WO2019202499A1

WO2019202499A1 - Centrifugal seal with suction recirculation control for slurry pumps

Info

Publication number: WO2019202499A1
Application number: PCT/IB2019/053127
Authority: WO
Inventors: Luis Fernando Echeverri; John Semple Frater
Original assignee: Flsmidth A/S
Priority date: 2018-04-16
Filing date: 2019-04-16
Publication date: 2019-10-24

Abstract

A centrifugal seal system for a slurry pump (1) is provided with an adjustable wear ring (2) having an outer diameter (18) that is 1.3 to 2.1, and more preferably between 1.5 and 1.9 times the inlet diameter (17) of a suction orifice (33). The adjustable wear ring (2) acts in combination with a centrifugal expeller (5) that generates a differential backpressure to seal the slurry pump (1) and prevent leakage of the fluid pumped to the surroundings. The centrifugal expeller (5) has a diameter (12) which is 75 to 95%, and more preferably, between 82% and 90% of the diameter (19) of the impeller (7). The slurry pump (1) may comprise a seal clamp (44), one or more compression packing rings (47), and an axially-floating cartridge (48) comprising one or more lip seals (46) to prevent leakage when the slurry pump (1) is stopped.

Description

CENTRIFUGAL SEAL WITH SUCTION RECIRCULATION CONTROL FOR SLURRY PUMPS

CROSS-REFERENCE TO RELATED APPLICATIONS

This international patent application claims the benefit of United States Provisional Patent Application Serial No. 62/658,012 - which was filed on April 16, 2018.

FIELD OF THE INVENTION

This application pertains to centrifugal pumps, and more particularly, to an improved centrifugal seal system for centrifugal pumps (e.g., slurry pumps).

The disclosed centrifugal seal system comprises a pump design that allows optimum rear drive side sealing performance without compromising pump hydraulic performance.

It will become apparent from this disclosure that embodiments of the centrifugal seal system described herein offer various advantages and benefits not yet available in conventional slurry pumps.

BACKGROUND OF THE DISCLOSURE

Centrifugal seals, also known as dynamic or hydrodynamic seals, have been used to seal centrifugal pumps for many years. These devices incorporate a secondary rotor provided with vanes and known as centrifugal expeller, which rotates together with the impeller. Centrifugal expellers generate a backpressure gradient which, under the right conditions, can help prevent leakage of the fluid being pumped. A problem with centrifugal seals, is that they do not generate any pressure differential when the pump has been turned off and the impeller is not rotating. To prevent leakage while the pump is not operating, standard stationary sealing solutions are normally incorporated, such as for example gland compression packing rings and lip seals lubricated with grease or water. One disadvantage of these standard solutions when pumping slurries is that small leakages and/or dripping occurs when the pump stops as the seals wear, particularly when they are not frequently lubricated. Consequently, solids accumulate between the seal component and the shaft rotating surface, resulting in local wear around the seal area once the pump starts operating again.

An example of a centrifugal pump having a centrifugal expeller and impeller may be found in U.S. Pat. No. 5,609,468. Embodiments described herein aim to improve upon such prior devices.

Fluid dynamic equations for turbomachinery state that the head produced by rotating vanes is generally proportional to the square of the outer diameter. Accordingly, increasing the size of a centrifugal expeller, relative to the size of a pump’s impeller, rapidly increases the relative pressure difference generated. This increase in differential pressure enhances the sealing capacity of the centrifugal seal.

The sealing capacity of centrifugal seals generally increases as the axial clearance between the centrifugal seal vanes and the rear stationary wall is reduced; however, reducing the clearance between the centrifugal seal vanes and the rear stationary wall also requires adjusting the impeller towards the rear (i.e. , axially towards the drive) side of the pump. Adjusting the impeller towards the rear drive side of the pump has a major negative side effect: as the clearance at the front of the impeller increases with decreasing rear drive side clearance, suction recirculation ensues resulting in increased wear and hydrodynamic losses which reduce pump performance. It is well known that suction recirculation negatively affects pump hydraulic performance, reduces pump capacity, increases power consumption, and can severely increase wear rates (especially in the case of slurry pumps moving abrasive solids).

Accordingly, with conventional solutions currently available, there is a problematic compromise between pump sealing and hydraulic performance as the impeller is adjusted.

Embodiments of the present invention aim to solve this centrifugal seal problem by obviating the need to compromise between pump sealing and hydraulic performance. This is done by employing a relatively large centrifugal expeller in combination with an adjustable wear ring that controls suction recirculation in the manner described hereinafter. Additionally, a new configuration for stationary sealing is disclosed, which combines compression packing rings with lips seals arranged in such a way that leakage and wear are minimized, thereby reducing or eliminating the need for periodic lubrication.

OBJECTS OF THE INVENTION

It is, therefore, an object of the invention to provide a pump with a centrifugal seal system which circumvents the aforementioned drawbacks associated with conventional centrifugal slurry pumps.

