MULTIPHASE PUMP

Abstract

A multiphase pump for conveying a multiphase process fluid from a low pressure side to a high pressure side includes an outer housing, a casing, the casing having a pump inlet and a pump outlet for the process fluid, and a pump rotor capable of rotating about an axial direction arranged within the casing, and configured to convey the process fluid from the pump inlet to the pump outlet. The casing includes a plurality of stage segments, and the plurality of stage segments include an individual stage-segment, a low pressure segment arranged at the pump inlet and a high pressure segment arranged at the pump outlet, the individual stage-segment arranged between the high pressure segment and the low pressure segment, and the plurality of stage segments being held together by a sealing support structure, the casing being arranged within the outer housing.

Claims

1. A multiphase pump for conveying a multiphase process fluid from a low pressure side to a high pressure side, comprising: an outer housing; a casing, the casing having a pump inlet and a pump outlet for the process fluid; and a pump rotor capable of rotating about an axial direction arranged within the casing, and configured to convey the process fluid from the pump inlet to the pump outlet, the casing comprising a plurality of stage segments, and the plurality of stage segments comprising an individual stage-segment, a low pressure segment arranged at the pump inlet and a high pressure segment arranged at the pump outlet, the individual stage-segment arranged between the high pressure segment and the low pressure segment, and the plurality of stage segments being held together by a sealing support structure, the casing being arranged within the outer housing.

2. The multiphase pump in accordance with claim 1, wherein the individual stage-segment is a first individual stage-segment of a plurality of individual stage-segments, and the plurality of individual stage-segments includes a second individual stage-segment, the first individual stage-segment and the second individual stage-segment being arranged in tandem between the high pressure segment and the low pressure segment, and the plurality of stage segments are held together by the sealing support structure.

3. The multiphase pump in accordance with claim 1, wherein the pump rotor comprises a plurality of impellers and a shaft, the plurality of impellers being arranged in series on the shaft.

4. The multiphase pump in accordance with claim 3, further comprising a diffusor, the diffusor being arranged about the shaft, and disposed between two adjacent impellers of the plurality of impellers for directing the process fluid to the next impeller.

5. The multiphase pump in accordance with claim 4, wherein the diffusor is axially split into two semi-circular rings and the two semi-circular rings are arranged about the shaft.

6. The multiphase pump in accordance with claim 1, wherein the sealing support structure is a tie rod, the tie rod being connected to a multiplicity of of the plurality of stage segments.

7. The multiphase pump in accordance with claim 3, wherein the individual stage-segment is one of a plurality of first individual stage-segments of a plurality of individual stage-segments, and the plurality of individual stage-segments includes a plurality of second individual stage-segment, the first individual stage segments and the second individual stage segments are individual rings compressed together by the sealing support structure.

8. The multiphase pump in accordance with claim 6, wherein the low pressure segment comprises a first flange and the high pressure segment comprises a second flange, the tie rod being connected to the first flange and to the second flange.

9. The multiphase pump in accordance with claim 3, wherein the impellers are helico-axial impellers.

10. The multiphase pump in accordance with claim 2, wherein the plurality of individual stage-segments further comprises a third individual stage-segment, the first individual stage-segment being connected to the low pressure segment, the second individual stage-segment being connected to the high pressure segment and the third individual stage-segment being connected to the first individual stage-segment or the second individual stage-segment.

11. The multiphase pump in accordance with claim 10, wherein the third individual stage-segment is one of plurality of third individual stage-segments, each third individual stage-segment being connected to an adjacent individual stage-segment of the plurality of individual stage-segments.

12. The multiphase pump in accordance with claim 3, further comprising an impeller wear ring disposed between an impeller of the plurality of impellers and the casing, and a diffuser wear ring disposed between the shaft and the diffuse.

13. The multiphase pump in accordance with claim 1, wherein the multiphase pump is a vertical pump with the pump rotor extending in a vertical direction.

