A vacuum composite LNG cryogenic pipeline
By employing a double-layer composite pipeline structure and vacuum insulation design, the problems of insufficient flexibility and insulation effect of LNG cryogenic pipelines have been solved, achieving better bending performance and insulation effect, making it suitable for liquefied natural gas transmission at sea and on shore.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2023-06-19
- Publication Date
- 2026-05-26
AI Technical Summary
Existing LNG cryogenic pipelines have shortcomings in terms of flexibility, insulation performance, and mechanical properties, which limit their application scenarios.
It adopts a double-layer composite pipe structure, with the inner and outer layers consisting of spiral steel wire and a vacuum layer. The inner layer is made of stainless steel wire winding, the outer layer is a rubber sheath, and the middle vacuum layer provides heat insulation, forming a vacuum insulation effect.
It improves the bending flexibility and insulation effect of pipelines, reduces metal fatigue damage, enhances mechanical properties, and is suitable for offshore liquefied natural gas transmission and shore-based unloading.
Smart Images
Figure CN116624704B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a composite cryogenic pipeline for liquefied natural gas (LNG). The pipeline is used in various applications, including the transfer of LNG between floating liquefied natural gas systems (FLNG) and LNG carriers, unloading of LNG carriers on shore, and refueling at LNG refueling stations. The cryogenic LNG pipeline is a key piece of equipment for loading and unloading LNG. Background Technology
[0002] With increasing environmental awareness in my country, newly promulgated policies are driving energy transformation, and natural gas, as a clean energy source, has received much attention. Compared to onshore extraction and transportation, offshore natural gas extraction, transportation, and transmission are more difficult, requiring the overcoming of more technical challenges. Among these, LNG cryogenic pipelines, as a key piece of equipment, have a crucial structural design that affects the safe application of the natural gas transmission system.
[0003] LNG cryogenic pipelines have a wide range of applications, the most typical being unloading from floating liquefied natural gas (LNG) production, storage, and offloading (FSO) units and unloading operations on LNG carriers at docks. FSO units are a new type of floating production, storage, and offloading system that integrates the production, storage, and loading / unloading of LNG at sea. This system can conduct natural gas extraction operations in deep waters and perform preliminary processing and storage of the extracted gas. Once the FSO unit is full, the LNG must be unloaded onto LNG carriers for maritime transport. The loading and unloading process includes two methods: transfer using robotic arms and transfer using LNG cryogenic pipelines. Compared to robotic arm transfer, the LNG cryogenic pipeline method allows for a larger range of movement and greater flexibility between the two floating bodies. Figure 1 The image shows the unloading process of an offshore floating liquefied natural gas production, storage and offloading (LNG) unit.
[0004] The second most typical application scenario for LNG cryogenic pipelines is unloading operations from LNG carriers at a terminal. After arriving at the shore, LNG carriers must unload liquefied natural gas into LNG storage tanks. Dockless floating transport, being less costly and more environmentally friendly, is increasingly being widely adopted. The unloading process for dockless floating transport is as follows: when the LNG carrier approaches the shore, the transshipment platform in the dockless floating transport system pulls one end of the LNG cryogenic pipeline close to the LNG carrier, adsorbing it onto the LNG carrier. The cryogenic pipeline connecting the LNG carrier and the transshipment platform, as well as between the transshipment platform and the LNG storage tanks, is then used for unloading. After the transport is completed, the connection is disconnected, and a small transshipment platform pulls the cryogenic pipeline back to the shore. LNG carrier unloading operations at the shore are as follows... Figure 2 As shown.
[0005] Natural gas's main component is methane, which is gaseous at room temperature. Liquefied natural gas is only 1 / 625 the size of gaseous methane, thus requiring liquefaction for easier storage and transportation. Natural gas has a freezing point of -161.5℃; therefore, equipment in direct or indirect contact with it during transportation must withstand temperatures below -161.5℃ and remain undamaged under operating conditions. Secondly, to ensure normal liquefied natural gas transportation and meet certain flow requirements, the internal pressure of the pipeline must be sufficiently high, typically reaching 1–2 MPa. Furthermore, the pipeline must possess sufficient flexibility to ensure easy operation and resist damage from marine environmental loads, such as strength or fatigue failure.