It is another object of centrifugal seal system embodiments disclosed herein, to reduce wear that typically occurs with conventional centrifugal slurry pumps used in mining and other industrial operations.

It is a further object of centrifugal seal system embodiments disclosed herein, to mitigate, reduce, or eliminate suction recirculation (and consequences associated therewith) - especially when an impeller of a centrifugal slurry pump is adjusted to the rear side (e.g., to improve sealing).

It is another object of centrifugal seal system embodiments disclosed herein, to eliminate, or minimize, the need for periodic lubrication of stationary seal components used to prevent leakage while the pump is not operating, and to provide a more maintenance-friendly pump which requires less attention.

It is yet another object of centrifugal seal system embodiments disclosed herein, to attain improved overall sealing performance over prior pump designs and improved robustness for continuous operation in difficult industrial environments.

These and other objects will be apparent from the appended drawings and description herein.

Although every object is believed to be attained by at least one embodiment of the invention, there is not necessarily any one embodiment of the invention that achieves all of the objects of the invention.

BRIEF SUMMARY OF THE INVENTION

A slurry pump 1 is disclosed. The slurry pump 1 may comprise an impeller 7 having pumping vanes 31 having a first outer diameter 19 (i.e.,“Dimp”). The impeller 7 may further comprise rear drive side vanes 3.

The slurry pump 1 may further comprise a centrifugal expeller 5 having a second outer diameter 12 (i.e.,“Dee”). Rear drive side vanes 6 may be provided to the centrifugal expeller 5. The slurry pump 1 may further comprise an adjustable wear ring 2 positioned in front of impeller 7 and located between pump suction orifice 33 and front stationary wall 43 of the slurry pump 1. A first axial clearance 13 (i.e.,“See”) may exist between centrifugal expeller rear drive side vanes 6 and a rear side expeller-containing expeller ring 23 or a first rear stationary wall 24, adjacent a rear drive side 9 of the slurry pump 1.

A second axial clearance 14 (i.e.,“Srv”) may exist between the impeller 7 and a casing or rear liner 21 or a second rear stationary wall 25, adjacent a rear drive side 9 of the slurry pump 1.

A third axial clearance 16 (i.e.,“Swr”) may exist between the impeller 7 and the adjustable wear ring 2.

The first axial clearance 13 (i.e.,“See”) may be 0.01 to 20 mm. The second axial clearance 14 (i.e.,“Srv”) may be 0.01 to 20 mm. The third axial clearance 16 (i.e.,“Swr”) may be 0.01 to 5 mm. The second outer diameter 12 (i.e.,“Dee”) may be 75% to 95% of the first outer diameter 19 (i.e.,“Dimp).

The impeller 7 may further comprise front suction side vanes 4. The front suction side vanes 4 may extend radially and axially from the impeller 7, for example, in a direction along a pump axis 39 of the slurry pump 1 , for example - toward a front suction side 10 of the slurry pump 1.

The slurry pump 1 may further comprise a fourth axial clearance 15 (i.e.,“Sfv”) between the front suction side vanes 4 of the impeller 7 and a front stationary wall 43, adjacent a front suction side 10 of the slurry pump 1. The front stationary wall 43 may be a surface portion of a pump casing or casing liner 21 or a front suction side liner 20, without limitation.

In some embodiments, the ratio of the fourth axial clearance 15 (i.e.,“Sfv”) to the first outer diameter 19 (i.e., “Dimp”) may be 1 to 2.5 %. In some embodiments, the ratio of the fourth axial clearance 15 (i.e. ,“Sfv”) to the first outer diameter 19 (i.e.,“Dimp”) may be 1.2 to 2.1 %.

The slurry pump 1 may further comprise a third inner diameter 17 (i.e., “Dsuction”), which is associated with a suction orifice (33) of the impeller (7).

An outer diameter 18 (i.e.,“Dwr”) of the adjustable wear ring 2 may be 1.3 to 2.1 times the third diameter 17. The rear drive side vanes 3 of the impeller 7 may comprise a fourth outer diameter 11 (i.e.,“Drv”). The fourth outer diameter may be 91% to 104% of the first outer diameter 19, without limitation. For example, the fourth outer diameter may be 101 % to 104% of the first outer diameter 19. As another non-limiting example, the fourth outer diameter may be 102% or 103% of the first outer diameter 19, without limitation.

In some embodiments, the first axial clearance 13 may be less than 3 mm; for example, 0.01 to 1 mm. In some embodiments, the second axial clearance 14 may be less than 3 mm; for example, 0.01 to 1 mm.

In some embodiments the third axial clearance 16 may be less than 2 mm; for example, 0.01 to 1 mm. In some embodiments, the second outer diameter 12 may be 82% to 90% of the first outer diameter 19.

