Method for starting up a pump, and pump for carrying out the method

Abstract

The invention relates to a method for minimizing a hydraulic gap between an impeller and a pump housing of a centrifugal pump when the pump is started up for the first time. The hydraulic gap of the pump is defined between a rotating surface, which is formed by the impeller or is connected to the impeller, and a stationary surface, which is formed by the pump housing or is connected to the pump housing. The method is characterized in that the rotating surface is moved in the direction of the stationary surface by means of an axial force produced during an operation of the pump and is brought into frictional contact with the stationary surface at least when the pump is started up for the first time. At least one of the surfaces has an abrasive surface structure, as a result of which material is axially removed from the other surface until the axial movement of the rotating surface is limited by a separate stop means.

Description

[0001] Description

[0002] Procedure for commissioning a pump and pump for process execution

[0003] The invention relates to a method for minimizing a hydraulic gap between the impeller and the pump housing of a centrifugal pump during its initial commissioning.

[0004] For design reasons, there is a gap between the impeller and the pump housing that separates the pressure side from the suction side of the pump. Due to the difference in pressure upstream and downstream of the impeller, part of the pumped fluid, which has already been brought to a higher static pressure, flows back through the gap between the stationary and rotating parts of the pump (gap flow). The resulting power loss is referred to as gap loss.

[0005] To limit the resulting power losses, it is therefore desirable to keep the hydraulic gap between the impeller and the pump casing small. However, due to manufacturing tolerances, it is often difficult to manufacture the pump casing and impeller with the desired final dimensions to minimize the gap.

[0006] The object of the present invention is therefore to provide a solution to the above problem in order to keep the hydraulic gap between the impeller and the pump housing as small as possible and thereby minimize any hydraulic losses that may occur. This object is achieved by a method according to the features of claim 1. Advantageous embodiments of the method are the subject of the dependent claims. Furthermore, the problem is solved by a centrifugal pump according to the features of claim 11.

[0007] The core idea of ​​the invention is not to manufacture the components relevant for the gap to their final dimensions in advance, but instead to ensure that the hydraulic gap between the impeller and the pump housing is reduced to a minimum by running in the pump during initial commissioning. The hydraulic gap of the pump results between a rotating surface formed by the impeller or connected to the impeller and a surface formed by the pump housing or stationary connected to the pump housing. Due to the design, an axial force acts on the impeller and consequently on the rotating surface during pump operation, whereby the surface is pressed towards the stationary surface. According to the invention, it is proposed to design at least one of the surfaces forming the gap with an abrasive surface structure.During initial commissioning, a certain degree of axial movement of the impeller and thus relative movement of the two surfaces toward each other is permitted, so that both surfaces come into contact. The abrasive surface structure of one of the surfaces results in a defined axial material removal on the other surface. However, the axial movement of the surfaces toward each other is limited by an axial stop, so that after the desired axial material removal, the two surfaces are positioned at a minimal distance from each other, i.e., the smallest possible gap is created between the two surfaces.

[0008] With this inventive approach, the desired final dimension in the area of ​​the hydraulic gap is only achieved after a certain pump runtime. Ideally, the abrasive surface structure or the material type of the complementary surface section is dimensioned in such a way that a final dimension is achieved as quickly as possible, ideally after a maximum of 10 hours of runtime, preferably after a maximum of 5 hours. Ideally, sufficient material removal is also achieved significantly faster, for example, after just one hour, 30 minutes, or even less runtime.

[0009] As an advantageous embodiment, it is proposed to design the stationary surface with an abrasive surface structure. This forces axial material removal on the rotating surface. For example, it is conceivable that the rotating surface is formed by a section of the impeller itself, i.e. the impeller is initially manufactured with a certain oversizing and is then ground to the final dimension through the axial material removal. It is particularly preferred if the rotating surface is formed by an end face of the impeller that defines the suction mouth of the impeller, i.e. axial material removal occurs on this end face in the axial direction of the impeller. Alternatively, the rotating surface can of course also have the abrasive surface structure and axial material removal can occur on the stationary surface.

[0010] It is also conceivable that a separate component, e.g. a ring, is mounted on the pump housing, whereby the ring has an abrasive surface structure and comes into contact with the front side of the impeller.

