapes. Finally, a suchlike device permits the elastic cushioning of forces between the end of the pumping pipe and the housing.
According to some embodiments, a suchlike tank may contain one or a plurality of the following characterizing features.
According to one embodiment, the securing arms extend perpendicularly to the generatrix direction of the collar.
According to one embodiment, the guideway of said at least one of the securing arms contains:
According to one embodiment, the elastic member of said at least one of the securing arms contains a plurality of elastic washers engaged on the guide rod and supported, on the one hand, on an end surface of the guide tube and, on the other hand, on an abutment surface that said other of the distal arm portion and the proximal arm portion contains.
According to one embodiment, the elastic member of said at least one of the securing arms contains a first elastic element and a second elastic element mounted in series between the distal portion and the proximal portion of said securing arm, the first elastic element exhibiting a first rigidity and the second elastic element exhibiting a second rigidity that is higher than the first rigidity. Thanks to these characterizing features, the securing arm is able to absorb different forces, the one of the elastic elements thus enabling the absorption of forces of low intensity, for example forces associated with a vibration generated by the pump, whereas the other elastic element enables the absorption of larger forces, for example associated with an earthquake or with the action of the waves on a ship in which the tank is installed.
According to one embodiment, the cylindrical collar is made from metal, the securing device containing in addition a sliding block made from a polymer material mounted on an internal face of the cylindrical collar and intended to bear against the pipe. Thanks to these characterizing features, the collar is slidably mounted on the end of the pumping pipe, and thus, in the event of a contraction of the pumping pipe, for example associated with the introduction of LG into the tank, and that of LNG, the collar remains mounted on the pumping pipe. This sliding block may be produced and secured in different ways, for example by gluing or screwing.
According to one embodiment, the internal face of the cylindrical collar exhibits a groove developing in the radial thickness of the cylindrical collar perpendicularly to the generatrix of the cylindrical collar, the sliding block being accommodated in said groove and projecting radially towards the interior beyond the internal face of the cylindrical collar.
According to one embodiment, the groove develops in an annular manner about the generatrix direction of the cylindrical collar.
According to one embodiment, the sliding block is made from high-density polyethylene or from polytetrafluoroethylene.
The bearing pad may adopt numerous forms, for example with one or a plurality of abutment surfaces, for example plane or cylindrical. According to one embodiment, the bearing pad of at least one of the securing arms contains:
According to one embodiment, the first plane and the second plane are perpendicular.
According to one embodiment, the cylindrical collar contains a first half cylinder and a second half cylinder secured together and jointly forming the cylindrical collar.
According to one embodiment, the collar contains a shoulder projecting radially towards the exterior from an external face of the cylindrical collar, each securing arm being mounted on the shoulder.
According to one embodiment, the collar contains lugs welded on the shoulder, the arms being mounted directly on said lugs of the shoulder. According to one embodiment, the lugs are directly welded on the cylindrical collar, the securing arms being mounted on said lugs.
According to one embodiment, the invention also provides a fluid-tight and insulating tank containing a housing, for example at the level of a bottom wall of the tank, said housing being open towards the interior of the tank, and a loading pipe or unloading pipe arranged in the tank, one end of the pipe being accommodated in the housing, the pipe containing in addition an above-mentioned securing device, the cylindrical collar being mounted on the end of the pipe, the bearing pad of the securing arms of said securing device bearing against a peripheral lateral wall of the housing.
According to one embodiment, the tank contains in addition a pump housed in the pipe, said pump being capable of loading or unloading a fluid respectively into or from the housing.
According to one embodiment, the tank is configured for the transport and/or the storage of liquefied natural gas.
A suchlike tank may be part of a shore-based storage facility, for example for the storage of LNG, or may be installed in a floating, coastal or deep-water structure, notably an LNG carrier, a floating storage and regasification unit (FSRU), a floating production storage and offloading unit (FPSO) and the like.
According to one embodiment, a ship for the transport of a cold liquid product contains a double hull and an above-mentioned tank disposed in the double hull.
According to one embodiment, the invention also provides a method of loading or unloading a suchlike ship, in which a cold liquid product is conveyed through insulated pipes from or towards a floating or shore-based storage facility towards or from the tank of the ship.
