Pump for cryogenic liquids

Abstract

A pump (1) for cryogenic liquids, the pump comprising at least one static seal (2) capable of providing a seal between a first mechanical part (3) and a second mechanical part (8), the first mechanical part (3) having a duct (4) intended to contain cryogenic liquid, the duct having an opening (5) at one end (6) of the first mechanical part, the said end (6) of the first mechanical part having a contact surface (7), the seal having a first face (9) which abuts against the contact surface (7) of the first mechanical part (3) and a second face (10) which abuts against a contact surface (11) of the second mechanical part (8) located at one end (15) of the second mechanical part, the contact surface (7) of the first mechanical part (3) comprising at least one closed groove (12) surrounding the opening (5) of the end (6) of the first mechanical part.

Description

Technical Field

[0001] The present invention relates to cryogenic equipment for the production, storage or use of cryogenic liquids. Specifically, the present invention relates to a pump for ensuring the flow of cryogenic liquids in the above equipment. The present invention is particularly suitable for pumps for liquid hydrogen.

Background Art

[0002] Cryogenic liquid pumps include several static seals that ensure sealing against the external environment of the pump or between internal compartments of the pump. These seals generally have an annular shape, and cryogenic liquid can be seen inside them. The seal is maintained between the contact surfaces by two or more elements depending on the nature of the seal, its housing, and the position of the seal within the pump. For example, the seal may be placed between two parallel surfaces having only two contact surfaces on either side of it, may be placed in a groove with a triangular cross-section having three contact surfaces, or may be placed in a groove with a rectangular cross-section having four contact surfaces.

[0003] In cryogenic pumps according to the prior art, a copper seal or a biased seal, such as a spring-loaded lip seal, is generally seen between two parallel contact surfaces.

[0004] The support surfaces for the static seals of cryogenic pumps according to the prior art are smooth surfaces, but may have machining marks. These surfaces are generally obtained by turning or milling.

[0005] Advancement of the cutting tool during machining forms spiral marks, creating leakage paths for cryogenic liquids.

[0006] The contact surfaces for the static seals of cryogenic pumps according to the prior art can also have smooth surfaces without obvious machining marks. They are obtained, for example, by a first turning or milling operation followed by finishing.

[0007] This type of surface condition is advantageous as it has no machining marks, but any impurities between the seal and the static seal create leakage paths. Similarly, surface marks and scratches caused by objects during, for example, pump assembly, handling or maintenance can also create leakage paths for cryogenic liquids.

[0008] Therefore, those surfaces may change over time. As a result, even minor defects can lead to non - negligible leakage rates.

[0009] Leakage paths of small dimensions may not be a problem for certain cryogenic liquids, but due to the small size of hydrogen molecules, they are a problem for hydrogen.

[0010] Seals used in cryogenic pumps are generally made of copper. Due to the limited elastic limit of copper, the presence of impurities between the seal and its contact surface can accentuate the risk of leakage.

[0011] The present invention provides a new solution to this problem.

Summary of the Invention

[0012] According to the present invention, a cryogenic liquid pump is proposed, the pump comprising at least one static seal intended to ensure a seal between a first mechanical part and a second mechanical part, the first mechanical part having a duct intended to contain a cryogenic liquid and having an opening at one end of the first mechanical part, the said end of the first mechanical part having a contact surface, the seal having a first face in contact with the contact surface of the first mechanical part and a second face in contact with the contact surface of the second mechanical part provided at one end of the said second mechanical part, the contact surface of the first mechanical part comprising at least one closed groove surrounding the opening of the end of the first mechanical part, the second mechanical part having a duct intended to contain a cryogenic liquid and having an opening at one end of the second mechanical part, the seal having an opening connecting the openings of the first and second mechanical parts, and the contact surface of the second mechanical part comprising at least one closed groove surrounding the opening of the end of the second mechanical part.

[0013] Advantageously, according to the present invention, the contact surface of the first mechanical part comprises a plurality of continuous closed grooves starting from the opening of the duct of the first mechanical part, the first groove being the closest to the opening and the second groove and subsequent grooves surrounding the grooves arranged closer to the opening of the duct of the first mechanical part.

