Method for manufacturing a pressure vessel and pressure vessel

Abstract

The present invention relates to a method for manufacturing a pressure vessel and the corresponding pressure vessel. The invention proposes a method for manufacturing a pressure vessel, in which first a pressure vessel blank is manufactured having at least one liner type 4 and a cylindrical pipe operatively connected thereto, and subsequently, for example, a fiber composite material is wrapped onto the pressure vessel blank. In one embodiment, the method for manufacturing a fiber-reinforced pressure vessel is characterized by the steps of manufacturing a pressure vessel blank including at least one liner type 4 (3) and a cylindrical pipe operatively connected thereto (2), and overlapping the pressure vessel blank.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a pressure vessel and each pressure vessel.

Background Art

[0002] The market for pressure vessels, particularly those reinforced with fiber composite materials, is growing continuously. The increase in natural gas production and gas flaring requires storage in pressure vessels, especially in countries without the corresponding pipeline network. In addition, the automotive industry, which is highly involved in the development of fuel cell vehicles, requires that the fuel be stored in the form of gaseous hydrogen under high pressure in a pressure vessel. Other types of vehicles that use hydrogen can be railway vehicles, airplanes, and ships. Even in spacecraft, applications are conceivable. Regarding the transportation of pressure vessels, the transportation of heavy pressure vessels is associated with unnecessary large amounts of energy consumption and thus leads to excessive high transportation costs, so it is desirable to have lightweight pressure vessels.

[0003] Currently used cylindrical fiber-reinforced pressure vessels have a reinforcing layer made of a fiber composite material, which is produced from fibers embedded in a matrix material. This layer is wound onto the inner vessel (called the liner) of the pressure vessel using a winding method, and the inner vessel functions as the winding core. Winding is a preferred process for manufacturing the fiber composite layer, and it is efficient in terms of time and cost. The reinforcing layer made of the fiber composite material provides a pressure vessel with the necessary mechanical rigidity, while the inner vessel ensures, for example, the airtightness of the pressure vessel. For Type 3 pressure vessels, for example, a metal inner vessel (metal liner) made of aluminum or steel is employed. For Type 4 pressure vessels, the non-load-bearing inner vessel (liner) is made of plastic. Plastic liners are generally produced by blow molding, rotational molding, or welding of individual components. Materials with good hydrogen permeability (polyamide or polyethylene, especially high-density polyethylene, etc.) can be used. Pressure vessels must withstand very high internal pressures. Currently, for example, hydrogen tanks in automobiles are filled to a pressure of approximately 700 bar. In particular, pressure vessels may not rupture even in the event of a collision. Therefore, such pressure vessels are designed with a cylindrical central component closed on both sides by what is called a "pole cap." To compensate for manufacturing tolerances, the reinforcing layer is appropriately oversized. The reinforcing layer can be manufactured, for example, by a filament winding method, and the wrapping of the pressure vessel occurs in a single operation. In other words, the fibers are wound on the plastic liner in a single operation, circumferentially, diagonally, or in the form of a helical layer. This makes the manufacture of such pressure vessels complex and expensive.

[0004] Therefore, it is desirable to make production more efficient. [Overview of the project] [Means for solving the problem]

[0005] An object of the present invention is to provide a method for manufacturing a fiber-reinforced type 4 pressure vessel, which can be carried out more efficiently and inexpensively than methods known in the latest art, and which impose at least the same requirements on the pressure vessel. Furthermore, an object of the present invention is to disclose each of the pressure vessels.

[0006] The first objective is achieved using a manufacturing method which comprises at least one type 4 liner and a cylindrical pipe operably connected thereto, in which first a pressure vessel semi-finished product is produced, and then a fiber composite material is wound, for example, over the semi-finished product.

