WO2003098049A1

WO2003098049A1 - Multistage pump, particularly of the immersion type

Info

Publication number: WO2003098049A1
Application number: PCT/IB2003/001872
Authority: WO
Inventors: Riccardo Fornasa
Original assignee: Vertical S.R.L.
Priority date: 2002-05-15
Filing date: 2003-05-14
Publication date: 2003-11-27
Also published as: EP1509700B1; EP1509700A1; ATE506541T1; DE60336810D1; CN100366914C; CN1653269A; AU2003232947A1; ITVI20020095A1

Abstract

A multistage pump, particularly of the immersion type, comprises an outer tubular jacket (2) defining a longitudinal axis (L), a plurality of adjacent stages (3) which are arranged hydraulically in series and inserted slidably inside the tubular jacket (2), and a main shaft (4) which is coaxial with the longitudinal axis (L). Each stage has at least one impeller (5) coupled to the main shaft (4) and a diffusion duct (6), means for connecting an electric motor (24), an intake element (7) and a delivery element (8) mounted respectively upstream and downstream of the stages (3) so as to lock them axially. The intake element (7) and delivery element (8) are secured removably to the jacket (2) close to its longitudinal ends by means of substantially transverse connecting members (9) which may be accessed from the outside of the jacket (2). The delivery element (8) comprises a hollow tubular portion (14) which houses inside it a non-return valve (15) inserted slidably so that it may be extracted axially outwards.

Description

MULTISTAGE PUMP, PARTICULARLY OF THE IMMERSION TYPE

Technical field

The present invention is applicable in the field of electric immersion pumps and relates in particular to a multistage pump according to the preamble of Claim 1.

State of the art

Immersion pumps are generally used to raise liquids from relatively great depths and, therefore, must develop a high head. This objective is achieved by means of pumps having various stages arranged in series. It is known from the state of the art that pumps of this type usually comprise a non-return valve, an element for connection with the motor group, an outer tubular jacket inside which various stages are arranged on top of each other hydrauiically in series. Each individual stage comprises at least one impeller and a diffusion duct. The stages, stacked one on top of the other, must be fixed to the jacket and this technical problem may be resolved by means of various measures.

A solution to this problem is described in US patent document No. 2667128 and in English patent document No. 211848 and consists in forming threaded seats located on the inner surface of the tubular jacket close to the two longitudinal ends. Screwed flanges, which have a roughly discoidal or annular form and lock together the assembly composed of the various stages, are housed in said seats.

The main drawback of this method consists in the high cost as a result of the machining of the threadings and the small dimensional tolerances required. Moreover, the assembling and disassembling steps are laborious and extremely difficult owing to problems of seizure.

A second type of solution for fixing and keeping the stages of the pump joined together is described in US patent document No. 3487432 an in German patent document No. 9407942U and consists in the use of a number of external tie-rods in order to exert the compressive force able to maintain the correct positioning of the stage assembly. Said external tie-rods may be formed in such a way as to keep also the motor support joined to the main body of the pump.

However, this known method is not devoid of a number of known drawbacks either. In fact, the external tie-rods constitute an additional dimension, which is particularly problematic given that these pumps are generally inserted inside long and narrow cavities. Moreover, the external tie-rods may be deformed easily during transportation and installation of the pump as a result of their considerable length.

European patent No. 0267445 describes a multistage pump which is characterized in that the stage assembly is kept in position by means of bearing and centring elements which protrude radially towards the inside of the tubular jacket. These bearing and centring elements engage with a pressing chamber, arranged on the delivery side, and with a locking plate, arranged on the intake side.

This solution facilitates the step of assembling the stages and the delivery non- return valve, but has the drawback that the disassembly of the non-return valve leaves the stages free to move axially. It therefore becomes necessary to reposition the stages every time the non-return valve is disassembled. Moreover, the form of the bearing and centring elements is such that the thrust exerted by the fluid on the non-return valve, upon closing of said valve, is transmitted to the stages, impairing their working life over time.

Disclosure of the invention

A general object of the present invention is that of eliminating the abovementioned drawbacks by providing a multistage pump which is easy to use and whose manufacture is advantageous from a cost point of view. A main object is that of providing a multistage pump which is easy to assemble and disassemble and is such that the main components and those subject to wear can be easily and quickly replaced.

