JET PUMP

Abstract

A jet pump (26) includes an elongate tubular housing (30) that has a longitudinal axis (A), an upstream first end (32) and a downstream second end (34). A nozzle assembly (50) and a mixing tube/diffuser assembly (52) are removably received within the housing (30). The housing (30) includes a first inlet vent (40) for a HP first fluid, a second inlet vent (42) for a LP second fluid and an outlet vent (48) at the downstream second end (34) of the housing for the combined first and second fluids. The first and second inlet vents (40, 42) extend non-axially through a circumferential wall (31) of the tubular housing. The nozzle assembly (50) and the mixing tube/diffuser assembly (52) can removed from the housing (30) through the upstream first end (32).

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 to British application no. GB 1405229.4 filed Mar. 24, 2014, and the disclosure of said British application is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to a jet pump and in particular, but not exclusively, to a jet pump for use in the oil and gas industries.

BACKGROUND

Jet pumps or eductors are passive devices that use energy from a high pressure (HP) fluid source to boost the pressure of a low pressure (LP) fluid. The terms jet pump, eductor, ejector and gas jet compressor are used in various industries and refer to the same general type of device. The HP and LP fluids may each consist of liquids, gases or a mixture of liquids and gases.

FIGS. 1 and 2 show the key features of a typical jet pump. HP fluid from a HP source passes through a HP inlet 4 to a jet pump 6, where it passes through constriction known as a nozzle assembly 8 that increases the velocity of the fluid. In this way part of the potential (pressure) energy of the HP fluid is converted to kinetic energy (high velocity fluid). As a result, the pressure of the fluid in a nozzle discharge zone 10 in front of the nozzle assembly 8 drops significantly.

LP fluid from a LP source passes through a LP inlet 12 and is introduced into the jet pump at the nozzle discharge zone 10, where it is entrained in the flow of fluid emerging from the nozzle assembly 8. The mixture of fluids then passes through a mixing tube 14 where momentum and energy are exchanged between the fluids. The mixture finally passes through an expanding diffuser 16 where the velocity of flow normalises and pressure recovery takes place. The pressure at the outlet 18 of the jet pump will be at an intermediate value between the pressures of the HP and LP fluids at the inlets 4, 12.

Jet pumps have been used successfully in a variety of applications onshore or near the bottom of oil or gas wells. In such situations the HP fluid may be gas or a high pressure liquid such as oil or water. The LP fluid could be gas, or liquid (oil and/or water), or a mixture of gas and liquid.

For maximum efficiency, the dimensions of the nozzle assembly 8 and the mixing tube/diffuser assembly 14, 16 must be selected according to the pressures, flow rates and types of fluids delivered to the jet pump. In some jet pumps the nozzle 8 and the mixing tube/diffuser 14, 16 comprise replaceable components that are mounted within a housing 20. This allows the internal components 8, 14, 16 to be removed and exchanged if the operating conditions change.

In most jet pumps used for onshore or offshore applications the HP inlet 4 is in line with axis of the jet pump as shown in FIGS. 1 and 2, whilst the LP inlet 12 comprises a Tee junction 12, such that the LP inlet is at 90 degrees to the longitudinal axis A of the jet pump. In other words, the jet pump has an axial HP inlet 4, an axial outlet 18 and a non-axial LP inlet 12. The nozzle assembly 8 can be introduced into the jet pump through the HP inlet 4 at one end of the housing 20. There is also a patented jet pump system (GB2384027B) that enables the nozzle assembly 8 to be removed and replaced through the HP inlet end 4 of the jet pump, while the mixing tube/diffuser section 14, 16 can be removed and replaced through the outlet end 18 of the jet pump.

When the jet pump is in operation and removal and replacement of the internal components is needed, a spool piece comprising a flanged length of pipe (not shown) must be removed from both the HP inlet end 4 and the outlet end 18 of the jet pump to provide access to the internal components. Sufficient space must be available at both ends of the jet pump to allow the nozzle assembly 8 and the mixing tube/diffuser assembly 14, 16 to be pulled out of the housing 20. This operation is time consuming and requires re-installing the spool pieces after the installation of the new internal components, followed by tightening the bolts at both HP inlet and outlet ends 4, 18 and checking the system for leaks.

SUMMARY

It is an object of the present invention to provide a jet pump that mitigates one or more of the aforesaid disadvantages.