In some embodiments, the slurry pump 1 may further comprise a centrifugal expeller seal having a seal clamp 44, one or more compression packing rings 47 adjacent to the centrifugal expeller 5, and an axially-floating cartridge 48 comprising one or more lip seals 46. The axially-floating cartridge 48 may, as shown, surround a pump shaft 36 which drives the impeller 7 and expeller 5 of the slurry pump 1. The axially-floating cartridge 48 may be configured to move along pump axis 39 to permit compression of the one or more compression packing rings 47 via the seal clamp 44. The seal clamp 44 and axially-floating cartridge 48 may be positioned further to the rear drive side 9 of the slurry pump 1 than the one or more compression packing rings 47, without limitation.

BRIEF SUMMARY OF THE DRAWINGS

To complement the description which is being made, and for the purpose of aiding to better understand the features of the invention, a set of drawings illustrating the new and novel centrifugal seal system is attached to the present specification as an integral part thereof, in which the following has been depicted with an illustrative and non-limiting character.

FIG. 1 illustrates a slurry pump 1 provided with a centrifugal seal system according to a preferred embodiment. The figure identifies some of the main components incorporated into the centrifugal seal system design. One or more components of the centrifugal seal system may be applied to a centrifugal pump, such as a centrifugal slurry pump, without limitation.

FIG. 2 presents flow visualization studies showing the air-liquid interphase observed during testing of a prototype of an embodiment of the centrifugal seal system disclosed. The figure depicts a rear drive side of a pump 1 employing a clear panel as a portion of the rear drive side expeller ring 23. The figure further depicts where balance between pump internal fluid pressure and air at atmospheric pressure occurs 27, and/or how fluid leakage can be prevented by generating a strong vortex via a centrifugal expeller 5 having rear drive side vanes 6.

FIG. 3 illustrates a cross section of a slurry pump 1 provided with the centrifugal seal system according to certain embodiments. The centrifugal seal system comprises suction recirculation control capability by virtue of employing an axially adjustable wear ring 2. Several design parameters that have been found to be important for achieving optimum sealing, pumping hydraulic performance, and maximum wear life are suggested in FIG. 3 as well as in FIG. 7.

FIG. 4 illustrates an isometric cross-sectional view of a pump 1 according to certain preferred embodiments. The figure more clearly shows a front suction side of a preferred embodiment of a pump 1 adjacent a fluid inlet 32 (i.e. ,“pump suction nozzle”) of the pump 1.

FIG. 5 is a close-up view of FIG. 4 more clearly illustrating an adjustable wear ring 2 and one possible manner in which the same may be axially adjusted along a pump axis 39 using a number of jackscrews 30 extending through a front suction side liner 20 and being distributed circumferentially around a pump suction nozzle or inlet 32.

FIG. 6 shows yet another isometric cross-sectional view of a pump 1 according to certain preferred embodiments, presenting the centrifugal seal system disclosed with a slurry pump provided with wear-resistant polymeric and hard metal liners at the top and the bottom of the figure respectively.

FIG. 7 is a table presenting preferred design parameters for the centrifugal seal system disclosed that have been found to achieve optimum sealing, pumping performance, and maximum wear life.

FIGS. 8 and 9 present a new stationary seal configuration responsible for stopping leaks when the pump 1 is not operating and the centrifugal expeller 5 has stopped rotating, wherein compression packing ring(s) may be combined with one or a plurality of lip seal(s) resulting in a solution that eliminates or reduces the need for periodic lubrication and which reduces solids migration between seal components between pump start/stop cycles. In the following, the invention will be described in more detail with reference to drawings in conjunction with exemplary embodiments.

DETAILED DESCRIPTION

While the present invention has been described herein using exemplary embodiments of a centrifugal pump or centrifugal seal system for a centrifugal pump, it should be understood that numerous variations and adaptations of a centrifugal seal system having suction recirculation control will be apparent to those of ordinary skill in the field from the teachings provided herein.

The detailed embodiments shown and described in the text and figures should not be construed as limiting in scope; rather, all design features should be considered to be exemplary or suggestive in nature. Accordingly, this invention is only limited by the appended claims.

The inventors have recognized a novel and heretofore unappreciated method of sealing a pump 1 , such as a slurry pump, with a system comprising a relatively large centrifugal expeller 5 (relative to the size of its impeller 7), in concurrence with an adjustable wear ring 2 that permits axial adjustment of the impeller 7 in a direction aligned with a pump axis 39, to the rear drive side of a pump where a shaft 36 is rotated in a bearing housing 37 to drive rotation of the impeller 7.