[0007] The term "pressure vessel" encompasses all types and shapes of pressure vessels, including an inner vessel, also called a liner. Type 4 pressure vessels have a liner made of thermoplastic material that is mechanically reinforced by a fibrous composite material on the outside, so that the pressure vessel meets the requirements for construction in terms of pressure resistance. In principle, these pressure vessels are cylindrical with convex ends on both sides of a cylindrical central component. These ends, called pole caps, are used for pressure sealing of the central component. For reinforcement of the pressure vessel, an outer layer made of fibrous composite material is wrapped over the outside of the inner vessel, potentially simultaneously forming the exterior of the pressure vessel. The inner vessel can be produced using various techniques, e.g., welding, injection molding, or blow molding of the components. The pole caps can also be installed on the central component after production, e.g., by welding. Separate pole caps can be manufactured, e.g., by injection molding. Pressure vessels with thermoplastic inner containers have very low weight, which is important for applications such as means of transport; on the other hand, contents such as hydrogen can be stored under high pressure with low loss (since suitable thermoplastic materials have sufficiently low hydrogen permeability, and the required rigidity is provided by an outer layer made of fiber composite material).

[0008] Generally, a fiber composite material for a fiber composite layer consists of two main components, which, as specified herein, are fibers embedded in a matrix material that creates strong bonds between the fibers. In this case, the fiber composite material can be wound from one fiber or from multiple fibers, which are wound closely together and in contact with one another. The fibers to be wound are already impregnated with the matrix material. This results in a fiber layer in which additional fibers are wound in further fiber layers until the fiber composite material has a desired thickness and forms a corresponding fiber layer having this thickness. The outer layer is wound with several layers made from the fiber composite material, and the different layers may include fibers positioned at different fiber angles with respect to the cylindrical axis of the pressure vessel. In one embodiment, each of the fiber layers made from the first and / or additional fibers, e.g., the second fiber, comprises multiple fiber layers. The composite provides high-quality fiber composite material properties, such as high strength, that could be provided by either of the two individual components involved. The reinforcing effect of fibers in the fiber direction is achieved when the elastic modulus of the fibers in the longitudinal direction exceeds the elastic modulus of the matrix material, when the elongation at break of the matrix material exceeds the elongation at break of the fibers, and when the fracture resistance of the fibers exceeds the fracture resistance of the matrix material. The fibers that can be used are any type of fiber, e.g., glass fibers, carbon fibers, ceramic fibers, steel fibers, natural fibers, or synthetic fibers. The matrix material used for fiber composite layers is, in principle, duromer. The material properties of the fibers and matrix materials are known to those skilled in the art, and as a result, those skilled in the art can select suitable combinations of fibers and matrix materials for producing fiber composite materials for specific applications. In this specification, individual fiber layers in a fiber composite region may comprise a single fiber or multiple equal or different fibers.

[0009] The term "thermoplastic material" refers to plastics that can be plastically deformed within a specific temperature range. This process is reversible, meaning it can be repeated an indefinite number of times by cooling and reheating to a molten state, given that thermal decomposition of the material does not occur due to overheating. This distinguishes thermoplastic materials from duloplasts (or duromers) and elastomers. Another inherent property of thermoplastic materials is that they can be welded, for example, in contrast to duromers.

[0010] This invention proposes the first manufacturing of pressure vessel semi-finished parts. In this method, the manufacturing of pressure vessel semi-finished parts is separated from the manufacturing of the pressure vessel as a whole. Thus, pressure vessel semi-finished parts are produced separately. Here, and hereafter, “separate production” refers to production separate from the actual production of the pressure vessel, in particular, production preceding it. The actual production of the pressure vessel is carried out, for example, by winding fiber composite material onto the pressure vessel semi-finished parts. By providing pressure vessel semi-finished parts separately, optimal conditions for production can be ensured, and the efficiency and quality of this component, and therefore the entire pressure vessel, can be increased. Furthermore, in this method, the geometric shape of the pressure vessel is determined not by a liner, but solely by a ready-made cylindrical pipe, and thus, the manufacturing precision in terms of the length and diameter of the pressure vessel is increased.

[0011] More specifically, this production method may include steps of manufacturing and processing pole cap reinforcements, manufacturing and processing cylindrical pipes, installing connecting pieces (bosses) in the liner, joining the cylindrical pipes and pole caps to the liner, for example, fixing the positions of the cylindrical pipes and pole cap reinforcements by point bonding, winding spiral and circumferential layers made of fiber composite material over the resulting semi-finished products, and curing the entire system.