According to one aspect of the present invention there is provided a jet pump including an elongate tubular housing that has a longitudinal axis, an upstream first end and a downstream second end, a nozzle assembly and a mixing tube/diffuser assembly, said nozzle assembly and said mixing tube/diffuser assembly being removably received within the housing, a first inlet vent for a HP first fluid, a second inlet vent for a LP second fluid and an outlet vent at the downstream second end of the housing for the combined first and second fluids, wherein the first and second inlet vents extend non-axially through a circumferential wall of the tubular housing, and wherein the nozzle assembly and the mixing tube/diffuser assembly can removed from the housing through the upstream first end thereof.

The configuration of the jet pump makes it possible to remove the nozzle assembly and the mixing tube/diffuser assembly through the upstream first end of the housing without disconnecting the HP and LP feed lines from the jet pump. The internal components of the jet pump can therefore be removed and replaced relatively quickly and easily, thus enabling the jet pump to be adapted readily to different operating conditions to ensure that it operates efficiently.

Advantageously, one or both of the first and second inlet vents extend through a circumferential wall of the tubular housing at an angle θ relative to the longitudinal axis, where 0°<θ≦90°. The first and second inlet vents may extend through the circumferential wall of the tubular housing at an angle of 90° relative to the longitudinal axis. Alternatively, they may extend through the circumferential wall of the tubular housing at an acute angle relative to the longitudinal axis so that the HP and LP fluids entering the housing have a component of velocity in the direction of flow through the housing.

Advantageously, the jet pump includes a removable closure member at the upstream first end of the housing. The removable closure member may for example comprise a blind flange plate that is removably attached to the upstream first end of the housing in order to seal that end of the housing hermetically.

Advantageously, the nozzle assembly and the mixing tube/diffuser assembly are interconnected by a link assembly, allowing them to be removed as a unit from the housing.

Advantageously, the link assembly is configured such that the nozzle assembly and the mixing tube/diffuser assembly are separable. This makes it possible to replace either nozzle assembly or the mixing tube/diffuser assembly, without replacing the other assembly.

Advantageously, the jet pump includes a pull-out assembly connected to the nozzle assembly for extracting the nozzle assembly and the mixing tube/diffuser assembly from the housing through the upstream first end thereof. This simplifies extraction of the nozzle assembly and the mixing tube/diffuser assembly from the housing.

Advantageously, the pull-out assembly is separable from the nozzle assembly. The pull-out assembly and the nozzle assembly may for example be interconnected by separable screw threads. This allows the nozzle assembly to be replaced without replacing the pull-out assembly.

Advantageously, the jet pump includes a tubular sleeve element that interconnects the pull-out assembly and the nozzle assembly.

Advantageously, the tubular sleeve element includes a fluid flow passageway configured to allow HP fluid to flow from the first inlet vent to the nozzle assembly.

Advantageously, the first inlet vent extends through the circumferential wall of the tubular housing upstream of the nozzle assembly.

Advantageously, the second inlet vent extends through the circumferential wall of the tubular housing downstream of the nozzle assembly and upstream of the mixing tube/diffuser assembly. Preferably, the second inlet vent extends through the circumferential wall of the tubular housing in the vicinity of a nozzle discharge zone immediately downstream of the nozzle assembly.

According to one preferred aspect of the present invention there is provided a Tee spool piece 40 for the introduction of the HP fluids. Therefore, unlike conventional jet pumps, the HP fluid entry is also at 90 degrees to the longitudinal axis of the jet pump via flange 44. In this arrangement access to the internals of the jet pump, which are the nozzle assembly 58 and the mixing tube 52 and diffuser 68, is via a flanged end 36 of the jet pump which is normally closed by the blind flange 49. This arrangement therefore allows the internals to be pulled out of the jet pump from one end which is not connected to HP or LP inlets or the discharge lines and results in not needing to remove spool pieces attached to the HP inlet and the discharge line of the jet pump.

BRIEF DESCRIPTION OF DRAWINGS

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a sectional side view of a known jet pump;

FIG. 2 is a sectional isometric view of a known jet pump, and

FIG. 3 is a sectional side view of a jet pump according to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 3 shows a jet pump 26 according to a first embodiment of the invention. The jet pump 26 comprises a substantially cylindrical tubular elongate housing 30 having a circumferential wall 31, a first end 32 and a second end 34. A first flange plate 36 is provided at the first end 32 of the housing 30 and a second flange plate 38 is provided at the downstream second end 34 of the housing 30. The housing 30 also includes first and second inlet pipes 40, 42, which extend outwards from the housing substantially perpendicular to the longitudinal axis A of the housing 30. The first and second inlet pipes 40, 42 are provided at their outer ends with inlet flange plates 44, 46 respectively and comprise inlet vents that extend through the circumferential wall 31 of the housing 30. The first and second inlet pipes 40, 42 are displaced axially from one another, the first inlet pipe 40 being located towards the first end 32 of the housing 30, while the second inlet pipe 42 is located towards the middle of the housing 30, midway between the first and second ends 36, 38. The first and second inlet pipes 40, 42 are connected in use to HP and LP delivery lines (not shown) to receive HP and LP fluids respectively.

