EP3803122A1

EP3803122A1 - Method for determining or monitoring the state of an eccentric screw pump

Info

Publication number: EP3803122A1
Application number: EP19728623.0A
Authority: EP
Inventors: Johannes Schulz; Sascha Plazar
Original assignee: Seepex GmbH
Current assignee: Seepex GmbH
Priority date: 2018-06-05
Filing date: 2019-05-29
Publication date: 2021-04-14
Also published as: WO2019233859A1; DE102018113347A1

Abstract

The invention relates to a method for determining or monitoring the state of an eccentric screw pump which has a stator and a rotor which rotates in the stator with a pump frequency. The time curve of an operating parameter of the pump is provided, said time curve pulsating periodically with the pump frequency or a multiple of the pump frequency, and the pulsation amplitude of the time curve depends on the state of the eccentric screw pump, wherein the pulsation amplitude is ascertained, and the state of the eccentric screw pump is determined by comparing the pulsation amplitude with one or more comparison values.

Description

Method for determining or monitoring the condition of a

Cavity Pump

Description:

The invention relates to a method for determining or monitoring the state (eg operating state, wear state or fault state) of an eccentric screw pump which has a stator made of an elastic material and a rotor rotating at a pump frequency in the stator. In such an eccentric screw pump, the rotor z. B. via at least one coupling rod, which is also referred to as a propeller shaft, connected to a drive. The pump has a z. B. suction side connected to the stator pump housing, z. B. suction on which is usually a housing opening, for. B. has an inlet opening, for the medium to be delivered. Furthermore, the pump has a to the stator z. B. pressure side connected pump housing, z. B. a pressure port and / or a pressure-side line. Such a progressing cavity pump is a pump from the group of rotary displacement pumps, which are used to promote a variety of media and in particular high-viscosity liquids in different industries. The media to be delivered can be z. B. also contain solids.

The stator consists z. B. of an elastic, preferably elastomeric material and is usually surrounded by a one-piece or multi-part stator shell or stator housing. The pump housing connected on the suction side to the stator is generally referred to as a suction housing, and the housing connected to the stator on the pressure side as a discharge nozzle. In principle, however, it is also possible to operate such a pump in the opposite direction of conveyance. The rotating and at the same time the eccentricity ensuring connection between the drive or the connecting shaft on the one hand and the rotor on the other hand via

the coupling rod arranged in the pump housing. The coupling rod can be z. B. be connected via a rotor-side joint with the rotor and a drive-side joint with the drive shaft or connecting shaft. In principle, however, embodiments with a flexible coupling rod without joints are also covered by the scope of protection.

Such progressing cavity pumps are z. B. from DE 10 2014 112 552 A1, DE 10 2010 037 440 A1 and WO 2009/024279 A1. In practice, the eccentric screw pumps or their components are subject to wear during operation, so that maintenance work or maintenance measures are required at regular intervals. Typical wear parts are in particular the elastic stator, but also the rotor rotating in the elastic stator. It is therefore known to monitor the wear of these components during operation by determining suitable parameters. So there is z. Example, the ability to register the flow or the flow rate and to compare these values with the respective speeds of the rotor. Similarly, the back pressure of the pump compared to the speed can be determined. With the methods known so far, an indirect determination of the state of wear thus takes place.

Alternatively, from DE 20 2005 008 989 U1 an eccentric screw pump is known in which the stator is associated with a sensor, are measured with the compressions and / or movements of the stator or the elastic material in the course of the rotation of the rotor. The sensor may be z. Example, to act a pressure transducer or a force transducer, which is integrated in the stator and registers compressions of the stator. This is a measurement signal as a function of time

registered and to determine the state of wear, the determined time-dependent measurement signal is compared with stored reference signals. It is exploited that with increasing material removal in the region of the stator and the transmitted from the rotor during the rotation of the elastomeric stator pressure or compression decreases. If a pressure signal is detected and registered at a certain point in time and it is determined that the pressure signal is substantially lower than the previously stored reference signals, then this is a reliable indication of a corresponding wear of the stator. Due to the periodic operation of the rotor, the measurement signal registered as a function of time is a periodic signal. While the period or frequency of this signal at a given rotor frequency usually does not change with increasing wear, the amplitude of the periodic signal decreases with increasing wear, since the pressure acting on the pressure sensor or the path registered by the displacement sensor correspondingly decreases. The principle known so far is based directly on the periodic compression of the stator in the course of the rotation of the rotor.