[0014] The closed grooves are formed, for example, by a cutting tool during a machining operation. For example, the closed grooves are formed by a cutting tool during machining by turning the contact surface. To obtain these closed grooves, the tool advances towards or from the duct such that the cutting edge of the tool projects from the surface. As a result, the machining is carried out through a series of successive machining steps. Consider an example where the machining of the support surface is carried out from the outside thereof, i.e., from the point furthest radially from the duct. The cutting tool is arranged in a first position radially when it is in a position retracted from the surface being machined. Next, the tool is advanced towards the surface to carry out a first machining operation. When this is completed, the tool is retracted from the support surface and then moved to a second position radially closer to the duct. Next, the tool is advanced towards the surface to carry out a second machining operation. This operation is repeated the number of times necessary to machine the entire support surface.

[0015] To obtain machining of the entire support surface, the radial displacement of the tool between two machining operations and the depth of penetration of the tool during machining are adapted according to the shape and dimensions of the cutting face of the tool. This includes the same number of closed grooves as the number of operations of carrying out machining after the radial displacement of the tool in the retracted position.

[0016] Advantageously, the contact surface of the second mechanical part includes a plurality of successive closed grooves starting from the opening of the second mechanical part, the first groove being closest to the opening, and the second groove and subsequent grooves of the contact surface of the second mechanical part being arranged closer to the opening at the end of the second mechanical part, surrounding the grooves of the contact surface of the second mechanical part.

[0017] The presence of the closed grooves according to the invention on both opposing contact surfaces between which the seal is arranged makes it possible to ensure sealing on both sides of the seal.

[0018] Advantageously, the closed grooves are concentric. They may be circular. The distance between two adjacent closed grooves may be the same for all the closed grooves present on the bearing surface.

[0019] Advantageously, the closed grooves form a closed channel defined by a protruding edge. These are engraved into the seal by local deformation of the seal due to compression of the seal caused by the clamping force applied by two support surfaces. As a result, the edge forms a continuous barrier that prevents leakage of cryogenic liquids.

[0020] Advantageously, the static seal also ensures sealing with a third mechanical component, the seal having a third face that contacts the contact surface of the third mechanical component, and the contact surface of the third mechanical component being characterized by the absence of grooves.

[0021] The static seal can also ensure sealing with a third mechanical component depending on its nature and position within the pump, the seal having a third face that contacts the contact surface of the third mechanical component, and the pump being characterized by the absence of grooves on the contact surface of the third mechanical component. This type of seal is particularly found between the head and the liner, and between the liner and the pump cylinder. The housing formed by the seal and the three mechanical components within which the seal is placed is advantageously triangular in cross-section like the seal. In this case, the static seal advantageously forms a toroid with a triangular cross-section.

[0022] Advantageously, the static seal is made of a polymer. The polymer has an elastic limit higher than that of copper. Moreover, the polymer is completely resistant to cryogenic temperatures. The polymer has excellent sealing properties compared to metals. They handle traction and creep well. By using the polymer, it also helps to compensate for any defects that may be present on the support surface of the static seal. The polymer has plasticity and mechanical properties that allow it to conform better to these defects than copper, which improves the sealing in the static seal.

[0023] Advantageously, the static seal can be made of polytetrafluoroethylene (PTFE), or polychlorotrifluoroethylene (PCTFE), or polyimide. These materials are particularly advantageous because they have a low coefficient of expansion compared to other polymers. As a result, the static seal can better maintain good dimensional stability even when exposed to temperatures in the range from cryogenic temperatures to ambient temperature.

[0024] The pump according to the present invention is particularly suitable for pumping liquid hydrogen.

Brief Description of the Drawings

[0025] Other features and advantages of the present invention will become apparent while reading the following detailed description with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0026] Referring to FIG. 1, a flat static seal 2 placed between the first machine part 3 and the second machine part 8 can be seen. The static seal functions to block a duct 4 having a shaft A intended to receive a cryogenic fluid in the first part 3, and the seal is shown in the operating position.

[0027] Referring to FIG. 2, the same flat static seal 2 as in FIG. 1 can be seen, but it is in an assembled position for easier explanation of the present invention. The duct 4 has an opening 5 at one end 6 of the first machine part, the above-mentioned end 6 of the first machine part has a contact surface 7, and the seal has a first surface 9 that abuts against the contact surface 7 of the first machine part 3 and a second surface 10 that abuts against the contact surface 11 of the second machine part 8 provided at one end 15 of the second machine part.

