Centrifugal pump assembly

Abstract

A centrifugal pump assembly (2) includes an impeller, an electric drive motor (4), driving the impeller (12), and a back-flow channel (24), forming a flow connection from a delivery side (18) to a suction side (16). A valve (26), in a pressure-dependent manner, closes the flow connection. A control device (28) adjusts/sets the speed (n) of the drive motor (4), and is configured with a venting function for venting the centrifugal pump assembly (2) on operation. According to the venting function, after the detection of an air accumulation, the speed (n) of the drive motor (4) is automatically reduced, and subsequently the speed (n) is rapidly increased again. A method is also provided for removing an air accumulation from a centrifugal pump assembly during operation, which method includes reducing the speed (n) of the centrifugal pump assembly and subsequently rapidly increasing the speed (n) of the centrifugal pump again.

Claims

1. A centrifugal pump assembly comprising: at least one impeller; an electric drive motor driving the impeller; a back-flow channel forming a flow connection from a delivery side of the impeller to a suction side of the impeller; a valve closing, in a pressure-dependent manner, the flow connection; and a control device setting a speed of the drive motor, said control device being further configured, after a detection of an air accumulation by way of the control device, to automatically reduce the speed of the drive motor and subsequently rapidly increase the speed of the drive motor again.

2. A centrifugal pump assembly according to claim 1, wherein the control device is further configured such that the speed of the drive motor is reduced to such an extent that the valve of the back-flow channel opens.

3. A centrifugal pump assembly according to claim 1, wherein the control device is further configured such that the speed of the drive motor is increased to a maximal speed.

4. A centrifugal pump assembly according to claim 1, wherein the control device is further configured such that the speed of the drive motor is increased to a maximum speed in less than three seconds.

5. A centrifugal pump assembly according to claim 1, wherein the control device detects the air accumulation based on the control device further having a monitoring function to recognize an air accumulation by way of electrical power consumption falling below a defined first limit valve at a certain speed.

6. A centrifugal pump assembly according to claim 5, wherein the control device is configured such that the first limit value for the electrical power consumption lies above a second limit value for the electrical power consumption, wherein said second limit value signals a dry running of the centrifugal pump assembly.

7. A centrifugal pump assembly according to claim 1, wherein a rotation axis of the drive motor and of the at least one impeller extends horizontally in a defined operational position.

8. A centrifugal pump assembly according to claim 1, further comprising at least another impeller and a common shaft, wherein the centrifugal pump assembly is configured as a multi-stage pump with at least two impellers which are driven by the common shaft.

9. A centrifugal pump assembly according to claim 8, wherein the back-flow channel connects the delivery side of one of the impellers, which is last in the flow direction, to the suction side of a first of the impellers.

10. A house water system for delivery or pressure increase or both delivery and pressure increase in a water supply, the house water system comprising a centrifugal pump assembly comprising: at least one impeller; an electric drive motor driving the impeller; a back-flow channel forming a flow connection from a delivery side of the impeller to a suction side of the impeller; a valve closing, in a pressure-dependent manner, the flow connection; and a control device setting a speed of the drive motor, said control device being further configured, after a detection of an air accumulation by way of the control device, to automatically reduce the speed of the drive motor and subsequently rapidly increase the speed of the drive motor again.

11. A method for removing an air accumulation from a centrifugal pump assembly comprising at least one impeller, an electric drive motor driving the impeller, a back-flow channel forming a flow connection from a delivery side of the impeller to a suction side of the impeller, a valve in the back-flow channel closing, in a pressure-dependent manner, the flow connection and a control device setting a speed of the drive motor during operation thereof, the method comprising the steps of: in a reducing step, reducing a speed of the drive motor of the centrifugal pump assembly, wherein the speed of the drive motor, in the reducing step, is reduced to such an extent that the valve in the back-flow channel between the delivery side and the suction side of the centrifugal pump assembly opens; and subsequently, in an increasing step, rapidly increasing the speed of the drive motor of the centrifugal pump assembly.

12. A method according to claim 11, wherein in the increasing step, the speed of the drive motor of the centrifugal pump assembly is increased to the maximal speed.

13. A method according to claim 11, wherein the speed of the drive motor, in the increasing step, is increased to the maximal speed in less than three seconds.