The second end 34 of the housing 30 provides an outlet 48 for fluids flowing out of the jet pump. The first end 32 of the housing is closed and sealed by a blind flange plate 49, which is bolted to the first flange plate 36.

A nozzle assembly 50 and a mixing tube/diffuser assembly 52 are removably mounted within the tubular body of the housing 30. The nozzle assembly 50 includes a tubular cylindrical body 54 having a cylindrical mounting portion 56 at one end and a hollow conical nozzle portion 58 at the other end, which leads to the nozzle outlet 60. The mounting portion 56 carries a pair of O-rings 62 in grooves on its outer surface, which form a seal with the inner surface of the cylindrical housing 30 and prevent HP fluid from inlet 40 from bypassing the nozzle assembly and flowing directly to the mixing tube/diffuser assembly 52.

The mixing tube/diffuser assembly 52 comprises a tubular body that has a sliding fit within the downstream part of the housing 30. The tubular body has a longitudinal bore that includes a converging upstream portion 64, a central mixer portion 66 of constant diameter and a diverging downstream portion 68. The upstream portion 64, which comprises the inlet to the mixing tube/diffuser assembly 52, is located in the vicinity of the nozzle discharge zone 70, which is just downstream of the nozzle 60, to receive fluids discharged from the nozzle 60. The downstream end of the mixer tube/diffuser assembly 52 is located close to the downstream second end 34 of the housing. The mixer tube/diffuser assembly 52 carries a pair of O-rings 72 in grooves on its outer surface, which form a seal with the inner surface of the cylindrical housing 30.

The nozzle assembly 50 is connected by a tubular cylindrical section 74 to an extractor device 76 located towards the first end 32 of the housing. The extractor device 76 includes a connector piece 78 that extends axially towards the first end 32 of the housing. When the blind flange plate 49 is removed, the extractor device 76 can be engaged by an extractor tool (not shown) and withdrawn axially from the housing 30 through the first end 32, thereby removing the nozzle assembly 50.

The cylindrical section 74 has an opening 80 through which a high pressure first fluid HP can flow from the first inlet pipe 40 to the interior of the nozzle assembly 50, so that it can be discharged through the nozzle 60.

The mixer tube/diffuser assembly 52 is linked to the nozzle assembly 50 by a link structure 82, for example comprising a set of link bars that extend from the mounting portion 56 of the nozzle assembly to the upstream end of the mixer tube/diffuser assembly 52. This link structure 82 can be permanently attached to the nozzle assembly 50 and the mixer tube/diffuser assembly 52 for example by welding so that the two assemblies 50,52 form a single component, or it can be designed to allow the nozzle assembly 50 and the mixer tube/diffuser assembly 52 to be separated. For example, the nozzle assembly 50 and the mixer tube/diffuser assembly 52 may be connected by separable bolts.

The bars comprising the link structure 82 are spaced apart to provide an opening 84 through which a low pressure second fluid LP can flow from the second inlet pipe 42 into the nozzle discharge zone 70 downstream of the nozzle 60. The LP second fluid can then combine with the first fluid discharged through the nozzle 60, and the combined first and second fluids CF can then mix as they flow together through the mixer tube/diffuser assembly 52 towards the outlet 48.

In use, a high pressure first fluid HP flows through the first inlet tube 40 upstream of the nozzle assembly 50 and is discharged through the nozzle 60 into the low pressure nozzle discharge zone 70 immediately downstream of the nozzle 60. The nozzle 60 is constricted to increase the velocity of the fluid as it is discharged from the nozzle. In this way the potential (pressure) energy of the first fluid is converted to kinetic energy as the fluid emerges from the nozzle 60. This reduces the pressure at the low pressure nozzle discharge zone 70.

A low pressure second fluid LP passes through the second inlet pipe 42 and is introduced into the low pressure nozzle discharge zone 70 downstream of the nozzle 60. The second fluid is combined in the nozzle discharge zone 70 with the first fluid emerging from the nozzle 60 and the first and second fluids are mixed within the mixing tube 66 downstream of the nozzle 60 to form a combined fluid CF. The combined fluid CF then passes through the expanding diffuser 68, where the velocity of the combined fluid CF normalises and pressure recovery takes place. Finally, the mixture of fluids exits the jet pump 26 at outlet 48. The combined fluid CF at the outlet 48 will be at an intermediate pressure value that lies between the pressures of the HP and LP fluids at the first and second inlets 40, 42.

