Method for releasing blockage of rotary pump and rotary pump

Abstract

The invention relates to a method for releasing clogging of a rotary pump (1) by means of a bypass line (9) which branches off from a pressure line (8) of the rotary pump (1) and / or from a pump housing (2) of the rotary pump (1) and which can be activated by means of a bypass valve (11), the method has the step of opening the bypass valve (11) when an operating parameter of the rotary pump (1) during delivery of a liquid that may contain solid content exceeds or falls below a blockage threshold value.

Description

Technical Field

[0001] The invention relates to a method for releasing a blockage of a rotary pump using a pressure line. The invention also relates to a rotary pump having a pressure line. Background Art

[0002] The rotary pump is known from the prior art and is used to convey liquids by means of the rotational movement of the impeller. The liquid to be conveyed enters the pump chamber of the rotary pump via the suction opening on the suction side, is picked up by the rotating impeller and is thus conveyed to the pressure line on the pressure side.

[0003] Solid components contained in the liquid can accumulate in the region of the impeller and inside the pump housing and thus have a negative impact on the hydraulic and / or mechanical efficiency of the rotary pump to the point of causing the rotary pump to become clogged and fail.

[0004] Although various methods for releasing a rotary pump blockage are known from the prior art, current practice shows that the known methods are not ideal for effectively releasing a rotary pump blockage and safely and reliably protecting the rotary pump from damage due to blockage. Summary of the invention

[0005] Starting from this situation, the object of the present invention is to specify a method for improving the release of a blockage in a rotary pump and a corresponding rotary pump.

[0006] The object of the present invention is achieved by the features of a method for releasing a blockage of a rotary pump. Advantageous design solutions are given in the specific embodiment.

[0007] Accordingly, the object is to provide a method for releasing a blockage of a rotary pump by means of a bypass line branching off from a pressure line of the rotary pump (downstream of the pressure line) and / or a pump housing of the rotary pump and which can be activated by a bypass valve, the method comprising the following steps:

[0008] The bypass valve is opened when operating parameters of the rotary pump during the conveyance of a liquid which may contain solid components exceed or fall below a blockage threshold value, which serves in particular as an indication of a blockage.

[0009] The key point of the present invention is that, in particular in the event of a blockage, the delivery power and / or delivery volume of the rotary pump is increased or decreased by reducing or increasing the system characteristic curve of the rotary pump, especially for a certain period of time. The reduction or increase of the system curve is carried out by opening the bypass line with the help of a bypass valve, thereby reducing the total resistance caused by the connection of the bypass line or the loss overcome by the rotary pump and thus moving the intersection of the pump characteristic curve and the system characteristic curve to a higher flow rate. A higher flow rate releases the blockage. Part of the liquid transported by the bypass line can be introduced into the pump pit so that it can be transported again by the rotary pump subsequently. The proposed method can be applied to rotary pumps in wet and dry arrangements.

[0010] In other words, the proposed method enables the rotary pump to transition to a safer operating state, especially in a short time, through which blockages in the rotary pump can be cleared. In the event of a blockage, the bypass valve activates the bypass line. The short circuit formed in this way between the pressure side and the suction side of the rotary pump reduces the head of the rotary pump, resulting in a shift of the operating point of the rotary pump to a higher pump volume flow. As a result, the flow velocity in the impeller and screw of the rotary pump increases and the flow conditions are also improved, which is conducive to the conveying of solids contained in the liquid, such as fibers and spinning materials. Once the blockage has been cleared, the bypass line can be deactivated again by closing the bypass valve.

[0011] A rotary pump is generally referred to as a flow machine that provides mechanical power to the liquid to be conveyed by means of a rotational movement. Preferably, the rotary pump is designed as a sewage pump in a dry or wet arrangement for conveying waste water. Preferably, the rotary pump can be used in hydraulic installations of buildings or other applications.

[0012] During normal operation of the rotary pump, the housing of the rotary pump motor can be arranged above the pump housing of the rotary pump, in which an impeller driven by the motor via a shaft is arranged to convey the liquid, wherein the motor housing is fixedly connected to the pump housing and / or can be designed as an integral part. Similarly, the rotary pump and the motor can respectively have their own shafts, wherein these shafts can be connected to each other via a coupling device. Preferably, the shaft extends inwardly from the motor housing into the pump housing on the drive side and / or is fixedly connected to the shaft on the drive side of the impeller. Correspondingly, the inlet for the liquid to be conveyed can preferably be arranged at the bottom or below the pump housing.