[0006] Ordinary steel pipes cannot meet the above requirements, and the structure of LNG cryogenic pipelines must be designed. The mainstream LNG cryogenic pipelines can be roughly divided into two categories: the first is corrugated metal hose, and the second is composite hose.
[0007] Corrugated metal pipes are classified into reinforced corrugated metal pipes and vacuum-insulated corrugated metal pipes according to their insulation methods.
[0008] Reinforced corrugated metal pipe structure, such as Figure 3 As shown, the innermost layer is a corrugated pipe layer, used to contain liquefied natural gas and withstand internal radial pressure loads; the annular space separated by the sealing layer is used for leak monitoring; the armor layer provides axial tensile strength; the insulation layer keeps the internal liquefied natural gas cool and prevents ice formation on the outermost layer of the pipeline; the outer sheath layer isolates seawater and provides external protection. If the outer sealing layer is replaced with the same corrugated pipe structure as the inner layer, the annular area between the inner and outer corrugated pipes can be designed as a vacuum insulation layer, which can be used for leak monitoring. This type of pipeline is called a vacuum-insulated corrugated metal pipe, and its structure is as follows. Figure 4 As shown. Compared to reinforced corrugated metal pipe structures, vacuum-insulated corrugated metal pipes offer superior insulation performance, and compared to multi-insulation-layer structures, the pipe structure is simpler and requires fewer layers.
[0009] Reinforced corrugated metal pipes are made by winding multiple layers, which is relatively easy to manufacture and results in a stable structure. However, due to the large thickness of the insulation layer and the large inner diameter of the entire pipe, its bending stiffness is also relatively high. Vacuum-insulated corrugated metal pipes achieve better insulation through a vacuum structure, preventing excessive pipe thickness. However, since both the inner and outer corrugated pipe layers are made of metal (such as 316 stainless steel), the toughness of metal materials deteriorates in ultra-low temperature environments. When the pipe undergoes large deformation, the metal layer is prone to strength failure. In addition, metal materials are susceptible to fatigue damage under cyclic loading.
[0010] Compared to corrugated metal pipes, which are formed by non-bonded stacking of layers, composite pipes are formed by the interaction of layers through mechanical relationships. The inner and outer layers are spiral steel wires, and the misalignment of half a pitch between these two spiral steel wires holds the middle film layer and braided layer in place. Conversely, the film layer and braided layer keep the two spiral steel wires mutually fixed, forming a self-stabilizing pipe structure. For example... Figure 5 The diagram shows a composite pipeline structure. The membrane layer is in direct contact with liquefied natural gas (LNG) and serves to contain LNG and prevent it from seeping in. The braided layer, as the main load-bearing layer of the composite pipeline, forms the pipeline's external structure, withstands tensile and bending loads, and protects the membrane layer from damage.
[0011] Composite pipes are primarily made of non-metallic materials, with the inner and outer helical steel wires (metallic components) not serving as the main load-bearing structure, making them less prone to plastic failure. Furthermore, the larger helical corrugation angles created by the extrusion of composite pipes allow for greater bending curvature and superior pipe flexibility. However, composite pipes have poor insulation properties and are prone to frost formation on the outer layer. Generally, to improve insulation and external protection, a multi-layered pipe is added to the outer layer, known as a "pipe-in-pipe" structure. However, due to the large number of pipe layers in this structure, the overall flexibility of the pipe is significantly reduced, and its advantages over corrugated metal pipes are not fully realized.
[0012] In summary, several traditional LNG cryogenic pipelines all have certain drawbacks and limitations, severely restricting their application scenarios. Therefore, there is a need for an LNG cryogenic pipeline with better bending flexibility, superior insulation, and more stable mechanical properties. This invention employs a double-layer composite pipeline structure and utilizes vacuum insulation, which significantly improves the insulation effect while maintaining the overall flexibility of the pipeline. Summary of the Invention
[0013] To address the aforementioned problems in the existing technology, this invention provides a vacuum composite LNG cryogenic pipeline.
[0014] The technical solution adopted in this invention is as follows:
[0015] A vacuum composite LNG cryogenic pipeline has four functional layers from the inside out: an inner composite pipeline layer, a vacuum layer, an outer composite pipeline layer, and an outer sheath layer.