[0028] The seal includes a first face 9 intended to abut against the contact surface 7 of the first part 3. The seal also includes a second face 10 intended to abut against the contact surface 11 of the second part 8. The contact surface 7 of the first mechanical part includes a closed groove according to the invention. The contact surface 11 of the second mechanical part, since it is not necessary to ensure a sealing function, does not need to have a closed groove according to the invention. After placing the seal between the two mechanical parts, a clamping force is applied by the two mechanical parts to compress the seal. The seal is made of a polymer and deforms during compression. As shown in FIG. 8, the closed groove present on the contact surface 7 includes a protruding edge that forms a closed ridge 18 between two closed channels 17. Compression of the seal and its elastic material allows the seal face 9 to fit perfectly with the contact surface of the first mechanical part 3. As a result, the seal fills the channels 17 and the protruding edge is engraved into the seal to form a continuous barrier, which are many obstacles to the flow of liquid between the seal face 9 and the contact surface 7 of the first mechanical part. As a result, the seal can completely block the opening 5 of the duct 4 of the first mechanical part.

[0029] Referring to FIG. 3, a flat static seal 2 placed between a first mechanical part 3 and a second mechanical part 8 according to an example of an embodiment of the present invention can be seen. The static seal makes it possible to ensure the sealing of the fluid continuity between the duct 4 of the first part 3 and the duct 13 of the second part 8, which is intended to receive cryogenic liquids. The seal is shown in the operating position.

[0030] Referring to FIG. 4, the same flat static seal 2 as in FIG. 3 can be seen, but it is in an assembled position to facilitate the description of the present invention. The second machine part 8 has a duct 13 having an opening 14 at one end 15 of the second machine part. The seal has an opening 16 connecting the openings 5, 14 of the first and second machine parts. The seal includes a first face 9 intended to abut against the contact surface 7 of the first part 3. The seal also includes a second face 10 intended to abut against the contact surface 11 of the second part 8. In this example, the seal must ensure a seal on its two opposing faces 9, 10. Thus, the two contact surfaces 7, 11 include a closed groove according to the present invention. As in the example shown in FIG. 1, after the seal is placed between the two machine parts, a clamping force is applied by the two machine parts to compress the seal. Compression of the seal and its elastic material allows the two support surfaces to fit perfectly with the contact surfaces of the two machine parts. As a result, the seal fills the channels 17 of both contact surfaces, and their protruding edges are engraved into the seal to form a continuous barrier, preventing the flow of liquid between the two faces of the seal and the contact surfaces of the machine parts. As a result, a seal is guaranteed during the passage of cryogenic liquid from duct 4 to duct 13.

[0031] Referring to FIG. 5, a static seal 2 with a triangular cross-section placed between a first machine part 3, a second machine part 8, and a third machine part 19 according to an example of an embodiment of the present invention can be seen. The static seal makes it possible to ensure the fluid continuity between the duct 4 of the first part 3 and the duct 13 of the second part 8, and the seal is shown in the operating position. The housing formed by the three machine parts in which the seal is placed has a triangular cross-section.

[0032] Referring to FIG. 6, the same static seal 2 as in FIG. 5 can be seen, but it is in an assembly position that facilitates the description of the present invention. The seal includes a first face 9 intended to abut against a contact surface 7 of a first part 3. The seal includes a second face 10 intended to abut against a contact surface 11 of a second part 8. The seal also includes a third face 20 intended to abut against a contact surface 21 of a third part 19. In this example, the seal must ensure sealing on two opposite faces 9, 10 of the seal. Since this function is ensured by these two faces, the third face 20 of the seal does not need to ensure sealing. Nevertheless, it is advantageous to also ensure sealing to strengthen the overall sealing obtained by the seal. Only the two opposite contact surfaces 7, 11 include a closed groove according to the present invention. The third contact surface 21 is completely smooth and thus has no groove.

[0033] The third contact surface functions, in particular, as a guide during seal installation. As a result, the third face 20 of the seal slides on the contact surface 21 of the third mechanical part during seal installation during the assembly of the pump. Due to the different expansion of the third mechanical part compared to the other two mechanical parts, sliding of the third face of the seal can also occur on the contact surface of the third mechanical part. If a groove is present on the third mechanical part, the groove will damage the seal by an effect similar to machining.

[0034] Advantageously, the seal has a triangular cross-section that is slightly larger than the cross-section of the housing in which it is placed. As a result, during seal compression by tightening of the first two parts 3, 8, the force applied by the two contact surfaces including the closed groove according to the present invention causes deformation of the seal towards the third contact surface. This configuration makes it possible to optimally fill the volume in which the seal is placed while ensuring good contact between the seal and all the contact surfaces.

