AT16482U1 - System for monitoring the condition of a conveyor belt - Google Patents

Abstract

There is provided a system and method for monitoring the condition of a conveyor belt, wherein the conveyor belt (9) is arranged to rotate about at least one drive drum (20) and a tail pulley (21) and wherein an electric motor (22, 23) is arranged is to drive the drive drum (20). At least one sensor unit (10, 11, 13) is arranged to determine at least one sensor signal (1, 2, 3, 7) representing at least one operating variable of the electric motor (22, 23). At least one data processing unit (6) is arranged in the system for deriving from the at least one sensor signal (1, 2, 3, 7) at least one corresponding time-dependent data signal, to detect irregularities (27, 28) in the at least one data signal that indicate in that a splice point (26) of the conveyor belt (9) passes the drive drum (20) and / or the tail pulley (21) to determine, from a change in shape or frequency of the irregularities (27, 28), whether the condition of the conveyor belt has changed, and to send a signal (30) reflecting a change in the state of the conveyor belt to at least one display unit, a storage unit and / or a decision making unit.

Description

The invention relates to a system and a method for monitoring the condition of a conveyor belt according to the preamble of claim 1 and claim 13, wherein the conveyor belt is arranged to rotate about at least one drive drum and a tail pulley, an electric motor for driving the drive drum and the system has at least one sensor unit.

Conveyor belt systems are used in various industries and especially in mining for bulk and cheap transportation. The essential part of a conveyor belt system is the conveyor belt which carries the bulk material such as coal or lignite or the goods and continuously conveys them from one point to the next over a long distance. In the mining industries, the conveyor systems are exposed to severe environmental conditions that cause wear on the conveyor belt material and damage the belt, such as cracks and tears. Such damage not only reduces the life of the conveyor, but also results in an unexpected production stop if not noticed in time to organize the maintenance of the belt. Since the conveyor continuously moves under normal operating conditions, it is difficult to monitor the condition of the belt and to measure the state of wear or any damage.

In the art it is known to incorporate embedded measuring parts such as load sensors, induction loops or antennas additionally in the conveyor belt material. These embedded measuring parts interact with, for example, wireless communication or via ultrasonic or inductive signals with corresponding contactless receivers, the receivers being attached to the mechanical structure of the conveyor system.

For example, US 6,047,814 discloses a method for monitoring a continuously moving belt, wherein two transducers are arranged in or on the belt in the connecting region of the belt, wherein the connecting region is the region in which the ends of the conveyor belt are connected to each other. The transducers each send a signal to an external transceiver unit as they pass through an operating range of the transceiver unit. The transducers are integrated circuits that are conductively connected to a coil. Due to the fact, the transducers are arranged inside the connection area, since it has been recognized that the connection area is a weak point of the conveyor belt which has to be monitored for loosening indications.

DE 10 2008 018 238 A1 discloses a device for nondestructive detection of an operating state of elastic components, such as conveyor belts made of rubber. In the conveyor belt, elastomer pulse transmitters are embedded in two so-called measuring ranges, wherein the first measuring range has a different time behavior of its tensile strength in comparison to the second measuring range. The device further comprises a sensor station by means of which magnetic fields originating from the elastomeric pulse generators can be detected when they pass the sensor station, the magnetic fields then being processed for information on the expansion or extension of the corresponding measuring range.

US 4,436,198 describes a conveyor belt crack detection system wherein a plurality of antennas are embedded in the belt generally transverse to the direction of travel of the belt and wherein the respective antennas pass in capacitive coupling relationship to a transceiver a crack detection station and an electrical signal to the transmitter / Send recipient. A crack or crack in the conveyor belt material is detected by the fact that the antennas are broken and send no signal to the transmitter / receiver.