14. The multiphase pump in accordance with claim 1, further comprising a drive operatively connected to the pump rotor, the drive configured to rotate the pump rotor, the drive being arranged inside the housing of the multiphase pump.

15. The multiphase pump in accordance with claim 1, wherein the multiphase pump is configured to be installed on the sea ground.

16. The multiphase pump in accordance with claim 1, wherein the sealing support structure is a tie rod connected to the low pressure segment and the high pressure segment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The invention will be explained in more detail hereinafter with reference to the drawings.

[0055] FIG. 1 is a cross-sectional view of a first embodiment of a multiphase pump according to the invention.

[0056] FIG. 2 is a cross-sectional view of a second embodiment of a multiphase pump according to the invention.

[0057] FIG. 3 is an embodiment of a multiphase pump according to the invention with an axially split diffusor.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0058] FIG. 1 shows a cross-sectional view of an embodiment of a multiphase pump according to the invention. The multiphase pump is designed as a centrifugal pump for conveying a multiphase process fluid from a low pressure side LP to a high pressure side HP.

[0059] In the following description reference is made by way of an example to the important application that the multiphase pump 1 is designed and adapted for being used as a subsea pump in the oil and gas industry. In particular, the multiphase pump 1 is configured for installation on the sea ground, i.e. for use beneath the water-surface, in particular down to a depth of 100 m, down to 500 m or even down to more than 1000 m beneath the water-surface of the sea. In such applications the multiphase process fluid is typically a hydrocarbon containing mixture that has to be pumped from an oilfield for example to a processing unit beneath or on the water-surface or on the shore. The multiphase mixture constituting the process fluid to be conveyed can include a liquid phase, a gaseous phase and a solid phase, wherein the liquid phase can include crude oil, seawater and chemicals, the gas phase can include methane, natural gas or the like and the solid phase can include sand, sludge and smaller stones without the multiphase pump being damaged on the pumping of the multiphase mixture.

[0060] It goes without saying that the invention is not restricted to this specific example but is related to multiphase pumps 1 in general. The invention can be used in a lot of different applications, especially in such applications where the multiphase pump is installed at locations which are difficult to access.

[0061] The casing 10 of the multiphase pump 1 comprises a pump inlet 2 through which the multiphase process fluid enters the pump at the low pressure side LP as indicated by the arrow, and a pump outlet 3 for discharging the process fluid with an increased pressure at the high pressure side HP as indicated by the arrow. Typically, the pump outlet 3 is connected to a pipe or a piping (not shown) for delivering the process fluid to another location. The pressure of the process fluid at the pump outlet 3, i.e. at the high pressure side HP, is typically considerably higher than the pressure of the process fluid at the pump inlet 2, i.e. at the low pressure side LP. A typical value for the difference between the high pressure and the low pressure side is for example 50 to 200 bar.

[0062] The casing 10 of multiphase pump 1 is designed as a radially split staged casing 10 with several stage segments 51, 52, 71, 72, 73, and is able to withstand the pressure generated by the multiphase pump 1 as well as the pressure exerted on the multiphase pump 1 by the environment. The several stage segments 51, 52, 71, 72, 73 comprise several different casing parts, which are connected to each other to form the casing 10. Whereby the several stage segments 51, 52, 71, 72, 73 comprise a high pressure segment 52 disposed on the high pressure side HP at an pump outlet 3, a low pressure segment 51 disposed on the low pressure side LP at an pump inlet 2, a first individual stage-segment 71, a second individual stage-segment 72 and a third individual stage-segment 73. The stage segments 51, 52, 71, 72, 73 are arranged in tandem wherein the first individual stage-segment 71, the second individual stage-segment 72 and the third individual stage-segments 73 are arranged between the low pressure segment 51 and the high pressure segment 52. The low pressure segment 51 is designed as suction casing and the high pressure segment is designed as discharge casing.

