Method for controlling an eccentric screw pump

Abstract

The invention relates to a method for controlling an eccentric screw pump which has - a stator (1), - a rotor (2) rotating with a pump frequency in the stator (1), - a drive (6) for the rotor, - a stator clamping device (12) and - a control device (10), wherein the clamping (2) of the stator (1) can be set by means of the stator clamping device (12), wherein the control device (10) is provided with an operating parameter of the pump, and wherein the clamping (w) of the stator (1) is set / varied depending on the operating parameter. An operating parameter is used which pulses periodically with the pump frequency or a multiple of the pump frequency. An average value (Δp), averaged over at least one period, and the pulsation amplitude (ΔpPP) are determined from the operating parameter. The clamping (w) is iteratively changed by means of the stator clamping device (12) depending on the average value (Δp) until a maximum value of the average value is reached and / or is iteratively changed depending on the pulsation amplitude until a minimum value of the pulsation amplitude (ΔpPP) is reached.

Description

[0001] Method for controlling an eccentric screw pump

[0002] Description:

[0003] The invention relates to a method for controlling an eccentric screw pump, which has an (elastic) stator, a rotor rotating in the stator (eccentrically) at a pump frequency, a drive for the rotor, a stator clamping device and a control device, wherein the clamping of the stator (relative to the rotor) can be adjusted with the stator clamping device, wherein an operating parameter of the pump is measured or made available and wherein the clamping of the stator is adjusted (or varied) depending on the operating parameter.

[0004] In such an eccentric screw pump, the rotor is connected to the drive, for example via at least one coupling rod or a similar element, so that the rotor or its rotor end rotates eccentrically relative to the drive axis. The pump can, for example, have a pump housing connected to the stator on the suction side, which is also referred to as the suction housing and which generally has a housing opening, e.g. an inlet opening, for the medium to be pumped. Furthermore, the pump can have a pump housing connected to the stator on the pressure side, for example, which in practice is also referred to as the pressure port. An eccentric screw pump is a pump from the group of rotating positive displacement pumps that is used to pump a wide variety of media, in particular highly viscous liquids, in various industrial sectors. The media to be pumped can also contain solids.

[0005] The stator consists, for example, of an elastic, preferably elastomeric material and is generally surrounded by a one-piece or multi-piece stator shell or stator housing. According to the invention, the clamping of the (elastic) stator is adjustable using the stator clamping device. For this purpose, the stator can, for example, have a shell made up of several shell segments which form clamping segments and can be clamped against the rotor in the radial direction to change the clamping, e.g. using one or more adjusting elements. The invention also encompasses eccentric screw pumps with a stator clamping device which, to change the clamping, works not (only) in the radial direction but alternatively (or additionally) in the axial direction on the elastic stator. It is always possible to vary the clamping of the stator (relative to the rotor) with the stator clamping device (e.g. via the control device) depending on a measured operating parameter.

[0006] The rotating connection, which simultaneously ensures eccentricity, between the drive or drive shaft or connecting shaft on the one hand and the rotor on the other is established, for example, via the coupling rod arranged in the pump housing. The coupling rod can be connected to the rotor, for example, via a rotor-side joint and to a drive shaft or connecting shaft via a drive-side joint. Alternatively, designs with a flexible coupling rod without joints are also included.

[0007] The rotor is helical, preferably with a relatively large pitch and thread depth and a relatively small core diameter. It is arranged eccentrically in the stator or in the through-hole of the stator, and the stator or its helical interior has one more thread turn than the rotor. The invention relates to clamped pumps, i.e. the rotor diameter is larger than the stator inner diameter or the diameter of the through-hole. In such clamped pumps, the rotor - with ideal movement - rests against the inner surface of the stator or the inner surface of the through-hole via one or more uninterrupted sealing lines. The sealing lines separate delivery chambers from one another, which move (continuously) from the suction side to the pressure side or from the inlet side to the outlet side as the rotor rotates. The sealing line orThe sealing lines separate and seal the delivery chambers from each other, so that the suction side of the stator is sealed against the pressure side.