Axial adjustment of the shaft 36, in conjunction with impeller 7 and centrifugal expeller 5, along axis 39 may be performed to minimize the centrifugal expeller 5 clearance 13 (i.e. ,“See”), and the rear impeller vanes 3 clearance (i.e. ,“Srv”), while an adjustable wear ring 2 may be adjusted tightly towards the impeller 7 to minimize the front clearance 16 (i.e.,“Swr”) on a suction side pump 1 , without limitation. Axial adjustment of the adjustable wear ring 2 may be performed manually by rotating a number of jackscrews 30 through a front suction side liner 20 or outer casing 22. Adjustment of jackscrews 30 may be made to optimize the axial clearance 16 (i.e.,“Swr”) between the front suction side of the impeller 7 and the rear drive side of the adjustable wear ring. Any suitable hydraulic, electric, or pneumatic actuator known in the art or envisaged by skilled artisans can be alternatively used to adjust the jackscrews 30.

By adjusting the impeller 7, together with centrifugal seal 5, towards the rear side 9 of the pump 1 , the rear clearances between rotating vanes 3, 6 and stationary walls 24, 25 is reduced, resulting in stronger vortices and consequently higher sealing capacity.. Moreover, by virtue of the specified design features disclosed herein, the clearance 16 (i.e., “Swr”) at the front suction side of the impeller 7 can be minimized by adjusting the wear ring 2 and therefore suction recirculation problems can be prevented and/or hydrodynamic losses minimized.

A centrifugal seal with suction recirculation control for slurry pumps is further disclosed. The seal aims to maximize sealing performance without compromising hydraulic pumping performance. The seal may also reduce pump components wear in slurry transport systems.

Turning now to the figures, a pump 1 comprises a pump axis 39 extending between a front suction side 10 of the pump 1 and a rear drive side 9 of the pump 1. The pump 1 may comprise a suction nozzle or inlet 32 and a discharge nozzle or outlet 34. The pump suction nozzle 32 may comprise an outer casing 22 or a front suction side liner 20 defining a suction orifice 33 for incoming slurry to flow through. Slurry entering the pump suction nozzle 32 enters the space confined by pump casing or casing liner 21 and other pressure containing components such as the rear expeller ring 23 and front suction liner 20. The pump 1 may further comprise a bearing housing 37 supporting a shaft 36 which rotates about the pump axis 39. The pump 1 may further comprise a frame 38 which may be affixed to a foundation or other structure via a mount 35.

An impeller 7 and centrifugal expeller 5 rotate around the pump axis 39. The impeller 7 and centrifugal expeller 5 are driven by a shaft 36 which is rotated by a motor or drive (not shown). The impeller 7 rotates within the casing or casing liner 21 transferring energy to the fluid as it conveys the flow from the pump suction nozzle 32 to the pump discharge nozzle 34.

An adjustable wear ring 2 closes a front suction side gap 16 or axial clearance 16 (i.e., “Swr”) between the impeller 7 and adjustable wear ring 2. The adjustable wear ring 2 may be moved relative to pump axis 39, for example, by turning one or more jackscrews 30. Jackscrews 30 may surround the pump suction nozzle 32 and extend through the front suction side liner 20 and/or outer casing shell 22 as shown in FIG. 4. The jackscrews 30 may be rotated to push adjustable wear ring 2 closer to the front suction side of the impeller 7, such that the axial gap 16 can be made narrow, thereby compensating for wear and optimizing the pump 1 to reduce or eliminate recirculation.

Impeller rear drive side vanes 3 are located on a rear drive side 9 of the pump’s impeller 7. Impeller front suction side vanes 4 are located on a front suction side 10 of the pump’s impeller 7. Centrifugal expeller rear drive side vanes 6 are located on a rear drive side 9 of the pump’s centrifugal expeller 5.

In some embodiments, the impeller 7 may comprise an annular cutout 40 adjacent its hub 41 surrounding shaft 36. The annular cutout 40 may receive a protuberance 8 extending from a second rear stationary wall 25 of a rear drive side casing 22 or rear liner 21. The rear drive side casing liner 21 may form a portion of an outer casing 22 of the pump 1. The outer casing 22 may be of the split style as shown, and may receive a protective wear liner 21 , without limitation. The pump 1 has a diameter 11 (i.e. ,“Drv”) associated with the impeller’s 7 rear drive side vanes 3. The pump’s centrifugal expeller 5 has a diameter 12 (i.e., “Dee”). The pump 1 has a suction diameter 17 (i.e., “Dsuction”), typically associated and close in size to the suction orifice 42 of the impeller 7. The pump 1 has a diameter 18 (i.e.,“Dwr”) associated with its adjustable wear ring 2. The pump’s impeller 7 has impeller pumping vanes 31 , and there is a diameter 19 (i.e.,“Dimp”) associated with the impeller pumping vanes 31.

The pump 1 further comprises an axial clearance 13 (i.e.,“See”) between the centrifugal expeller vanes 6 and the expeller ring 23 or first rear stationary wall 24, adjacent a rear drive side of the pump 1.