[0012] In another advantageous embodiment, the cylindrical pipes are manufactured separately. This allows for the production of pipes from various materials using the optimal manufacturing method for each material. In addition, the manufacturing of the cylindrical pipes can be easily automated in this method, further increasing manufacturing efficiency.

[0013] In another advantageous embodiment, the cylindrical pipe is wrapped with a fiber composite material. This material can be, for example, carbon fiber reinforced plastic (CFC). Components made from CFC are lightweight, but they also possess very high hardness. When the cylindrical pipe is made from the same group of materials that cover and subsequently wrap the pressure vessel semi-finished product, this has the advantage of connecting the pressure vessel semi-finished product with the layer that covers and wraps it, thereby increasing the overall hardness of the pressure vessel. By manufacturing the cylindrical pipe as a fiber composite component on a separate winding machine, the wrapping speed and the number of fibers wrapped simultaneously can be increased. In this method, the cylindrical pipe can be produced from a different type of fiber than the rest of the pressure vessel. This can be an advantage for specific applications. Furthermore, the cycle time of the actual vessel winding machine (on which the pressure vessel is then manufactured by winding the fibers onto the pressure vessel semi-finished product) can be substantially reduced. This is particularly advantageous because, due to its simple cylindrical geometric shape, the cylindrical pipe is simpler than a pressure vessel and can therefore be manufactured on an inexpensive winding machine. While a pressure vessel has a pole cap over which a helical layer must be wrapped, in one embodiment, the cylindrical pipe can be produced solely by winding a circumferential layer. In addition, by manufacturing the cylindrical pipe separately, different fiber angles can be introduced into the circumferential layer, or different types of fibers with different stiffnesses can be introduced into the product more easily than in conventional production.

[0014] Cylindrical pipes can also be manufactured with thinner wall thicknesses than the overall container, reducing the risk of fiber warping and thus increasing fiber resistance.

[0015] In another advantageous embodiment, the cylindrical pipe is wound on a metal winding core. Fiber deposition can be carried out more precisely on the metal winding core than on a plastic liner. The use of fibers can be improved in this method. Furthermore, the metal winding core can be manufactured with great precision, which also enables the production of very precise inner diameters of the cylindrical pipes or semi-finished cylindrical pipes wound on it. This results in reduced manufacturing tolerances and can lead to an increase in the filling volume of the pressure vessel with equal assembly space.

[0016] In another advantageous embodiment, the cylindrical pipe is manufactured on a long winding core such that one winding yields several panels. In other words, a semi-finished cylindrical pipe is first wound from which the cylindrical pipe is cut to a certain length. In particular, if a metal winding core is used, its hardness allows for the winding of very long semi-finished cylindrical pipes. Winding particularly long semi-finished cylindrical products and then cutting them to a certain length to produce metal pipes further increases production efficiency. However, it is also possible to manufacture the cylindrical pipe to its final dimensions on a winding core using a "board disc," thereby eliminating the need to cut to a certain length or other finishing processes.

[0017] In another advantageous embodiment, the cylindrical pipe is hardened only partially at most. This facilitates mechanical manipulation and work, and allows the winding to produce intermaterial bonding during the final hardening after winding. Herein, in principle, the use of a partially hardened pipe is preferred over a fully hardened pipe, however, the use of the latter is not entirely ruled out.

[0018] In another embodiment, the cylindrical pipe is extruded. This is a very economical manufacturing method. Using extrusion, in particular, very long semi-finished pipes can be produced, from which the cylindrical pipe can be cut to a certain length. However, long fiber-reinforced materials and duroplastic materials in particular cannot be extruded, and thus, with respect to extrusion, short fiber-reinforced thermoplastics such as fiber-reinforced polyamides can be used, but this may come with disadvantages over wrapped pipes in terms of hardness.

[0019] In another embodiment, the cylindrical pipe is formed by pultrusion. Pultrusion allows for the processing of materials with longer fibers (up to continuous fibers) than materials that can be processed by extrusion. Due to the longer fibers, the hardness of the pipe thus produced can be increased compared to pipes produced by extrusion.