According to one embodiment, the invention also provides a transfer system for a cold liquid product, the system containing an above-mentioned ship, insulated pipes arranged so as to connect the tank installed in the hull of the ship to a floating or shore-based storage facility and a pump for conveying a flow of cold liquid product through the insulated pipes from or towards the floating or shore-based storage facility towards or from the tank of the ship.
Certain aspects of the invention start from the idea of securing a pipe in a housing. Certain aspects of the invention start from the idea of providing a securing device capable of being installed in housings exhibiting different dimensions and/or shapes. Certain aspects of the invention start from the idea of providing a securing device enabling the transmission of forces between the pipe and the housing to be limited.
The invention will be better understood, and other aims, details, characterizing features and advantages thereof will be appreciated more clearly from a perusal of the following description of a plurality of particular embodiments of the invention, which are given solely for illustrative and non-restrictive purposes, with reference to the accompanying drawings.
In the following description, a description is given of a securing device capable of being mounted on a pipe housed in a sump structure in the bottom wall of a tank for the storage and/or the transport of LNG. The bottom wall designates a wall, preferably of generally planar form, situated in the bottom of the tank in relation to the earth's gravitational field. Furthermore, the overall geometry of the tank may be of different types. Polyhedral geometries are the most common. A cylindrical, spherical or other geometry is also possible. Furthermore, a suchlike tank may be installed in different structures such as a double hull of a ship, a shore-based facility or the like. Likewise, a suchlike securing device may be used in any wall and in any type of tank containing a housing into which a pipe discharges.
In the following description and in the claims, the terms “lower” and “upper” are used in order to define the relative position of one element with respect to another. The term “radial” is used in the description and the claims with respect to a longitudinal axis of the pumping pipe, one element developing radially towards the exterior developing radially as it moves away from the longitudinal axis of the pumping pipe, and one element developing radially towards the interior developing radially in the direction of the longitudinal axis of the pumping pipe.
A fluid-tight and insulating tank for the transport and the storage of LNG contains tank walls mounted on a supporting structure 1 and exhibiting a structure having multiple layers superimposed in a direction of thickness. Thus, each tank wall contains a secondary thermally insulating barrier 2, a secondary fluid-tight membrane 3 supported by the secondary thermally insulating barrier 2, a primary thermally insulating barrier 4 supported by the secondary fluid-tight membrane 3 and a primary fluid-tight membrane 5 supported by the primary thermally insulating barrier 4. This primary fluid-tight membrane 5 is intended to be in contact with a product contained in the tank, for example LNG.
The tank contains lateral walls that are connected in a fluid-tight manner to a bottom wall 6. The bottom wall 6 contains a sump structure locally interrupting the primary fluid-tight membrane 5. In a version that is not represented here, the membrane primary 5 covers the interior of the sump.
The sump structure contains a rigid container 7 arranged through the thickness of the bottom wall 6. The rigid container 7 contains a bottom wall 8 and lateral walls 9. In the example illustrated in
A suchlike sump thus forms a bottom point of the tank occupying a reduced surface at the bottom of the tank, which makes it possible to reduce the volume of liquid which is not able to be delivered during unloading of the tank. A pumping pipe 12 contains an end 13 housed in the rigid container 7. An unloading pump (not illustrated) is housed in the pump pipe 12. This pump is arranged in order to suck the product contained in the tank towards the top of the tank, the pump containing a suction element (not illustrated) situated at the level of the end 13 of the pumping pipe 12.
In the embodiment illustrated in
In order to ensure the stability of the end 13 of the pumping pipe 12 in the rigid container 7, a securing device 15 is installed on said end 13 of the pumping pipe 12.
The securing device 15 illustrated in
In the embodiment illustrated in
Prior to the installation of the securing device 15, the elastic members 18 are kept under pretension in order to retain the securing arms 17 in their retracted position. In this retracted position, each securing arm 17 exhibits a length smaller than the distance separating the pumping pipe from the zone of the lateral wall 9 against which it is to be supported. The securing device 15 thus exhibits dimensions that are smaller than the dimensions of the rigid container 7 and may thus be inserted easily into said rigid container 7. The prestressing of the elastic members 18 is in the order of 20 kN to 50 kN, for example. This prestressing may be produced advantageously in the factory by appropriate hydraulic means. The elastic members 18, once constrained, may be locked in this position by tie-rods which will be withdrawn during installation of the securing device 15 in the tank.