[0013] The liquid preferably comprises water or another liquid medium, such as sewage. As it may contain solid components, the liquid may include solids, such as any kind of dirt, in particular excrement, sediment, sand, or even smaller pieces of wood, brush cuttings, textiles, rags or the like. Preferably, the motor housing and / or the pump housing are made of metal, in particular cast iron or stainless steel, ceramic and / or made of plastic.

[0014] The expression "during the conveying of liquid" refers in particular to the normal operation of the rotary pump, i.e. when the rotary pump conveys a fluid as a liquid, which may be mixed with the above-mentioned solid components. In this regard, "liquid that may contain solid components" means in particular that during normal operation, on the one hand only liquid is conveyed, but the liquid may generally be mixed with undesirable solid components (e.g. part or even most of them), which may lead to partial or complete blockage of the rotary pump. The bypass line is preferably designed as a pipe, in particular a bypass pipe. The pressure line is preferably also designed as a pipe and / or a pressure sleeve. The expression "branching out" preferably means that the bypass line is connected to the pressure line, the main pipeline of the rotary pump and / or the suction line of the rotary pump in a fluid-tight manner. The pressure line preferably extends in a straight line within the branching range. In this regard, "activatable" preferably means that the bypass valve is openable and closable.

[0015] Operating parameters are characteristic parameters of the liquid conveyed by the rotary pump, such as the power consumed by the rotary pump, the torque of the rotary pump motor, the rotational speed of the rotary pump impeller and / or the current consumed by the rotary pump, vibrations, but also liquid parameters, such as volume flow, pressure, or head of the rotary pump. Operating parameters can also refer to characteristic parameters of the rotary pump and / or the operation of the rotary pump, which are calculated based on the operating parameters. Blockages exist in particular when the operating parameters exceed or fall below a blockage threshold, in particular when the operating parameters deviate from fixed values, especially when operating without blockage. Blockages may be characterized by, for example, fibrous spinning material as a solid component blocking around the impeller front edge or blocking the impeller channel, the pumping data, in particular the operating parameters, may change in an undesirable manner, the pump power is reduced and / or a malfunction of the rotary pump occurs. In this regard, blockages may have occurred in the following cases: the pump power deviates from the normal operation of the rotary pump by, for example, 5%, 10%, 20% or 50%, or the impeller speed drops to zero (i.e., the impeller is stuck by solid components). Exceeding or falling below a blockage threshold value means, in particular, that the blockage threshold value deviates in terms of its value from blockage-free operation.

[0016] For example, the blockage threshold value can be a tolerance range in the case where the power consumed by the rotary pump during 2, 5, 10, 30 or 60 seconds exceeds or falls below the power measured at the corresponding speed in the unblocked state by 5%, 10%, 20% or 50%. Before the preparation phase of the method, in the so-called commissioning phase in the unblocked state, the speed of the rotary pump is changed (especially during normal operation) and the relationship between the speed and the power consumed by the rotary pump is stored as a speed-power reference curve, i.e., DL reference, as the operating characteristic curve of the centrifugal pump. In this regard, the blockage threshold value can exceed the operating characteristic curve of the rotary pump during normal operation by 5%, 10%, 20% or 50%.

[0017] The bypass line preferably branches off from the pressure line at a right angle. Further preferably, the pressure line and / or the bypass line have a circular cross section. Preferably, the bypass valve is fully opened, wherein it is however also conceivable that the bypass valve is only partially opened, for example opened to 25%, 50% or 75%, and / or partially opened depending on the degree of solid content. It is also conceivable that the bypass valve is opened in discrete steps. It is also conceivable that after each step, a check is made whether a blockage threshold value is undershot or exceeded, i.e. whether the blockage has been released, and if so, the bypass valve is closed again, otherwise the bypass valve is opened further step by step. Instead of a stepwise opening, a continuous opening is also feasible.

[0018] According to a preferred improvement, the method comprises the following steps: after opening the bypass valve:

[0019] When the blockage threshold is below or exceeded and / or after a predetermined period of time, the bypass valve is closed; or

[0020] When the blockage threshold is not fallen below or exceeded after a predetermined alarm duration, an alarm is triggered, an unclogging procedure is initiated and / or the swing pump is shut down.