[0016] The inner composite pipe layer, from the inside out, consists of: a first inner spiral steel wire layer 1, made of stainless steel wire wound at a certain angle; a second layer, a first sealing layer 2, which serves to contain and seal the internal liquefied natural gas; a third layer, a first braided layer 3, which is the main load-bearing layer of the inner composite pipe layer, bearing the compression between the inner and outer spiral steel wires, resisting the internal pressure of the liquefied natural gas, and improving mechanical properties; a fourth layer, a second sealing layer 4, which provides a sealing function for the vacuum layer area; and a fifth layer, a first outer spiral steel wire layer 5, also made of stainless steel wire wound at a certain angle, offset from the first inner spiral steel wire 1 by half a pitch, locking the second sealing layer 4 and the first braided layer 3, so that the inner composite pipe layer itself forms a stable pipe structure.
[0017] The vacuum layer is formed by an annular area between the inner composite pipe layer and the outer composite pipe layer. The two layers are supported by an insulating gasket 6. During the manufacturing process of the low-temperature pipe, the internal air is vented to form a vacuum insulation function.
[0018] The innermost and outermost layers of the outer composite pipe layer are the second inner spiral steel wire layer 7 and the second outer spiral steel wire layer 10; the second layer is the third sealing layer 8, which seals the vacuum layer area, preventing air or liquid from penetrating into the vacuum layer area; the third layer is the third braided layer 9, which serves as the main load-bearing layer of the outer composite pipe layer, ensuring that the outer composite pipe layer area has sufficient resistance to tensile, bending, and extrusion loads.
[0019] The outer sheath layer includes an outer sheath 11, which prevents seawater penetration and erosion and resists external damage.
[0020] Furthermore, the first inner spiral steel wire layer 1 is formed by spirally winding steel wire into a spring shape. In order to ensure that the bending flexibility of the low temperature pipeline meets the requirements, the winding angle of the steel wire is usually large enough, above 85°.
[0021] Furthermore, the first inner spiral steel wire layer 1 supports the inner composite pipe layer area, preventing it from collapsing radially inward under the pressure of the outer layer, and cooperates with the first outer spiral steel wire layer 5 to fix the first sealing layer 2, the first braided layer 3, and the second sealing layer 4. The first inner spiral steel wire layer 1 is generally made of metal. Since it is in direct contact with liquefied natural gas, it needs to ensure sufficient mechanical properties at low temperatures. This layer is mostly made of stainless steel, such as 316L stainless steel, 304 stainless steel, etc.
[0022] Furthermore, the first sealing layer 2 is made of a thin-film material tightly spirally wound around the first inner spiral steel wire layer 1, providing sufficient clamping force to prevent loosening, misalignment, or detachment during manufacturing or use. The first sealing layer 2 is capable of containing liquefied natural gas without seepage or leakage under high pressure. The first sealing layer 2 can be made of perfluoroethylene propylene (PFEP), a material that does not chemically react with natural gas and exhibits stable mechanical properties in ultra-low temperature environments. In addition, PFEP provides excellent sealing performance and can fulfill the sealing function of cryogenic pipelines.
[0023] Furthermore, the first braided layer 3 is made of braided material tightly spirally wound around the outside of the first sealing layer 2. Sufficient tension must be maintained during the winding process to ensure tight winding and prevent loosening. The braided material used in the first braided layer 3 has excellent tensile strength, providing sufficient tensile reserve capacity for the pipeline. Generally, the winding angle of the braided material is relatively large to ensure the pipeline has bending flexibility. Under the clamping of the first inner spiral steel wire layer 1 and the first outer spiral steel wire layer 5, the first braided layer 3 forms the main load-bearing and transmission structure of the thin-walled pipe structure. Under internal pressure load, in addition to bearing part of the internal pressure load itself, it transmits the remaining internal pressure load to the first outer spiral steel wire layer 5; similarly, under the compression of the outer layer, the load can be transmitted to the first inner spiral steel wire layer 1.
[0024] Furthermore, the second sealing layer 4 is the same as the first sealing layer 1, and its function is to seal the vacuum layer area to prevent air or liquid from entering.
