PUMP ARRANGEMENT

Description

[0001] The invention relates to a pump arrangement according to the preamble of claim 1.

[0002] Such a centrifugal pump arrangement, also known as a double casing or jacketed casing pump, is shown, for example, in DE 199 27 135 A1.

[0003] In this type of centrifugal pump, the pump is enclosed in a jacket-like casing. The casing, equipped with suction and discharge ports and optionally intermediate sampling points, is closed with a cover in a plane perpendicular to the shaft. These are typically multi-stage pumps used as high- and ultra-high-pressure pumps, particularly as boiler feed pumps. Within the casing, several pressure stage housings are arranged axially in series. Each pressure stage comprises a pump impeller and, optionally, a stationary guide vane.

[0004] The individual pressure stage housings of each pressure stage are typically designed together with the pump shaft as a single, integrated pump unit. The flow transition from the last guide vane or the last pressure stage housing to the discharge port usually occurs via a flow chamber within the casing or via a separate insert for an end spiral in the transition area.

[0005] Feed pumps often have multiple pressure zones within the externally visible casing, which forms the pressure shell. If these pressure zones are adjacent, they must be sealed against each other under all possible operating conditions, i.e., under all occurring loads. This is usually achieved using special static seals. However, during operation, i.e., under load, the installation space provided for these seals is subject to deformation or displacement compared to the unloaded state. This leads to significant stress on the seal and can therefore reduce the reliability of its sealing function.

[0006] WO 2013 120549 A1 discloses a sealing arrangement for a high-pressure chamber, comprising a boundary element with an outer sealing surface and a closure element with an inner sealing surface. The boundary element is flexible in the area of ​​the outer sealing surface to such an extent that it can compensate for movement of the inner sealing surface of the closure element.

[0007] The invention aims to provide a pump arrangement that eliminates the cause of this sealing problem, namely the excessive differential deformation of the components surrounding the seal.

[0008] This problem is solved by a pump arrangement according to the features of claim 1. Advantageous embodiments of the centrifugal pump are the subject of the dependent claims.

[0009] According to the invention, it is proposed that the outer diameter of the second section of the ring-shaped second part and the inner diameter of the first region of the sleeve-like first part are designed at their overlapping regions such that the first region is spaced away from the second section with very little clearance or comes into contact with it, thereby preventing or limiting deformation of the first region of the sleeve-like part inwards or in the direction of the axis of rotation.

[0010] Advantageously, the second section of the ring-shaped part has means for connecting the annular space to the second pressure space.

[0011] According to the invention, it is proposed that the second section of the second part has a lateral surface in which at least one groove is provided which is connected to the annular space or is directly connected to the annular space.

[0012] In a further advantageous embodiment, the ring-shaped part has a third section adjoining the second section of the second part, wherein at least one axial groove extending parallel to the axis of rotation in the outer shell surface of the third section, which forms a channel with the shell housing, or at least one axial bore extending parallel to the axis of rotation is formed near the outer shell surface, wherein the axial groove or the axial bore opens into the second pressure chamber.

[0013] Advantageously, a radially circumferential gap is provided at the transition from the second section to the third section, which is connected on the one hand to the at least one groove and on the other hand to the at least one axial groove or the at least one axial bore extending in the outer surface of the third section.

[0014] In an advantageous alternative embodiment, the second part has at least one axial bore extending substantially parallel to the axis of rotation, which directly connects the annular space with the second pressure space.

[0015] Exemplary embodiments of the invention are shown in the drawing and are described in more detail below. It shows the Fig. 1 shows a partial view of a pump arrangement in section with a first embodiment of the pressure stage housing according to the invention, Fig. 2 shows an enlarged section from the Fig. 1 and Fig. 3 the partial view in section of a stepped housing according to the invention in the embodiment according to Fig. 1 and Fig. 2 Fig. 4 shows a partial view of a second embodiment of the stepped housing according to the invention in section in the installed state. Fig. 5 shows a partial view of the stepped housing according to the invention. Fig. 4Fig. 6 shows a partial view of a third embodiment of the stepped housing according to the invention in section in the installed state.