During installation of the securing device 15 on the pumping pipe 12, the collar 16 is secured in a first step to the lower end 13 of the pumping pipe 12, the securing arms 17 still being in the retracted position. The securing device is mounted on the pumping pipe 12 in such a way that each securing arm 17 develops radially from the collar 16 in the direction of an angle of the rigid container 7 formed by two adjacent lateral walls 9. Once the collar 16 has been mounted on the end 13 of the pumping pipe 12, the elastic members 18 are released in order to deploy the securing arms 17. The bearing pads 19 are then pushed back and are kept supported against the lateral walls 9 of the rigid container 7 by the elastic member 18. More specifically, with respect to
Suchlike telescopic securing arms 17 equipped with elastic members 18 permit the installation of the securing device 15 in rigid containers 7 exhibiting varied dimensions and shapes, the elastic members 18 being compressed to a greater or lesser extent, and the securing arms 17 being deployed to a greater or lesser extent according to the dimensions and shapes of the rigid container 7. Furthermore, the elastic members 18 enable forces to be absorbed between the end 13 of the pumping pipe 12 and the lateral walls 9 of the rigid container 7. In addition, suchlike securing with the help of securing arms 17 held in compression in the rigid container 7 does not require the lateral wall 9 of the rigid container 7 to be traversed in order to ensure the securing of the pumping pipe, thereby avoiding the generation of thermal bridges with the exterior of the tank. In addition, the elastic members 18 make it possible to compensate advantageously for the contraction of the material of the securing arms 17, thus permitting the secure attachment of the lower end of the pumping tank regardless of whether the tank is full of LNG at −162° C. or is empty and at ambient temperature.
Depending on the nature and the intensity of the forces to be absorbed, the securing of the pipe to the container may be envisaged solely with the help of the securing arms 17 or likewise with the help of supplementary supporting devices, as explained below with reference to
In the embodiment illustrated in
In a variant illustrated in
The securing device 15 is described below in more detail with respect to
The collar 16 is produced as two metallic half collars 23 in the form of circular, preferably symmetrical half cylinders. These two half collars 23 are mounted together about the end 13 of the pumping pipe 12 by any appropriate means. Thus, each half collar 23 may exhibit at one of its circumferential ends an edge 24 projecting radially towards the exterior. The edges 24 of the two half collars 23 are joined together, for example by bolting or by welding, in order to form and secure the collar 16 on the end 13 of the pumping pipe 12.
An anti-rotation system is proposed in order to lock the collar 16 in rotation on the end 13 of the pumping pipe 12. In the embodiment illustrated in
In a variant illustrated in
A ring 25 developing in a radial plane, that is to say perpendicular to a longitudinal axis of the pumping pipe 12, is secured by welding to the collar 16. This ring 25 is preferably installed on the collar 16 after said collar 16 has been secured to the end 13 of the pumping pipe 12 in order to add rigidity to the collar 16. As a variant, each half collar 23 could contain a prefabricated half ring. This ring 25 projects radially towards the exterior from the collar 16. A plurality of lugs 26, typically one for each securing arm 17, are secured by welding on the ring 25. These lugs 26 project radially towards the exterior. Each lug 26 contains an upper plate 27 developing in a radial plane and a lower plate 28 developing in a radial plane in parallel to the upper plate 27. In a variant that is not illustrated here, the lugs 26 are directly welded on the cylindrical collar 16 or on each half collar 23.
Each securing arm 17 is rotatably mounted on a respective lug 26 about an axis of rotation parallel to a generatrix direction of the collar 16. The upper plates 27 and the lower plates 28 each exhibit an orifice in which there is mounted a pin 29 of a corresponding securing arm 17. Each securing arm 17 exhibits a certain degree of displacement in rotation about the axis of rotation defined by the pin 29. For each securing arm 17 in service, this degree of displacement is limited by the variation in the length of the elastic member 18.