[0025] Furthermore, the first outer spiral steel wire layer 5 is wound into a spring shape by spiraling steel wire. During the winding process, it is offset from the first inner spiral steel wire layer 1 by half a pitch, and the winding force is large enough that its pre-tightening force can press the first sealing layer 2, the first braided layer 3, and the second sealing layer 4 into a corrugated shape.
[0026] Furthermore, the innermost layer of the outer composite pipe layer is the second inner spiral steel wire layer 7, and the outermost layer is the second outer spiral steel wire layer 10. The two layers have the same function as the first inner spiral steel wire layer 1 and the first outer spiral steel wire layer 5 in the inner composite pipe layer, which fix the third sealing layer 8 and the second braided layer 9.
[0027] Furthermore, the third sealing layer 8 and the second sealing layer 4 cooperate to seal the vacuum layer area.
[0028] Furthermore, the vacuum layer between the inner and outer composite pipe layers is formed by the annular space between the second sealing layer 4 of the inner composite pipe layer and the third sealing layer 8 of the outer composite pipe layer. To prevent the second sealing layer 4 and the third sealing layer 8 from contacting each other, an insulating gasket 6 is provided at every 5 pitch intervals, and the insulating gasket 6 is supported on the first outer spiral steel wire layer 5 and the second inner spiral steel wire layer 7.
[0029] Furthermore, each insulating ring 6 has an arc-shaped cross-section on both the top and bottom sides to support the steel wire and prevent it from easily falling off during the rotation or sliding of the wire. The cross-section has a hollow structure in the middle, reducing weight and the heat transfer rate between the inner and outer composite pipe layers. The insulating ring 6 is wound in a circle along the pipe's circumference, with its pitch being the same as the first outer spiral steel wire layer 5 and the second inner spiral steel wire layer 7. To reduce the heat transfer rate, the insulating ring 6 should be made of a material with a low thermal conductivity. During the manufacturing process of the cryogenic pipe, the air inside the vacuum layer is evacuated, giving this layer a vacuum insulation function.
[0030] Furthermore, the outer sheath layer includes an outer sheath 11, which is typically made of rubber material to prevent seawater from entering the pipe and reduce the corrosion of the metal by seawater or air.
[0031] In addition, the functional layers such as the second braided layer 9 and the second outer spiral steel wire layer 10 will not be damaged under external friction or other forms of damage.
[0032] The present invention has the following beneficial effects:
[0033] (1) The cryogenic pipeline of the present invention is composed of two nested composite pipes. The corrugations of the composite pipes are formed by extrusion. Compared with the structure of metal corrugated pipe formed by plastic extrusion, its bending flexibility is better. Therefore, the cryogenic pipeline with both inner and outer pipes made of composite pipes has lower bending stiffness and better bending flexibility than the cryogenic pipeline with both inner and outer pipes made of metal corrugated pipes. It can also withstand a smaller bending radius without damage. Since its stress layer is a non-metallic structure, it is not prone to fatigue damage under external tensile, bending and other cyclic loads.
[0034] (2) The low-temperature pipeline of the present invention has a superior heat preservation effect due to the use of vacuum insulation. Low-temperature pipelines that are insulated by wrapping the outer layer with heat insulation material often have an excessively large outer diameter due to the excessive thickness of the insulation layer, which increases the storage and transportation costs and reduces the flexibility of the pipeline. In the present invention, the vacuum insulation method is used instead of wrapping with heat insulation material, which reduces the overall thickness of the pipeline while improving the heat preservation effect.
[0035] (3) The stress transmission of the cryogenic pipeline of the present invention is more reasonable, and it is less likely to cause local misalignment or damage. The internal pressure load is transmitted layer by layer from the inside to the outside, and each layer bears part of the force, preventing damage caused by excessive force on a single layer. Similarly, external extrusion loads are transmitted layer by layer from the outside to the inside, and each layer will bear part of the external force.
[0036] (4) Due to the spiral structure of the inner and outer steel wires, they will twist during the stretching process. Therefore, the use of composite pipes with the same spiral direction and pitch ensures good synchronization of the two twists and prevents damage due to high internal stress in the low-temperature pipe. For other misalignments between the two composite pipes, the insulation gasket will not slip due to its own structure and structural deformation, thus ensuring its supporting function.
