ES2714830T3 - Centrifugal pump stage, centrifugal pump and use of a pump - Google Patents

Abstract

Pump stage for a centrifugal pump, comprising an impeller unit (10) provided with an axial hub (11) suitable for mounting on a pump shaft of the centrifugal pump coaxial therewith; a diffuser unit (20) extending on a first face of said impeller unit (10); a suction cover (30) associated with said diffuser unit (20) and extending on a second face of said impeller unit (10); a washer (27) housed in a fixed position in a seat (26) of the diffuser unit (20); said drive unit (10), in operation, being in sliding contact with said cover (30), along an annular portion (13a) extending to said second face, and floating inside said diffuser unit (20). ); characterized in that said drive unit (10) is associated with an adjusting ring (40) fixedly mounted on said axial hub (11) and configured such that it can be slidably supported on a washer (27) housed in a fixed position on a corresponding seat (26) of the diffuser unit (20) of an adjacent pump stage.

Description

DESCRIPTION

Fire pump stage, fire pump and use of a pump

Technical field

The present invention relates to a pump stage for use in a centrifugal pump, in particular of the submerged type.

Background Technique

It has been known that, for the transfer of a liquid from a lower space to an upper space, pump elements are generally used, such as submerged pumps in particular. Known submerged pumps generally have an external tubular sleeve provided with a plurality of radial openings for fluid inlet, usually called suction openings, and with an opening for the exit of the liquid, called an outlet opening. The operating elements of the pump are housed inside the sleeve. The operating elements are composed of a pump unit and a motor unit, usually of an electric type, suitable for operating the transfer of the liquid from the suction openings to the outlet opening.

The pump unit is usually made by means of one or more stages, each comprising a rotating element, capable of being driven in rotation by the motor axis of the motor unit, and by the stationary elements suitable for transmitting the liquid from one stage to another, until the exit opening.

US Patent 7,290,984 discloses, for example, a centrifugal pump having more stages, in which each stage comprises a drive unit, a stationary disk unit and a diffuser unit, arranged on the motor shaft or the impeller shaft More specifically, the disk drive is disposed adjacent to a first side of the drive unit; The diffuser unit is arranged adjacent to a second side of the drive unit. The impeller hub is provided with floating sealing means, supported by the diffuser unit, suitable for reducing liquid recirculation. A thrust washer, arranged on the motor shaft, is suitable to engage with the impeller hub and the mentioned sealing means of the impeller hub. A sliding coupling ring, fixed to the stationary disk drive, is coupled with a corresponding impeller surface.

In essence, the sealing means of the hub are composed of a circular disk-shaped flange that has a series of radial projections for coupling with the corresponding seats in the form of the diffuser body, around the passage opening of the shaft. The flange encloses a cup-shaped cube portion provided with a circular opening in the transverse part.

A specific problem of which the users of pumps of the known type complain is the progressive wear and deterioration of the moving parts that are in redproco contact, in which the sealing is carried out. In particular, the impeller is normally held in sliding support, in an annular portion thereof, in the disc facing it. The axial thrust acting on the impeller also acts on the disc and, due to the wear effect produced by the operation, this causes progressive wear and deterioration of the parts. This fact obviously limits the life of the pump, especially in the presence of grains of sand in the liquid of the pump. US Patent 3,265,001 describes a multistage centrifugal pump in which the impeller of each stage is supported floating in the relative diffuser unit. The impeller hub is in fact axially mounted slidably on the motor shaft through which it is rotated; The floating impeller stroke is limited by suitable stop means, for example, annularly, mounted on the motor shaft. The impeller is supported in sliding contact, along an annular portion, in the aforementioned cover of the diffuser unit, to compensate for a sealing zone between the rotating part and the static part of the stage. More particularly, the impeller is supported by means of a thrust bearing placed under the hub of the same impeller, in support on a seat of the underlying diffuser.

Said solution makes it possible to reduce the wear and deterioration of the elements in operation, in particular in the event that sand or other abrasive grains are present in the liquid to be pumped. The impeller is mounted floating, therefore, it allows to prevent the abrasive grains from stopping in the sliding contact sealing areas, which thus prevents such particles from increasing the wear and deterioration phenomena. At the same time, it is necessary to limit the time that the phenomenon of the liquid leakage of the rotating part is possible to the static part of each stage of the centrifugal pump, in order to avoid a decrease in the pump performance. For this reason, a sufficient seal between the rotating part and the static part of each stage of the centrifugal pump must be guaranteed.

The solutions known in the specific field do not fully meet the requirements mentioned above.

Divulgation

The task of the present invention is to solve the aforementioned problems, by means of the elaboration of a pump stage that guarantees a high level performance, as well as a long resistance in any operating condition.