[0021] As mentioned before, the volume flow in the rotary pump is increased by opening the bypass valve, so that the blockage can be released. Conveniently, the proposed design scheme is used to check whether the blockage has been released. In this regard, being lower than or exceeding the blockage threshold value can be equivalent to the blockage being released. Alternatively or simultaneously, it can be checked after a predetermined time period, for example after 2, 5, 10, 20, 30 or 60 seconds, whether it is not lower than or exceeded the blockage threshold value again. If it is lower than the blockage threshold value again and / or after a predetermined time period, the bypass valve is especially completely closed. If it is still not lower than or exceeded the blockage threshold value after a predetermined alarm duration, this state of the rotary pump indicates that the bypass valve may not have been opened before so that the blockage is released. In this case, the triggering of the alarm (for example, due to being caused by a control device) and / or the shut-off of the rotary pump are conveniently carried out to protect the rotary pump from damage. The predetermined alarm duration can be 2, 5, 10, 20, 30 or 60 seconds and / or preferably greater than a predetermined time period. The alarm can be triggered only electronically, for example by sending a message to a higher-level control device, a network server, software or the like. In principle, so-called unclogging programs known from the prior art can also be used to release the blockage, which generally involve a time-limited and / or repeated, in particular repeated at certain intervals and / or alternating operation of the motor in the first direction and / or in the second direction of rotation, in particular in the forward direction and / or in the reverse direction.

[0022] According to another preferred embodiment, the method comprises the following steps: when the blockage threshold is exceeded or fallen below:

[0023] The speed of the impeller conveying the liquid which may contain solid components is varied, in particular increased.

[0024] By changing the rotational speed (especially within a limited time), in particular by increasing or decreasing the rotational speed, the effect of releasing the blockage by opening the bypass valve can be further improved. Because by changing or increasing or decreasing the rotational speed, the following solid components present in the conveyed liquid, which for example get stuck on the impeller edge and / or the tongue of the spiral body, settle in the half-open impeller gap and / or the spiral path and thus cause the rotary pump to block, can be released more effectively in conjunction with the opening of the bypass valve. The rotational speed is changed or increased or decreased, in particular by 5%, 10% or 20%, and this can be done in steps and / or intermittently. Preferably, the rotational speed is changed or increased or decreased while the bypass valve is opened, and / or the speed is changed or increased or decreased during the same time that the bypass valve is opened.

[0025] According to a preferred improvement, the bypass line leads to the pump sump and / or the suction line on the suction side of the rotary pump. The bypass line connects the pump pressure side to the pump sump or the suction line. Preferably, the suction port on the suction side is arranged in the pump sump as an inlet of the rotary pump in such a way that the impeller extends into the pump sump.

[0026] According to another preferred design, the diameter of the bypass line is at least 20%, 30%, 40% or 50% smaller than the diameter of the pressure line or is equal to the diameter of the pressure line. In other words, it is preferred that the size of the bypass line is much smaller than that of the pressure line, in particular the bypass line has a smaller inner diameter. Experiments have shown that for a DN100 pressure pipeline, a DN32 bypass line is sufficient to increase the pressure side volume flow of the liquid by 20%. The bypass line can also have an inner diameter of the same size as the pressure line.

[0027] According to a preferred development, the bypass line is connected to the pressure line by means of a Y-piece, which is particularly oriented opposite to the main flow direction. Such an oppositely oriented Y-piece makes it possible to ensure that as few solid components as possible (e.g. pulp) enter the bypass line and have to be conveyed again by the rotary pump.

[0028] According to another preferred design, a grid, in particular an open-hole flow guide device, is provided between the pressure line and the bypass line. Preferably, the grid is provided close to the branch from the pressure line toward the bypass line. The size and / or diameter of the solid components, in particular the solid components at the input end of the bypass line, can be limited by the grid or the open-hole flow guide device.

[0029] According to a preferred improvement, the bypass valve is implemented as a slide valve and / or a valve, in particular, as a check valve. In principle, the bypass valve can be implemented as any valve. However, it is preferred that the bypass valve is designed to be electrically actuated and / or remotely controllable, so that the bypass valve can be actuated, for example, by a control device, that is, it can be opened and closed. In addition, the bypass valve can also be manually actuated. The slide valve is also referred to as a stop valve or a water valve, which is generally understood to be a component for completely opening or closing the entire flow cross-section of the bypass line. In the design scheme as a check valve, the bypass valve is preferably designed so that the flow can only be away from the pressure line. The bypass valve is preferably arranged adjacent to the pressure line or arranged downstream of the pressure line, for example, arranged between the pressure line and the slide valve.