[0011] The stationary surface is formed by an annular surface of the inner wall of the pump housing, oriented perpendicular to the axial direction, against which the impeller's face is moved by the axial movement. This annular surface section of the inner wall then comes into direct frictional contact with the impeller's face during initial pump start-up, resulting in the desired axial material removal on the impeller. After reaching the axial end stop, the impeller then rotates without further contact with the vertical surface of the pump housing, resulting in a minimal hydraulic gap between the pump housing and the impeller's face.

[0012] The stop device can be an axial bearing, which has a rotating axial bearing part fixed to the pump shaft and a thrust bearing part fixed to the pump housing. Such an axial bearing is initially manufactured with a defined initial gap upon delivery, allowing the desired axial movement of the shaft and thus of the pump impeller toward the stationary surface on the pump housing. However, the axial bearing limits the maximum axial displacement, so that only a defined axial material removal is possible. For example, it is conceivable that the axial bearing is the motor bearing.

[0013] Material removal from the impeller was suggested above. However, it is also conceivable that a so-called wear ring or a wear ring bearing is incorporated in the area between the impeller and the pump housing. In this case, the hydraulic gap between the pump impeller and the pump housing is defined between the rotating ring and the stationary ring of the wear ring bearing. The method according to the invention can also be applied to such a design in that the components of the wear ring bearing are not manufactured directly to size, but rather a certain oversizing occurs, so that when the pump is first put into operation, a defined axial material removal takes place in order to manufacture the wear ring bearing to the desired final dimensions with the smallest possible gap.

[0014] For example, it is conceivable that material removal occurs on a raceway bearing ring attached to the pump housing. A raceway bearing ring, fixed to the impeller's face on the suction inlet side and rotating with the impeller, then comprises the required abrasive surface structure to ensure the necessary material removal on the fixed raceway bearing ring. Alternatively, however, it is also conceivable that material removal occurs on the rotating bearing ring attached to the impeller's face on the suction inlet side, and that the bearing ring attached to the pump housing has the abrasive surface structure.

[0015] The abrasive surface structure can be applied to the surface on the inner wall of the pump housing or to the ring of the split ring bearing by applying an abrasive coating, for example, one coated with diamond particles. Applying a film, particularly a film coated with diamond particles, to the surface is also conceivable. It is also conceivable to produce the abrasive surface structure by means of adaptive or machining of the surface. A suitable abrasive surface structure can be created, for example, by a corresponding sawtooth profile, which thus exhibits the desired roughness and thus ensures abrasion on the contacted surface.

[0016] In addition to the method according to the invention, the present invention relates to a centrifugal pump, in particular a centrifugal pump which is suitable for carrying out the method according to the invention. Such a centrifugal pump comprises a pump housing and an impeller rotatably mounted in the pump housing, wherein a hydraulic gap exists between a rotating surface formed by the impeller or connected to the impeller and a stationary surface formed by the pump housing or connected to the pump housing. It is essential to the invention that the rotating surface or the stationary surface is provided with an abrasive surface structure and that a certain axial movement of the impeller in the direction of the stationary surface is possible during pump operation, so that axial material abrasion is enabled either on the rotating or alternatively on the stationary surface until the axial movement is limited by an axial stop.

[0017] It is advantageous if the stationary surface of the pump housing includes an abrasive coating or, alternatively, is provided with a friction-increasing film. The coating or film has, for example, a diamond-coated structure. Alternatively, an abrasive surface structure can be achieved using material-removing or additive processes, particularly in the form of a sawtooth profile. Alternatively, a separate component with abrasive properties can also be used.

[0018] The rotating surface of the impeller is made of a softer material, particularly plastic, so that the abrasive surface structure can achieve axial material removal. It is also conceivable for the impeller to consist of different components, particularly plastic components, with a softer plastic material being used in the area of ​​the impeller's suction port end face. Such an impeller can be manufactured particularly easily using a two-component injection molding process.

[0019] In the case of a split ring bearing, the rotating bearing of the split ring is made of a ceramic material. The fixed ring of the split ring bearing can be made of a carbon-based material, which is significantly softer and thus allows for a certain amount of material removal. Likewise, the rotating ring can be made of a carbon-based material and the fixed ring of a ceramic material.

[0020] The fixed ring of the split ring bearing can be fixed axially and circumferentially to the pump housing by means of a separate carrier ring. Additionally, the fixed ring can be mounted on the pump housing in a floating manner by means of an elastic ring to allow for a certain amount of compensating movement.