[0016] Figure 1 Figure 1 shows a pump assembly designed as a centrifugal pump with a casing 1. An insert 2 is at least partially arranged in the casing 1. The insert 2 comprises a shaft 3 rotatably arranged about an axis of rotation A by a drive (not shown), e.g., an electric motor. In the illustrated embodiment, several impellers 4 are arranged one behind the other on the shaft 3. In this embodiment, the impellers 4 are radial impellers.

[0017] The insert 2 further comprises several so-called pressure stage housings 5, wherein the pressure stage housing according to the invention is designated 5'. Each impeller 4 is surrounded by a pressure stage housing 5 or 5'. Adjacent pressure stage housings 5, 5' are abutting each other. In the exemplary embodiment, the dividing joint between the pressure stage housings 5, 5' is metal-to-metal sealed.

[0018] In each pressure stage housing 5, 5', a guide vane 6 is provided, arranged downstream of the respective impeller 4 in the flow direction of the pumped medium. The guide vane 6 is connected to the pressure stage housing 5, 5' in a rotationally fixed manner by means of an interference fit or other suitable means. A suction port 7 is integrally formed on the casing 1, through which the operating medium enters the centrifugal pump. The operating medium exits the pump assembly via a discharge port 8. In the illustrated embodiment, the casing 1 has an intermediate outlet 9. A certain proportion of the pumped medium can be conveyed through at least one radial opening 10 in one of the central pressure stage housings 5 ​​into a first pressure chamber 11, which is arranged between the pressure stage housings 5, 5' and the casing 1, and discharged via the intermediate outlet 9.The pressure chamber 11 is separated by a seal 12 from a second pressure chamber 13 near the pressure port 8, in particular below it in an inflow area to the pressure port 8, or inside the pressure port 8. The pressure in the second pressure chamber 13 is at least one stage higher than the pressure in pressure chamber 11, up to n-1 times the stage pressure, where n represents the number of stages.

[0019] In the Fig. 1 A multi-stage pump arrangement with six pressure stages and five pressure stage housings 5, 5' is shown. It is understood that the number of pressure stages must be at least two, but can otherwise vary arbitrarily. Furthermore, it is conceivable that all pressure stages can be formed by means of pressure stage housings 5' according to the invention.

[0020] As from the Fig. 2 evident, which shows an enlarged section of the Fig. 1As shown, the seal 12 separates the pressure chamber 11, which tapers towards the seal 12 to a relatively narrow first annular gap 14, from a channel 15 that communicates with the second pressure chamber 13 in the area of ​​the pressure nozzle 8. Fig. 2 further shows how the seal 12 interacts with the casing 1 and the pressure stage housing 5' according to the invention, as well as the arrangement of the guide wheel 6 and the arrangement of the impeller 4 placed on the shaft 3 rotating about the axis of rotation A inside the pressure stage housing 5'.

[0021] The Fig. 3 separately shows the cup- or pot-shaped pressure stage housing 5' according to the Fig. 2 The compression stage housing 5' comprises a sleeve-like first part 16 and an annular disc-like second part 17. The sleeve-like first part 16 has a first area 18 with an enlarged inner diameter and a second area 19 with a reduced inner diameter.

[0022] At the transition from the first region 18 to the second region 19 of the sleeve-like first part 16, the sleeve-like part 16 is connected to the ring-shaped second part 17. Both parts 16 and 17 can be welded together or manufactured as a single piece, e.g., by means of 3D printing. Alternatively, parts 16 and 17 can be screwed together.

[0023] The ring-shaped part 17 has a first section 20 and a second section 21 with a cylindrical surface 22. In the illustrated embodiment, the cylindrical surface 22 is essentially cylindrical but also has a conical section. At least one groove 23 is provided in the cylindrical surface 22, giving the section 21 depressions and protrusions 24 with the cylindrical surface 22. In the illustrated embodiment, the at least one groove 23 runs essentially parallel to the axis of rotation A.