Within said task, an additional scope of the present invention is to provide a pump stage with reduced wear and deterioration of the moving parts in contact with each other, to give the pump a longer useful life.

Another scope of the present invention is to provide a pump stage that facilitates the assembly of the pump unit.

An additional scope of the invention is to provide a pump stage that has a simple practical and functional conception, provided with a surely reliable operation, versatile use, as well as a relative economic cost.

The aforementioned ranges are achieved, in accordance with the present invention, by means of the pump stage according to claim 1.

In accordance with the present invention, the pump stage comprises a driving unit that is supported floating inside a relative diffuser unit through an adjustment ring mounted fixed on an axial hub of the driving unit and held in sliding support on a washer housed in a fixed position in a corresponding seat of the diffuser unit of an adjacent pump stage.

The drive unit is in sliding contact, along an annular portion extended on said second face, with a suction cap associated with said diffuser unit.

According to an advantageous aspect of the invention, in a step of starting or interrupting, between said annular portion of the driving unit and said cover, a small clearance is defined, such as to minimize the hydraulic losses by means of extraction without Contact.

Preferably, said clearance is equal to a few decimeters.

Advantageously, at the end of said starting or interrupting step, the driving unit is in support with said adjustment ring on said washer of the diffuser unit of the adjacent pump stage and with said annular portion in said cover.

In this way, the hydraulic thrust acting on the drive unit is distributed on two support surfaces, that is the cover in which the annular portion of the impeller is in support and the washer of the adjacent pump stage in which the ring of adjustment is in support.

Preferably, the adjusting ring protrudes from a part of the axial hub of the drive unit and axially crosses said cover of the diffuser unit to engage in sliding support to said washer of the diffuser unit of the adjacent pump stage.

Preferably, said washer is housed in a seat manufactured in a circular opening made axially by said diffuser unit.

Preferably, the adjusting ring is made of a low friction coefficient material and is held in a sliding support on a metal washer.

Preferably, the adjustment ring is made of plastic material, for example, a polymer having a low coefficient of friction and high strength without the need for lubrication.

Preferably, said washer is housed in a seat manufactured in a circular opening made axially up to said diffuser unit.

Preferably, the cover comprises a disk of metallic or partially metallic material, which has in the center a circular opening with a raised flange in which said annular portion of said driving unit is in sliding contact.

The invention also relates to a centrifugal pump comprising a pump unit formed by a plurality of pump stages, as described above.

An object of the invention is also the use of a centrifugal pump stage that provides a start or interruption step in which said drive unit is arranged in support with said adjustment ring on said washer of the pump stage diffuser unit. adjacent and in which between said annular portion of the drive unit and said cover a free space is defined. The width of said free space is progressively reduced due to wear and deterioration of said adjustment ring, until it is canceled out in a normal operating condition or speed, in which said annular portion of the drive unit is in support on said cover.

The interruption of the pump determines a slight wear and deterioration of the adjustment ring which is thus polished and thus acquires a high resistance.

Description of the drawings

The details of the invention will be more evident from the detailed description of a preferred embodiment of the pump stage according to the invention, illustrated by way of indication in the attached figures, in which:

Figure 1 shows an axial cross-sectional view of the pump stage according to the invention; Figure 2 shows an exploded and perspective view of the same pump stage;

Figure 3 shows an axial cross-sectional view of a pair of pump stages in mounting position. Better mode

With particular reference to such figures, the pump stage, for use in a centrifugal pump, in particular of the submerged type, known per se and therefore not represented in the figures, has been indicated for clarity in its entirety with the number 1.

The pump stage 1 comprises a driving unit 10 having an axial hub 11, to be associated with a motor shaft of the electric pump, not shown. The impeller 10 is mounted floating inside a corresponding diffuser unit 20, to which an aspiration cover 30 becomes integral. The diffuser unit 20 extends on a first face of the drive unit 10; the cover 30 extends on a second opposite face of the drive unit. In the vertical operating position, the first face of the driving unit 10 is arranged in the upper part, substantially horizontal, while the second face is arranged in the lower part.

More particularly, the driving unit 10 is composed of an upper part 12 that extends transversely from the axial hub 11 and a substantially disc-shaped lower part 13. The parts 12, 13 of the driving unit 10 are preferably made of a plastic material that is very sharp and resistant, of the type, for example, of polyoxymethylene and the like. The upper part 12 shapes the first face mentioned above of the driving unit 10; The lower part 13 shapes the second face mentioned above of the driving unit 10. The upper part 12 of the driving unit 10 shapes, in angularly distributed positions, a series of walls 14 which extend in the form of spiral from the central zone towards the peripheral zone of the driving unit 10. The walls 14 form, in cooperation with the lower part 13 of the driving unit 10, the respective flow channels 15 for the liquid to be pumped.