[0037] (5) The present invention has a wide range of applications, and can be applied to the tandem unloading of liquefied natural gas at sea, the shore unloading of liquefied natural gas ships, and the refueling of natural gas at refueling stations. Moreover, due to the good flexibility and insulation of the pipeline, the outermost layer will not be affected by the low temperature of the inner layer and will not freeze. Therefore, the low temperature pipeline can be operated manually, making it more convenient to use. Attached Figure Description
[0038] Figure 1 A schematic diagram of unloading a floating liquefied natural gas production, storage and offloading (LNG) unit at sea.
[0039] Figure 2 A schematic diagram of LNG carrier unloading operations at the shore end;
[0040] Figure 3 Diagram of a reinforced corrugated metal pipe structure;
[0041] Figure 4 This is a structural diagram of a vacuum-insulated corrugated metal pipe.
[0042] Figure 5 This is a diagram of a composite pipeline structure.
[0043] Figure 6 This is a structural diagram of the cryogenic pipeline of the present invention.
[0044] Figure 7(a) is a structural diagram of the inner composite pipe layer region of the present invention; Figure 7(b) is a partial enlarged view.
[0045] Figure 8(a) is a structural diagram of the outer composite pipe layer of the present invention; Figure 8(b) is a partial enlarged view.
[0046] Figure 9 This is an enlarged view of the vacuum layer region between the inner and outer composite pipe layers of the present invention.
[0047] Figure 10(a) is a diagram of the low-temperature pipeline skeleton of the present invention; Figure 10(b) is a partial enlarged view.
[0048] Figure 11 This is a diagram of a single insulating pad ring in this invention.
[0049] In the figure: 1 First inner spiral steel wire layer; 2 First sealing layer; 3 First braided layer; 4 Second sealing layer; 5 First outer spiral steel wire layer; 6 Insulation gasket ring; 7 Second inner spiral steel wire layer; 8 Third sealing layer; 9 Second braided layer; 10 Second outer spiral steel wire layer; 11 Outer sheath. Detailed Implementation
[0050] The present invention will now be described in detail with reference to the accompanying drawings.
[0051] The overall structure of the cryogenic pipeline of the present invention is shown in the attached figure. Figure 6 The diagram illustrates a structural example of a novel LNG cryogenic pipeline, which consists of four functional layers from the inside out: an inner composite pipeline layer, a vacuum layer, an outer composite pipeline layer, and an outer sheath layer.
[0052] The inner composite pipe layer, from the inside out, consists of the following layers: the innermost layer is the first inner spiral steel wire layer 1, which is made of stainless steel wire wound at a certain angle; the second layer is the first sealing layer 2, which serves to contain and seal the internal liquefied natural gas; the third layer is the first braided layer 3, which is the main load-bearing layer of the inner composite pipe layer, bearing the compression between the inner and outer spiral steel wires, resisting the internal pressure of liquefied natural gas, and improving the tensile, bending, and torsional mechanical properties of the cryogenic pipe; the fourth layer is the second sealing layer 4, which provides a sealing function for the vacuum layer area; and the fifth layer is the first outer spiral steel wire layer 5, which is also made of stainless steel wire wound at a certain angle, offset from the first inner spiral steel wire 1 by half a pitch, and holds the second sealing layer 4 and the first braided layer 3 in place, so that the inner composite pipe layer itself forms a stable pipe structure.
[0053] The vacuum layer area is formed by an annular region between the inner composite pipe layer area and the outer composite pipe layer area. The two are supported by an insulating gasket ring 6. During the manufacturing process of the low-temperature pipe, the internal air is vented to form a vacuum insulation function.
[0054] The innermost and outermost layers of the outer composite pipe layer are both the second inner spiral steel wire layer 7 and the second outer spiral steel wire layer 10; the second layer is the third sealing layer 8, which seals the vacuum layer area so that air or liquid does not penetrate into the vacuum layer area; the third layer is the third braided layer 9, which serves as the main load-bearing layer of the outer composite pipe layer.
[0055] The outer sheath layer includes an outer sheath 11, which prevents seawater penetration and erosion and resists external damage.
