Pump for cryogenic liquids

Abstract

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

Description

Technical Field

[0001] The present invention relates to cryogenic equipment for producing, storing or using cryogenic liquids. The present invention particularly relates to a pump for ensuring the flow of cryogenic liquids in said equipment. The present invention is particularly suitable for pumps for liquid hydrogen. Background Art

[0002] A pump for cryogenic liquids comprises several static seals which ensure the sealing of the pump with respect to its external environment or between the internal compartments of the pump. These seals generally have a toric shape inside which the cryogenic liquid can be found. Depending on the nature of the seal, its housing and the location of the seal in the pump, the seal is held between the contact surfaces by two or more elements. For example, the seal may be placed between two parallel surfaces with only two contact surfaces on either side thereof, it may be placed in a triangular cross-section groove with 3 contact surfaces, or even in a rectangular cross-section groove with 4 contact surfaces.

[0003] In cryopumps according to the prior art, a copper seal or an energized seal, such as a lip seal with a spring, is usually found between two parallel contact surfaces.

[0004] The supporting surfaces of static seals for cryogenic pumps according to the prior art can be smooth surfaces, but with machining traces. These surfaces are usually obtained by turning or milling.

[0005] The advancement of the cutting tool during machining forms a spiral trace, thereby creating a leakage path for the cryogenic liquid.

[0006] The contact surfaces of the static seals for cryopumps according to the prior art may also have smooth surfaces without obvious machining traces. These surfaces are obtained, for example, by a first turning operation or a first milling operation followed by modification.

[0007] This type of surface condition is advantageous due to the absence of machining marks, but any impurities between the seal and the static seal will create a leak path. Similarly, surface marks, scratches caused by objects, such as during pump assembly, handling or maintenance, can also create leak paths for cryogenic liquids.

[0008] These surfaces can therefore change over time and the slightest defect can therefore lead to non-negligible leakage rates.

[0009] Small size leak paths may not be a problem for some cryogenic liquids, but are problematic for hydrogen due to the small size of the hydrogen molecule.

[0010] Seals used in cryogenic pumps are usually made of copper. Since copper has a finite elastic limit, the presence of impurities between the seal and its contact surface increases 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, which includes at least one static seal, which is intended to ensure sealing between a first mechanical component and a second mechanical component, the first mechanical component having a pipe intended to accommodate the cryogenic liquid, the pipe having an opening in one end of the first mechanical component, the end of the first mechanical component having a contact surface, the seal having a first face in contact with the contact surface of the first mechanical component and a second face in contact with the contact surface of the second mechanical component arranged at one end of the second mechanical component, characterized in that the contact surface of the first mechanical component includes at least one closed groove surrounding the opening in the end of the first mechanical component, and characterized in that the second mechanical component includes a pipe intended to accommodate the cryogenic liquid, the pipe having an opening in the end of the second mechanical component, the seal having an opening connecting the opening of the first mechanical component and the opening of the second mechanical component, and characterized in that the contact surface of the second mechanical component includes at least one closed groove surrounding the opening in the end of the second mechanical component.

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

[0014] For example, during the machining operation, the closed groove has been formed by the cutting tool. For example, during the machining performed by turning the contact surface, the closed groove is formed by the cutting tool. In order to obtain these closed grooves, the tool advances toward or from the pipeline, so that the cutting edge of the tool is exposed from the surface in this way. Therefore, machining is performed by a series of continuous machining steps. Take the machining of the support surface from the outside of the support surface (that is, the point farthest from the pipeline in the radial direction) as an example. When the cutting tool is in a position retracted from the surface to be machined, the cutting tool is radially positioned at a first position. Then, the tool advances toward the surface to perform a first machining operation. Once the operation is completed, the tool is retracted from the support surface and then radially moved to a second position closer to the pipeline. Then, the tool advances toward the surface to perform a second machining operation. Repeat the operation as needed for multiple times to machine the entire support surface.

[0015] The importance of the radial displacement of the tool between two machining operations and the penetration depth of the tool during machining are adjusted according to the shape and size of the cutting surface of the tool to obtain machining of the entire support surface. This will include as many closed grooves as the radial displacement of the tool in the retracted position and the subsequent machining operations.