The invention is based on the technical problem of providing a method with which the state of an eccentric screw pump, for. As a state of wear, operating state or fault condition can be reliably determined.

To solve this object, the invention teaches a method for determining or monitoring the state of an eccentric screw pump, which has a stator and a rotor rotating at a pump frequency in the stator,

wherein the time course of an operating parameter of the pump is provided which periodically pulsates with the pump frequency or a multiple of the pump frequency and whose pulsation amplitude depends on the state of the eccentric screw, wherein (from the time profile of the operating parameter) the pulsation amplitude is determined and by comparing the Pulsation amplitude with one or more comparative values of the state of

Eccentric screw pump is determined. Comparative values can be z. B. determined in advance and stored in a memory. However, it is also possible to determine the comparison values during operation and to store them in the memory. Thus, comparison values may be determined dynamically based on a plurality of values taken during (normal) operation, e.g. B. by means of statistical or neural processes in the sense of machine learning. Thus, also learned comparative values or a (parameterized) algorithm, which is used to determine a comparison value, come into consideration. Such

Comparative values or algorithms can, for. B. be learned during operation of the pump. They are z. B. stored in a volatile memory (register, RAM).

Particularly preferably, the operating pressure of the eccentric screw pump is made available as an operating parameter, and the pulsation amplitude of the pressure pulsation is determined. In an ideal system, the operating pressure of the eccentric screw pump does not vary with the rotation or rotational frequency of the pump, ie a perfect eccentric screw pump is free from pressure pulsations in relation to the operating pressure. In practice, eccentric screw pumps are indeed comparatively low in pulsation, yet they have certain pressure pulsations that respond to the changing sealing lines during

a revolution and minimal geometry differences of rotor and stator are due. The invention has recognized that the pulsation amplitude of the pressure pulsation depends very significantly on the wear of the relevant components of an eccentric screw pump, in particular stator and / or rotor. This is due to the fact that with increasing wear of the rotor and / or stator, the sealing line and the delivery chamber changes and this can be clearly seen in the temporal pressure curve and exploit for a determination of wear or wear monitoring. The constant or decreasing or increasing pressure during operation of an eccentric screw pump on a time scale in the seconds or minutes range is therefore in practice superimposed on a periodically varying pressure pulsation and the pulsation amplitude of this pressure pulsation increases with increasing wear of the stator and / or the rotor. By determining the Pulsationsamplitude at a certain time or monitoring the Pulsationsamplitude over a period of time and a comparison with previously stored comparison values can be in a simple way the state of wear of the eccentric screw, z. B. of the stator and / or rotor determine / monitor. Alternatively, the determination or monitoring of the state of a pump but also refer to a fault condition of the pump, z. B. on a dry run or overpressure of the pump.

From the time course of the operating parameter, z. As the operating pressure of the pump, the pulsation amplitude and consequently the amplitude of the pressure pulsation can be determined directly and thus on the state, for. B. state of wear can be closed. In a preferred embodiment, however, the pulsation amplitude is not determined directly from the temporal pressure curve, but the time profile of the periodically pulsating operating parameter, z. B. the temporal pressure curve, is first in one

Frequency response transformed, z. B. by a Fourier transform. From this frequency curve can be used as a measure of the wear of the pump, the amplitude in the pump frequency (ie, the first Flaronic) or a harmonic in this frequency curve, z. B. the first harmonic (second Flarmonischen) or the second harmonic (third Flarmonischen) determine the frequency response. Surprisingly, experiments have shown that the amplitude development of the pressure pulsation in the first harmonic of the pump frequency is even greater than in the pump frequency itself, so that preferably not from the frequency spectrum for the evaluation of the amplitude of the pump frequency, but a harmonic of the pump frequency, z. B. the first or second harmonic is used. In detail, reference is made to the figure description. It is within the scope of the invention, the operating pressure of the pump or the pressure pulsations directly by a pressure measurement, for. B. to determine with a pressure gauge. Preferably, the determination of the operating pressure on the pressure side of the stator, z. B. in or on a pressure side connected to the stator discharge port or in or on a pressure side connected to the stator line.