[0056] The specific implementation method is as follows:
[0057] Figure 7 shows the inner composite pipe layer area. The first layer is the first inner spiral steel wire layer 1, which is made of steel wire spirally wound into a spring shape. To ensure that the bending flexibility of the low-temperature pipe meets the requirements, the winding angle of the steel wire is usually large enough, above 85°. The inner spiral steel wire layer 1 supports the inner composite pipe layer area, preventing it from collapsing radially inward under the compression of the outer layer, and cooperates with the first outer spiral steel wire layer 5 to fix the first sealing layer 2, the first braided layer 3, and the second sealing layer 4. The first inner spiral steel wire layer 1 is generally made of metal. Since it is in direct contact with liquefied natural gas, it needs to ensure sufficient mechanical properties at low temperatures. This layer is mostly made of stainless steel, such as 316L stainless steel, 304 stainless steel, etc.
[0058] Figure 7 shows the second layer, which is the first sealing layer 2. It can be made of a thin-film material tightly spirally wound around the first inner spiral steel wire layer 1, providing sufficient clamping force to prevent loosening, misalignment, or detachment during manufacturing or use. The first sealing layer 2 can contain liquefied natural gas and prevent seepage and leakage even under high pressure. The first sealing layer 2 can be made of perfluoroethylene propylene (PFEP), a material that does not chemically react with natural gas and has stable mechanical properties in ultra-low temperature environments. Furthermore, PFEP has excellent sealing performance and can fulfill the sealing function of cryogenic pipelines.
[0059] Figure 7 shows the third layer, the first braided layer 3, which is made of braided material tightly spirally wound around the outside of the first sealing layer 2. Sufficient tension must be maintained during the winding process to ensure tight wrapping and prevent loosening. The braided material used in the first braided layer 3 has excellent tensile strength, providing sufficient tensile reserve for the pipeline. Generally, the winding angle of the braided material is relatively large to ensure the pipeline's bending flexibility. Under the clamping of the first inner spiral steel wire layer 1 and the first outer spiral steel wire layer 5, the first braided layer 3 forms the main load-bearing and transmission structure of the thin-walled pipe structure. Under internal pressure load, in addition to bearing part of the internal pressure load itself, it transmits the remaining internal pressure load to the first outer spiral steel wire layer 5; similarly, under the compression of the outer layer, the load can be transmitted to the first inner spiral steel wire layer 1.
[0060] Figure 7 shows the fourth layer, which is the second sealing layer 4. This layer is the same as the first sealing layer 1, and its function is to seal the vacuum layer area to prevent the entry of air or liquid. Figure 7 also shows the outermost layer, which is the first outer spiral steel wire layer 5. This layer is formed by spirally winding steel wire into a spring shape. During the winding process, it is offset from the first inner spiral steel wire layer 1 by half a pitch, and the winding force is large enough that its preload can press the first sealing layer 2, the first braided layer 3, and the second sealing layer 4 into a corrugated shape.
[0061] Figure 8 shows the outer composite pipe layer area. The innermost layer is the second inner spiral steel wire layer 7, and the outermost layer is the second outer spiral steel wire layer 10. Their function is the same as that of the first inner spiral steel wire layer 1 and the first outer spiral steel wire layer 5 in the inner composite pipe layer area, fixing the third sealing layer 8 and the second braided layer 9. The second layer is the third sealing layer 8, which works in conjunction with the second sealing layer 4 to seal the vacuum layer area. The third layer is the second braided layer 9, which ensures that the outer composite pipe layer area has sufficient resistance to tensile, bending, and compressive loads.
[0062] Appendix Figure 9 The vacuum layer between the inner and outer composite pipe layers is formed by the annular space between the second sealing layer 4 of the inner composite pipe layer and the third sealing layer 8 of the outer composite pipe layer. To prevent contact between the second sealing layer 4 and the third sealing layer 8, as shown in Figure 10, an insulating gasket 6 is placed at every 5 pitch intervals. The insulating gasket 6 is supported on the first outer spiral steel wire layer 5 and the second inner spiral steel wire layer 7. The shape of each insulating gasket 6 is shown in Figure 10. Its cross-section has rounded upper and lower sides to support the steel wire and prevent it from falling off during the rotation or slippage of the steel wire. The cross-section is hollowed out in the middle to reduce weight and the heat conduction rate between the inner and outer composite pipe layers. The insulating gasket 6 is wound in a circle along the pipe, and its pitch is the same as that of the first outer spiral steel wire layer 5 and the second inner spiral steel wire layer 7. To reduce the heat conduction rate, the insulating gasket 6 should be made of a material with a low thermal conductivity. During the manufacturing process of cryogenic pipelines, the air inside the vacuum layer is evacuated, giving the layer a vacuum insulation function.