[0016] Advantageously, the contact surface of the second mechanical component comprises a plurality of continuous closed grooves starting from the opening of the second mechanical component, the first groove being closest to the opening, the second groove and subsequent grooves of the contact surface of the second mechanical component surrounding the contact surface of the second mechanical component being positioned closer to the opening in the end of the second mechanical component.

[0017] The presence of a closed groove according to the invention on two opposing contact surfaces between which the seal is positioned allows ensuring the seal on both sides of the seal.

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

[0019] Advantageously, the closed groove forms a closed channel delimited by the protruding edges. These closed grooves are impressed into the seal by local deformation of the seal due to the compression of the seal caused by the tightening force applied by the two supporting surfaces. These edges thus form a continuous barrier that prevents the cryogenic liquid from escaping.

[0020] Advantageously, the static seal also ensures sealing with a third mechanical part, the seal having a third face in contact with a contact surface of the third mechanical part, characterised in that the contact surface of the third mechanical part lacks a groove.

[0021] According to its nature and location in the pump, the static seal can also ensure sealing with a third mechanical part, the seal having a third face in contact with a contact surface of the third mechanical part, the pump being characterized in that the contact surface of the third mechanical part lacks a groove. This type of sealing is present in particular between the head and the liner and between the liner and the pump cylinder. The housing formed by these three mechanical parts, in which the seal is placed, is advantageously triangular in section, just like the seal. In this case, the static seal advantageously forms a circular ring of triangular section.

[0022] Advantageously, the static seal is made of a polymer. The elastic limit of polymers is higher than that of copper. In addition, these polymers tolerate low temperatures very well. Compared to metals, these polymers have excellent sealing properties. These polymers handle traction and creep very well. The use of polymers also helps to compensate for any imperfections that may be present on the supporting surface of the static seal. The polymer has plasticity and mechanical properties that allow it to adapt to these imperfections better than copper, which improves the seal at the static seal.

[0023] Advantageously, the static seal may be made of polytetrafluoroethylene (PTFE) or polychlorotrifluoroethylene (PCTFE) or polyimide. These materials are particularly advantageous because their coefficient of expansion is low compared to other polymers. Thus, the static seal is better able to maintain good dimensional stability even when subjected to a temperature range from cryogenic to ambient temperature.

[0024] The pump according to the 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 during reading the following detailed description, and for an understanding of these features and advantages reference will be made to the accompanying drawings, in which:

[0026] Figure 1 is a schematic partial view (section) of a pump at the level of a static seal placed between two contact surfaces for blocking a pipeline, the seal being in the working position;

[0027] Figure 2 The contact surfaces of the seal are shown in an exploded view at the seal level for better visualization. Figure 1 A schematic partial view of the pump at the level of the static seal;

[0028] Figure 3 is a schematic partial view (section view) of a pump according to an example of embodiment of the invention at the level of a static seal placed between two contact surfaces, wherein the static seal ensures the seal during the continuity of the pipe between the two components, the seal being in the working position;

[0029] Figure 4 The contact surfaces of the seal are shown in an exploded view at the seal level for better visualization. Figure 3 A schematic partial view of the pump at the level of the static seal;

[0030] Figure 5 is a schematic partial view (section view) of a pump according to an example of an embodiment of the invention at the level of a static seal placed between three contact surfaces, wherein the static seal ensures sealing during the continuity of the pipe between two components, the seal being in working position;

[0031] Figure 6 The contact surfaces of the seal are shown in an exploded view at the seal level for better visualization. Figure 5 A schematic partial view of the pump at the level of the static seal;

[0032] Figure 7 is a schematic partial view (top view) of a contact surface including a groove according to an example of an embodiment of the present invention; and

[0033] Figure 8 yes Figure 7 Schematic partial view (cross-sectional view) of the contact surface. DETAILED DESCRIPTION

[0034] Reference Figure 1 , a flat static seal 2 can be seen placed between a first mechanical part 3 and a second mechanical part 8, wherein the static seal serves to block a duct 4 of the first part 3 with axis A, which duct is intended to receive a cryogenic fluid, the seal being shown in the working position.