[0021] Further advantages and features of the invention will be explained in more detail below with reference to an embodiment illustrated in the drawings. They show:

[0022] Fig. 1 : a sectional view through the impeller of a centrifugal pump according to a first embodiment of the invention,

[0023] Fig. 2: a perspective top view of the housing of the centrifugal pump for the first embodiment,

[0024] Fig. 3: a sectional view through the housing according to Fig. 2,

[0025] Fig. 4: a sectional view through the centrifugal pump according to the invention according to the first embodiment, Fig. 5: an enlarged detailed view according to the sectional view of Fig. 4,

[0026] Fig. 6: a sectional view through the housing of a centrifugal pump according to a second embodiment of the invention,

[0027] Fig. 7: a sectional view through the housing of a centrifugal pump according to a third embodiment of the invention,

[0028] Fig. 8: a perspective top view of the housing of the centrifugal pump for the third embodiment of the invention and

[0029] Fig. 9: the inserted ring for the third version.

[0030] Figure 1 shows a sectional view of an impeller 1 for a centrifugal pump according to the invention, according to a first embodiment. The impeller 1 comprises a suction opening 4 located coaxially to the rotation axis, which is formed by a cylindrical projection 4a. The bearing 10 of a split ring seal, which rotates with the impeller 1, is arranged at the outer end of the projection 4a. The outer annular surface 10a represents the rotating surface and, in the embodiment shown in Figure 1, is designed as a continuous annular surface.

[0031] The impeller 1 is manufactured from plastic, for example, by injection molding. The ceramic bearing ring 10 is then injected during the impeller injection molding process, so that it is fixed in the axial direction of the pump at the suction port 4. Axial fixation is achieved by a back-injection molding 11 of the bearing ring 10.

[0032] The stationary part of the split ring bearing consists of the stationary bearing ring 30, which is secured in the axial direction by a bearing ring carrier 31. The suction channel 40 in the pump housing 50 can be seen in the sectional view in Figure 3. The suction channel 40 has a double stage with the first shoulder 41 and the second shoulder 42, located closer to the impeller, each of which is formed by a stepped increase in the diameter of the suction channel 40. On the first stage 41, the stationary bearing ring 30 is mounted on an O-ring 32, which allows the bearing ring 30 to be moved slightly away from the impeller in order to compensate for any deviations from the plane-parallelism of the surfaces 10a, 30a. The bearing ring carrier 31 is then placed on the next stage 42 and fixed to the housing 50 in a rotationally fixed manner and immovably in the axial direction. The bearing ring 30 is therefore located in the axial direction between impeller 1 and pump housing 50.

[0033] Both bearing ring carrier 31 and bearing ring 30 have circular openings that are coaxial with each other. The inner diameter of bearing ring carrier 31 is selected to be larger so that the sliding surface 30a of bearing ring 30 is exposed (see Figure 2). Furthermore, the inner diameter of bearing ring carrier 31 is selected to be larger than the outer diameter of the cylindrical suction port 4 of impeller 1, so that the cylindrical projection 4a of the impeller can be accommodated in the inner diameter of bearing ring carrier 31.

[0034] Fig. 2 also shows that the bearing ring carrier 31 is provided with axial grooves 33, into which complementary projections 34 of the bearing ring 30, extending in the axial direction toward the impeller 1, engage. This mechanical form-fitting connection creates a rotationally fixed connection between the bearing ring 30 and the bearing ring carrier 31.

[0035] The hydraulic gap of the pump then exists between the rotating surface 10a of the rotating bearing ring 10 and the stationary surface 30a of the bearing ring 30. The bearing ring 30 is made of a soft, carbon-based material.

[0036] The ceramic material of the rotating bearing ring 10, in particular the surface 10a, is provided with abrasive properties, for example: by a defined roughness on the axial running surface from the sintering process, by applying an abrasive layer, for example with diamond particles, by using a ceramic-diamond mixture as bearing material, by a defined surface shape that is embossed with the help of additive manufacturing, e.g. ball caps.

[0037] The overall structure of the pump is shown in the longitudinal section of Fig. 4. The pump housing 50 comprises the suction port 51 and the discharge port 52. The impeller sits on the pump shaft 53, which is driven by the motor 54. An axial bearing is arranged in the motor housing between the hydraulic system and the motor 54. The axial bearing consists of a ceramic axial bearing part 57, which is fixed to the shaft 53 by means of the axial bearing carrier 56 and rotates together with the shaft, and a carbon axial bearing part 58, which is fixed in the motor housing. In the delivery state, there is an axial gap 59 of a few hundredths of a millimeter (0.01 - 0.2 mm) between the axial bearing surfaces 57 and 58.