The pump 1 further comprises an axial clearance 14 (i.e.,“Srv”) between the rear drive side vanes 3 of the impeller 7 and the casing liner 21 or second rear stationary wall 25. The pump 1 further comprises an axial clearance 15 (i.e., “Sfv”) between front suction side vanes 4 of the impeller 7 and the front side liner 20 or a front stationary wall 43, adjacent a front suction side 10 of the pump 1. It should be noted that in some embodiments, the front suction side vanes 4 of the impeller 7 may be optionally omitted, without limitation. The front stationary wall 43 may be a surface portion of casing 22, or casing liner 21 and/or a surface portion of front suction side liner 20, without limitation.

As suggested in FIG. 1 , a pump 1 may include a centrifugal seal system which incorporates a centrifugal expeller 5 and an impeller 7. Unlike with conventional designs, the expeller 5 disclosed herein is relatively large in diameter with respect to the diameter of the impeller 7. The expeller 5 is configured with rear drive side vanes 6 and the impeller 7 may also be provided with rear drive side vanes 3. The expeller 5 and impeller 7 are provided in combination with an adjustable wear ring 2 (e.g., an FLSmidth® millMAX® adjustable wear ring). In some embodiments, the adjustable wear ring 2 provided in the centrifugal seal system may be one as disclosed in U.S. Pat. No. 5,921 ,748).

In some embodiments, a centrifugal seal system may comprise an adjustable wear ring 2 having an outer diameter ratio of “Dwr” 18 to“Dsuction” 17 that is between 1.3 and 2.1 , without limitation. That is, the ratio of the outer diameter

18 of the adjustable wear ring 2 to the inner diameter of the suction orifice 17 of the inlet 32 may be between 1.3 and 2.1 , without limitation. More preferably, the centrifugal seal system may comprise an adjustable wear ring 2 having an outer diameter ratio“Dwr / Dsuction” which is between 1.5 and 1.9, without limitation. The centrifugal seal system may be employed with a centrifugal expeller 5 having a diameter ratio“Dee / Dimp” in the range 75-95%, and more preferably 82-90%, without limitation. That is, an outer diameter 12 of the centrifugal expeller 5 may be greater than or equal to 75% of the outer diameter 19 of the impeller pumping vanes 31 ; but less than or equal to 95% of the outer diameter

19 of the impeller pumping vanes 31 , without limitation.

The centrifugal seal system may include an impeller 7 provided with a plurality of vanes 4 on its front suction side; for example, over a front shroud of the impeller 7. An axial clearance 15 (i.e. ,“Sfv”) between the tip of these vanes 4 and a front stationary wall of the pump such as an inner surface 43 of lining 21 preferably exceeds the size of the largest solid particles contained in a slurry to be conveyed by the pump.

For example, in some embodiments, a ratio of axial clearance 15 to the diameter 19 of impeller pumping vanes 31 of the impeller 7 (i.e.,“Sfv / Dimp”) of between 1 and 2.5% is desired, without limitation - wherein “Sfv” is equal to axial clearance 15 and“Dimp” is equal to the outer diameter 19 of the pumping vanes 31 of the impeller 7. In more preferred embodiments, an“Sfv / Dimp” ratio of 1.2 to 2.1% may be employed with the centrifugal seal system, without limitation. It is preferred that the clearance Sfvis larger than the largest solid particle contained in the slurry to be transported using the pump 1.

In some embodiments, the centrifugal seal system may allow adjustment of the impeller 7 towards the rear drive side of the pump 1 (i.e. , closer towards bearing housing 37), thereby minimizing the centrifugal expeller and impeller rear drive side vane clearances 13, 14, without limitation.

In some embodiments, the axial clearance 13 (i.e., “See”) may equal axial clearance 14 (i.e.,“Srv”), without limitation.

In some embodiments, axial clearance 13 (i.e., “See”) may be between approximately 0.01 mm and 20 mm, without limitation. However, it is preferable that axial clearance 13 is between 0.1 mm and 5 mm, (e.g., less than 3.0 mm). For example, in some embodiments, axial clearance 13 (i.e., “See”) may be between approximately 0.5 mm and 1.0 mm, or, between approximately 0.01 mm and 1.0 mm, without limitation.

In some embodiments, axial clearance 14 (i.e., “Srv”) may be between approximately 0.01 mm and 20 mm, without limitation. However, it is preferable that axial clearance 14 is between 0.1 mm and 5 mm, (e.g., less than 3.0 mm). For example, in some embodiments, axial clearance 14 (i.e., “Srv”) may be between approximately 0.5 mm and 1.0 mm, or, between approximately 0.01 mm and 1.0 mm, without limitation.

Adjustment of adjustable wear ring 2 may function to minimize the clearance in front of the impeller, for example, to a range wherein the axial clearance 16 (i.e., “Swr”) between impeller 7 and adjustable wear ring 2 is between approximately 1.0 and 2.0 mm, without limitation. In some embodiments, axial clearance 16 (i.e., “Swr”) may be between approximately 0.01 mm and 5.0 mm, without limitation. However, it is preferable that axial clearance 16 is less than 2.0 mm. For example, in some embodiments, axial clearance 16 (i.e., “Swr”) may be between approximately 0.5 and 1.0 mm, or, between approximately 0.01 mm and 1.0 mm, without limitation.