An alternative solution for identifying the condition of a conveyor belt is known, for example, from US Pat. No. 7,427,767 B2, which describes a device which records two-dimensional images of successive band sections. The captured images are transmitted to an evaluation device where the images are compared with reference images

AT16 482U1 2019-10-15 c Austrianiictiei pater taird chen and at least one statement on the condition of the tape is determined. The images are taken using either electromagnetic radiation, i. visible, infrared or ultraviolet light, or penetrating radiation, in particular X-ray detected.

DE 31 11 219 A1 discloses a system and method for monitoring the condition of a conveyor belt according to the preamble of claim 1 and claim 13, respectively; There is disclosed an apparatus for preventing one or more conveyor belts in a belt conveyor system from being slit longitudinally through objects which are trapped at the loading points and / or transfer points for the goods to be carried. The apparatus in each case comprises a monitoring member for each loading point and / or transfer point, the member having indicative values for the movement of the goods to be carried, for example the transport rate, or for the load of the drive, for example the engine power Comparative unit transmits. The comparison unit compares this value with a previously received characteristic value and, in the event of a deviation exceeding a predetermined deviation, transmits a shutdown command to the associated drive motor.

It is an object of the present invention to improve the systems and methods for monitoring the condition of a conveyor belt.

This object is achieved by a system and method according to the independent claims.

In the system according to the invention, the at least one sensor for determining at least one sensor signal is arranged, which represents at least one operating variable of the electric motor, which drives the drive drum, and at least one data processing unit is arranged to derive at least one Detecting irregularities in the at least one data signal indicating that a splice point of the conveyor belt passes the drive drum and / or the tail pulley, determining from a change in shape or the frequency of irregularities, whether or not the state of the conveyor belt has changed, and sending a monitoring output signal, which reflects a change in the state of the conveyor belt, to at least one display unit, a storage unit and / or a decision making unit.

The method according to the invention includes the method steps performed by the at least one sensor unit and by the data processing unit.

With the proposed system and method, it is no longer necessary to incorporate embedded sensor elements or measurement parts into the conveyor belts or to provide specific external sensors, such as an image capture device. Instead, sensor information of the drive motor, which is available for normal operation of the conveyor belt, is used for condition monitoring. Accordingly, the cost of setting up, operating and maintaining a condition monitoring system is significantly reduced as compared to known systems.

In one or more time-dependent data signals derived from the sensor information, irregularities are detected indicating the times when the splice of the tape passes the drive drum and / or the tail pulley. The splice point is the point at which the ends of the conveyor belt are connected to form a joint or assembly. The joint is made by blanketing or butting, straight or oblique, and is held together by vulcanization or mechanical means. The splice site can also be used as an assembly

AT16 482U1 2019-10-15 cc Austriaiictie pater taird agency or liaison office.

In general, the invention is based on the recognition of the fact that the above-mentioned irregularities can be permanently observed in measurement signals taken on a conveyor belt system, since the splice site has different mechanical characteristics than the rest of the conveyor belt because it is stronger , As a result, the splice exerts other forces on the drive drum and / or tail pulley than the rest of the belt.

When the condition of the conveyor belt changes, i. E. As the strip material weakens and begins to elongate, or when cracks and cracks also occur, which also lead to incipient elongation of the strip, the shape and / or frequency of the irregularities begins to differ from those irregularities that occur in an intact conveyor belt occur. According to the invention, these differences are detected by the data processing unit and a corresponding monitor output signal is displayed and / or stored and / or sent to a decision making unit for deciding whether maintenance or replacement of the conveyor belt becomes necessary.

Therefore, a system and method for non-destructive monitoring of the condition of the conveyor belt is presented, which is easy to implement in an existing conveyor system. Since usually available sensor information of the electric motor is used, the effort for incorporating measuring parts into the strip material and for arranging a corresponding receiving device or an external sensor device on the conveyor belt system is avoided.

Preferably, the at least one operating variable of the electric motor is either a voltage, a current, a rotational speed, an acceleration, a torque or a force signal, and the at least one sensor unit is a current and / or voltage sensor, a speed pulse generator, a Torque transducers, such as a strain gauge, or a force transducer.