[0020] In another advantageous embodiment, the liner has an outer shape for receiving a cylindrical pipe so that the cylindrical pipe can be securely engaged with the liner. In particular, if this secure engagement occurs at the transition from the cylindrical portion of the pressure vessel to the pole cap, especially if the pole cap has pole cap reinforcement, problems during cold filling can be avoided. If the secure engagement occurs on only one side of the pressure vessel, the cylindrical pipe can be pushed onto the liner from the other side. If the outer shape of the liner has a recess, the cylindrical pipe can be placed in it, i.e., if the secure engagement occurs on both sides of the liner, the cylindrical pipe can be joined to the liner by a shrinkage process.

[0021] Typically, the boss, liner, and cylindrical pipe form a single surface. The three components are then covered by wrapping them together. In one embodiment, the cylindrical pipe may be in direct contact with the metal boss, while the plastic liner will not be in direct contact with the reinforcing wrapping. In an alternative, advantageous embodiment, pole cap reinforcement is applied to at least one pole area of ​​the liner before the pressure vessel semi-finished product is covered with wrapping. Like the pressure vessel semi-finished product, the pole cap reinforcement can also be manufactured separately, facilitating the production of the pole cap reinforcement and thus achieving an optimal reinforcement effect. In this case, the cylindrical pipe typically does not come into direct contact with the metal boss.

[0022] In another advantageous embodiment, the cylindrical pipe is pressed onto the liner. By this method, a separately manufactured cylindrical pipe can be joined to the liner with undercuts that can reliably engage with the cylindrical pipe. In addition, pressing allows for the establishment of a biased connection between the liner and the cylindrical pipe, which can be advantageous in terms of the possible formation of a gap between the liner and the cylindrical pipe during the operation of the pressure vessel. Pressing can be mechanically produced, for example, by applying a partial vacuum into the interior of the liner. This causes a temporary contraction of the liner diameter. The pipe can then slide over the liner. When the partial vacuum is removed, the liner expands relative to the interior of the pipe.

[0023] In another advantageous embodiment, the cylindrical pipe is thermally joined to the liner. For this purpose, the liner may be substantially cooled and / or the cylindrical pipe may be heated before joining. By cooling, the liner shrinks, i.e., its diameter decreases. Alternatively, the diameter of the cylindrical pipe increases during heating. After joining, when the temperatures equalize, a shrinkage joint is produced.

[0024] In another advantageous embodiment, the cylindrical pipe is adhesively bonded to the liner. In this way, an integral connection can be produced in addition to the shrink fit, which can minimize or even completely prevent the formation of a gap between the liner and the cylindrical pipe during operation of the pressure vessel.

[0025] For the adhesive bonding, it has proven advantageous for the inner circumference of the cylindrical pipe to be at least partially pretreated before bonding. This can be achieved, for example, by chemical or mechanical pretreatment. For example, the inner circumference of the cylindrical pipe can be roughened by a grinding method. In this way, the surface of the inner circumference of the cylindrical pipe is increased, which helps to achieve a stronger adhesive bond. Another example of such a treatment is treatment by laser.

[0026] Furthermore, the surface of the inner circumference can be structured. This measure can serve to deprive any gas that may enter between the liner and the cylindrical pipe and avoid liner buckling.

[0027] The treatment of the inner circumference of the cylindrical pipe is only possible by its separate manufacture.

[0028] The invention further relates to a pressure vessel manufactured by the method described above.

[0029] The embodiments described above can be used individually or in any combination, departing from the reference numbers of the claims, to implement the device according to the invention.

Brief Description of the Drawings

[0030] These and other aspects of the invention are shown in detail in the figures as follows.

[0031] [Figure 1] FIG. 1 is a cross-section through part of a pressure vessel according to the invention. [Figure 2]Figure 2 shows a cross-section through a portion of another pressure vessel according to the present invention. [Modes for carrying out the invention]

[0032] Figure 1 shows a cross-section through a portion of a pressure vessel according to the present invention. In particular, the figure shows a cross-section through the wall of a pressure vessel according to the present invention. On its exterior, the pressure vessel wall has a winding 1 made of a fiber composite material. The winding 1 is applied over a pressure vessel semi-finished product comprising a cylindrical pipe 2 and a liner as an inner layer. The cylindrical pipe 2 is located within the area of ​​the cylindrical central portion 6 of the pressure vessel. The liner 3 has an outer shape for receiving the cylindrical pipe 2 so that the cylindrical pipe 2 engages securely with the liner 3. This secure engagement is located at the transition from the cylindrical central portion 6 to the pole cap region 7 of the pressure vessel. The outer shape of the liner 3 has a recess into which the cylindrical pipe 2 is placed. The secure engagement can be such that it acts axially and / or radially.