14. A method according to claim 11, wherein the air accumulation in the centrifugal pump assembly, which is to be removed, is recognized by way of electrical power consumption falling below a defined limit value at a certain speed.

15. A method for removing an air accumulation from a centrifugal pump assembly comprising at least one impeller, an electric drive motor driving the impeller, a back-flow channel forming a flow connection from a delivery side of the impeller to a suction side of the impeller, a valve closing, in a pressure-dependent manner, the flow connection, and a control device setting a speed of the drive motor during operation thereof, the method comprising the steps of: in a reducing step, reducing a speed of the drive motor of the centrifugal pump assembly; and subsequently, in an increasing step, rapidly increasing the speed of the drive motor of the centrifugal pump assembly; wherein the air accumulation in the centrifugal pump assembly, which is to be removed, is recognized by way of electrical power consumption falling below a defined limit value at a certain speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a sectioned view of a house water system according to the invention, with a centrifugal pump assembly according to the invention;

(3) FIG. 2 is an in an enlarged view showing detail II of FIG. 1;

(4) FIG. 3 is a connection diagram of the centrifugal pump assembly according to FIG. 1;

(5) FIG. 4 is a connection diagram according to FIG. 3, in the condition of an air accumulation in the first stage of the centrifugal pump assembly;

(6) FIG. 5 is a connection diagram according to FIG. 4, with the reduction of the speed;

(7) FIG. 6 is a connection diagram according to FIG. 5, with a renewed increase of the speed;

(8) FIG. 7 is a connection diagram according to FIG. 6, with a further operation of the pump assembly;

(9) FIG. 8 is a graph showing the working regions of the centrifugal pump assembly according to the invention, in a representation of the electrical power against speed; and

(10) FIG. 9 is a sectioned view along the line IX-IX in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(11) Referring to the drawings, the house water system according to FIG. 1 comprises a centrifugal pump assembly 2 which has an electric drive motor 4 as well as four pump stages 6, said pump stages being connected to the rotor 10 of the electric drive motor 4 via a common shaft 8. Each of the pump stages 6 comprises an impeller 12 which is arranged on the shaft 8 in a rotationally fixed manner.

(12) FIG. 1 shows the envisaged operational position of the centrifugal pump assembly 2, according to which the rotation axis x of the shaft 8 extends horizontally.

(13) Diffusers are arranged between the impellers of the individual pump stages in the known manner. The flow direction through the four pump stages 6 is from the left to the right in FIG. 1. The first impeller 12 which is distanced furthest from the drive motor 4 is the entry-side impeller and is in connection with the suction connection 14 via a suction channel 16. The impeller 12 which is situated closest to the drive motor 4 forms the impeller 12 which is last in the flow direction. The flow path at the exit side of the last impeller 12 runs out into an annular channel 18 which surrounds the pump stages 6 and which forms a delivery channel. This delivery channel is connected to the delivery connection 20 of the house water system. A pressure accumulator 22 which is connected to the delivery channel between the annular channel 18 and the delivery connection 20 is moreover integrated into the house water system.

(14) A backflow channel 24 which forms a flow path from the delivery side to the suction side of the centrifugal pump assembly is formed between the annular channel 18 and the suction channel 16. A spring-biased valve 26 (see FIGS. 2 and 9) which can close the backflow channel in a pressure-dependent manner is arranged in this backflow channel 24. The valve 26 is configured as a strip-like or leaf-like spring which is impinged by the pressure in the annular channel 18, and with a sufficient pressure is pressed against a valve seat 27 surrounding the backflow channel 24 at its end which faces the annular channel 18. The valve 26 is configured such that it closes above a predefined pressure difference between the suction channel 16 and the annular channel 18, and opens below this predefined pressure difference, by way of it coming into contact on the valve seat 27 or disengaging from the valve seat 27. On starting operation of the centrifugal pump assembly 2, an adequate pressure is still not yet present at the delivery side, so that the pressure difference between the suction channel 16 and the annular channel 18 is firstly essentially zero or very low. In this condition, firstly a certain fluid quantity is delivered by the pump stages 6 via the backflow channel 24 into the circuit, in order to achieve a first pressure build-up in the annular channel 18 and thus a suction in the suction channel 16 and at the suction connection 14. The priming of the pump assembly, in particular a self-priming is assisted by way of this. If an adequately high pressure is formed in the annular channel 18, then the valve 26 closes the backflow channel 24, and the centrifugal pump assembly 2 goes over into normal operation, i.e. the fluid which exits out of the fourth and the last pump stage 6 is delivered to the delivery connection 20 in a complete manner, and, as the case may be, into the pressure accumulator 22.