The at least one data signal may represent an amplitude over time or a frequency spectrum, wherein the time dependence of the frequency spectrum is achieved by repeatedly deriving the spectrum for subsequent times from the corresponding sensor signal.

The at least one data processing unit may either be an independent processing device, or it may comprise two or more processing devices that work together, where the two or more processing devices may be integrated into one and the same computing device or in separate units.

In a preferred embodiment, one or more of the processing devices are integrated components of an electrical transducer, in particular a frequency converter, wherein the transducer is connected to the electric motor and arranged to supply it with a current and / or a voltage. Most electric motors today are supplied and controlled by a corresponding electrical converter, the control being carried out in a processing device belonging to the converter. This processing device is supplied with one or more sensor signals representing one or more operating variables of the engine and derives from these sensor signals the corresponding time-dependent data signals needed for the control functions, such as current, voltage, torque and / or speed , Accordingly, it is particularly advantageous to apply the presented monitoring method in those cases in which the drive motor of the conveyor belt is supplied via an electrical converter, since the required data signals are already present and need only be further processed with respect to the irregularities.

The at least one data processing unit may be arranged to determine whether or not the state of the conveyor belt has changed by comparing the shape and / or the frequency of the irregularities, either with a corresponding threshold

3.15

AT16 482U1 2019-10-15 austriictiei p3LPrL3ir, L or with the form and frequency of a reference irregularity, the reference irregularity advantageously representing an intact and functional conveyor belt. Alternatively, a model-based state observer may be used to determine the condition or condition of the conveyor belt.

The shape of the irregularities can be determined from a change in the amplitude level and / or from a change in the width of the peak values of the irregularities.

In one embodiment of the system and corresponding method, the at least one sensor unit for determining a first sensor signal and a second sensor signal are arranged, which represent a first and a second operating variable of the electric motor, and wherein the at least one data processing unit for deriving first and second data signals and for detecting irregularities either in the first signal when the corresponding operating variable of the electric motor is controlled to follow a first reference variable, or in the second signal when the corresponding operating variable of the electric motor is controlled to follow a second reference variable.

The first sensor signal may be, for example, a speed signal, and the second sensor signal may be a torque signal. The speed and torque are mechanical operating variables of the electric motor, both of which are controllable. In general, since a control algorithm generally responds to and attempts to reduce any unwanted irregularities, the effects of the splice in the data signals corresponding to a controlled variable may become less visible than compared to the data signals of an uncontrolled variable. Therefore, it is proposed to look for the irregularities in the signal of an uncontrolled variable, i. to observe the irregularities in the speed signal when the torque of the motor is controlled, and vice versa.

The system and method for monitoring the condition of the conveyor belt may be extended by additionally considering a vibration data signal that may be derived in the form of an acceleration or speed sensor signal provided by a vibration measurement unit, the vibration measurement unit monitoring the vibration of a machine component, which is attached to the electric motor, such as the engine drum, a gearbox or a bearing, measures.

In a further extension of the system, the conveyor belt is additionally configured to rotate about a tensioning drum and the at least one data processing unit is adapted to determine a change in the condition of the conveyor belt by additionally considering a displacement sensor signal provided by a distance measuring unit incorporating the Displacement of the tensioning drum measures.

Still further, a tape tension signal provided by a force measuring unit and / or an image sensor signal provided by a radiation sensor observing the conveyor belt may be considered.

The invention and its embodiments will be apparent from the example and its embodiments, which is described below in conjunction with the accompanying drawings; show it:

1 shows a conveyor belt with a splice, FIG. 2 shows a system for monitoring the condition of a conveyor belt, FIG. 3 shows a part of the system of FIG. 2 with further sensor units, FIG. Fig. 4 is a graph of the cylinder force of the drive drum of Fig. 1; Fig. 5 is a time dependent frequency spectrum of the rotational speed of the motor driving the conveyor belt of Fig. 1;

4.15

Fig. 6 shows a time-dependent frequency spectrum of the torque of the motor which drives the conveyor belt of Fig. 1; Fig. 7 shows the amplitude / time course diagrams for rotational speed and torque of the engine of Fig. 1 at different times.