As an alternative to the operating pressure can be used as operating parameters z. B. also provided the torque or the motor current of the pump drive available or used. In this case, the pulsation amplitude of the torque pulsation or motor current pulsation is determined. So z. As the wear on the stator and / or rotor in a Exzenterschenkenpumpe typically not only to pressure pulsations, but also to pulsation-like changes in the torque of the pump, which is why the torque pulsation can be used as operating parameters. Farther

lead the pulsation-like changes in torque to a pulsating power consumption or current consumption, so that the power consumption or current consumption can be used as operating parameters. Likewise, wear-related changes to the rotor-stator geometry of the pump lead to periodic or pulsating changes in structure-borne noise, so that the structure-borne noise can also be used as an operating parameter.

First, according to the invention, the determination or monitoring of a state of wear of the pump, for. B. rotor and / or stator in the foreground. On the other hand, however, a specific operating state or fault state can be determined or monitored, for. As a dry run, overpressure, insufficient or excessive clamping of a braced stator, changes in the rotor / stator geometry, z. As the sealing line, or swelling of the stator in media incompatibility.

In principle, the invention also includes the analysis of the time course of other operating parameters of a pump which pulse periodically with the pump frequency and the pulsation amplitude of which depends on the state of the eccentric screw pump. Such an operating parameter may be provided by measurement in the manner described, i. H. be measured. Alternatively, it is also possible to measure the respective operating parameters not directly, but to calculate from directly measured values. Preferably, a transformation of the time profile into a frequency spectrum takes place in the manner already described.

The method according to the invention also has the advantage that the occurrence of the frequencies which are of interest for wear as multiples of the pump frequency, which is known or can easily be determined, is a simple one

and effective filtering of the data of influences from the process or the system allows.

The invention also relates to a monitoring device for an eccentric screw pump or an eccentric screw pump with such a monitoring device for carrying out the described method. Such a monitoring device thus comprises means, e.g. For example, an electronic evaluation unit, a computer or the like, which are suitable (and set to program technology) to perform the described method for determining and monitoring the state of the eccentric screw pump. Such a monitoring device can, for. Example, have a sensor for measuring the operating parameter or be connected to such a sensor. For a sensor, it may be z. B. to act a pressure sensor for detecting and continuously recording the operating pressure of the eccentric screw pump. In addition, the monitoring device may have an optical and / or an acoustic display, with which the determined state of the eccentric screw pump is displayed. The monitoring device with optical or acoustic display can in principle be integrated directly into the eccentric screw pump, so that the state of wear or an operating or fault state can be displayed directly on the eccentric screw pump. Preferably, however, a separate monitoring device is provided which only has to access the operating parameters of the eccentric screw pump. In this respect, the monitoring device can also be a computer or computer that is set up to carry out the described method and consequently to determine or monitor the state of the eccentric screw pump. The inventive method can, for. B. as a computer program or computer program product for

Be provided, which includes instructions with which such a monitoring device, for. As a computer / computer or the like, the described method is executed. Thus, such a computer program z. B. on a standard computer, tablet or smartphone and install the necessary for the implementation of the method operating parameters or the time profile of the operating parameters can be wired or wirelessly transmitted to the device and with the help of the computer program can be from the transmitted operating parameters or operating data determine the state of wear.

Incidentally, however, the invention not only detects the determination of the state of wear of the eccentric screw pump, but alternatively also the determination and monitoring of an operating or fault condition, for. B. a dry run of the eccentric screw pump. Because the pulsation amplitude of the operating parameter, z. B. the pressure pulsations, changes even with a dry run of the pump over a normal operation, so that according to the invention also a dry run protection for an eccentric screw pump can be realized. Incidentally, the determination or monitoring of other operating conditions, eg. As interference conditions into consideration, in particular the monitoring of changes in geometry of the rotor and / or stator.