As visible in
The pumping pipe 12 contracts in the course of a change in the temperature in the tank, for example in the course of loading LNG at −162° C. During this contraction, which represents a contraction in the order of 87 mm for a pumping pipe of 30 m in length, the securing of the collar 16 on the pumping pipe 12 may be compromised by the vertical displacement due to the thermal contraction of the pumping pipe 12. As a consequence, the collar 16 may no longer be maintained on the pumping pipe 12 in a stable manner. Suchlike wedges 33 made from a polymer material permit a sliding support of the collar 16 on the pumping pipe 12, the collar thus being maintained in a secured position in the level of the sump on the pumping pipe 12 by means of these wedges 33. In the case of an anti-rotation system of the kind described above with respect to
Given that the four securing arms 17 of the securing device 15 are similar, a single securing arm 17 is described below with respect to
The securing arm 17 contains a proximal arm portion 34 and a distal arm portion 35. These arm portions 34 and 35 are formed by aligned hollow rigid rods.
A first end 36 of the proximal arm portion 34 contains a pin 29 collaborating with the lug 26. A second end 37 of the proximal arm portion 34 collaborates with a central portion 38 of the securing arm 17 described below with respect to
The distal arm portion 35 contains a first end 39, on which there is mounted the pad 19 capable of rotation about an axis parallel to a generatrix direction of the collar 16. A second end 40 of the distal arm portion 35 collaborates with the central portion 38 of the securing arm 17.
The pad 19 contains a main body 41 bearing a pin 42 housed in a hub of the first end 39 of the distal arm portion 35. A first spacer 43 develops from the main body 41 of the pad 19, the first bearing surface 20 being mounted on an end of the first spacer 43 opposite the main body 41. A second spacer 44 develops from the main body 41 of the pad 19, the second bearing surface 20 being mounted on an end of the second spacer 44 opposite the main body 41. The first spacer 43 and the second spacer 44 develop perpendicularly one to the other. Each bearing surface 20 develops in a plane perpendicular to the direction of development of the spacer on which it is mounted. The pads are made from metal in order to collaborate with the lateral walls 9 of the rigid container 7 with friction, thereby offering improved support of the pads 19 on the lateral walls 9.
In the case of a rigid container 7 made from thick sheets, the pads 19 may exhibit abutment surfaces 20 of square, round, planar or cylindrical form and exhibiting characteristic dimensions, for example in the range between 5 cm and 50 cm.
In an embodiment in which the container is not as rigid and exhibits a more fragile structure, for example containing a fine primary fluid-tight membrane supported by a thermally insulating barrier, materials other than insulating foam may be installed in the primary thermally insulating barrier at the level of the abutment zones of the pads 19. Thus, the lateral walls 9 of the container may be reinforced by the installation of laminate or composite material. In this case, the abutment surfaces of the pads may exhibit a square form having a side length of 20 cm in order to withstand loads in the order of 17,000 N, or also having a side length of 30 cm in order to withstand loads of 40,000 N. However, in the case of a fluid-tight membrane exhibiting corrugations, the abutment surfaces 20 exhibit dimensions that are limited by the distance separating two successive corrugations. The securing device 15 thus makes it possible to install the abutment surfaces 20 outside individual zones of the membrane, for example between two corrugations in the case of a corrugated primary fluid-tight membrane 5.
The distal sleeve 45 contains a cylindrical guide tube 48 developing coaxially with the distal sleeve 45 and exhibiting a hollow internal portion. The proximal sleeve 46 contains a guide rod 49 developing coaxially with the proximal sleeve 46 and complementary to the hollow portion of the guide tube 48. The guide rod 49 is inserted into the hollow portion of the guide tube 48 in such a way as to permit guiding by sliding between the distal sleeve 45 and the proximal sleeve 46.
The elastic member 18 is supported by the guide rod 49. Typically, the elastic member contains a plurality of Belleville washers 59 mounted on the guide rod 49. The Belleville washers 59 illustrated in
The guide rod 49 in addition supports a first compression limiter 52 and a second compression limiter 53. Each compression limiter 52, 53 contains a hollow cylindrical portion, respectively 54 and 55, having a diameter that is larger than the diameter of the Belleville washers 59 closed at one of its ends by a bottom, respectively 56 and 57.
The first group of Belleville washers 59 is supported between a radially internal face of the guide tube 48 and the bottom 56 of the first compression limiter 52. The cylindrical portion 54 of the first compression limiter 52 surrounds a part of the Belleville washers 59 of said first group of Belleville washers 59.