[0030] According to another preferred embodiment, the operating parameter is selected from the power consumed by the rotary pump, the torque of the motor of the rotary pump, the rotational speed of the impeller of the rotary pump and / or the current consumed by the rotary pump. In addition, other operating parameters can be envisaged, such as head, values ​​acquired by a pressure sensor, a volume flow sensor and / or a vibration sensor. Corresponding sensors can be provided for detecting the operating parameters, such as a power sensor, a torque sensor, a rotational speed sensor and / or a current sensor. Preferably, the operating parameters are continuously detected so that a blockage can be reacted to immediately by opening the bypass valve.

[0031] The object is also achieved by a rotary pump having a pressure line and / or a pump housing, a bypass line branching off from the pressure line and / or the pump housing and being activated by means of a bypass valve, and a control device, wherein

[0032] The control device is configured to open the bypass valve when an operating parameter of the rotary pump during the conveyance of a liquid that may contain solid components exceeds or falls below a blockage threshold.

[0033] The control device preferably has a microprocessor or the like. The control device can be an integral component of the rotary pump, arranged at the rotary pump (for example at the rotary pump housing), arranged remotely from the rotary pump and / or can be part of a "cloud" particularly remote from the rotary pump. For detecting operating parameters, sensors directly or indirectly connected to the motor, the shaft, the impeller and / or to the rotary pump, particularly the housing, the motor housing and / or the pump housing of the rotary pump and / or sensors for monitoring the motor, the shaft, the impeller and / or the rotary pump can be provided, for example power sensors, torque sensors, rotation speed sensors, current sensors, power sensors and / or voltage sensors (as are particularly known from the prior art in each case).

[0034] According to a preferred improvement, the control device is further configured to: after opening the bypass valve, close the bypass valve when the value is below or above the blockage threshold and / or after a predetermined time period; or trigger an alarm, start the unblocking procedure and / or shut down the rotary pump when the value is not below or above the blockage threshold after a predetermined alarm duration.

[0035] According to another preferred design, the rotary pump has an impeller for conveying a liquid possibly containing solid components, and the control device is further configured to increase the rotational speed of the impeller of the liquid possibly containing solid components when a blockage threshold is exceeded or fallen below.

[0036] According to a preferred development, the rotary pump has a suction-side pump sump and / or a suction line into which a bypass line opens.

[0037] According to another preferred design, the diameter of the bypass line is at least 20%, 30%, 40% or 50% smaller than the diameter of the pressure line or is equal to the diameter of the pressure line.

[0038] According to a preferred development, the bypass line is connected to the pressure line by means of a Y-piece, in particular oriented opposite to the main flow direction, and / or a grid, in particular an open-pored flow guide, is provided between the pressure line and the bypass line.

[0039] Further embodiments and / or advantages of the rotary pump appear to a person skilled in the art analogously to the method described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention will be explained in detail below with reference to the accompanying drawings using preferred embodiments.

[0041] In the attached picture:

[0042] Figure 1 A schematic view of a rotary pump showing a method for implementing a method for releasing a blockage of a rotary pump according to a preferred embodiment of the present invention, and

[0043] Figure 2 Show according to Figure 1 Pump characteristic diagram of a rotary pump, where the head is plotted as a function of the volume flow. DETAILED DESCRIPTION

[0044] Figure 1 A schematic view of a rotary pump 1 is shown for carrying out the method described below for releasing a blockage of the rotary pump 1 according to a preferred embodiment of the present invention.

[0045] A rotary pump 1 designed as a submersible pump generally comprises a pump housing 2 and a suction opening 3 on the suction side arranged below the pump housing 2 in the figure, which serves as an inlet. A shaft (not shown) is arranged in the pump housing 2, which extends vertically in the figure. The shaft is driven by a motor 4 (only shown briefly), which is arranged vertically opposite to the suction opening 3. In the pump housing 2, an impeller 5 is arranged facing the suction opening 3 (only shown briefly), which is driven by the motor 4 via the shaft. In addition, the rotary pump 1 has a microprocessor-based control device 6 (in Figure 1 The control device 6 can be integrated into the rotary pump 1, arranged on the rotary pump (for example, fastened to the pump housing 2) and / or arranged outside the rotary pump 1. In addition, the rotary pump 1 has a sensor 7 for detecting operating parameters of the rotary pump 1.