[0008] Eccentric screw pumps of the type described above are known, for example, from DE 10 2014 112 552 A1, DE 10 2010 037 440 A1 and WO 2009 / 024279A1.

[0009] DE 10 2018 113 347 A1 also discloses a method for determining or monitoring the condition of an eccentric screw pump, wherein the temporal progression of an operating parameter of the pump, e.g. a pressure or a pressure difference, is provided, which pulsates periodically with the pump frequency and whose pulsation amplitude depends on the condition of the eccentric screw pump. In an ideal system, the operating pressure of the eccentric screw pump does not vary with the rotation or rotation frequency of the pump, i.e. an ideal eccentric screw pump is free of pressure pulsations relative to the operating pressure. In practice, eccentric screw pumps are indeed comparatively low in pulsation, but they still exhibit certain pressure pulsations which are attributable to the changing sealing lines during one revolution and minimal geometric differences between the rotor and stator.DE 10 2018 113 347 A1 is based on the finding that the pulsation amplitude of the pressure pulsation depends on the wear of the relevant components of an eccentric screw pump, so that statements about the wear condition of the pump can be made by analyzing the pressure pulsations.

[0010] During the use of progressive cavity pumps, there is a practical need to monitor pump operation and provide certain operating parameters. This concerns, for example, monitoring the actual flow rate of a progressive cavity pump. For this purpose, special flow sensors are used in practice, with which the flow rate can be measured directly. The disadvantage of such flow sensors is the high investment costs, making them uneconomical for many applications. For this reason, it has already been proposed to determine the flow rate only approximately based on the pump characteristic curve and knowledge of the current pump speed.Since this approximate flow rate determination is based on the pump characteristic curve, which is usually specified by the pump manufacturer and applies to the pump in new condition, the flow rate estimate becomes increasingly inaccurate with this approach as the pump components wear. The actual condition of the pump components cannot be taken into account in this flow rate estimate. Therefore, a decreasing flow rate, for example, can go unnoticed and thus lead to a process shutdown.

[0011] Based on this problem, the older, unpublished German patent application 10 2022 119 147.8 proposes monitoring the actual flow rate of a progressing cavity pump using a simplified sensor system, in particular a pressure measurement. The flow rate is determined using a virtual sensor based on favorable measured variables and taking into account the actual rotor / stator wear and the associated geometric changes. The focus of this older, unpublished patent application is monitoring and thus the possibility of predicting maintenance requirements. Based on the determination of pressure pulsations, a mathematical model can be used to determine the actual return flow and, from this, the effective flow rate, thus allowing conclusions to be drawn about the pump's wear status.

[0012] Based on the previously known and previously published prior art, the invention is based on the object of creating a method with which the operation of an eccentric screw pump can be controlled in an improved manner using simplified technical means. In particular, the clamping of the stator should be optimised on the basis of simplified measurements. To achieve this object, the invention teaches, in a generic method of the type described above, that an operating parameter is used as the operating parameter, e.g. measured, which pulsates periodically with the pump frequency (or a multiple of the pump frequency), that from the operating parameter, on the one hand, an average value averaged over at least one period and, on the other hand, the pulsation amplitude are determined, and that the clamping with the stator clamping device is iteratively changed depending on the average value, e.g. increased, until a maximum value of the average value is reached (ieuntil the mean value no longer increases) and / or the clamping with the stator clamping device is iteratively changed (e.g. increased) as a function of the pulsation amplitude until a minimum value of the pulsation amplitude is reached, i.e. until the pulsation amplitude no longer decreases. The clamping is therefore controlled to a maximum of the mean value and / or a minimum of the pulsation amplitude. However, it is not necessary to specify a maximum value to be achieved for the mean value and / or minimum value for the pulsation amplitude in the control system, but control to a maximum value or minimum value preferably means that the iterations are run through until the mean value no longer increases and / or the pulsation amplitude no longer decreases, i.e. until (in each case) a (specified) change difference is reached or undershot.