The diffuser unit 20 has a cylindrical outer body 21, preferably made of rigid plastic material, for example, a reinforced thermoplastic material. A profiled plate 22 having a circular opening 23 centrally extends from the upper part of the cylindrical body 21 inwards. Above the plate 22, a series of keys 24 are formed in angularly distributed positions, and spirally extend from the central area to the peripheral area of the diffuser unit 20. The keys 24 shape respective flow channels 25 for the liquid to pump.

The plate 22 forms, in the opening 23, a seat 26 for housing a washer 27 preferably of metal material, for example, stainless steel. The washer 27 has an inside diameter smaller than the diameter of the opening 23.

The suction cover 30 is in the form of a disk that has a circular opening 31 centrally; The disc 30 is preferably made of metallic or partially metallic material, for example, stainless steel. In the opening 31, the disk 30 has an outwardly curved area suitable for shaping a raised flange 32 with respect to the plane of the same disk 30. The disk 30 is peripherally coupled to a corresponding shoulder made along the lower edge of the cylindrical body 21 of the diffuser unit 20.

An adjusting ring 40 is associated inferiorly with the axial hub 11 of the drive unit 10, suitable for coupling, in the mounting configuration, to the upper face of the washer 27 with thrust bearing functions. The adjustment ring 40 is fixed to the hub 11. More specifically, the adjustment ring 40 is inserted into a portion of reduced diameter 16 of the hub 11, to result in an overhang of a part of the same hub 11. The ring of adjustment 40 is preferably made of plastic material, for example, a low friction polymer with a high strength and which does not require lubrication, of the type of ether ketone (PEEK) polyether.

The operation of the pump stage is easy to understand from the above description.

In the mounting configuration inside the tubular body of the pump, the individual pump stages that shape the pump unit are coupled to each other through the serial insertion into the motor element. More particularly, the external cylindrical body 21 of the diffuser unit 20 is inserted into the base of the body cylindrical 21 of the underlying diffuser unit (see Figure 3). In such a configuration, the disk 30, which closes the diffuser unit 20 lower, turns out to be locked against the cylindrical body 21 of the underlying diffuser unit.

The driving unit 10, arranged inside the space dimensioned between the diffuser unit 20 and the disc 30 of the pump stage, is in support through the adjusting ring 40 in the washer 27 housed in the corresponding seat 26 of the underlying diffuser unit. In practice, in the mounting configuration of the drive unit 10, the pump stage is held in sliding support on the washer 27 of the diffuser unit 20 of the underlying pump stage.

On the other hand, the lower part 13 of the driving unit 10 is in sliding contact along an annular portion 13a, substantially internal, with the raised flange 32 of the disc 30 closing in a lower way the diffuser unit 20.

In practice, during use, the driving unit 10 is supported floating on the diffuser unit 20 relative to the pump stage through the adjusting ring 40 of low friction plastic material, fixed to the hub 11 and held in sliding support on the metal washer 27 fixedly fixed in the diffuser unit of the underlying pump stage; the driving unit is in sliding contact, along an inner annular portion 13a of the lower disc 13, with the flange 32 of the metal material cover 30 of the diffuser unit.

More particularly, during the first activation of the substantially interrupting pump, the hydraulic thrust acting on the driving unit 10 is supported by the adjusting ring 40 held in sliding support on the metal washer 27; while between the annular portion 13a of the lower disk 13 of the impeller and the flange 32 of the cover 30 there is a free space, which is a small clearance, for example, equal to a few decimilimeters, so that the hydraulic leakage losses are reduced to the minimum, without contact.

The interruption of the pump determines the appearance of slight wear and deterioration in the adjusting ring 40, which in this way is polished and, consequently, acquires a high resistance to wear and deterioration. Wear of the adjusting ring 40 progressively reduces the clearance between the annular portion 13a of the lower disk 13 of the impeller and the flange 32 of the cover 30, until the lower disk 13 contacts the flange 32 of the cover 30. In this way, hydraulic leakage losses are almost completely eliminated between the two sealing surfaces, which in this way improves the flow rate and the performance of the hydraulic head.

Furthermore, in this way, the hydraulic thrust acting on the driving unit 10 is distributed in the cover 30 of the diffuser unit 20, which reduces wear and deterioration of the moving parts in contact. This causes the extension of the life of the pump also in the presence of grains of sand in the pumped liquid.

It should be noted that even in the case of incorrect assembly, possibly due to physical imperfections, in the event that the contact between the lower disk 13 of the impeller and the flange 32 of the cover 30 does not occur before contact between the adjusting ring 40 and metal washer 27, wear and deterioration of the upper cradle caused the progressive decrease of the adjusting ring 40 in washer 27, which again balances the axial thrust.

Therefore, the pump stage according to the present invention achieves the scope of guaranteeing a high level of performance in any operating condition, as well as facilitating the assembly of the pump unit.