[0038] During pump operation, there is an axial force at every operating point which acts from the motor 54 in the direction of the hydraulics and presses the pump impeller 1, in particular the surface 10a, onto the surface 30a of the bearing ring 30. In the delivered state, the surfaces 10a, 30a are therefore in contact. After the pump is initially switched on, the running-in process starts. Due to the abrasive properties of the ceramic of the rotating bearing ring 10, the carbon on the surface 30a of the bearing ring 30 is ground down. During this process, the rotor slides towards the pump housing according to the ground down axial length. This process continues until the axial bearing 57, 58 in the motor housing comes into play, i.e. the rotating axial bearing part 57 has overcome the initial gap 59 and strikes the stationary axial bearing part 58. The axial force then applied was absorbed by the axial bearing 57, 58, and the grinding process in the area of ​​the surfaces 10a, 30a came to a standstill.

[0039] The resulting gap between bearing ring 10 on impeller 1 and bearing ring 30 in pump housing 50 is reduced to a few hundredths of a millimeter. As an alternative to the design shown in Figures 1 to 5, bearing ring 10 could of course also be made of a softer material (e.g., carbon-based material or soft plastic) and bearing ring 30 of a harder material (e.g., carbon-based material or soft plastic).

[0040] Ceramic) and includes the necessary abrasive surface structure.

[0041] A further embodiment of the centrifugal pump according to the invention is shown in Fig. 6. Compared to the first embodiment of Figs. 1 to 5, no split ring bearing 10, 30 is incorporated in the area of ​​the impeller 1. Instead, a suction-side end face 10a' of the impeller 1 runs directly on the step 41 of the pump housing. On this step surface 41, an abrasive layer is also applied directly to the material of the pump housing 50. This friction-increasing layer can be a coating or a friction-increasing film (e.g., a diamond-coated layer).

[0042] In the delivery state, the axial end face 10a' of the impeller 1 rests against the friction-increasing layer 41. When the pump is now started, the running-in process begins. Due to the abrasive properties of the coating on the shoulder 41, the end face 10a' of the impeller 1 is ground down axially. During this process, the rotor slides towards the pump housing 50 according to the ground-down length. This process continues until the actual axial bearing 57, 58 in the motor housing comes into play. The axial force then applied is absorbed by the axial bearing 57, 58, and the grinding process on the impeller 1 comes to a standstill. The gap thus created between the impeller 1 and the shoulder 41 of the pump housing 50 now has a maximum roughness of both surfaces 10a', 41 and is therefore reduced to a few hundredths.

[0043] Figures 7 to 9 show yet another, third exemplary embodiment. In this variant, an extra ring 30 with an abrasive surface structure is inserted on the shoulder 41 of the pump housing 50, which grinds the end face of the impeller 1 during initial pump operation, as in the second exemplary embodiment. The ring 30' is fixed to the pump housing 50 by means of a carrier 31, as in the first embodiment. The abrasive properties of the bearing ring 30' are created by a type of sawtooth profile 35 on its surface 30a'. In the embodiments of Figures 6-9, an additional ring made of a softer material could also be attached to the end face of the impeller in order to accelerate the axial material wear. It is also conceivable, for example, for such a ring to be made of plastic, i.e. the impeller is manufactured using a 2-component injection molding process, with a softer plastic material being used in the area of ​​the suction mouth.

Claims

Patent claims 1. Method for minimizing a hydraulic gap between the impeller (1) and the pump housing (50) of a centrifugal pump during initial commissioning, wherein the hydraulic gap of the pump is defined between a rotating surface (10a, 10a') formed by the impeller (1) or connected to the impeller and a stationary surface (30a, 30a', 41) formed by the pump housing (50) or connected to the pump housing (50), characterized in that the rotating surface (10a, 10a') is moved by an axial force acting during pump operation in the direction of the stationary surface (30a, 30a', 41) and is brought into frictional contact therewith at least during initial commissioning, and at least one of the surfaces (10a, 10a', 30a, 30a', 41) has an abrasive surface structure, whereby an axial material removal is effected on the other surface until the axial movement the rotating surface (10a, 10a') is limited by a separate stop means (57, 58).