Fig. 1 shows a simple conveyor belt 9, which rotates about a drive drum 20 and a tail pulley 21. The conveyor belt is comparatively short with a length of about 18 meters. The conveyor belt has a splice 26, the splice being the location where the ends of the tape material overlap and are secured together. Other and especially longer conveyor belts may have more than one splice. The splice point of the conveyor belt of Fig. 1 is about 4 meters long. An electric motor 23 drives the drive drum, wherein a gear 24 is arranged between the motor 23 and the drive drum 21.

Figure 4 shows a measurement signal of a force transducer on the cylinder of the tail pulley 21 of Figure 1. In addition to the force signal shown as a solid line at the top of the graph, Figure 4 also shows the number of tape cycles, i. the number of revolutions of the tape. The corresponding line is the dashed line at the bottom of the diagram. As can be seen, the 111th and 112th cycles are shown in full length.

The conveyor belt 9 of Fig. 1 and 4 is intact, without cracks or cracks. The operating status shown in Fig. 4 is a linear acceleration of the conveyor belt. Accordingly, the cylinder force should simply show a linear increase. However, there are two irregularities in the form of peaks 27 in the force signal during the 111th cycle at times T1 and T2, and two irregularities in the form of peaks 28 occur at times T3 and T4 during the 112th cycle. As the inventors have recognized, these peak values are not exceptions but occur frequently and coincide with the passing of the splice point on the drive drum 20 or the deflection drum 21. In other words, the first of the two peaks 27 and 28 always occurs when the splice 26 passes the drive drum 20, and the second of the two peaks 27 and 28 indicates the passage of the tail pulley 21.

Other tests have shown that it is also possible to observe similar types of irregularities in the signals of the rotational speed and the electric current and torque of the motor.

FIGS. 5 to 7 show the results of long-term tests of the conveyor belt 9 of FIG. 1. Fig. 5 shows a series of frequency spectrums of the rotational speed n of the motor 23 generated at successive points over time t. In this specific example, each frequency spectrum was calculated about 30 minutes after the previous one, so that Fig. 5 covers a total period of about 2 days. The amplitude and frequency ranges are both adjusted so that the dominant amplitude of the actual motor frequency is not visible. A first series of significant amplitudes belongs to the frequency of rotation f1 of the conveyor belt 9, and a second series of even higher amplitudes belongs to the corresponding first harmonic f2, i. Referring to Fig. 4, it can be seen that the rotational frequency f1 corresponds to the time difference between the respective first one of the two peak values 27 and 28, i.e., the rotational frequency f1. is defined by the time the conveyor belt takes to pass one of the drums 20 and 21, respectively. The fact that the frequency of rotation f1 is so clearly visible in the frequency spectrum is due to the effect of the splice site described above.

Fig. 6 differs from Fig. 5 only in that the torque M of the motor 23 is shown instead of the rotational speed n. Here, the amplitudes at the rotational frequency f1 of the conveyor belt 9 and at its first harmonic f2 also stand out strongly.

It will now be explained with reference to Fig. 7, as the long-term tests of the conveyor belt 9 were performed. In Fig. 7 is a filtered speed signal n_filt and a filtered Dreh5 / 15

AT16 482U1 2019-10-15 of the motor 23 for successive periods of time, filtering with a bandpass filter for extracting the first harmonic f2 from the respective signals n and M, and the upper diagrams of each filtered signal, n_filt1 and M_filt1, both showing a first time period at the beginning of one of the tests, the graphs in the middle, n_filt2 and M_filt2, belong to a second time period in the middle of the test, and the respective lower graphs, n_filt3 and M_filt3, both a third Period near the end of the test show.