Such a result is essentially obtained thanks to the idea of the invention of making the impellers 10 of the different pump stages floating with respect to the relative diffusers 20 so that the axial thrusts are divided into two support surfaces, the cover 30 which supports the annular portion 13a of the impeller and the washer 27 of the adjacent pump stage that supports the adjusting ring 40, thereby optimizing the cradle over time.

On the other hand, this makes it easier to assemble the different pump stages.

Such a solution also allows to obtain a wider tolerance with respect to the concentricity of the different components, with the advantage of being able to provide more pump stages.

Finally, the pump stage according to the present invention allows to improve the performances of the pump, which is to provide fewer pump stages, while generating the same flow rate.

It should be noted that the materials used for the sliding couplings between the impeller 10 and the disc 30 and between the adjusting ring 40 and the washer 27 allow the friction effects to be minimized, while at the same time ensuring a seal Efficient liquid passage. Such materials are chosen appropriately, also taking into account the possible presence of sand grains and the like in the liquid.

An additional advantage offered by the pump stage according to the invention is due to the considerable simplification of the internal sealing system and therefore to the reduced costs that this entails, also in mounting terms.

The pump stage described by way of indication is susceptible to numerous modifications and variants according to the different requirements, within the scope of the appended claims.

In practice, the embodiment of the invention, the materials used, as well as the shape and dimensions, may vary depending on the requirements, within the scope of the appended claims. In the event that the technical characteristics mentioned in each claim are followed by reference signs, said reference signs were strictly included in order to improve the understanding of the claims and therefore were not considered restrictive in any way over the scope of each element identified by way of example by such reference signs.

Claims (10)

1. Pump stage for a centrifugal pump, comprising a drive unit (10) provided with an axial hub (11) suitable for being mounted on a pump shaft of the coaxial pump with it; a diffuser unit (20) extending on a first face of said driving unit (10); a suction cover (30) associated with said diffuser unit (20) and extending on a second face of said driving unit (10); a washer (27) housed in a fixed position in a seat (26) of the diffuser unit (20); said driving unit (10), in operation, in sliding contact with said cover (30), along an annular portion (13a) extending to said second face, and floating inside said diffuser unit (20 ); characterized in that said drive unit (10) is associated with an adjustment ring (40) fixedly mounted on said axial hub (11) and configured so that it can be held in sliding support on a washer (27) housed in a fixed position in a corresponding seat (26) of the diffuser unit (20) of an adjacent pump stage. 2. Pump stage according to claim 1, characterized in that it is configured so that, in a starting or interrupting step, between said annular portion (13a) of said driving unit (10) and said cover (30) is formed a small clearance, such as to minimize hydraulic leakage losses without contact. 3. Pump stage according to claim 1 or 2, characterized in that said adjusting ring (40) protrudes from a part of said axial hub (11) of the drive unit (10) and axially crosses said lid (30) of the drive unit (20) for engaging in sliding support to said washer (27) of the diffuser unit (20) of the adjacent pump stage. 4. Pump stage according to claim 2 or 3, characterized in that it is configured so that at the end of said starting or interrupting step, said driving unit (10) can be in support with said adjusting ring (40) on said washer (27) of the diffuser unit (20) of the adjacent pump stage and with said annular portion (13a) in said cover (30). 5. Pump stage according to one of the preceding claims, characterized in that said adjusting ring (40) is made of a material of low friction coefficient and high resistance to wear and deterioration and can be held in sliding support on said washer (27) of metallic material of the diffuser unit (20) of the adjacent pump assembly. 6. Pump stage according to one of the preceding claims, characterized in that said washer (27) is housed in a seat (26) made in a circular opening (23) axially composed of said diffuser unit (20). 7. Pump stage according to one of the preceding claims, characterized in that said cover (30) comprises a disk of metallic or partially metallic material having centrally a circular opening (31) with a raised flange (32) in which said annular portion (13a) of said drive unit (10) is in sliding contact. 8. Centrifugal pump comprising a pump unit composed of a plurality of pump stages according to one of the preceding claims. 9. Use of a centrifugal pump according to claim 8, characterized in that it provides a starting or interruption stage in which said drive unit (10) is arranged in support with said adjustment ring (40) on said washer (27) of the diffuser unit (20) of the adjacent pump stage and in which between said annular portion (13a) of said impeller unit (10) and said cover (30) a free space is formed, the width of said free space is subjected to a progressive reduction by means of a wear effect of said adjusting ring (40), until it is canceled under a condition of speed or normal operation, in which said annular portion (13a) of said driving unit (10) is in support on said cover (30). 10. Use of a pump according to claim 9, characterized in that by said wear and deterioration effect, in said starting or interrupting step, said adjusting ring (40) is polished and, consequently, acquires a high resistance.