[0013] Preferably, the operating pressure of the pump or the medium to be pumped in or on the pump is provided as the operating parameter (preferably by measurements), and on this basis the mean value and / or the pulsation amplitude of this operating parameter, i.e. the pressure pulsation, is evaluated. The operating pressure is particularly preferably the measurement or determination of a pressure difference, preferably the difference between the pressure on the pressure side of the stator, on the one hand, and the pressure on the suction side of the stator, on the other hand. In practice, however, it may also be sufficient to carry out only one pressure measurement, e.g., the measurement of the pressure on the pressure side, for example, when the pressure on the suction side is constant or essentially constant, so that a pressure difference can be deduced from a pressure measurement alone. Alternatively, an operating parameter other than pressure can also be used, e.g.a torque which also shows pulsations.

[0014] The invention is based on the knowledge that eccentric screw pumps with adjustable clamping have proven particularly successful in practice, as the clamping can be changed, e.g. readjusted, as wear increases. This increases the efficiency of the pump and also the operating times and service life. The optimal setting of the clamping is of great importance for problem-free operation. If the clamping is too low, the (undesired) backflow increases and the flow rate is reduced. If the clamping is set too high, however, the increased friction between the rotor and stator can lead to an increased drive torque, which can reduce the efficiency of the entire system. For this reason, iterative control and regulation procedures are already being used in practice to set the optimal clamping. In the prior art, the flow rate orThe flow rate is measured directly using flow sensors and the optimal clamping is controlled on this basis.

[0015] In contrast, the invention has recognized that in the course of controlling an eccentric screw pump and in particular in the course of controlling or regulating the optimal clamping, a real measurement of the flow rate can be dispensed with, since the effective or actual flow rate of a pump - depending on the application - is related or correlated with the mean value of an operating parameter and / or with the pulsation behavior of certain operating parameters.

[0016] It should be noted that pumps or progressive cavity pumps are operated in different applications and / or under different conditions. Therefore, the invention primarily considers two different application cases or scenarios, preferably in combination.

[0017] In a first scenario, the operating pressure, e.g. the differential pressure, is directly related to the flow rate, i.e. the flow rate. The pressure difference, which represents the flow rate, is largely determined by the components at the pump outlet, i.e. the pressure-side components. In this case, the actual flow rate, which can in principle be used to optimize the clamping, can be approximated by an average value of the operating pressure, e.g. the pressure difference, preferably by an average value averaged over at least one period. This average value is then determined from the measured pressure values ​​or differential pressure values. On this basis, the clamping is changed (e.g. increased) depending on this average value until a maximum value of this average value is reached, i.e. until the average value no longer increases.A second scenario is to be distinguished from this first scenario, an application in which the differential pressure is not directly related or correlated with the flow rate. An example of this is an application in which a container is filled with a fluid using the pump and the fluid level is significantly above the operating head of the pump. In such a case, the evaluation of the averaged differential pressure (i.e. the mean value) is not suitable as a representative value for the flow rate. Theoretically, a change in the flow rate would also change the averaged differential pressure, but in this second application this change would be too small for practical consideration. The invention is based on the finding that these application cases can be excellently taken into account by (alternatively or additionally) recording the pulsation behavior of the respective operating parameter, e.g. the pressure.

[0018] The flow rate monitored in the state of the art for pump control is sensitively dependent on a backflow that is opposite to the ideal flow rate and results from an imperfect seal or sealing line between the rotor and stator and thus depends on at least one gap in the sealing line between the rotor and stator. The gap or backflow depends on the pressure difference, i.e. the difference between the pressure on the pressure side and the pressure on the suction side. The pressure difference leads to an (almost) constant tilt of the rotor, e.g. around a Y-axis, which influences this backflow. This is because the tilt of the rotor lifts the rotor away from the stator and thus creates a crescent-shaped gap in the sealing line. In addition to such a constant or "static" tilt (e.g. around a Y-axis), which results from a static pressure difference, varying (periodic) tilts of the rotor (e.g. around the X-axis) occur.These change the volume of the cavity open on the pressure side, resulting in pressure pulsations or pulsations in the pressure difference. The periodic tilting of the rotor (e.g. around the X-axis) leads directly to periodic changes in the pressure difference, i.e. the pulsation amplitude (e.g. of the pressure pulsations) is related to the tilting of the rotor and thus to the size of the gap, and this in turn is related to the backflow. By evaluating the pressure pulsations or the pulsation amplitude of the pressure pulsations, the backflow can be modeled accordingly. This basically makes it possible to determine the actual flow rate using a mathematical model, taking into account the measured pressure difference and, in particular, the pulsation amplitude of the pressure pulsations determined from this. According to the invention, an absolute determination of the backflow orof the actual flow rate can, however, be dispensed with, since the focus is on controlling the eccentric screw pump, namely controlling or regulating the clamping of the stator (e.g. during operation). According to the invention, an operating parameter, e.g. the pressure and in particular a pressure difference, can be measured repeatedly (e.g. as a series of measured values) and the pulsation amplitude can be determined from this. This pulsation amplitude can flow directly into the control or regulating circuit for controlling or regulating the optimal clamping as a control or regulating variable. It is therefore not necessary to determine absolute values ​​for the flow rate from the determined pulsation amplitude, but rather it is sufficient to determine the qualitative change in the pulsation amplitude, which leads to a greatly simplified control of operation and, in particular, to a greatly simplified setting of the optimal clamping of the stator relative to the rotor.