A further object of the invention is that of providing a multistage pump which combines a significant ease of assembly and replacement of the components which have a high mechanical strength.

Another particular object of the invention is that of providing a multistage pump which is reliable and is capable of retaining its optimum mechanical and fluid- dynamic characteristics over a long time.

A further object is that of providing a multistage pump which offers a good performance and restricts losses in head, particularly of the non-return valve.

These objects, as well as others which will emerge more clearly hereinafter, are achieved, according to Claim 1 , by a multistage pump, particularly for submerged pumping devices, comprising an outer tubular jacket defining a longitudinal axis, a plurality of adjacent stages which are slidably inserted inside the tubular jacket, a main shaft which is coaxial with the longitudinal axis, each stage having at least one impeller coupled with the main shaft and a diffusion duct, means for connecting an electric motor, and an intake element and a delivery element mounted respectively upstream and downstream of the plurality of stages so as to lock and prestress them axially, characterized in that the intake and delivery elements are removably secured to the jacket close to its longitudinal ends by means of substantially transverse connecting members which are accessible from the outside of the jacket. The delivery element comprises a hollow tubular portion which houses inside it a non-return valve which is inserted slidably so that it may be extracted axially outwards.

Owing to this particular configuration, it is possible to assemble easily the stages inside the tubular jacket, also making the operations of disassembling the pump and the stages contained therein particularly easy. Moreover, the non-return valve, which is positioned close to the delivery side, may be extracted easily from its seat. Disassembly of the valve does not have any effect on the stages stacked up inside the tubular jacket, which remain locked in their correct position. Said characteristic feature means that it is not necessary to reposition the stages inside the tubular jacket after extracting the valve, thereby reducing the time required for replacement of said valve.

Moreover, the thrusts exerted by the fluid on the non-return valve, for example as a result of the water hammer effect, are transmitted to the delivery element and not to the stages, reducing the stresses on said stages.

Preferably, the intake element comprises an intake flange provided with intake openings and removably coupled to an annular interface. The annular interface may be inserted inside the tubular jacket in contact with the last stage of the plurality of stages and is provided with holes for securing it to said jacket.

This particular configuration allows the intake flange to be removed, leaving the annular interface attached to the tubular jacket. The clear advantage of this feature lies in the fact that different motors may be mounted on the same pump by means of simple operations, it being merely required to replace the intake flange which connects the motor to the pump and the coupling joint which connects the shafts.

Brief description of the drawings

Further features and advantages of the invention will be more clearly understood from the detailed description of a preferred but not exclusive embodiments of a pump according to the invention, illustrated by way of a non-limiting example with the aid of the attached illustrative drawing sheets:

FIG. 1 shows a view of the pump assembly according to the invention, partially cross-sectioned along a longitudinal axial plane; FIG. 2 shows a view of the pump according to the invention, cross- sectioned along a transverse plane indicated by the line ll-ll shown in FIG. 1 ;

FIG. 3 shows a cross-sectional view of a portion of the pump according to the invention; FIG. 4 shows a cross-sectional view of an enlarged detail of the portion shown in FIG. 3;

FIG. 5 shows a cross-sectional view of a portion of the pump according to the invention;

FIG. 6 shows a cross-sectional view of an enlarged detail of the portion shown in FIG. 5;

FIG. 7 shows a cross-sectional view of an enlarged detail of the pump according to the invention.

Detailed description of a preferred embodiment

With particular reference to the abovementioned figures, a multistage pump according to the invention, which is denoted in its entirety by reference number 1 and may be used in particular submerged in fluids containing silt, sand and other suspended materials, is described.

The pump 1 comprises an outer tubular jacket 2 defining a longitudinal axis L, a plurality of adjacent stages 3 which are arranged hydrauiically in series and inserted slidably inside the tubular jacket 2, and a main shaft 4 which is coaxial with the longitudinal axis L.

Each stage 3 comprises an impeller 5 which is keyed onto the main shaft 4 and a diffusion duct 6 which directs the fluid to the mouth of the successive stage and modifies the velocity vector of the fluid in a convenient manner.