[0063] Appendix Figure 6 The inner and outer sheath layer area includes the outer sheath 11, which is usually made of rubber material to prevent seawater from entering the pipe and reduce the corrosion of the metal by seawater or air. In addition, functional layers such as the second braided layer 9 and the second outer spiral steel wire layer 10 will not be damaged under the condition of external friction or other damage.
[0064] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.
Claims
1. A vacuum-composite LNG cryogenic pipeline, characterized in that, From the inside out, the layers are: inner composite pipe layer, vacuum layer, and outer composite pipe layer. The inner composite pipe layer area consists of the following layers from the inside out: a first inner spiral steel wire layer (1), which is made of stainless steel wire wound at a certain angle; a second layer is a first sealing layer (2), which serves to contain and seal the internal liquefied natural gas; a third layer is a first braided layer (3), which is the main load-bearing layer of the inner composite pipe layer; a fourth layer is a second sealing layer (4), which provides a sealing function for the vacuum layer area; and a fifth layer is a first outer spiral steel wire layer (5), which is also made of stainless steel wire wound at a certain angle, which holds the second sealing layer (4) and the first braided layer (3) in place, so that the inner composite pipe layer area itself forms a stable pipe structure. The vacuum layer is formed by an annular area between the inner composite pipe layer and the outer composite pipe layer. The two layers are supported by an insulating gasket (6). During the manufacturing process of the low-temperature pipe, the air inside the vacuum layer is emptied, which has a vacuum insulation function. The vacuum layer is formed by the annular space between the second sealing layer (4) and the third sealing layer (8). There is an insulating gasket (6) every 5 pitch intervals. The insulating gasket (6) is supported on the first outer spiral steel wire layer (5) and the second inner spiral steel wire layer (7). The insulating gasket (6) has an arc-shaped cross-section on the upper and lower sides and a hollow structure in the middle of the cross-section. The insulating gasket (6) is wound around the pipe in a circle, and its pitch is the same as that of the first outer spiral steel wire layer (5) and the second inner spiral steel wire layer (7). The innermost and outermost layers of the outer composite pipe layer are the second inner spiral steel wire layer (7) and the second outer spiral steel wire layer (10), respectively. Their functions are the same as those of the first inner spiral steel wire layer (1) and the first outer spiral steel wire layer (5) in the inner composite pipe layer. The second layer is the third sealing layer (8), which seals the vacuum layer area so that air or liquid does not penetrate into the vacuum layer area. The third layer is the third braided layer (9), which serves as the main load-bearing layer of the outer composite pipe layer.
2. The vacuum composite LNG cryogenic pipeline according to claim 1, characterized in that, The outermost layer of the vacuum composite LNG cryogenic pipeline is the outer sheath layer, which includes an outer sheath (11). This layer prevents seawater penetration and erosion and resists external damage.
3. The vacuum composite LNG cryogenic pipeline according to claim 1, characterized in that, The first inner spiral steel wire layer (1) is formed by spirally winding steel wire into a spring shape, with the winding angle of the steel wire being above 85°.
4. The vacuum composite LNG cryogenic pipeline according to claim 1, characterized in that, The first outer spiral steel wire layer (5) is wound into a spring shape by a steel wire spiral. During the winding process, it is misaligned with the first inner spiral steel wire layer (1) by half a pitch. Its pre-tightening force can press the first sealing layer (2), the first braided layer (3), and the second sealing layer (4) into a corrugated shape.
5. A vacuum composite LNG cryogenic pipeline according to claim 1, characterized in that, The first inner spiral steel wire layer (1) is made of metal.
6. The vacuum composite LNG cryogenic pipeline according to claim 1, characterized in that, The first sealing layer (2) is made of a thin film material tightly spirally wound on the first inner spiral steel wire layer (1).
7. A vacuum composite LNG cryogenic pipeline according to claim 2, characterized in that, The outer sheath (11) is made of rubber, the first inner spiral steel wire layer (1) is made of stainless steel, and the first sealing layer (2) is made of polytetrafluoroethylene propylene.