[0035] Reference Figure 2 , you can see Figure 1 2, but in an assembled position convenient for describing the invention. The duct 4 has an opening 5 in one end 6 of a first mechanical part, said end 6 of the first mechanical part having a contact surface 7, the seal having a first face 9 against the contact surface 7 of the first mechanical part 3 and a second face 10 against a contact surface 11 of a second mechanical part 8 arranged at one end 15 of said second mechanical part.

[0036] The seal comprises a first face 9, which is intended to abut against a contact surface 7 of a first component 3. The seal further comprises a second face 10, which is intended to abut against a contact surface 11 of a second component 8. The contact surface 7 of the first mechanical component comprises a closed groove according to the invention. According to the invention, the contact surface 11 of the second mechanical component does not need to have a closed groove, since it does not have to ensure the sealing function. After positioning the seal between the two mechanical components, a tightening force is applied by the two mechanical components to compress the seal. The seal is made of a polymer, which deforms during compression. As Figure 8 As shown, the closed groove present on the contact surface 7 comprises a protruding edge forming a closed ridge 18 between two closed channels 17. The compression of the seal and its elastic material allows the sealing face 9 to completely match the contact surface of the first mechanical part 3. The seal thus fills the channels 17 and the protruding edge is impressed into the seal, forming continuous barriers that present as many obstacles to the flow of liquid between the face 9 of the seal and the contact surface 7 of the first mechanical part. The seal thus allows the opening 5 of the duct 4 of the first mechanical part to be completely blocked.

[0037] Reference Figure 3 , one can see 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 invention, wherein the static seal allows ensuring the sealing of fluid continuity between a duct 4 of the first part 3 and a duct 13 of the second part 8, the duct being intended to contain a cryogenic liquid, the seal being shown in a working position.

[0038] Reference Figure 4 , you can see Figure 3 The same flat static seal 2 as in the example, but in an assembly position that facilitates the description of the invention. The second mechanical part 8 has a duct 13, which has an opening 14 in one end 15 of the second mechanical part. The seal has an opening 16 connecting the opening 5 of the first mechanical part and the opening 14 of the second mechanical part. The seal comprises a first face 9, which is intended to abut against a contact surface 7 of the first part 3. The seal also comprises a second face 10, which is intended to abut against a contact surface 11 of the second part 8. In this example, the seal must ensure sealing on its two opposite faces 9, 10. Therefore, the two contact surfaces 7, 11 comprise closed grooves according to the invention. As Figure 1In the example shown, after the seal is positioned between the two mechanical components, a tightening force is applied by the two mechanical components to compress the seal. The compression of the seal and its elastic material will allow the two support surfaces to completely match the contact surfaces of the two mechanical components. Therefore, the seal fills the channels 17 of the two contact surfaces, and their protruding edges are embossed into the seal, thereby forming a continuous barrier, preventing the flow of liquid between the two faces of the seal and the contact surfaces of the mechanical components. Therefore, the sealing during the transmission of the cryogenic liquid from the pipeline 4 to the pipeline 13 is ensured.

[0039] Reference Figure 5 , a triangular-section static seal 2 can be seen placed between a first mechanical part 3, a second mechanical part 8 and a third mechanical part 19, according to an example of an embodiment of the invention, wherein the static seal allows ensuring fluid continuity between a duct 4 of the first part 3 and a duct 13 of the second part 8, the seal being shown in an operating position. The housing formed by the three mechanical parts, in which the seal is placed, has a triangular cross-section.

[0040] Reference Figure 6 , you can see Figure 5 The same static seal 2 as in the embodiment of the present invention is provided, but in an assembly position that facilitates the description of the invention. The seal comprises a first face 9, which is intended to abut against a contact surface 7 of a first component 3. The seal comprises a second face 10, which is intended to abut against a contact surface 11 of a second component 8. The seal also comprises a third face 20, which is intended to abut against a contact surface 21 of a third component 19. In this example, the seal must ensure sealing on its two opposite faces 9, 10. To ensure this function on these two faces, the third face 20 of the seal does not need to ensure sealing. However, advantageously, the third face also ensures sealing to strengthen the overall sealing obtained by the seal. Only two opposite contact surfaces 7, 11 comprise closed grooves according to the invention. The third contact surface 21 is completely smooth and therefore has no grooves.