[0063] In the embodiment shown in FIG. 1 the first individual stage-segment 71 is connected to the low pressure segment 51, the second individual stage-segment 72 is disposed at the high pressure segment 52 and the plurality of third individual stage-segments 73 is disposed at the first individual stage-segment 71 and/or the second individual stage-segment 72 and/or connected to each other. The embodiment shown comprises a plurality of third individual stage-segments 73, each third individual stage-segments 71, 72, 73 being disposed at the adjacent individual stage-segment 71, 72, 73. The low pressure segment 51 comprises a first flange 511 and the high pressure segment 52 comprises a second flange 521. A tie rod 81 is disposed at the casing 1 and connected to the first flange 511 and to the second flange 521. The tie rod 81 is the sealing support structure, which puts the radial split segments 51, 52, 71, 72, 73 under pressure so that the staged casing 1 is held together.

[0064] The multiphase pump 1 further comprises a pump rotor 4 rotating about an axial direction A in an operating state of the multiphase pump. In a manner known per se the pump rotor 4 is configured for conveying the process fluid from an inlet annulus at the low pressure side LP to a discharge annulus at the high pressure side HP (not shown).

[0065] The pump rotor 4 comprises a shaft 41 rotatable about the axial direction A and one impeller (single stage pump; not shown) or a plurality of impellers 42 (multistage pump) arranged in series along the axial direction A for conveying the process fluid from the inlet 2 to the outlet 3 and thereby increasing the pressure of the process fluid. Each impeller 42 is fixed to the shaft 41 in a torque-proof manner. Each impeller 42 can be designed for example as a radial impeller or as an axial impeller or as a semi-axial impeller. Furthermore, there are a plurality of diffusors 6 disposed between two adjacent impellers. Impeller wear rings 91 are disposed between (in radial direction between) the casing 10 and the impellers 42 and diffusor wear rings 92 are disposed between (radial direction) the casing 10 and the diffusors 6

[0066] For rotating the shaft 41 of the pump rotor 4, the shaft 41 is operatively connected to a drive unit (drive) (not shown), which might be a separate unit located outside a housing of the pump 1, or which might be integrated into the housing. For subsea applications the drive unit is usually arranged inside the housing.

[0067] Using the drive unit, the pump rotor 4 is driven during operation of the pump 1 for a rotation about the axial direction A that is defined by the longitudinal axis of the pump rotor 4.

[0068] FIG. 2 shows a cross-sectional view of a second embodiment of a multiphase pump according to the invention. FIG. 2 shows a similar structure to FIG. 1, but a different sealing support structure is used.

[0069] The embodiment shown in FIG. 2 has individually bolted stage segments where each stage segment 51, 52, 71, 72, 73 is individually bolted to the adjacent stage segment 51, 52, 71, 72, 73 by a sealing support structure 82, and the first and last stage casing bolted to the suction casing/low pressure segment 51 and last stage diffuser/high pressure segment 52 respectively by the sealing support structure 82.

[0070] The individual stage-segments 71, 72, 73 are disposed between the high pressure segment 52 and the low pressure segment 51.

[0071] It goes without saying that the multiphase pump 1 according to the invention can be designed as a vertical or horizontal pump with the pump rotor 4 extending in the vertical or horizontal direction respectively, i.e. perpendicular to the direction of gravity.

[0072] FIG. 3 shows an embodiment of a multiphase pump according to the invention with an axially split diffusor 6.

[0073] The multiphase pump comprises a plurality of diffusors 6 which are arranged in series about a shaft 41, wherein each diffusor 6 is disposed between two adjacent impellers 42 for directing the process fluid to the next impeller 42.

[0074] Thereby, the diffusors 6 are axially split into two semi-circular rings and the two semi-circular rings are arranged about the shaft 41.

[0075] Due to the axially split diffuser the rotor can be assembled without reducing the balance of the rotor, since the axially split diffuser sandwiches the rotor and then the stage segments can be slid over the top.