[0019] At the heart of the invention is the optimal clamping of the stator relative to the rotor. The stator not only ensures the described sealing of the rotor, but also forms a radial bearing for the rotor. The actual movement of the rotor is therefore not only determined by the specified rotor-stator geometry, but also depends on the dynamic forces acting on the rotor and the limited stiffness of the rotor-stator contact. Increased tension and thus greater clamping force result in the rotor-stator geometry adapting to the ideal geometry, i.e., the rotor's deviations from the ideal motion path are reduced.

[0020] Furthermore, the change in clamping – as described – affects the aforementioned pressure pulsations. The increased tension and consequently increased clamping increases the stiffness of the rotor-stator contact and forces the rotor closer to the ideal motion path. This reduces the pressure pulsations. The invention takes advantage of this relationship by iteratively changing the clamping depending on the pulsation amplitude until a minimum value of the pulsation amplitude is reached.

[0021] The invention therefore enables optimal operation of a progressing cavity pump with optimal clamping without requiring flow measurement for clamping control. This eliminates the need for expensive flow sensors. Rather, the method according to the invention can be implemented using simple and cost-effective sensors, in particular one or more pressure sensors. The pressure measurement allows, in particular, the pulsation amplitude of the pressure or pressure difference to be determined, which directly influences the clamping control, without the need for complex evaluation of the pulsation amplitude using mathematical models.

[0022] The consideration or evaluation of the pulsation amplitude occurs alternatively or in addition to the described evaluation of the mean value. In a particularly preferred embodiment, the method according to the invention is designed such that the (two) described application cases are optimally covered, i.e., both the averaged operating parameter relevant for the first application case, e.g., the mean operating pressure, and the pulsation amplitude relevant for the second application case are taken into account. The method then operates universally, and the optimal clamping can always be set, regardless of which application case is implemented in practice.

[0023] To take the first application into account, the clamping with the stator clamping device is changed iteratively depending on the mean value of the pressure or differential pressure, e.g. increased, until a maximum value of the mean value is reached. To take the second application into account, the clamping with the stator clamping device is changed iteratively depending on the pulsation amplitude, as already described, until a minimum value of the pulsation amplitude is reached. In this control system, control is therefore carried out on the one hand to the maximum of the mean value of the pressure difference and on the other hand to the minimum of the pulsation amplitude (the pressure difference). For this purpose, it is not necessary to specify a minimum value to be achieved orIt is not necessary to specify a maximum value, but in the sense of a normal control, the clamping is changed iteratively (in particular increased) until the respective parameter (mean value of the pressure difference or pulsation amplitude) no longer increases or no longer decreases and until a predetermined change or difference is reached or undercut.

[0024] In any case, it is expedient according to the invention to determine, from the provided operating parameter, e.g., from a measured parameter difference, e.g., the operating pressure or the pressure difference, on the one hand, an average value (as a static pressure difference) averaged over at least one period and, on the other hand, the pulsation amplitude (as a dynamic pressure difference) and to take this into account in the iterative change of the clamping.