In some embodiments, a centrifugal seal system may comprise a stationary protuberance 8 projecting into an annular cutout 40 of the impeller 7 adjacent an inner diameter of rear drive side vanes 3 of the impeller near the impeller’s hub 41 , without limitation. In some embodiments, the protuberance may closely correspond to the annular cutout 40 to assist sealing performance, without limitation. Such a configuration may serve to prevent the entry of solids into a chamber of the pump the centrifugal expeller 5.

Turning now to FIGS. 8 and 9, in some embodiments, to prevent leakage of a sealing a pump 1 when is not operating (i.e. , when the centrifugal expeller 5 is not spinning), a new stationary seal configuration may be provided to the pump 1. The seal configuration may comprise one or more compression packing ring(s) 47 combined with lip seals 46, acting enclosed between a wear resistant shaft sleeve 45 and seal clamp 44. Seal clamp 44 is preferably axially adjustable along axis 39 and responsible for compressing the packing ring 47, while the lips seals 46 are contained within a floating cartridge 48 that is free to move axially along axis 39, thereby allowing transmission of the seal clamp 44 load to compress the packing ring 47. The seal clamp 44 may be axially adjustable using axial adjustment means 49, which may comprise any mechanical means known in the art, for example, a threaded interface as shown. It is envisaged that hydraulic, pneumatic, linear actuators, and other means for axial adjustment (not shown) may be employed to adjust the positioning of seal clamp 44 along axis 39.

This unique and novel configuration makes it possible to adjust (compression of) the packing ring 47 at any time during operation of pump 1. The packing ring 47 is the seal component directly in contact with the slurry in the centrifugal expeller chamber, and serves as a physical barrier protecting the lip seals 46 from ingress of solids, therefore extending their service life. This arrangement results in a system that can operate without leaks reliably for prolonged periods with little or no lubrication necessary.

FIG. 8 shows a non-limiting embodiment of a seal clamp 44 which utilizes a plurality of jacking screws as its axial adjustment means 49. FIG. 9 shows another non-limiting embodiment of a seal clamp 44 which threadedly engages expeller ring 23, and is further provided with a spanner wrench hole which alternatively serves as axial adjustment means 49. While not shown, it will be appreciated by those skilled in the art that the spanner wrench hole shown in FIG. 9 may be replaced by other forms of torque engagement surfaces (e.g., one or more external torque engagement surfaces not limited to hexagonal surfaces), without limitation.

EXAMPLE

The table in FIG. 7 presents preferred design parameters for the centrifugal seal system disclosed that have been found to be important for achieving optimum sealing, pumping performance, and maximum wear life: wherein:

“Dimp” (depicted in the figures as numeral 19) - represents an outer diameter of impeller pumping vanes (e.g., main impeller vanes located within the impeller);

“Dwr” (depicted in the figures as numeral 18) - represents an outer diameter of an adjustable wear ring;

“Dsuction” (depicted in the figures as numeral 17) - represents an inner diameter of a pump suction nozzle; “Dee” (depicted in the figures as numeral 12) - represents an outer diameter of a centrifugal expel ler;

“Drv” (depicted in the figures as numeral 11) - represents an outer diameter of impeller rear vanes;

“Swr” (depicted in the figures as numeral 16) - represents a suction side axial clearance between an impeller and a wear ring, adjacent a front suction side 10 of a pump 1 ;

“Sfv” (depicted in the figures as numeral 15) - represents a suction side axial clearance between front suction side vanes of an impeller and a front stationary wall 43, adjacent a front suction side 10 of a pump 1 ;

“See” (depicted in the figures as numeral 13) - represents a rear drive side axial clearance between centrifugal expeller vanes and a expeller ring wall (or a first rear stationary wall), adjacent a rear drive side 9 of a pump 1 ;

“Srv” (depicted in the figures as numeral 14) - represents a rear drive side 9 axial clearance between rear vanes 3 of an impeller 7 and a stationary casing or rear liner wall (or a second rear stationary wall 25), adjacent a rear drive side 9 of a pump 1 ;

Preliminary tests suggest that an embodiment of the centrifugal seal system disclosed herein meets or exceeds the sealing capability of commercially- available slurry pumps. Adjustment of the adjustable wear ring 2 has proved effective to control suction recirculation when the impeller 7 is adjusted to the rear side of the pump 1. With the embodiment of the centrifugal seal system disclosed herein, there are little to no evident losses in hydraulic efficiency. The centrifugal seal system presented herein may be incorporated to a pump 1 in order to provide excellent sealing capacity. Embodiments of the centrifugal seal system may demonstrate user-friendliness, as they may enable the impeller 7 to be adjusted axially within the pump 1 without significant problems of compromising sealing or negatively-affecting pump hydraulic performance. The centrifugal seal system may offer sufficient sealing capacity for slurry pump applications where leakage associated with conventional compression packing is unwelcome; or, where no good quality water is available for cooling and lubrication of the packing rings (i.e., poor gland seal water scenarios). The centrifugal seal system may further reduce or avoid the need for ancillary equipment, thereby reducing maintenance and/or capital costs.