The general objective of the test was to place the conveyor belt under considerable mechanical stress to simulate severe operating conditions and to find out whether weakening the conveyor belt in measured operating variables of the motor 23 would be apparent. During the third period of Fig. 7, the conveyor belt 9 began to show marked signs of wear, and thereafter the test ended with the conveyor belt 9 starting to rupture.

As can be seen from the upper diagrams of n_filt and M_filt, the amplitudes in both signals increase and decrease cyclically, each cycle lasting approximately 50 seconds. This is due to an external force exerted periodically on conveyor 9 with an exact cycle time of 50 seconds to simulate cyclic loading on the belt.

It has been recognized that just before the conveyor belt begins to rupture, the amplitudes of n_filt and M_filt are significantly reduced, i. E. the amplitudes of the respective first harmonics f2 of the tape rotation frequency f1 are decreased, where these amplitudes are equal to the peak values in the rotation speed n and the torque M of the motor caused by the splice. This effect can be clearly seen not only in FIG. 7, but also in FIGS. 5 and 6, where the amplitudes of n and M decrease toward the end of the time axis t. A possible explanation for the reduced amplitudes is that the stiffness of the splice decreases with increased wear of the strip material, so that the mechanical impact on the drive and tail pulley is less strong.

Torque M and rotational speed n are mechanical operating variables of the motor 23. Since the torque M corresponds to the electric current, similar effects as described above have also been manifested in this electrical operating variable of the motor 23.

As the inventors have realized, due to the irregularities or peak values occurring in the sensor signals of the operating variables of the motor 23, these signals can be used for implementing a system and a method for monitoring the condition of the conveyor belt 9. Examples of the components of such a system are shown in FIGS. 2 and 3.

In Fig. 2 is a top view of the motor 23 and gear 24, which exert a force on the drive drum 20 of the conveyor belt 9 is shown. The motor 23 is a permanent magnet induction motor. For operating the motor 23, a frequency converter 12 is set up. During normal operation of the conveyor belt 9, the frequency converter 12 receives current signals 1 and 2 from a current sensor unit 13, the current signals 1 and 2 representing the stator currents of two of the three windings of the motor 23. From the two current signals 1 and 2, a processing unit 31 in the converter 12 derives a data signal 3 of the rotational speed n and a data signal 7 of the torque M of the motor 23 and determines signals for the voltages 32, 33, 34 which are applied to the three windings of the motor 23 should be created. The three voltages 32 to 34 are then generated by the power electronics part of the converter 12.

To implement a system and method for monitoring the condition of the conveyor belt 9, a further data processing unit 6 is arranged, which receives the data signals 3 and 7 of the rotational speed and the torque from the transducer 12. The data processing unit 6 recognizes in at least one of the data signals 3 and 7 the irregularities or peak values which indicate that the splice point 26 is the drive drum 20

6.15

AT16 482U1 2019-10-15 austriictiei iBlfrUril and / or the tail pulley 21 has happened. These irregularities or peaks are detected at multiple timings, so that a change in the shape or frequency of the irregularities can be detected, and from this change, it is determined whether or not the condition of the conveyor belt has changed. If the findings explained above with respect to FIGS. 4 to 6 are applied, the data processing unit 6 would detect an impending crack in the conveyor belt 9 from a reduction in the amplitude of the first harmonic f2 in the data signal 3 or in the data signal 7 or in both data signals or in corresponding frequency spectra. In a final step, the processing unit 6 sends a monitor output signal 30, which is preferably a data message, to at least one of a display unit, a storage unit, such as a datalogger or history server, and / or a decision making unit. The output signal 30 reflects the detected change in the state of the conveyor belt. For example, in the example of Figs. 4-6, the output signal 30 could be an alarm indicating that the rapid occurrence of a crack in the conveyor belt 9 is likely, or it could be a direct instruction to stop the conveyor belt 9 as soon as possible, and maintenance perform. The data signal 30 may be transmitted continuously, or only if a change in the state of the conveyor occurs.