[0025] The combination of these two considerations for the two different scenarios leads to a particularly preferred embodiment of the invention, in which control or regulation is carried out both as a function of the mean value and as a function of the pulsation amplitude. This will be discussed again in the description of the figures.

[0026] The analysis of operating parameters, e.g., differential pressure, is always performed as a basis for the optimal clamping adjustment based on the knowledge that the operating parameter, e.g., the pressure differential, is related to the flow rate. However, within the scope of the invention, it is not necessary to actually determine the flow rate quantitatively. Rather, a qualitative analysis of changes in the operating parameter, e.g., the mean value and the pulsation amplitude, is sufficient.

[0027] The invention is used for eccentric screw pumps which are equipped with a stator clamping device by means of which the clamping of the stator relative to the rotor can be changed, preferably in both directions, i.e. the clamping can be increased by means of the stator clamping device and, if necessary, reduced again and consequently released, i.e., relaxed.

[0028] This particularly preferably applies to an eccentric screw pump with a stator clamping device that has a shell that surrounds the stator at least in part and has a plurality of shell segments (as clamping segments). These clamping segments can be clamped radially against the rotor, e.g., with one or more adjusting elements, to change the clamping. The invention therefore preferably relates to an eccentric screw pump with a stator clamping device that allows the stator to be variably clamped radially against the rotor. Such an eccentric screw pump is described, for example, in WO 2016 / 034341 A1.

[0029] Alternatively, the invention also includes eccentric screw pumps in which the elastic stator is clamped against the rotor by means of a stator clamping device acting in the axial direction.

[0030] In principle, embodiments are also covered in which the clamping is varied in other ways, e.g. by electroactive materials integrated into the stator and / or by stators which are equipped with cavities, channels or the like which can be subjected to pressure in order to change the clamping.

[0031] Preferably, an (electronic) control device is implemented, which is, for example, connected to or integrated into the stator clamping device. According to the invention, the described control method is integrated into such a control device, i.e., the control device is equipped with a suitable algorithm for controlling the pump. This makes it possible to adjust the pump during operation, i.e., the clamping can be automatically adjusted to the optimal operating point during operation. Alternatively, it is also possible to actively optimize the clamping during operating breaks.

[0032] Consequently, it is particularly preferred to implement automated control of the optimal clamping by equipping the stator clamping device with a mechanical adjustment mechanism (e.g., with actuators). Alternatively, the invention also encompasses embodiments in which the clamping is adjusted manually, e.g., by an operator. Even in such a case, the described operating parameters can be determined with the aid of a control device, which is then designed as an analysis device or monitoring device, and the aforementioned characteristic values ​​(mean value and / or pulsation amplitude) can be calculated therefrom. Depending on this, a specification for the adjustment of the clamping is iteratively output, which can then, however, be implemented manually rather than mechanically. The intervention of an operator is limited to the mere implementation of the adjustment specified by the control system, e.g.,Increasing the clamping force by a specified increment. This also allows the clamping force to be optimally adjusted iteratively through repeated measurements and calculations, and the resulting increase in the clamping force.

[0033] An essential component of the eccentric screw pump is the elastic stator, which can be variably clamped against the rotor via the stator clamping device. This can be a one-piece stator. Particularly preferred is an eccentric screw pump in which the stator is designed as a longitudinally split stator consisting of at least two partial shells (half shells), which can be clamped against each other using the stator clamping device to vary the clamping. Such solutions are generally known (see, for example, WO 2009 / 024279 A1 and DE 10 2014 112 552 A1 as well as WO 2016 / 034341 A1).