In some embodiments, the centrifugal seal system may comprise a novel centrifugal expeller seal with suction recirculation control for slurry pumps. The system may comprise a configuration as substantially shown in the appended drawings.

Embodiments disclosed herein may involve the installation of one or more centrifugal expellers 5 (or repellers) behind the impeller 7. The same may be provided in combination with the addition of a number of rear drive side vanes 3 positioned over a back-shroud of the impeller 7. As the centrifugal expeller 5 rear vanes 6 and impeller 7 rear vanes 3 rotate, their combined action may generate a pressure differential that (partially or fully) counterbalances pressure differences between the pump fluid internal pressure produced by the impeller 7, and the surrounding atmospheric pressure, without limitation. Under certain conditions, the same can effectively seal, thereby preventing fluid leakage from the pump 1 as the balance with atmosphere occurs within the centrifugal seal.

FIG. 2 presents flow visualization studies showing the air-liquid interphase observed during prototype testing of a preferred embodiment of a centrifugal seal system. The figure illustrates where balance between pump internal fluid pressure and air at atmospheric pressure occurs and further suggests how fluid leakage may be substantially or completely prevented. In particular, FIG. 2 shows a liquid-gas interface 27 between a liquid phase 26 and a gas phase 28.

The fluid 26 pumped by the pump 1 may comprise water, slurry, or a liquid and solid and gas combination, without limitation. The gas phase 28 may comprise air, for example. A pressure gauge 29 is shown in FIG. 2. The pressure gauge 29 shown indicates“zero (0) PSIG” or“atmospheric” pressure.

The centrifugal seal system may incorporate a large centrifugal expeller 5, for example, one having an outer diameter 12 which is approximately 75-95% of the impeller diameter 19, without limitation. In some preferred embodiments, the expeller 5 may comprise an outer diameter 12 which is approximately 82-90% of the impeller 19 diameter, without limitation.

The large expeller 5 may work in combination with an adjustable wear ring 2, such as the FLSmidth® millMAX® adjustable wear ring (U.S. Pat. No. 5,921 ,748), without limitation. The combination may enable adjustment (e.g., axial adjustment along pump axis 39) of an impeller 7 to the rear (drive side) of the pump 1 for maximum sealing capacity, while the resulting clearance 16 at the front (suction side) of the impeller 7 can be compensated for by adjusting the wear ring 2 (to close the gap 16 therebetween). By enabling closure of the clearance 16 at the front side of the impeller 7 using the adjustable wear ring 2, suction side recirculation can be controlled and hydraulic performance losses avoided. Moreover, when pumping slurries, the service life of the pump components may be maximized.

Where ranges are disclosed herein, the range may be inclusive of each high and low value listed. All patent publications mentioned herein are hereby incorporated by reference, in their entirety for any and all purposes, as if fully set forth herein. LIST OF ENUMERATED IDENTIFIERS IN THE DRAWINGS

1 Pump

2 Adjustable wear ring

3 Impeller rear drive side vanes

4 Impeller front suction side vanes

5 Centrifugal expeller

6 Centrifugal expeller rear drive side vanes

7 Impeller

8 Protuberance

9 Rear drive side of pump

10 Front suction side of pump

11 Diameter of impeller drive side rear vanes (Drv)

12 Diameter of centrifugal expeller (Dee)

13 Axial clearance (See) between centrifugal expeller vanes and a containing rear expeller ring (or a first rear stationary wall), adjacent the rear drive side of pump

14 Axial clearance (Srv) between rear vanes of an impeller and a casing or rear liner wall (or a second rear stationary wall), adjacent the rear drive side of pump

15 Axial clearance (Sfv) between front suction side vanes of an impeller and a front side stationary wall, adjacent the front suction side of pump

16 Axial clearance (Swr) between impeller and adjustable wear ring

17 Diameter (Dsuction) of impeller suction orifice

18 Diameter (Dwr) of adjustable wear ring

19 Diameter (Dimp) of main impeller pumping vanes, inside impeller

20 Front suction side liner

21 Casing liner

22 Outer casing

23 Expeller ring

24 First rear stationary wall 25 Second rear stationary wall

26 Liquid phase (e.g., water, slurry)

27 Liquid-gas interface

28 Gas phase (e.g., air)

29 Pressure gauge (e.g., indicating zero PSIG or atmospheric pressure)

30 Jackscrew

31 Impeller pumping vanes

32 Pump suction nozzle or inlet

33 Suction orifice

34 Pump discharge nozzle or outlet

35 Mount

36 Shaft

37 Bearing housing

38 Frame

39 Pump axis

40 Annular cutout

41 Impeller hub

42 Impeller suction orifice

43 Front stationary wall (of casing 22 or casing liner 21 or front suction side liner 20)

44 Seal clamp

45 Shaft sleeve

46 Lip seals

47 Compression packing ring

48 Lip seals floating cartridge

49 Axial adjustment means (e.g., jacking bolt, internal/external torque application surface, spanner wrench hole(s), hexagonal profile, threaded interface, pneumatic/hydraulic actuator, etc.)