In Fig. 2, an alternative drive concept of the drive drum 20 and alternative ways to obtain sensor signals of operating variables are shown in dashed lines. Instead of an engine and transmission, a gearless motor 22 mechanically coupled in direct connection with the shaft or cylinder of the drive drum 20 could be used. A sensor signal 36 of the rotational speed of the motor 22 is obtained by a speed encoder 10, and a sensor signal 37 of the torque by a torque transducer 11. These two signals 36 and 37 are transmitted to the frequency converter 12 where they are in the manner described above and processed and used for the purpose of controlling the motor 22. The processing unit 31 generates the data signal 3 of the rotation speed of the motor 22 from the sensor signal 36 and sends it to the processing unit 6. In contrast to the example described above with respect to the motor 23 with gear 24, the data signal 7 of the torque of the motor 22 by the processing unit 6 instead of being generated by the processing unit 31 of the converter 12 from the sensor signal 37. The data signals 3 and 7 are used again to monitor the condition of the conveyor belt 9 in the same manner as described above.

In addition to the operating variables of the motors 22 and 23, further sensor information may be used to improve the reliability and availability of the output signal 30 of the processing unit 6. For example, a vibration measurement unit 18 may provide a vibration sensor signal 17, wherein the vibration measurement unit 18 measures the vibration of a machine component mounted on the engine 23, such as the cylinder of the drive drum 20, the transmission 24, or a bearing in the shaft of the drive drum 20. In the vibration sensor signal 17, the passage of the splice 26 on one of the drums 20 or 21 can be seen in a manner similar to the operation variable of the motor 23.

Further sensor information that can be used by the processing unit 6 to improve the condition monitoring result is shown in FIG. Compared to Fig. 2, only the gearless motor 22 is shown together with the drive drum 20, this time in a side view. The conveyor belt 9 is arranged for further rotation about a tensioning drum 16 and a further deflection drum 25. The tensioning drum 16 is used for exerting a predefined tension on the conveyor belt 9, wherein the tension is achieved by a displacement of the tensioning drum 16. The displacement 38 is measured by a distance measuring unit 15 and supplied to the processing unit 6 as a displacement sensor signal 5. In addition, the tension 39 of the conveyor belt 9 can be measured by a force measurement 14 and transmitted as a belt tension sensor signal 4 to the processing unit 6.

In addition, the condition monitoring processing unit 6 may take into account an image sensor signal 8 provided by a radiation sensor 19 which

7/15

AT16 482U1 2019-10-15 culturally piktertei the conveyor belt 9 is observed.

All of these sensor signals can be obtained without requiring the inclusion of embedded sensor parts or elements in the conveyor belt, that is, all of these sensor methods are non-invasive and can be set up and implemented with significantly low cost.

Claims (13)