[0034] The invention also relates to a control device for an eccentric screw pump, which according to the invention comprises means suitable or configured to carry out the described method. The control device, which is preferably an electronic control for optimizing the clamping of the pump, is therefore also protected separately. The control device can be structurally integrated into the pump or be available as a separate component (of a pump system). The control device can have at least one sensor for measuring the operating parameter or be connected to such a sensor. The sensor can be a pressure sensor for measuring an operating pressure. Preferably, two sensors can be provided, namely a first sensor for measuring the operating pressure on the pressure side and a second sensor for measuring the operating pressure on the suction side of the stator.The claimed control device comprises suitable hardware equipped with corresponding software for carrying out the described method. This hardware comprises, for example, a computer. In addition, the monitoring device can have a sensor in the manner described. The control device can, for example, be connected to the stator clamping device, particularly in the case of a stator clamping device for mechanical or automated adjustment of the clamping. Alternatively, the control device can also be configured to output commands intended, for example, for manual adjustment of the clamping by an operator. In principle, as an alternative to pressure measurement, the invention also includes the measurement of the temporal progression of other operating parameters of a pump which pulsate periodically at the pump frequency and whose pulsation amplitude depends on the clamping of the stator.Such an operating parameter can be made available by a measurement in the manner described, i.e. measured. Alternatively, it is also possible not to measure the operating parameter directly, but to calculate it from directly measured values. For example, as an alternative to the operating pressure, the torque or the motor current of the pump drive can also be made available or used as an operating parameter. In this case, the pulsation amplitude of the torque pulsation or motor current pulsation is determined. For example, wear on the stator and / or rotor of an eccentric screw pump typically leads not only to pressure pulsations due to the changing clamping, but also to pulsation-like changes in the pump torque, which is why the torque pulsation can be used as an operating parameter. Furthermore, the pulsation-like changes in the torque lead to a pulsating power consumption orCurrent consumption, so that the power consumption or current consumption can also be used as an operating parameter. Likewise, wear-related changes in the rotor-stator geometry of the pump lead to periodic or pulsating changes in structure-borne noise, so that structure-borne noise can also be used as an operating parameter.

[0035] The invention also relates to an eccentric screw pump that is equipped with a control device of the described type or is connected to such a control device. The eccentric screw pump has a stator, a rotor, a drive, and a stator clamping device. This stator clamping device is preferably equipped with or connected to the control device according to the invention, wherein the control device is configured to carry out the described method. An eccentric screw pump is preferably realized that is configured to carry out the method according to the invention.

[0036] Finally, the invention also relates to a computer program comprising instructions (or an algorithm) which cause the monitoring device to carry out the claimed method and / or the eccentric screw pump to be operated in the claimed manner.

[0037] The invention will be explained in more detail below with reference to drawings which merely represent an exemplary embodiment.

[0038] Fig. 1 a (schematically simplified) eccentric screw pump with a control device for controlling the clamping of the stator and

[0039] Fig. 2 shows a process diagram for controlling or regulating the clamping of an eccentric screw pump.

[0040] Fig. 1 shows, by way of example, a conventional eccentric screw pump which has a stator 1 made of an elastic material and a rotor 2 rotating in the stator 1. In addition, a (merely indicated) stator clamping device 12 is provided which, in the exemplary embodiment, has a casing 3 surrounding the stator and having a plurality of casing segments, wherein these casing segments form clamping segments which are adjustable to change the clamping of the stator 1 relative to the rotor 2. The stator clamping device 12 thus serves to vary the clamping of the stator relative to the rotor. For this purpose, the stator clamping device can be equipped with suitable adjusting elements 13, for example for automated adjustment of the clamping. Details are not shown.

[0041] The pump further comprises a suction housing 4 and a connection port 5, also referred to as the discharge port. The pump also comprises a pump drive 6, which operates on the rotor 2 via a coupling rod 7. The coupling rod 7 can be connected to the drive 6 or a drive shaft via a drive-side coupling joint 8 and to the rotor 2 via a rotor-side coupling joint 9.

[0042] According to the invention, the eccentric screw pump is equipped with a control device 10, which is connected to the stator clamping device 12 for adjusting the clamping of the stator 1. For this purpose, it is only indicated in Fig. 1 that the (electronic) control device 10 is connected to adjusting elements 13 of the stator clamping device 12 (not shown in detail) for varying the clamping of the stator relative to the rotor 2.