[0046] A pressure line 8 is provided on the pressure side of the rotary pump 1, which extends from the pump housing 2. The pressure line 8 is connected to the pump housing 2 by means of a 90° elbow and therefore extends vertically or straightly upwards away from the pump housing 2 in the plane of the drawing. A bypass line 9 first branches off vertically from the straight extension of the pressure line 8, i.e. horizontally in the plane of the drawing. The bypass line 9 therefore extends vertically downwards in the plane of the drawing by means of a further 90° elbow, thus finally opening into a pump sump 10 of the rotary pump 1, which is only briefly shown. The suction port 3 of the rotary pump 1 likewise extends into the pump sump 10.

[0047] A bypass valve 11 is provided at the horizontal portion of the bypass line 9. Figure 1 1, which is shown as a manually actuated valve on the one hand, but can be activated by the control device 6, i.e. it can be opened or closed electrically. According to the proposed method, the control device 6 is designed to open the bypass valve 11 when an operating parameter of the rotary pump 1 during the conveyance of a liquid that may contain solid components exceeds or falls below a blockage threshold value, as explained in detail below.

[0048] Figure 2 Shown according to Figure 11 shows a pump characteristic diagram of a rotary pump 1, in which the head is plotted as a function of the volume flow. During normal operation, the rotary pump 1 operates at a normal operating point 13, which is located at the intersection of the pump characteristic curve 12 and a system characteristic curve 14 of the pressure line 8, which is embodied as DN 100. If the rotary pump 1 is blocked, for example due to a blockage, seizure of the impeller 5 by solid components during the conveying of the liquid, or the formation of additional friction components, the operating parameter of the rotary pump 1 exceeds / falls below a blockage threshold value. The operating parameter is characterized by the power consumed by the rotary pump 1, which in the event of a blockage exceeds a predetermined time period (for example 5 seconds or 10 seconds more than the blockage threshold value) and / or exceeds a predetermined tolerance (for example 5% or 10% more than the blockage threshold value). In addition, other operating parameters can be realized, such as the current consumed by the rotary pump 1, the rotational speed, the volume flow, the head, the pressure value and / or the torque of the rotary pump 1.

[0049] As soon as the operating parameters of the rotary pump 1 exceed / fall below the clogging threshold value during the conveying of the liquid, for example due to the increasing solid content in the liquid, the control device 6 opens the bypass valve 11. As a result of the opening, the normal operating point 13 on the pump characteristic curve 12 moves toward the common system characteristic curve 15 of the pressure line 8 (embodied as DN 100, diameter 100 mm) and the bypass line 9 (embodied as DN 65, diameter 65 mm) to the clean operating point 16. Figure 2 It can be seen that the volume flow at the cleaning operating point 16 is greater than at the normal operating point 13 of the rotary pump 1. By increasing the volume flow, solid components that clog the impeller 5 can be released. The speed of the impeller 5 can be increased in parallel with the opening of the bypass valve 11, which helps to release the blockage.

[0050] After the bypass valve 11 has been opened in this way, the control device 6 checks, for example, 5 or 10 seconds after the bypass valve 11 is opened, whether the blockage threshold value is again exceeded and / or closes the bypass valve 11 after a predetermined time period (for example, 5 or 10 seconds after the bypass valve 11 is opened). As long as the blockage threshold value is exceeded after a predetermined alarm duration (for example, 5 or 10 seconds after the bypass valve 11 is opened), that is, a blockage still exists, an alarm is triggered and / or the rotary pump 1 is shut down.

[0051] Return to Figure 1 The bypass line 9 is connected to the pressure line 8 by means of a T-shaped piece or a Y-shaped piece 17 oriented in the opposite direction to the main flow direction. Figure 1The grid 18 is only briefly shown and is designed as an open-hole flow guide. The bypass valve 11 can also be designed as a slide valve and / or a non-return valve. The sensor 7 for detecting the operating parameter of the rotary pump 1 can be arranged in particular in a contacting manner, in close proximity and / or rigidly on the motor 4, in connection with the shaft, on the pump housing 2, on the motor housing of the motor 4 and / or in connection with the impeller 5. In the case of a current sensor, the sensor 7 measures the motor current consumed by the motor 4, or in the case of an operating parameter being the power consumed by the motor 4, the sensor measures the electrical power consumed by the motor 4 or the rotary pump 1.