Claims

1. A slurry pump (1) comprising:

an impeller (7) having pumping vanes (31) and rear drive side vanes (3), the pumping vanes (31) having a first outer diameter (19, Dimp);

a centrifugal expeller (5) having a second outer diameter (12, Dee) and rear drive side vanes (6);

an adjustable wear ring (2) positioned in front of impeller (7) and located between a pump suction orifice (33) and a front suction liner (20) or casing liner (21) or casing (22) stationary wall (43) of the slurry pump (1);

a first axial clearance (13, See) between the rear drive side vanes (6) of the centrifugal expeller (5) and an expeller ring (23) or a first rear stationary wall (24), adjacent a rear drive side (9) of the slurry pump (1);

a second axial clearance (14, Srv) between the rear vanes (3) of impeller (7) and a casing or rear liner (21) or a second rear stationary wall (25), adjacent the rear drive side (9) of the slurry pump (1);

a third axial clearance (16, Swr) between the impeller (7) and the adjustable wear ring (2);

wherein the first axial clearance (13, See) is 0.01 to 20 mm;

wherein the second axial clearance (14, Srv) is 0.01 to 20 mm;

wherein the third axial clearance (16, Swr) is 0.01 to 5 mm; and wherein the second outer diameter (12, Dee) is 75% to 95% of the first outer diameter (19, Dimp).

2. The slurry pump (1) according to claim 1 , wherein the impeller (7) further comprises front suction side vanes (4) extending radially and axially from the impeller (7) in a direction along a pump axis (39) of the slurry pump (1) and toward a front suction side (10) of the slurry pump (1);

3. The slurry pump (1) according to claim 2, wherein the slurry pump (1) further comprises a fourth axial clearance (15, Sfv) between the front suction side vanes (4) of the impeller (7) and a front stationary wall (43), adjacent a front suction side (10) of the slurry pump (1).

4. The slurry pump (1) according to claim 3, wherein the ratio of the fourth axial clearance (15, Sfv) to the first outer diameter (19, Dimp) is 1% to 2.5%.

5. The slurry pump (1) according to claim 4, wherein the ratio of the fourth axial clearance (15, Sfv) to the first outer diameter (19, Dimp) is 1.2% to 2.1 %.

6. The slurry pump (1) according to any one of the preceding claims, further comprising a third diameter (17, Dsuction), which is associated with a suction orifice (33) of the impeller (7).

7. The slurry pump (1) according to claim 6, wherein a outer diameter (18, Dwr) of the adjustable wear ring (2) is 1.3 to 2.1 times the third diameter (17, Dsuction).

8. The slurry pump (1) according to any one of the preceding claims, wherein the rear drive side vanes (3) of the impeller (7) comprise a fourth outer diameter (11 , Drv), and wherein the fourth outer diameter is 91 % to 104% of the first outer diameter (19, Dimp).

9. The slurry pump (1) according to claim 8, wherein the fourth outer diameter is 102% to 103% of the first outer diameter (19, Dimp).

10. The slurry pump (1) according to any one of the preceding claims, wherein the first axial clearance (13, See) is less than 3 mm, or, 0.01 to 1 mm.

11. The slurry pump (1) according to any one of the preceding claims, wherein the second axial clearance (14, Srv) is less than 3 mm, or, 0.01 to 1 mm.

12. The slurry pump (1) according to any one of the preceding claims, wherein the third axial clearance (16, Swr) is less than 2 mm, or, 0.01 to 1 mm.

13. The slurry pump (1) according to any one of the preceding claims, wherein the second outer diameter (12, Dee) is 82% to 90% of the first outer diameter (19, Dimp).

14. The slurry pump (1) according to any one of the preceding claims, further comprising a centrifugal expeller seal having:

a seal clamp (44),

one or more compression packing rings (47) adjacent to the centrifugal expeller (5), and

an axially-floating cartridge (48) surrounding a shaft (36) driving the impeller (7) and expeller (5) and being configured to move along pump axis (39) to permit compression of the one or more compression packing rings (47) via the seal clamp (44); the axially-floating cartridge (48) comprising one or more lip seals (46);

wherein the seal clamp (44) and axially-floating cartridge (48) are positioned further to the rear drive side (9) of the slurry pump (1) than the one or more compression packing rings (47).