An intake element 7 and a delivery element 8 are mounted respectively upstream and downstream of the stages 3 so as to lock and prestress them axially. Said intake 7 and delivery elements 8 are secured removably to the tubular jacket 2 close to its longitudinal ends by means of substantially transverse connecting members 9 which may be accessed from the outside of the jacket 2. In this way, it is possible to remove these connecting members 9 directly from the outside, without the need to disassemble other parts first.

The transverse connecting members 9 may consist of annular constraining elements 10 which are inserted with a precision-fit into the through-holes 12 and into corresponding holes 13 of the intake element 7 and delivery element 8. These constraining elements 10 are kept in position by means of locking screws 11. Conveniently, said holes are 13 angularly equidistant so that they are uniformly distributed along an outer circumference of the intake element 7 and delivery element 8.

The delivery element 8 comprises a tubular portion 14 on which approximately half the holes 13 are positioned and which is secured to the jacket 2 by means of the constraining elements 10 and the locking screws 11. The tubular portion 14 is hollow inside and formed in such a way as to receive inside it a non-return valve 15. The non-return valve 15 is inserted slidably inside the tubular portion 14 in such a way that it may be extracted axially outwards.

The tubular portion 14 is provided internally with an annular groove 16, against which the non-return valve 15 bears when said valve is inserted completely. When the non-return valve 15 is positioned in this way, it may be locked by means of an elastic locking ring 17 inserted into an internal annular seat 18 of the tubular portion 14.

The lower part of the tubular portion 14 has the function of keeping the stages 3 locked in position, while the central part of this portion has the function of containing the non-return valve 15 so that said valve may be inserted and extracted without coming into contact with the stages 3 and without causing any axial sliding of the stages 3. The intake element 7 comprises an intake flange 19 coupled with an annular interface 20 and a sleeve 21. The annular interface 20 may be inserted inside the tubular jacket 2 and is provided with holes 13 for securing by means of the radial constraining elements 10 and the locking screws 11.

The sleeve 21 is placed in between the annular interface 20 and the jacket 2 and is located in contact, at one of its longitudinal ends, with the first stage of the plurality of stages 3 and, at its other end, with the intake flange 19.

Openings 22 are formed on the side surface of the sleeve 21 , said openings having dimensions such that the constraining elements 10 may pass through the sleeve 21 and that said sleeve may perform a longitudinal displacement of limited amount with respect to the length of the pump 1 , even when the constraining elements 10 are inserted.

The intake flange 19 comprises intake openings 23 and means 24 for connecting an electric motor (not shown in the drawings). Moreover, this intake flange 19 is secured removably to the annular interface 20 by means of a plurality of axial screws 25 which may be accessed from the outside.

The correct axial positioning of the stages 3 is guaranteed by the radial constraining elements 10 and by the annular interface 20 and is independent of the position of the axial screws 25 and of the type and presence or absence of the intake flange 19.

The axial screws 25, once completely tightened, make the intake flange 19 exert an axial thrusting action on the sleeve 21 , which in turn acts on the stages 3 and exerts a prestressing action on them. The thrust exerted by the intake flange 19 on the stages 3 does not alter the correct positioning of said stages.

If it becomes necessary to remove the radial constraining elements 10, the prestressing of stages 3 must first be eliminated by loosening the axial screws 25. Thus, the intake flange 19 and the motor connected thereto may be removed from the annular interface 20 without disassembling said interface. In this way, the stages 3 inserted inside the tubular jacket 2 remain locked even when the intake flange 19 is removed or replaced. By then assembling the appropriate intake flange 19 by means of the axial screws 25, optimum prestressing of the stages is automatically restored.

The means 24 for connecting the electric motor comprise a contact portion 26 of the intake flange 19, said contact portion being provided with a plurality of axial holes 27 for the passage of connecting screws 28 which may be secured to a counter-flange of the motor (not shown in the drawings).

Conveniently, the motor shaft is connected to the main shaft 4 by means of a coupling joint 29. This coupling joint 29 is rigidly connected to the main shaft 4 by means of a key 30 which is kept locked by a dowel pin 31 and may be disassembled and replaced so as to allow coupling with motor shafts of different sizes.