The second group of Belleville washers 59 is interposed between the bottom 56 of the first compression limiter 52 and a bottom 57 of the second compression limiter 53. The cylindrical portion 55 of the second compression limiter 53 surrounds a part of the Belleville washers 59 of the second group of Belleville washers 59.
The first elastic element 50 exhibits a rigidity lower than the rigidity of the second elastic element 51.
In a variant embodiment, the central portion 38 is mounted in the other direction, the rod 49 then being present on the side of the distal arm portion 35. A description will now be given of the operation of the securing device 15.
When the pump of the pumping pipe 12 is in operation, it generates vibrations of the end 13 of the pumping pipe 12. These vibrations are transmitted to the securing arms 17 by means of the collar 16. The first flexible elastic element 50 permits the absorption of the forces of low intensity caused by these vibrations of the pump in the pumping pipe 12. A suchlike first flexible elastic element 50 thus avoids the transmission of the vibrations generated by the pump from the pumping pipe 12 to the rigid container 7 and to the primary fluid-tight membrane 5 by means of the securing arms 17.
Conversely, during high stresses, for example associated with an earthquake in the case of a shore-based tank or under the effect of the swell in the case of a tank installed in a ship, forces of high intensity may be transmitted to the securing arms 17. These forces of high amplitude cannot be absorbed by the first flexible elastic element 50, which is compressed within the limit authorized by the first compression limiter 52. Typically, the Belleville washers 59 of the first group of Belleville washers 59 are compressed until the cylindrical portion 54 of the first compression limiter 52 comes into abutment against the guide tube 48, thereby preventing the supplementary compression of the first group of Belleville washers 59. The second, more rigid elastic element 51 then permits the absorption of these high-amplitude forces. The second group of Belleville washers 59 is compressed in turn and absorbs these high-amplitude forces.
Thus, the elastic members 18 of the securing arms 17 enable the end 13 of the pumping pipe 12 to be secured, while absorbing forces of different intensities between the rigid container 7 and the pumping pipe 12 in an elastic manner.
The rigidity of the elastic elements 50, 51 is advantageously selected depending on the order of magnitude of the envisaged displacements. Thus, depending on the envisaged displacements and also on the available length to the elastic member 18 in the rigid container 7, elastic elements may be proposed exhibiting a rigidity lying within a range from 300 N/mm to 8,000 N/mm, preferably between 500 and 5,000 N/mm.
Furthermore, the rigidity of the elastic elements 50, 51 is preferably selected so as to withstand the worst envisaged conditions, for example in response to an earthquake in the case of a tank full of liquid and of a pumping pipe 12 likewise full of liquid. In an illustrative embodiment, the elastic member 18 is configured to withstand an acceleration of 1 g in a given direction, which may generate a reaction force in the order of 34 kN that the elastic member must be able to absorb. These assumptions include the possibility, for example, of installing a second elastic element 51 exhibiting a rigidity in the order of 1,000 N/mm in order to achieve displacements in the range between 8 mm and 37 mm.
The technique described above may be utilized for securing any type of pipe in different types of reservoirs, for example for a tank of an LNG reservoir in a shore-based facility or in a floating structure such as an LNG carrier or the like.
With reference to
In a manner known per se, loading/unloading pipes 73 disposed on the upper deck of the ship may be connected, by means of appropriate connectors, to a maritime terminal or a port terminal for transferring a cargo of LNG from or towards the tank 71.
Pumps carried on board the ship 70, for example in the pumping pipe 12, and/or pumps equipping the shore-based facility 77 and/or pumps equipping the loading and unloading station 75 are used in order to generate the pressure necessary for the transfer of the liquefied gas.
Although the invention is described above in conjunction with a plurality of particular embodiments, it is obvious that it is not limited in any way in this respect and that it comprises all the technical equivalents of the means described here as well as their combinations, if the latter fall within the scope of the invention.
The usage of the verb “contain”, “comprise” or “include” and its conjugated forms does not exclude the presence of elements or stages other than those set out in a claim. The use of the indefinite article “a” or “an” for an element or a stage does not exclude the presence of a plurality of suchlike elements or stages, unless otherwise stipulated.
In the claims, any reference mark in parentheses should not be interpreted as a limitation of the claim.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1556351 | Jul 2015 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2016/051679 | 7/1/2016 | WO | 00 |