[0052] The described embodiments are only examples, which can be modified and / or supplemented in various ways within the scope of the claims. Each feature used to illustrate a certain embodiment can be used in any other embodiment independently or in combination with other features. Each feature used to illustrate an embodiment of a certain category can also be used in another category of embodiments in a corresponding manner.

[0053] Reference numerals list Rotary pump 1; Pump housing 2; Suction port 3; Motor 4; Impeller 5; Control device 6; Sensor 7; Pressure line 8; Bypass line 9; Pump pit 10; Bypass valve 11; Pump characteristic curve 12; Normal operation point 13; System characteristic curve 14; Common system characteristic curve 15; Cleaning operation point 16; T-shaped or Y-shaped piece 17; Grille 18.

Claims

1. A method for releasing a blockage of a rotary pump (1) by means of a bypass line (9) branching off from a pressure line (8) of a rotary pump (1) and / or a pump housing (2) of the rotary pump (1) and being activated by a bypass valve (11), the method comprising the following steps: When the operating parameters of the rotary pump (1) during the conveyance of a liquid which may contain solid components exceed or fall below a blockage threshold, the bypass valve (11) is opened.

2. The method according to claim 1, comprising the following steps: after opening the bypass valve (11): When the blockage threshold is fallen below or exceeded and / or after a predetermined period of time, the bypass valve (11) is closed; or When the blockage threshold is not fallen below or exceeded after a predetermined alarm duration, an alarm is triggered, a clearing procedure is started and / or the rotary pump (1) is shut down.

3. The method according to claim 1, comprising the following steps: in the event of exceeding or falling below the blockage threshold: The rotation speed of the impeller (5) conveying the liquid which may contain solid components is changed.

4. The method according to claim 1, wherein the bypass line (9) opens into a pump sump (10) on the suction side of the rotary pump (1) and / or into a suction line.

5. The method according to any one of claims 1 to 3, wherein the diameter of the bypass line (9) is at least 20%, 30%, 40% or 50% smaller than the diameter of the pressure line (8) or is equal to the diameter of the pressure line.

6. The method according to claim 1, wherein the bypass line (9) is connected to the pressure line (8) by means of a Y-piece (17) oriented opposite to the main flow direction.

7. The method according to any one of claims 1 to 3, wherein a grid (18) is arranged between the pressure line (8) and the bypass line (9).

8. The method according to claim 1, wherein the bypass valve (11) is embodied as a slide valve and / or a valve.

9. A method according to any one of claims 1 to 3, wherein the operating parameter is selected from the power consumed by the rotary pump (1), the torque of the motor of the rotary pump (1), the rotational speed of the impeller of the rotary pump (1) and / or the current consumed by the rotary pump (1).

10. A rotary pump (1), comprising: a pressure line (8) and / or a pump housing (2), a bypass line (9) branching off from the pressure line (8) and / or the pump housing (2) and capable of being activated by a bypass valve (11), and a control device (6), wherein the control device (6) is configured to open the bypass valve (11) when operating parameters of the rotary pump (1) during the conveyance of a liquid that may contain solid components exceed or fall below a blockage threshold value.

11. The rotary pump (1) according to claim 10, wherein the control device (6) is further configured to: after opening the bypass valve (11), When the blockage threshold is lowered or exceeded and / or after a predetermined period of time, the bypass valve (11) is closed; or When the blockage threshold is not fallen below or exceeded after a predetermined alarm duration, an alarm is triggered, a clearing procedure is started and / or the rotary pump (1) is shut down.

12. The rotary pump (1) according to claim 10, comprising an impeller for conveying the liquid possibly containing solid components, and wherein the control device (6) is further configured to: in the event of exceeding or falling below the blockage threshold, The rotation speed of the impeller (5) conveying the liquid which may contain solid components is changed.

13. The rotary pump (1) according to claim 10, comprising a suction-side pump sump (10) and / or a suction line into which the bypass line (9) opens.

14. A rotary pump (1) according to any one of claims 10 to 12, wherein the diameter of the bypass line (9) is at least 20%, 30%, 40% or 50% smaller than the diameter of the pressure line (8) or is equal to the diameter of the pressure line.

15. A rotary pump (1) according to any one of claims 10 to 12, wherein the bypass line (9) is connected to the pressure line (8) by means of a Y-piece oriented opposite to the main flow direction, and / or a grid (18) is arranged between the pressure line (8) and the bypass line (9).

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