The monitoring device according to the invention preferably has a memory in which the comparison values for the pulsation amplitudes required for the evaluation are stored, so that the determined pulsation amplitudes are compared with the stored pulsation amplitudes for determining a state of wear or operating state of the pump. Incidentally, the aforementioned dynamic determination and storage of comparison values can also be used with the monitoring device

be carried out so that appropriate algorithms for such a dynamic determination, for. B. may also be included in the monitoring device in the sense of machine learning. Incidentally, the monitoring device preferably has an electronic evaluation device which is set up to use the signals made available, for B. signals from a measuring device, with the required frequency resolution to capture and exploit. The sensor must also be able to detect the operating parameter with regard to the time resolution with the pump frequency. Incidentally, there is the possibility of using the information obtained with the method according to the invention on the state (state of wear or fault state) in different ways. On the one hand, mere information can take place in the sense of a visualization, so that maintenance measures can be carried out if necessary. However, there is also the option of the eccentric screw pump in dependence on the determined state, for. B. wear condition, to operate and consequently adapt the operation of the eccentric screw pump to the information determined. This is z. B. the ability to realize the invention in an eccentric screw pump with automated delivery, the z. B. in DE 10 2014 112 552 A1 is described.

It is also possible that the timing of the onset of wear determined by the system serves as the starting point for a wear history prediction based on other metrics.

In the following the invention will be explained with reference to drawings showing only exemplary embodiments. Show it

An eccentric screw pump with a monitoring device for monitoring the condition, for. B. state of wear,

2a to 2c show the time course of pressure pulsations of the eccentric screw pump,

3a to 3c, the pressure pulsation of Fig. 2a to 2c one

Frequency spectrum,

4 shows the development over time of the pulsation amplitudes.

In Fig. 1, a conventional eccentric screw pump is shown, which has a stator 1 made of an elastic material and a rotor 2 rotating in the stator 1, wherein the stator 1 is surrounded by a stator shell 3. Furthermore, the pump has a suction housing 4 and a connecting piece 5, which is also referred to as a discharge nozzle 5. The pump also has a pump drive 6 which operates on the rotor 2 via a coupling rod 7. The coupling rod 7 is connected via a drive-side coupling joint 8 to the drive 6 and a drive shaft and a rotor-side coupling joint 9 to the rotor 2.

In the illustrated embodiment, a pressure sensor 11 is provided in the region of the pressure port 5, with which the operating pressure of the eccentric screw pump is measured. The eccentric screw pump or the sensor 11 is connected to a monitoring device 10, with which the state of wear of the eccentric screw pump can be determined or monitored. This monitoring device 10 operates on the

Basis of the analysis of pressure pulsations. Even if an eccentric screw pump is relatively low in pulsation, pressure pulsations occur in practice, ie. H. the time profile of the operating pressure of the eccentric screw pump pulsates periodically with the pump frequency. The operating pressure which is generally constant on a time scale in the second or minute range during operation is therefore superimposed on a periodic analysis in an analysis in a higher-frequency range, the pulsation amplitude depending on the state of wear of the stator and / or the rotor, namely with the state of wear increases. This results from a comparative analysis of FIGS. 2a to 2c. These figures show the time course of the pressure pulsation Dr at a first time T1 in Fig. 2a with little wear and at a second time T2 with average wear in Fig. 2b and a third time T3 with high wear in Fig. 2c. It can be seen that the pulsation amplitude Dr increases significantly with increasing operating time of the pump and consequently increasing wear.