[0041] It is worth noting that the third contact surface serves as a guide during installation of the seal. Thus, during installation of the seal during assembly of the pump, the third face 20 of the seal slides on the contact surface 21 of the third mechanical component. The sliding of the third face of the seal on the contact surface of the third mechanical component may also be caused by the differential expansion of the third mechanical component relative to the other two components. If grooves are present on the third mechanical component, these grooves will damage the seal by an action similar to machining.

[0042] Advantageously, the seal has a triangular cross-section slightly larger than that of the housing in which it is placed. Thus, during compression of the seal by tightening the first part 3 and the second part 8, the force exerted by the two contact surfaces comprising the closed groove according to the invention causes the seal to deform towards the third contact surface. This configuration allows optimal filling of the volume in which the seal is placed, while ensuring good contact between the seal and all the contact surfaces.

[0043] Reference Figure 7 , a contact surface 7 of a mechanical component 3 comprising a plurality of closed grooves 12 according to an example of an embodiment of the invention can be seen, represented in top view.

[0044] The contact surface surrounds the pipe 4 intended to receive a cryogenic liquid. In this example, the closed grooves are circular and concentric around the axis A of the pipe 4, with a constant distance between two grooves and a constant distance between two consecutive grooves along the length of these grooves. The grooves can be of any shape other than circular. Thus, the distance from the groove to the axis of the pipe 4 can vary along the length of the groove. Similarly, the distance between two grooves can vary along the length of the groove, the grooves being closer in some places and farther apart in other places.

[0045] The distance between two consecutive grooves can also be different, the grooves being for example closer together near the pipe 4 and further apart outside the contact surface. The only restriction is that the grooves must be closed to stop the flow of cryogenic liquid.

[0046] Reference Figure 8 , it can be seen that according to Figure 7 The plane CC represented in Figure 7 The closed groove 12 present on the contact surface 7 comprises a protruding edge forming a ridge 18 between two closed channels 17.

Claims

1. A pump (1) for cryogenic liquids, the pump comprising at least one static seal (2), the static seal being suitable for ensuring 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 the cryogenic liquid, the duct having an opening (5) in one end (6) of the first mechanical part, the end (6) of the first mechanical part having a contact surface (7), the seal having a first face (9) resting against the contact surface (7) of the first mechanical part (3) and a second face (10) resting against a contact surface (11) of the second mechanical part (8) arranged at one end (15) of the second mechanical part, Features The contact surface (7) of the first mechanical part (3) comprises at least one closed groove (12) surrounding the opening (5) in the end (6) of the first mechanical part, characterised in that the second mechanical part (8) has a duct (13) intended to contain a cryogenic liquid, the duct having an opening (14) in the end (15) of the second mechanical part, the seal (2) having an opening (16) connecting the opening (5) of the first mechanical part and the opening (14) of the second mechanical part, and Characterized in that the contact surface (11) of the second mechanical part (8) comprises at least one closed groove (12) surrounding the opening (14) in the end (15) of the second mechanical part.

2. The pump according to claim 1, characterized in that The contact surface (7) of the first mechanical component (3) comprises a plurality of continuous closed grooves (12) starting from the opening (5) of the pipe (4) of the first mechanical component, the first groove being closest to the opening (5), the second groove and subsequent grooves surrounding the groove being positioned closer to the opening (5) of the pipe (4) of the first mechanical component.

3. The pump according to claim 1, characterized in that The contact surface (11) of the second mechanical component (8) comprises a plurality of continuous closed grooves (12) starting from the opening (14) of the second mechanical component, the first groove being closest to the opening (14), the second groove and subsequent grooves of the contact surface (11) of the second mechanical component (8) surrounding the grooves of the surface (11) of the contact surface of the second mechanical component (8) being positioned closer to the opening (14) in the end (15) of the second mechanical component.

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

5. Pump according to one of the preceding claims, characterized in that The closed groove (12) forms a closed channel (17) delimited by a protruding edge (18).

6. Pump according to one of the preceding claims, the static seal (2) also ensuring sealing with a third mechanical component (19), the seal having a third face (20) resting against a contact surface (21) of the third mechanical component (19), characterised in that The contact surface (21) of the third mechanical component (19) lacks a groove (12).

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

8. Pump according to one of the preceding claims, characterized in that The static seal (2) is made of 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. Pump according to one of the preceding claims, characterized in that The pump is suitable for pumping liquid hydrogen.

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