[0043] Furthermore, the control device 10 is equipped with or connected to one or more sensors 11a, 11b. In the illustrated embodiment, a pressure sensor 11a for determining the operating pressure on the pressure side is provided in the area of ​​the pressure nozzle 5, on the one hand, and a pressure sensor 11b for determining the operating pressure on the suction side is provided in the area of ​​the suction housing 4, on the other hand. According to the invention, the clamping (i.e., an iterative change in the clamping) of the stator 1 is controlled or regulated as a function of an operating parameter, wherein according to the invention an operating parameter is used which pulsates periodically at the pump frequency (or a multiple of the pump frequency), and whose pulsation amplitude is determined.In the illustrated embodiment, the operating parameter is the operating pressure, namely the pressure difference Δp between the pressure on the pressure side of the stator and the pressure on the suction side of the stator. For this purpose, the aforementioned pressures or pressure difference are recorded as series of measured values, and characteristic values ​​are calculated from them, in particular the mean value Δp and the pulsation amplitude Δp. PP .

[0044] A control algorithm is stored in the control device, the functionality of which is explained using the process diagram in Fig. 2 as an example. The control begins with a base setting for the clamping force w. Subsequently, the clamping force w is repeatedly increased by a specified incremental value in a closed-loop control manner. The control algorithm is based on simple pressure measurements, which can be easily and reliably implemented using inexpensive pressure sensors. The process shown in Fig. 2 considers two different scenarios or application cases that are relevant in connection with the measurement of the pressure difference.

[0045] Firstly, in a first scenario, application cases must be covered in which the differential pressure Ap itself is directly related to the flow rate. This is the case, for example, when an (open) valve is connected to the pressure side of the pump, which can be followed by other components. In this case, the differential pressure is determined by the flow resistance of the suction-side components of the pump. While in the prior art the clamping is adjusted as a function of a measured flow rate, in this first scenario the flow rate can simply be determined from the mean value Ap averaged over at least one period, from the measured pressure difference Ap or a series of measurements of the pressure difference Ap. This mean value Ap therefore replaces the flow rate measured in the prior art, whereby Fig.2 does not depend on absolute values ​​of the flow, but only on relative changes and thus also only on relative changes of the mean value Ap. In the method according to Fig. 1, in order to detect these cases, the clamping is iteratively increased depending on the mean value Äp until a maximum value of the mean value is reached, that is to say until the mean value no longer increases.

[0046] In addition, a second scenario considers cases where the differential pressure Ap is not directly related to the flow rate, i.e., cases where the variation in the flow rate does not directly lead to a significant or measurable pressure difference. However, in these cases, increasing the stator clamping w leads to a change in the aforementioned pressure pulsations, i.e., increasing the stator clamping reduces the pressure pulsations Ap. PP. Consequently, in order to optimize the clamping in the second scenario, the pulsation amplitude Ap PP of the pressure pulsations are monitored or analyzed. Consequently, the clamping w with the stator clamping device 12 is adjusted depending on the pulsation amplitude Ap PP Iteratively increases until a minimum value of the pulsation amplitude is reached, i.e., until the pulsation amplitude no longer increases. Once this state is reached, the control (or the iterative process) ends and the optimal value for the clamp w is reached.

[0047] In particular, the combination of these considerations—i.e., the consideration of various possible scenarios or application cases—leads to optimal results in the optimization of clamping based solely on the measurement of pressure values ​​or differential pressure values. This is based on the relationship between the flow rate and the differential pressure, on the one hand, and the pulsation amplitude of the pressure pulsations, on the other. It is interesting to note that only relative changes in the differential pressure and the pressure pulsations need to be incorporated into the control or regulation process, without the need to actually determine (absolute) flow rates from the pressure values ​​using mathematical models.

[0048] In practical applications, the flow rate will typically depend either on the mean value according to the first scenario or on the pulsation amplitude according to the second scenario, so that in the process shown in Fig. 2, often only the first loop or only the second loop is run through multiple times. However, it is preferable to store both queries in the algorithm to universally cover both cases.

[0049] The queries (mean value on the one hand and pressure pulsation on the other) are preferably carried out in the order shown. However, the reverse order is also possible.

[0050] The procedure outlined in Fig. 2 can be implemented, for example, with a pump like Fig. 1, but alternatively also with any other pump type with controllable clamping.

[0051] Preferably, the iterative optimization of the clamping is automated, as shown in the figures. For this purpose, means for mechanical adjustment of the clamping are provided (not shown in detail), which are controlled by the control device. However, the invention also encompasses embodiments with manual adjustment of the clamping.