[0024] The first section 18 of the sleeve-like part 16 surrounds both the first section 20 and partially also the second section 21 of the annular disc-like second part 17. The outer diameter of the first section 20 is smaller than the outer diameter of the second section 21. The outer diameter of the second section 21 of the annular disc-like part 17 and the inner diameter of the first section 18 of the sleeve-like part 16 are designed at their overlapping areas such that the first section 18 is spaced from the second section 21 with very little clearance or comes into contact with it.

[0025] Because the first section 20 of the annular disc-like second part 17 has a reduced outer diameter compared to the second section 21, an annular space 25 is formed between the sleeve-like first part 16 and the annular disc-like part 17. The annular space 25 is connected to the at least one groove 23 or fluidically directly connected to the groove 23. The first region 18 of the sleeve-like part 16 is elastically designed within certain limits due to the annular space 25.

[0026] The lateral surface 22 of the elevations 24 prevents or limits deformation of the elastic area 18 of the sleeve-like part 16 inwards or in the direction of the axis of rotation A.

[0027] Part 17 also has a third section 26 on the side facing away from the annular space 25, adjoining the second section 21.

[0028] The outer diameter of the second section 21 is smaller than the outer diameter of the third section 26. In the exemplary embodiment shown, the third section 26 has a step which may optionally be provided for fastening the pressure stage housing 5' to the outer casing.

[0029] The in Fig. 2 The channel 15 shown is formed by at least one axial groove (not shown) extending in the axial direction in the outer surface 27 of the third section 26, which interacts with the casing 1, wherein a radial connecting groove (not shown) is provided in the area of ​​the step, which connects the two axial groove sections in the outer surface 27. Alternatively, the axial grooves and the connecting groove can also be formed in the casing 1.

[0030] Since the first region 18 of the sleeve-like part 16 does not completely surround the second section 21, a radially circumferential gap 28 is formed at the transition from the second section 21 to the third section 26, which is connected to the at least one groove 23. The gap 28 also communicates with the axial groove extending in the axial direction in the outer surface 27 of the third section 26 and thus with the Fig. 2 Channel 15 as shown, and pressure chamber 13.

[0031] At the transition from the first area 18 to the second area 19 of the sleeve-like first part 16, a chamfer is provided, i.e., the outer diameter of the sleeve-like part 18 is larger than the outer diameter of the area 19, so that the installation of the seal 12 is possible without problems.

[0032] The Fig. 4 Figure 5 shows a further embodiment of the pressure stage housing 5' according to the invention in the installed state.

[0033] The Fig. 5 This shows in the Fig. 4 The pressure stage housing 5' shown in detail. The first sleeve-like part 16 essentially corresponds to that shown in the Figures 1 to 3 The illustrated embodiment of the pressure stage housing 5' requires no further explanation. The second section 21 of the second part 17, with the at least one groove 23 and the at least one projection 24 and the circumferential surface 22, as well as the annular space 25, also essentially correspond to those described in the Figures 1 to 4 described embodiments.

[0034] In the Fig. 4 and Fig. 5 In the illustrated embodiment of the pressure stage housing 5', at least one axial bore 29, formed substantially parallel to the axis of rotation A, is provided in the third section 26, which communicates with the gap 28 and opens into the second pressure chamber 13 in the area of ​​the pressure nozzle 8.

[0035] In the embodiment shown, no step is provided in section 26, but it can be combined with a step as in the Fig. 2 and 3 shown, provided.

[0036] As in the Fig. 6 As shown, in a further embodiment of the pressure stage housing 5', at least one axial bore 29 can be connected to or directly connected to the annular space 25 and extend through the second section 21 and the third section 26, opening into the second pressure space 13. The axial bore 29 thus connects the annular space 25 directly to the second pressure space 13 in the area of ​​the pressure port 8. Grooves in the outer surface 22 are therefore unnecessary.

[0037] In the exemplary embodiment shown, the third section 26 has a step, which, however, is not required in a fastening method of the pressure stage housing 5' as described in the Fig. 4 and 5 shown, but not needed.