[0035] Referring to FIG. 7, it can be seen that the contact surface 7 of the mechanical part 3 with a plurality of closed grooves 12 according to an example embodiment of the present invention is represented in a top view.

[0036] The contact surface surrounds a duct 4 intended to receive cryogenic liquid. In this example, the closed grooves are circular and concentric around the axis A of the duct 4, the distance between the two grooves is constant along the length of the grooves, and the distance between two consecutive grooves is constant. The grooves may be non-circular and of any shape. As a result, the distance from the grooves to the axis of the duct 4 may vary along the length of the grooves. Similarly, the distance between the two grooves may vary along the length of the grooves, and they may be closer in some places and farther in other places.

[0037] The distance between two consecutive grooves may be different, and they may be closer, for example, near the duct 4 and farther outside the contact surface. The only constraint is that the grooves must be closed so as not to interrupt the flow of cryogenic liquid.

[0038] Referring to FIG. 8, it can be seen that a cross-section of the contact surface of FIG. 7 by the plane CC shown in FIG. 7 is partially shown. The closed grooves 12 present on the contact surface 7 include a protruding edge portion that forms a ridge 18 between two closed channels 17.

Claims

**Claim 1** A pump (1) for cryogenic liquids, said pump comprising at least one static seal (2) suitable for ensuring a seal between a first mechanical part (3) and a second mechanical part (8), said first mechanical part (3) having a duct (4) intended to contain cryogenic liquid, said duct having an opening (5) at one end (6) of said first mechanical part, said end (6) of said first mechanical part having a contact surface (7), said seal having a first face (9) that abuts against said contact surface (7) of said first mechanical part (3) and a second face (10) that abuts against a contact surface (11) of said second mechanical part (8) provided at one end (15) of said second mechanical part, wherein said contact surface (7) of said first mechanical part (3) comprises at least one closed groove (12) surrounding said opening (5) of said end (6) of said first mechanical part, said second mechanical part (8) having a duct (13) intended to contain cryogenic liquid, said duct having an opening (14) at one end (15) of said second mechanical part, and said seal (2) having an opening (16) connecting said openings (5, 14) of said first and second mechanical parts, and wherein said contact surface (11) of said second mechanical part (8) comprises at least one closed groove (12) surrounding said opening (14) of said end (15) of said second mechanical part. A pump characterized thereby. **Claim 2** The pump according to claim 1, wherein said contact surface (7) of said first mechanical part (3) comprises a plurality of consecutive closed grooves (12) starting from said opening (5) of said duct (4) of said first mechanical part, a first groove being closest to said opening (5), and second and subsequent grooves surrounding grooves arranged closer to said opening (5) of said duct (4) of said first mechanical part. **Claim 3** The contact surface (11) of the second machine part (8) comprises a plurality of continuous closed grooves (12) starting from the opening (14) of the second machine part, with the first groove being closest to the opening (14), and the second groove and subsequent grooves of the contact surface (11) of the second machine part (8) surrounding the surface (11) of the contact surface of the second machine part (8) arranged closer to the opening (14) of the end (15) of the second machine part. The pump according to claim 1, characterized in that.

4. The pump according to claim 2 or 3, characterized in that the closed grooves (12) are concentric.

5. The pump according to any one of claims 1 to 4, characterized in that the closed grooves (12) form a closed channel (17) defined by a protruding edge (18).

6. The static seal (2) also ensures sealing with a third machine part (19), and the seal has a third face (20) that abuts against the contact surface (21) of the third machine part (19), and the contact surface (21) of the third machine part (19) has no grooves (12). The pump according to any one of claims 1 to 5, characterized in that.

7. The pump according to claim 6, characterized in that the static seal (2) forms a toroid with a triangular cross-section.

8. The pump according to any one of claims 1 to 7, characterized in that the static seal (2) is made of a polymer.

9. The pump according to claim 8, characterized in that the static seal (2) is made of polytetrafluoroethylene (PTFE).

10. The pump according to claim 8, characterized in that the static seal (2) is made of polychlorotrifluoroethylene (PCTFE).

11. The pump according to claim 8, characterized in that the static seal (2) is made of polyimide.

12. The pump according to any one of claims 1 to 11, characterized in that it is suitable for pumping liquid hydrogen.

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