[0052] In this case, which is not shown in detail, the control device generates action commands for an operator, which in particular concern the adjustment of the clamp by a predetermined value.

Claims

Patent claims:

1. Method for controlling an eccentric screw pump, which - a stator (1 ), - a rotor (2) rotating in the stator (1) at a pump frequency, - a drive (6) for the rotor, - a stator clamping device (12) and - a control device (10), wherein the clamping (w) of the stator (1) can be adjusted with the stator clamping device (12), wherein an operating parameter of the pump is made available to the control device (10), and wherein the clamping (w) of the stator (1) is adjusted / varied depending on the operating parameter, characterized in that that an operating parameter is used which pulsates periodically with the pump frequency or a multiple of the pump frequency that from the operating parameter, on the one hand, an average value (Zip) averaged over at least one period and, on the other hand, the pulsation amplitude (ApPP ) are determined and that the clamping (w) with the stator clamping device (12) is iteratively changed depending on the mean value (Zip), e.g. increased, until a maximum value of the mean value is reached and / or iteratively changed depending on the pulsation amplitude, e.g. increased, until a minimum value of the pulsation amplitude (Ap PP ) is reached.

2. Method according to claim 1, characterized in that an operating pressure of the pump or of the medium to be pumped in or on the pump is used as the operating parameter.

3. Method according to claim 1 or 2, characterized in that a parameter difference, e.g. a pressure difference, preferably the difference (Ap) between the pressure on the pressure side of the stator (1) and the pressure on the suction side of the stator (1), is used as the operating parameter.

4. Method according to one of claims 1 to 3, characterized in that the stator clamping device (12) is connected to the control device (10) and is designed as an automated clamping device for a mechanical adjustment of the clamping and that the control device (10) iteratively changes the clamping (w) with the stator clamping device (12) depending on the mean value (Äp), e.g. increases it, until a maximum value of the mean value is reached and / or iteratively changes iteratively depending on the pulsation amplitude, e.g. increases it, until a minimum value of the pulsation amplitude (Ap PP ) is reached.

5. Method according to one of claims 1 to 4, characterized in that the stator clamping device (12) comprises adjusting elements (e.g. adjusting screws, adjusting pins or adjusting rods) and / or actuating drives (e.g. electrical, electromotive, magnetic or hydraulic drives).

6. Method according to one of claims 1 to 5, characterized in that the stator clamping device (12) has a casing (3) which surrounds the stator (1) at least in regions and has a plurality of casing segments as clamping segments which can be clamped in the radial direction against the rotor (2) in order to change the clamping, for example with one or more adjusting elements (13).

7. Method according to claim 6, characterized in that the stator (1) is designed as a longitudinally split stator comprising at least two partial shells which can be clamped against one another with the stator clamping device (12) in order to change the clamping.

8. Method according to one of claims 1 to 7, characterized in that the operating parameter is provided by measurements, e.g. by measurements with one or more sensors (11a, b).

9. Control device for an eccentric screw pump, comprising means suitable for carrying out the method according to one of claims 1 to 8.

10. Control device according to claim 9, comprising at least one sensor (11a, b) for measuring the operating parameter.

11. Control device according to claim 10, comprising at least one pressure sensor for measuring an operating pressure, e.g. at least one pressure sensor (11a) for measuring the operating pressure on the pressure side of the stator and / or at least one pressure sensor (11b) for determining the operating pressure on the suction side of the stator (1).

12. A computer program comprising instructions that cause the monitoring device according to one of claims 9 to 11 to carry out the method according to one of claims 1 to 8.

13. Eccentric screw pump, which - a stator (1 ), - a rotor (2) rotating in the stator (1) at a pump frequency, - has a drive (6) for the rotor (2), a stator clamping device (12) and a control device (10), or is connected to a control device (10), characterized in that the clamping of the stator (1) can be adjusted using the stator clamping device (12) using a method according to one of claims 1 to 8.

14. Eccentric screw pump according to claim 13, characterized in that the control device is configured to carry out the method according to one of claims 1 to 8.

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