(15) The house water system and its centrifugal pump assembly 2 moreover comprise an electronic control device 28, whose electronic components are arranged on at least one circuit board 30 in electronics housing 32. The control device 28 serves for the activation of the drive motor 4, in particular for the speed regulation of the drive motor 4. The control device 28 can comprise a frequency converter for this, via which frequency converter the speed of the drive motor 4 can be changed.

(16) The house water system which is represented in FIG. 1 forms an integrated construction unit which encompasses the centrifugal pump assembly 2 with the electronics housing 32 and the control device 28 which is arranged therein, as well as the pressure accumulator 22, which is to say integrates these into a housing/casing. This integrated construction unit has essentially three connections, specifically the suction connection 14 and the delivery connection 20 as hydraulic connections, as well as an electrical connection 34 for energy supply.

(17) Apart from the venting on starting operation of the centrifugal pump assembly, the problem of gas bubbles being able to accumulate in the pump stages 6 and in particular in the first pump stage 6 occurs on operation. The control device 28 for this is provided with a venting function which serves for the removal of these gas bubbles out of the pump stages 6 and thus out of the complete centrifugal pump assembly 2, on running operation and essentially without compromising the functioning. This venting function is described in more detail by way of FIGS. 3-7.

(18) FIG. 3 in a schematic manner and in a connection diagram shows the construction of the house water system according to FIG. 1. The electric drive motor 4 can be recognized and this drives the four pump stages 6 which is to say the impellers 12 of these pump stages 6, in a successive manner in the flow direction. The pump stage 6 which is the first at the suction side is in connection with the suction connection 14 via the suction channel 16, whereas the pump stage 6 which is last in the flow direction runs out into the delivery channel 18 which is formed by the annular channel 18. This delivery channel in turn leads to the delivery connection 20 and is in connection with the pressure accumulator 22 which is not shown in FIG. 3. A check valve 36 is arranged in the delivery channel 18. The backflow channel 24 with the valve 26 which is arranged therein and which opens and closes in dependence on the pressure difference P moreover leads from the delivery channel 18 to the suction channel 16. The valve is shown in the closed condition in FIG. 3.

(19) The control device 28 which activates the electrical drive motor 4, considered schematically, comprises essentially two constituents, specifically on the one hand a control unit 38 and on the other hand a detection unit 40. The control unit 38 in the conventional manner serves for the speed control of the drive motor 4. For this, the control unit 38 is connected to a pressure sensor 42 which detects the pressure H at the exit side of the house water system, i.e. in the delivery channel 18 and at the delivery connection 20. The control unit 38 can maintain the pressure H at the delivery connection 20 in a desired, predefined value range by way of adjusting/setting the speed of the electrical drive motor 4.

(20) The detection device 40 serves for detecting undesirable gas accumulations or air accumulations in the pump stages 6, and in cooperation with the control unit 38, for providing the mentioned venting function. The detector unit 40 is connected to a power detection device 44, in order to detect the electrical power consumption or uptake P of the drive motor 4. The detection device 40 simultaneously via the control unit 38 acquires the speed n of the drive motor 4.

(21) The recognition of a gas accumulation is effected in the following manner. On operation, the pump assembly 2 via the pump stages 6, as is shown in FIG. 4, delivers a fluid flow 46 from the suction connection 14 to the delivery connection 20. Thereby, a gas accumulation can form on operation, in particular in the first pump stage 6. If the centrifugal pump assembly 2 is now operated at the maximally envisaged speed n, then this gas accumulation leads to the power of the pump assembly reducing and the electrical power consumption P also dropping.