[0038] When the pump assembly is put into operation, medium is drawn into the pump via the suction port 7 and flows to the pressure stage housing 5, which is the first one downstream of the suction port. The medium is guided by the impeller 4, via the guide vane 6 located downstream of the suction port, to the next pressure stage housing 5. A portion of the medium is conveyed into the pressure chamber 11 through at least one opening 10 in the stage housing 5 closest to the intermediate outlet 9. From there, it can be discharged from the pump via the intermediate outlet 9. The majority of the medium is fed to the subsequent pressure stage housings 5 ​​in a similar manner.

[0039] The last guide vane 6, from a fluid dynamics perspective, conveys the medium into the pressure chamber 13. From there, a portion of the medium passes according to the Figs. 1 to 3via the at least one channel 15 and the radially circumferential gap 28 into the at least one groove 23 in the second section 21 and subsequently into the annular space 25 or according to the Fig. 4 and 5 via the at least one axial bore 29 and the radially circumferential gap 28 into the at least one groove 23 and subsequently into the annular space 25 or according to the Fig. 6 directly via the at least one axial bore 29 from the pressure chamber 13 into the annular space 25. The pressure chamber 13, together with the at least one channel 15 or the at least one axial bore 29, the radially circumferential gap 28, the at least one groove 26 and the adjoining annular space 25, forms a medium-filled system of communicating spaces.

[0040] In the annular space 25, overpressure is established relative to space 11, which expands area 18 and thus presses radially against the casing. This ensures that the radial extent of the sealing space remains almost constant under all operating conditions.

Claims

1. Pump arrangement having - a barrel-type casing (1), - an insert (2) which is arranged at least partially in the barrel-type casing (1), wherein the insert (2) comprises a shaft (3), which is arranged so as to be rotatable about an axis of rotation (A) by a drive, and at least two pressure stages, which have respective pressure-stage casings (5, 5'), - an impeller (4) which is arranged on the shaft (3) and is surrounded in each pressure stage by the pressure-stage casing (5, 5'), and - a seal (12) which separates a first pressure space (11) from a second pressure space (13), wherein - the pressure-stage casing (5') comprises a first part (16) and a second part (17), - the first part (16) has a first region (18) of increased inner diameter and a second region (19) of reduced inner diameter, - the second part (17) has at least a first portion (20) of reduced outer diameter and a second portion (21) of increased outer diameter, and - the first region (18) of the first part (16) surrounds the first portion (20) and at least partially surrounds the second portion (21) of the second part (17) in such a way that an annular space (25) is formed between the first part (16) and the second part (17) and the annular space (25) is connected to the second pressure space (13), characterized in that the outer diameter of the second portion (21) of the second part (17) and the inner diameter of the first region (18) of the first part (16) are formed at their overlapping regions in such a way that the first region (18) is spaced apart from the second portion (21) with a very small amount of play or comes into abutment against said second portion.

2. Pump arrangement according to Claim 1, characterized in that the second part (17) has means (15, 23, 29) for connecting the annular space (25) to the second pressure space (13).

3. Pump arrangement according to Claim 2, characterized in that the second portion (21) of the second part (17) has a lateral surface (22) in which there is provided at least one groove (23) which is connected to the annular space (25).

4. Pump arrangement according to either of Claims 2 and 3, characterized in that the second part (17) has a third portion (26) which adjoins the second portion (21) of the second part (17), wherein at least one axial groove extending in the outer lateral surface (27) of the third portion (26) parallel to the axis of rotation (A) or at least one axial bore (29) extending parallel to the axis of rotation (A) and close to the outer lateral surface (27) is formed, wherein the axial groove and the axial bore (29) open out into the second pressure space (13).

5. Pump arrangement according to Claim 4, characterized in that a radially encircling gap 28 is provided at the transition from the second portion 21 to the third portion 26 and is connected to the at least one groove (23), on the one hand, and to the at least one axial groove extending in the outer lateral surface (27) of the third portion (26) or to the at least one axial bore (29), on the other hand.

6. Pump arrangement according to either of Claims 1 and 2, characterized in that the second part (17) has an axial bore (29) which connects the annular space (25) directly to the second pressure space (13).