2. Method according to claim 1, characterized in that the stationary surface (30a, 30a', 41) has the abrasive surface structure and an axial material removal takes place on the rotating surface (10a, 10a').

3. Method according to claim 1, characterized in that the rotating surface (10a, 10a') has the abrasive surface structure and an axial material removal takes place on the stationary surface (30a, 30a', 41).

4. Method according to one of the preceding claims, characterized in that the rotating surface (10a, 10a') is formed by an end face (10a') of the impeller (1) defining the suction mouth (4) of the impeller (1).

5. Method according to claim 4, characterized in that by means of the method material is removed in the axial direction on the end face (10a') of the impeller (1).

6. Method according to one of the preceding claims, characterized in that the stationary surface (30a, 30a', 41) is formed by an annular surface section (41) of the inner wall of the pump housing (50) which is perpendicular to the axial direction or by a ring (30') attached to the housing wall of the pump housing, against which the end face (10a') of the impeller (1) is moved.

7. Method according to one of the preceding claims, characterized in that the stop means is an axial bearing which has a rotating bearing part (57) fixed on the pump shaft (53) and a bearing part (58) fixed to the motor housing, wherein the axial bearing has a defined initial gap (59) in the delivery state in order to enable the axial material removal.

8. Method according to one of the preceding claims 1 to 3, characterized in that a split ring bearing (10, 30) is provided in the region of the suction mouth (4) of the impeller (1) and the two surfaces (10a, 30a) are formed by the components of the split ring bearing (10, 30).

9. Method according to claim 8, characterized in that a material removal is produced on a bearing ring (30) of the split ring bearing (10, 30) fixed to the pump housing (50) and a bearing ring (10) of the split ring bearing (10, 30) fixed to the front side on the suction mouth side and rotating with the impeller (1) has the abrasive surface structure.

10. Method according to claim 8, characterized in that a material removal is produced on a rotating bearing ring (10) of the split ring bearing (10, 30) fixed on the suction mouth side to the front side of the impeller (1) and a The bearing ring (30) of the split ring bearing (10, 30) fixed to the pump housing (50) has an abrasive surface structure.

11. Method according to one of the preceding claims, characterized in that the axial material removal is completed after a running time of a maximum of 10 hours, preferably a maximum of 5 hours, ideally less than 1 hour.

12. Method according to one of the preceding claims, characterized in that the abrasive surface structure is provided by applying an abrasive coating or film, for example by a coating or film coated with diamond particles, or is produced by means of an additive or subtractive manufacturing process.

13. Centrifugal pump, in particular for carrying out the method according to one of the preceding claims, comprising a pump housing (50) and an impeller (1) rotatably mounted in the pump housing (50), wherein a hydraulic gap exists between a rotating surface (10a, 10a') formed by the impeller (1) or connected to the impeller (1) and a stationary surface (30a, 30a', 41) formed by the pump housing (50) or connected to the pump housing (50), characterized in that the rotating surface (10a, 10a') or the stationary surface (30a, 30a', 41) is provided with an abrasive surface structure and, during pump operation, an axial movement of the impeller (1) in the direction of the fixed surface (30a, 30a', 41) is possible in order to achieve axial material removal on the rotating or stationary surface (10a, 10a', 30a, 30a', 41 ) until the axial movement is limited by an axial stop (57, 58).

14. Centrifugal pump according to claim 13, characterized in that a coating or a friction-increasing film, in particular a diamond-coated layer, is applied to the stationary surface of the pump housing (50) as an abrasive surface structure and / or the rotating surface (10a, 10a') on the impeller (1) is made of a soft material, in particular plastic consists, in particular the impeller (1) consists of different material components with a soft plastic material forming the rotating surface (10a, 10a').

15. Centrifugal pump according to claim 13, characterized in that Presence of a split ring bearing (10, 30), the rotating ring (10) of the split ring bearing (10, 30) consists of a ceramic material and the fixed ring (30) of the split ring bearing (10, 30) consists of a carbon-based material or the rotating ring (10) of the split ring bearing (10, 30) consists of a carbon-based material and the fixed ring (30) of the split ring bearing (10, 30) consists of a ceramic material.

16. Centrifugal pump according to claim 15, characterized in that the fixed ring (30) is fixed axially and circumferentially to the pump housing (50) by means of a support (31), in particular is mounted in a floating manner on an elastic ring (32).

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