Each stage of the plurality 3 comprises a wear ring 32 of the impeller 5 which may be removed manually without the aid of special tools or extractors.

The wear ring 32 of each stage is kept in the correct position by means of a circular seat 33 coupled with the diffusion duct 6 and an elastically prestressed element 34 placed in between said stage and the adjacent stage. This elastically prestressed element 34 has a tapered end portion 35 and a linked end portion 36 having two different functions. The joint action of the tapered portion 35, mounted in its correct position, and of the circular seat 33 creates the housing of the wear ring 32. The linked portion 36 is shaped so as to guide the outgoing fluid from the impeller 5 to the respective diffusion duct 6. From an operational point of view, when it is required to replace the non-return valve 15, the locking ring 17 is removed and the valve is extracted axially; the new non-return valve 15 is again inserted axially inside the tubular portion 14 until it bears against the annular groove 16; lastly, the locking ring 17 is placed back in the associated internal annular seat 18 of the tubular portion 14.

When it is required to disassemble the motor, it is possible to undo the connecting screws 28 and remove the motor from the contact portion 26.

If, however, it becomes necessary to use a motor provided with a different counter-flange on the same pump 1 , it is sufficient to undo the axial screws 25, removing in this way the intake flange 19 from the annular interface 20 and optionally the shaft coupling joint 29. An intake flange 19 having a contact portion 26 suitable for the new dimensions of the counter-flange of the motor is then assembled. In this way, it is possible to couple underwater motors with different radial dimensions, for example 6", 8", 10", to the same pump 1.

After prolonged operation of the pump 1 in the presence of high concentrations of abrasive substances (sand or silt), the wear ring 32 must be replaced regularly. For this purpose, it is necessary to loosen the axial screws 25, remove the radial constraining elements 10 and the locking screws 11 which pass through the holes 12 of the jacket 2 and disassemble the tubular portion 14. After this operation, it is possible to extract the stack of stages from the jacket 2 and replace the wear rings 32 manually, without using any equipment.

From what has been described above, it is clear that the pump according to the invention achieves the predetermined objects and particular attention is drawn to the drastic reduction in the time required for replacement of the non-return valve, the intake flange and the wear rings. In fact, disassembly of the valve and the intake flange does not have any effect on the stages stacked up inside the tubular jacket, which remain locked in their correct position. Moreover, attention is drawn to the fact that motors of different sizes may be mounted on the same pump by means of simple operations, after disassebling and replacing the intake flange and the coupling joint, which connect the pump to the motor.

An additional advantage is the improved protection of the inner stages. In fact, the transitory mechanical stresses created by water hammers are transmitted from the non-return valve to the delivery element, eliminating any effects on the inner stages. This contrivance safeguards the overall working life of the pump.

Another advantage consists in the fact that the maintenance costs of the pump are reduced significantly. In fact, the replacement of the worn wear rings may be performed manually, without the need for special tools. Moreover, the operations of disassembling the stages and replacing the wear rings are made particularly easy and advantageous in terms of cost as a result of the particular characteristic features of the pump according to the invention. In this way, the need to replace the whole group which supports and locks the wear ring is avoided.

The pump according to the invention may be subject to numerous modifications and variations, all of which fall within the inventive idea expressed in the accompanying claims. All the details may be replaced by other technically equivalent elements and different materials may be used according to the requirements, without departing from the scope of the invention.

Although the pump has been described with particular reference to the accompanying drawings, the reference numbers used in the description and the claims are used to facilitate understanding of the invention and do not constitute any limitation on the protective scope claimed.

The instant application is based upon and claims priority of patent application no. VI2002A000095, filed on 15.05.2002 in Italy, the disclosure of which is hereby expressly incorporated here in reference thereto.