A conveyor belt condition monitoring system in which the conveyor belt (9) is arranged to rotate about at least one drive drum (20) and a tail pulley (21) and in which an electric motor (22, 23) is arranged driving the drive drum (20), the system comprising at least one data processing unit (6), at least one sensor unit (10, 11, 13), the at least one sensor unit (10, 11, 13) being arranged at least one Sensor signal (1, 2, 3, 7), which represents at least one operating variable of the electric motor (22, 23), and the at least one data processing unit (6, 31) is arranged to • from the at least one sensor signal (1, 2, 3, 7) derive at least one corresponding time-dependent data signal, • detect irregularities (27, 28) in the at least one data signal, • determine from a change in shape or frequency of the irregularities (27, 28) whether the condition of the conveyor belt has changed, and • to send a monitoring output signal (30) reflecting a change in the condition of the conveyor belt to at least one display unit, a storage unit and / or a decision making unit, characterized in that the at least one data processing unit (30) 6, 31) is arranged to detect irregularities (27, 28) in the at least one data signal indicating that a splice (26) of the conveyor belt (9) passes the drive drum (20) and / or the tail pulley (21) , 2. A system according to claim 1, wherein the at least one operating variable is either a voltage, a current (1, 2), a rotational speed (3), an acceleration, a torque (7) or a force. 3. System according to claim 1 or 2, wherein the at least one sensor unit (10, 11, 13), a current and / or voltage sensor (13), a speed pulse generator (10), a torque transducer (11) or is a force transducer. A system according to any one of the preceding claims, wherein the at least one data signal represents an amplitude over time or a frequency spectrum. A system according to any one of the preceding claims, wherein the at least one data processing unit (6) is an independent processing device and / or integrated component of an electrical transducer (12) in which the transducer is connected to the electric motor (22, 23) and arranged to supply this with a current and / or a voltage. A system according to any one of the preceding claims, wherein the at least one data processing unit is arranged to determine whether the condition of the conveyor has changed by determining the shape and / or frequency of the irregularities having a corresponding threshold or shape and frequency of a reference irregularity or by using a model-based state observer. A system according to any one of the preceding claims, wherein the at least one data processing unit is arranged to detect a change in the shape of the irregularities from a change in the amplitude level and / or a change in the width of the peak values of the irregularities. A system according to any one of the preceding claims, wherein the at least one sensor unit is arranged to provide a first sensor signal (3) and a second sensor signal (7) each having first (n) and second (M) operating variables of the electric motor represent and determine, and wherein the at least one data processing unit (6) is arranged to derive corresponding first and second data signals and Irreg9 / 15 AT16 482U1 2019-10-15 cially, either in the first data signal (3) to determine when the corresponding operating variable (s) of the electric motor is controlled to follow a first reference variable, or in the second data signal (7) determine when the corresponding operating variable (M) of the electric motor is controlled to follow a second reference variable. A system according to any one of the preceding claims, wherein the at least one data processing unit is arranged to detect a change in state of the conveyor belt by taking into account a vibration sensor signal (17) transmitted from a vibration measuring unit (18) detecting the vibration of a conveyor belt measures provided on the electric motor machine component, is provided. A system according to any one of the preceding claims, wherein the conveyor belt is arranged to rotate about a tension drum (16) and wherein the at least one data processing unit is arranged to detect a change in state of the conveyor belt by providing a displacement sensor signal (5) provided by a distance measuring unit (15) which measures the displacement of the tensioning drum (16). A system according to any one of the preceding claims, wherein the at least one data processing unit is arranged to detect a change in the condition of the conveyor belt by taking into account a belt tension sensor signal (4) provided by a force measuring unit (14). A system according to any one of the preceding claims, wherein the at least one data processing unit is arranged to detect a change in state of the conveyor belt by taking into account an image sensor signal (8) received from a radiation sensor (19) monitoring the conveyor belt , provided. 13. A method for monitoring the condition of a conveyor belt, wherein the conveyor belt (9) is arranged to rotate about at least one drive drum (20) and a tail pulley (21) and in which an electric motor (22, 23) is arranged drive the drive drum (20), comprising the steps of: determining at least one sensor signal (1, 2, 3, 7) representing at least one operating variable of the electric motor (22, 23), deriving at least one corresponding time-dependent data signal from the at least one Sensor signal (1, 2, 3, 7), detection of irregularities (27, 28) in the at least one data signal, determination of whether the condition of the conveyor belt has changed, of a change in shape or times (T1 to T4 ) of the irregularities (27, 28), • transmission of a monitoring output signal (30), which reflects a change in the state of the conveyor belt, to at least one display unit, a storage unit and / or a decision making unit, characterized by the step of detecting irregularities (27, 28) in the at least one data signal indicating that a splice point (26) of the conveyor belt (9) drives the drive drum (20) and / or the tail pulley (12). 21) happened. For this 5 sheets of drawings