This effect becomes even clearer in the frequency spectra shown in FIGS. 3a to 3c. FIGS. 3a to 3c show the amplitude development A of the pressure pulsations in a frequency range, the functions according to FIGS. 3a to 3c respectively resulting from the functions according to FIGS. 2a to 2c by Fourier transformation. In the exemplary embodiment, the pump was operated at a pump frequency of 100 revolutions per minute and consequently a pump frequency of 1.7 Flz. FIGS. 3a to 3c show the pulsation amplitudes for the pump frequency at approximately 1.7 Hz and the first harmonic at approximately 3.3 Hz and the second harmonic at approximately 5 Hz and the third harmonic at approximately 6.7 Hz. It becomes clear that the pressure pulsations can be analyzed very significantly on the basis of the first harmonic of the frequency spectrum.

The amplitude development of the pressure pulsations, which is shown in FIGS. 3a to 3c for only three values, is plotted in FIG. 4 as a function of the operating time, wherein in a test by a suitable medium a particularly high degree of wear over a certain operating time has been produced. It can be seen that the pulsation amplitude for both the pump frequency and for the first three harmonic increases with increasing operating time, so that in this way determination and monitoring of the wear of the eccentric screw pump is possible, in particular by comparing the determined values with previously recorded comparison values ,

The monitoring device which is merely indicated in FIG. 1 and which detects the sensor data and evaluates it with evaluation electronics capable of "high-frequency" the sensor signals is used for this purpose. H. in a kHz range. The frequency spectra are then generated from the determined data and, by comparison with previously stored / determined data, the state of wear or also an interference state is determined.

Claims

claims:

A method of determining or monitoring the condition of a progressive cavity pump having a stator and a rotor rotating at a pump frequency in the stator, the timing of an operating parameter of the pump being provided which is periodic with the pump frequency or a multiple of the pump frequency pulsation and whose pulsation amplitude depends on the state of the eccentric screw pump, wherein the pulsation amplitude is determined and the state of the eccentric screw pump is determined by comparing the Pulsationsamplitude with one or more comparative values.

2. The method of claim 1, wherein as state a state of wear of the eccentric screw pump or an operating or fault condition, for. B. a

Dry or positive pressure, the progressive cavity pump is determined or monitored.

3. The method of claim 1 or 2, wherein an operating parameter is provided by a measurement.

4. The method according to any one of claims 1 to 3, wherein an operating parameter is provided whose Pulsationsamplitude of the

Wear state of the stator and / or the rotor depends.

5. The method according to any one of claims 1 to 4, wherein an operating parameter is provided, the pulsation amplitude with the

Wear state of the pump increases, preferably increases with the state of wear of the stator and / or the rotor.

6. The method according to any one of claims 1 to 5, wherein the operating pressure of the pump provided as operating parameters and the pulsation amplitude of the pressure pulsation is determined.

7. The method according to any one of claims 1 to 6, wherein the operating pressure or the pressure pulsation directly by a pressure measurement, for. B. with a pressure gauge is determined.

8. The method according to any one of claims 1 to 7, wherein the operating pressure on the pressure side of the stator, z. B. in or on a pressure side connected to the stator discharge port or in or on a pressure side connected to the stator line is measured.

9. The method according to any one of claims 1 to 5, wherein as the operating parameter, the torque or the motor current of the pump drive provided and the Pulsationsamplitude the torque pulsation or motor current pulsation is determined.

10. The method according to any one of claims 1 to 9, wherein the time course of the periodically pulsating operating parameter, for. B. the temporal pressure curve is transformed into a frequency response, z. B. by Fourier transformation, wherein from the frequency response, the amplitude in the pump frequency or a harmonic of the frequency response, z. B. the first harmonic, is determined as Pulsationsamplitude.

11. A monitoring device for an eccentric screw pump comprising means adapted to carry out the method according to one of claims 1 to 10.

12. Monitoring device according to claim 11, comprising at least one sensor for measuring the operating parameter and / or comprising a visual and / or acoustic display, with which the determined state of the eccentric screw pump is displayed.

13. Monitoring device according to claim 11 or 12, comprising a memory in which comparison values are stored, with which the determined pulsation amplitudes are compared.

A computer program comprising instructions for causing the monitoring device of any one of claims 11 to 13 to perform the method of any one of claims 1 to 10.

15. Eccentric screw pump with a monitoring device according to one of claims 11 to 13.