Claims

1. Multistage pump (1), particularly of the immersion type, comprising an outer tubular jacket (2) defining a longitudinal axis (L), a plurality of adjacent stages (3) which are slidably inserted inside said tubular jacket (2), a main shaft (4) which is coaxial with said longitudinal axis (L), each stage having at least one impeller (5) coupled to said main shaft (4) and a diffusion duct (6), means (24) for connecting an electric motor to said main shaft (4), an intake element (7) and a delivery element (8) which are locked axially respectively upstream and downstream of said plurality of stages (3), characterized in that said intake element (7) and delivery element (8) are secured removably to said jacket (2) close to its longitudinal ends by means of substantially transverse connecting members (9) which are accessible from the outside of said jacket (2).

2. Pump according to Claim 1 , characterized in that said transverse connecting members (9) comprise radial constraining elements (10) inserted by means of a precision fit into through-holes (12) and into corresponding holes (13) of said intake element (7) and delivery element (8) and kept in position there by means of respective locking screws (11).

3. Pump according to Claim 2, characterized in that said delivery element (8) comprises a tubular portion (14) having said holes (13) for the insertion of said constraining elements (10) and housing a non-return valve (15) inside internally thereof.

4. Pump according to Claim 3, characterized in that said non-return valve (15) is inserted slidably inside said tubular portion (14) so that it may be extracted axially outwards.

5. Pump according to Claim 4, characterized in that said holes (13) of said intake element (7) and delivery element (8) are substantially equidistant angularly.

6. Pump according to Claim 4, characterized in that said non-return valve (15) is mounted removably so as to bear against an annular groove (16) of said tubular portion (14) so as to allow it to be removed, thereby preventing the axial sliding of said stages (3).

7. Pump according to Claim 6, characterized in that said delivery element (8) comprises an elastic locking ring (17) housed in an internal annular seat (18) of said tubular portion (14) so as to keep said non-return valve (15) bearing against said annular groove (16).

8. Pump according to Claim 2, characterized in that said intake element (7) comprises an intake flange (19) provided with intake openings (23), an annular interface (20) arranged in contact with the last stage of said plurality of stages (3) and coupled to said intake flange (19), and a sleeve (21).

9. Pump according to Claim 8, characterized in that said annular interface (20) may be inserted inside said tubular jacket (2) and is provided with said holes (13) for precision fitting of said radial constraining elements (10).

10. Pump according to Claim 9, characterized in that said intake flange (19) is secured removably to said annular interface (20) by means of a plurality of axial screws (25) which are accessible from the outside so as to allow them to be removed while keeping said annular interface (20) assembled and said plurality of stages (3) locked axially.

11. Pump according to Claim 10, characterized in that said sleeve (21) is placed between said annular interface (20) and said jacket (2) and is in contact at one of its longitudinal ends with the first stage of said plurality (3) and at its other end with said intake flange (19).

12. Pump according to Claim 11 , characterized in that the side surface of said sleeve (21) has openings (22) for the passage of said constraining elements (10), said openings being able to allow the longitudinal displacement of said sleeve even when said constraining elements (10) are inserted.

13. Pump according to Claim 10, characterized in that said means (24) for connecting the electric motor comprise a contact portion (26) of said intake flange

(19) provided with a plurality of axial holes (27) for the passage of connecting screws (28) which may be secured to a counter-flange of the motor.

14. Pump according to Claim 13, characterized in that said means (24) for connecting the electric motor comprise a coupling joint (29) which is rigidly and removably connected to said main shaft (4).

15. Pump according to Claim 14, characterized in that said coupling joint (29) is connected to the main shaft (4) by means of a key (30) which is kept locked by a dowel pin (31) in such a way that it may be disassembled and replaced so as to allow motor shafts with different dimensions to be used.

16. Pump according to Claim 2, characterized in that each stage of said plurality (3) comprises a wear ring (32) of said impeller (5) which may be removed manually without the aid of special tools or extractors.

17. Pump according to Claim 16, characterized in that said wear ring (32) of each stage is kept in the correct position by means of a circular seat (33) coupled with said diffusion duct (6) and an elastically prestressed element (34) placed in between said stage and the adjacent one.

18. Pump according to Claim 17, characterized in that said elastically prestressed element (34) has a tapered end portion (35) which, together with the circular seat (33), axially delimits the housing of the wear ring (32) and a second linked end portion (36) which is conveniently shaped so as to guide the outgoing fluid from the impeller (5) to the respective diffusion duct (6).