(22) This is represented schematically in FIG. 8. The field 48 in FIG. 8, in which the electrical power consumption P is plotted against speed n, represents the region of normal operation. The normal operation 48 runs between a minimal speed n.sub.min and a maximal speed n.sub.max. Thereby, the electrical power consumption P lies between a lower limit P.sub.g and a maximal power consumption P.sub.max. With regard to the lower limit P.sub.g, it is the case of a predefined limit value, on falling short of which the detection unit 40 detects a gas accumulation. This is effected at maximal speed n.sub.max. If a gas accumulation forms in the pump assembly, this leads to the dropping of the exit pressure H or the differential pressure across the pump assembly. If, as described above, a regulation (closed-loop control) of the pressure H at the delivery connection 20 is carried out in the control unit 38, then this control unit 38 increases the speed of the drive motor 4, in order to increase the pressure. When the maximal speed n.sub.max is finally achieved with this, a comparison with the limit value P.sub.g for the electrical power consumption P can take place at this speed in the previously described manner. Alternatively, the speed could be increased to the value n.sub.max at certain points in time, preferably at regular points in time, by the detection unit 40 via the control unit 38. Moreover, it would also be possible to carry out a comparison with predefined limit values for the electrical power consumption P at other predefined speeds. With other speeds too, the electrical power consumption P drops below an associated predefined limit value in the case of an air accumulation. Below the limit value P.sub.g, two operating conditions 50 and 52 can be differentiated given a maximal speed n.sub.max, wherein the operating condition 50 represents an operating condition, in which a gas accumulation is present in the pump stages 6, and the operating condition 52 represents the dry running. With the dry running, the electrical power consumption P is even less, so that this can also be detected by the detection unit 40, and the electrical drive motor 4 can be switched off via the control unit 38 for example.

(23) If a gas or air accumulation is detected in the described manner, then the control device 28 starts a venting function. According to this venting function, firstly the speed n of the drive motor 4 is reduced by the control device 38 to such an extent, that the pressure difference P across the valve 26 reduces to such an extent that the valve 26 opens. As the case may be, the electrical drive motor 4 for this must be stopped by reducing the speed n to zero. This condition is represented in FIG. 5. In this condition, only a small or even no delivery flow exists, wherein this can be briefly compensated by the pressure accumulator 22, so that a complete pressure drop does not occur at the exit side of the delivery connection 20. Departing from this condition, the speed n of the drive motor 4 is increased very rapidly again by the control device 28, preferably in less than three or less than 2 seconds, to the maximal speed n.sub.max. This condition is represented in FIG. 6. In this condition, the valve 26 firstly remains opened due to the inertia and the initially still low pressure difference P. A circulating flow 54 of a mixture of water and gas or air through the pump stages 6 and the backflow channel 24 arises by way of this. The air accumulation firstly distributes in the circulating flow 54 due to this. The circulating flow 54 is abruptly prevented when the valve 26 closes again due to the increasing pressure difference P, as shown in FIG. 7, and the normal fluid flow 46 from the suction channel 16 through the four pump stages 6 into the delivery channel 18 sets in, wherein the gas bubbles which are now dispersed are entrained in this delivery channel and are flushed out of the delivery connection 20 via the check valve 36. The check valve 36 does not open until a sufficiently high pressure is built up in the delivery channel 18. The check valve 36 otherwise firstly remains closed due to the pressure in the conduit connecting to the delivery connection 20 and in the pressure accumulator. This is particularly the case at the beginning of the flow build-up, which was described by way of FIG. 6, i.e. with the rapid speed increase of the drive motor 4.

(24) The early detection of gas accumulations in the centrifugal pump assembly and according to the invention prevents the centrifugal pump assembly from reaching a condition, in which an adequate pressure build-up and adequate delivery flow is no longer given due to the gas or air accumulation. In contrast, one can ensure at an early stage that the gas accumulations are removed from the pump stages 6 by way of activating the venting function. Thereby, the operation is compromised to an insignificant extent, since the speed of the drive motor 4 only needs to be reduced briefly, or the drive motor 4 only needs to be switched off briefly. Brief pressure peaks possibly occur due to the rapid speed increase, but these as a whole lead to an insignificant reduction of the comfort.

(25) It is to be understood that the venting function can also be carried out independently of the described recognition of gas bubbles. The venting function could therefore also be started at certain, in particular regular time intervals if gas accumulations are suspected. Another type of detection of the gas accumulations is also possible.

(26) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.