In the present invention the HP and LP fluids are introduced into the jet pump through flanged inlets 40, 42, which are attached non-axially to the main body of the jet pump, typically either perpendicular to or at an acute angle to the longitudinal axis A of the jet pump. This arrangement leaves free the first end 32 of the jet pump (which under previous designs would have carried the HP nozzle) and allows access to the internal components 50, 52 of the jet pump without having to remove spool pieces connected to the first and second ends of the jet pump. The first end 32 of the housing 30 is blinded during the normal operation of the jet pump 26 by the blind flange plate 49, which can be removed to allow access to the internal components.

After removing the blind flange plate 49 from the flanged first end 32, the entire combined nozzle assembly 50 and mixing tube/diffuser assembly 52 can be pulled out of the housing 30 as a single unit, without having to remove any spool pieces from the first and second ends of the jet pump. The nozzle assembly 50 and/or the mixing tube/diffuser assembly 52 can then be removed and replaced as required.

In order to be able to remove the nozzle assembly 50 and the mixing tube/diffuser assembly 52 as a single unit this assembly has the following unique features.

The cylindrical section 74 has an opening 80 that faces the HP inlet pipe 40 to allow the HP fluid to enter the opening 80 and pass through the nozzle assembly 50. The nozzle assembly 50 is equipped with a pair of O-ring seals 62, which enable it to isolate the HP inlet 40 of the jet pump from the LP inlet 42 and the mixing tube/diffuser assembly 52. The seals 62 are preferably mounted on the nozzle assembly 50 so that when the nozzle assembly 50 is pulled out of the jet pump housing 30, the seals 62 are retrieved and can be replaced if needed.

The nozzle assembly 50 is linked to the pull out assembly 76 by the cylindrical section 74, wherein one end of the cylindrical section is attached to the body of the nozzle assembly 50 and the other end is attached to the pull out assembly 76. The cylindrical section 74 may be permanently attached to the body of the nozzle assembly 50, for example by welding, or it may be removably attached, for example by respective screw threads.

The link structure 82 is preferably welded to the outside body of the mixing tube/diffuser assembly 52. The bars comprising the link structure 82 can be of flat plate type, curved plate type or L-shaped to add to their stiffness if required. The cylindrical section 74 and the link structure 82 are strong enough to hold the mixing tube/diffuser assembly 52 and the nozzle assembly 50 together during operation of the jet pump 26 and also when the assemblies 50, 52 are pulled out of the housing 30 when it is necessary to change the design of the internal components or to install new internals components. The link structure 82, which is welded at one end to the nozzle assembly 50 and at the other end to the mixing tube/diffuser assembly 52, can be made in two separate sections that overlap one another and are bolted together to connect the nozzle assembly 50 and the mixing tube assembly 52. This feature also enables the two units (the nozzle assembly 50 and the mixing tube/diffuser assembly 52) to be separated from one another and replaced individually if needed after being pulled out or during transport.

The mixing tube/diffuser assembly 52 is held in a centralised position inside the jet pump housing 30 by two sets of rings 72 that are welded to the external surface of the mixing tube/diffuser assembly 52. These rings 72 can be equipped with seals to prevent fluids from entering the annular space between the mixing tube/diffuser assembly 52 and the housing 30. Alternatively, the rings 72 can be provided with weep holes or similar vent features if it is not necessary to seal the gap between the mixing tube 52 and the housing 30. In this case the rings 72 only serve to hold the mixing tube/diffuser assembly in position and prevent it from vibrating. If required, the annular space between the mixing tube/diffuser assembly 52 and the housing 30 can be filled with grease to prevent the ingress of fluids flowing through the jet pump 26. The rings 72 also act as dampeners to prevent the mixing tube/diffuser assembly 52 vibrating during operation.

The pull-out end assembly 76 is equipped with an extension part 78. This extension part 78 is designed to allow an external pull out device to be locked onto it, enabling the pull out device 76 and the nozzle/mixing tube assembly 50, 52 to be removed and re-installed in the housing 30. There are many suitable methods for enabling the external pull out device to be locked onto the internals pull out end.