[0033] Figure 2 shows a cross-section through a portion of a different pressure vessel according to the present invention. The pressure vessel has a pole cap reinforcement 4 within a pole cap region 7, which is applied over the pole cap region 7 before the winding is applied over the pressure vessel semi-finished product. Like the pressure vessel semi-finished product, the pole cap reinforcement 4 can also be manufactured separately, which facilitates the production of the pole cap reinforcement 4 and allows for the production of the pole cap reinforcement 4 so that such an optimal reinforcement effect is achieved. A connecting piece 5, also called a boss, is inserted into the pole cap reinforcement 4 and winding 1, and the connecting piece is used to fill the pressure vessel and to remove its contents (e.g., gas). The boss 5 is inserted into the pressure vessel so that the liner encloses it. In the embodiment shown in Figure 2, the liner 2 does not have a special outer shape for receiving the cylindrical pipe 2, but is a standard liner with a cylindrical outer shape without any undercuts.

[0034] The embodiments described herein are merely examples of the present invention and should not be understood as limitations. Alternative embodiments that can be considered by those skilled in the art are equally included within the scope of protection of the present invention.

[0035] (List of reference numbers) 1 roll 2 Cylindrical pipes 3 Liner Type 4 4. Reinforcement of pole caps 5 Bosses 6. Cylindrical central portion 7 Pole cap area

Claims

1. 1. A method of manufacturing a fiber reinforced pressure vessel, the method comprising: manufacturing a pressure vessel blank comprising at least one liner type 4 (3) and a cylindrical pipe (2) operatively connected thereto; overlapping the pressure vessel blank; A method characterized by:

2. 2. A method according to claim 1, characterized in that the cylindrical pipe (2) is manufactured separately.

3. 3. A method according to claim 2, characterized in that the cylindrical pipe (2) is wound from a fiber composite material.

4. 4. A method according to claim 3, characterized in that the cylindrical pipe (2) is wound on a metal winding core.

5. 5. A method according to one of claims 2 to 4, characterized in that the cylindrical pipe (2) is cut to length from a cylindrical semi-finished pipe.

6. Method according to one of claims 2-4, characterized in that the cylindrical pipe (2) is rolled to its final dimensions.

7. Method according to one of claims 2 to 6, characterized in that the cylindrical pipe (2) is at most partially hardened.

8. 3. A method according to claim 2, characterized in that the cylindrical pipe (2) is extruded.

9. 3. A method according to claim 2, characterized in that the cylindrical pipe (2) is pultruded.

10. The method according to one of claims 1 to 9, characterized in that the liner (3) has an external shape for receiving the cylindrical pipe (2) so that the cylindrical pipe (2) is securely engaged with the liner type 4 (3).

11. Method according to one of claims 1 to 10, characterized in that the boss (5) is in direct contact with the cylindrical pipe (2).

12. The method according to one of claims 1 to 11, characterized in that before the step of overlapping the pressure vessel blank, a pole cap reinforcement (4) is applied to at least one pole area of ​​the liner type 4 (3).

13. Method according to one of claims 1 to 12, characterized in that the cylindrical pipe (2) is pressed onto the liner type 4 (3).

14. 13. A method according to claim 12, characterized in that the cylindrical pipe (2) is thermally bonded to the liner type 4 (3).

15. Method according to one of claims 1 to 14, characterized in that the cylindrical pipe (2) is adhesively bonded to the liner type 4 (3).

16. 16. The method according to one of claims 1 to 15, characterized in that the cylindrical pipe (2) is at least partially treated at least on its inner circumference before it is operably connected to the liner type 4 (3).

17. A pressure vessel manufactured by the method according to one of claims 1 to 16.

Images