The blind flange plate 49 can be a standard blind flange, which is attached to the flange 36 at the first end 32 of the housing with bolts. Alternatively, the connection to the first end 32 of the housing can be of clamped type or of collet type, or any other connection mechanism available in the industry may be used as site conditions dictate. This also applies to the connections provided at the first and second inlet pipes 40, 42 and to the discharge flange 38 at the second end 34. All three types of connection, whether flanged, collet or clamp type, are industry standard connectors which can be used depending on the pressure rating of the system or their use for onshore, offshore or subsea applications.

Subsea Applications of the Jet Pumps

The combined nozzle assembly 50 and mixing tube/diffuser assembly 52 described above is ideal for use in subsea applications, as this allows the entire set of internal components to be pulled out with the help of a remotely operated vehicle (ROV) when needed without having to disconnect the inlet and outlet pipelines including the HP and LP inlet lines. The jet pump in this case can be installed in horizontal or vertical mode depending on the details of the subsea module and features included to assist the ROV to lock onto the module and pull out the internal components.

Claims

1. A jet pump including an elongate tubular housing that comprises a longitudinal axis, an upstream first end and a downstream second end, a nozzle assembly and a mixing tube/diffuser assembly, said nozzle assembly and said mixing tube/diffuser assembly being removably received within the housing, a first inlet vent for a HP first fluid, a second inlet vent for a LP second fluid and an outlet vent at the downstream second end of the housing for the combined first and second fluids, wherein the first and second inlet vents extend non-axially through a circumferential wall of the tubular housing, and wherein the nozzle assembly and the mixing tube/diffuser assembly can removed from the housing through the upstream first end thereof.

2. A jet pump according to claim 1, wherein one or both of the first and second inlet vents extend through a circumferential wall of the tubular housing at an angle θ relative to the longitudinal axis, where 0°<θ≦90°.

3. A jet pump according to claim 1, further including a removable closure member at the upstream first end of the housing.

4. A jet pump according to claim 1, wherein the nozzle assembly and the mixing tube/diffuser assembly are interconnected by a link assembly.

5. A jet pump according to claim 4, wherein the link assembly is configured such that the nozzle assembly and the mixing tube/diffuser assembly are separable.

6. A jet pump according to claim 1, further including a pull-out assembly connected to the nozzle assembly for extracting the nozzle assembly and the mixing tube/diffuser assembly from the housing through the upstream first end thereof.

7. A jet pump according to claim 6, wherein the pull-out assembly is separable from the nozzle assembly.

8. A jet pump according to claim 6, further including a tubular sleeve element that interconnects the pull-out assembly and the nozzle assembly.

9. A jet pump according to claim 8, wherein the tubular sleeve element includes a fluid flow passageway configured to allow HP fluid to flow from the first inlet vent to the nozzle assembly.

10. A jet pump according to claim 1, wherein the first inlet vent extends through the circumferential wall of the tubular housing upstream of the nozzle assembly.

11. A jet pump according to claim 1, wherein the second inlet vent extends through the circumferential wall of the tubular housing downstream of the nozzle assembly and upstream of the mixing tube/diffuser assembly.

12. A jet pump according to claim 2, further including a removable closure member at the upstream first end of the housing.

13. A jet pump according to claim 2, wherein the nozzle assembly and the mixing tube/diffuser assembly are interconnected by a link assembly.

14. A jet pump according to claim 3, wherein the nozzle assembly and the mixing tube/diffuser assembly are interconnected by a link assembly.

15. A jet pump according to claim 2, further including a pull-out assembly connected to the nozzle assembly for extracting the nozzle assembly and the mixing tube/diffuser assembly from the housing through the upstream first end thereof.

16. A jet pump according to claim 3, further including a pull-out assembly connected to the nozzle assembly for extracting the nozzle assembly and the mixing tube/diffuser assembly from the housing through the upstream first end thereof.

17. A jet pump according to claim 4, further including a pull-out assembly connected to the nozzle assembly for extracting the nozzle assembly and the mixing tube/diffuser assembly from the housing through the upstream first end thereof.

18. A jet pump according to claim 5, further including a pull-out assembly connected to the nozzle assembly for extracting the nozzle assembly and the mixing tube/diffuser assembly from the housing through the upstream first end thereof.

19. A jet pump according to claim 7, further including a tubular sleeve element that interconnects the pull-out assembly and the nozzle assembly.

20. A jet pump according to claim 6, wherein the first inlet vent extends through the circumferential wall of the tubular housing upstream of the nozzle assembly.

21. A jet pump according to claim 20, wherein the second inlet vent extends through the circumferential wall of the tubular housing downstream of the nozzle assembly and upstream of the mixing tube/diffuser assembly.