AU2006337950A1

AU2006337950A1 - Method for monitoring and/or testing without destruction a transmission element, and measuring arrangement for carrying out the method

Info

Publication number: AU2006337950A1
Application number: AU2006337950A
Authority: AU
Inventors: Manfred Baumler; Uwe Boker; Manfred Ziegler
Original assignee: RWE Power AG
Current assignee: RWE Power AG
Priority date: 2006-02-10
Filing date: 2006-12-02
Publication date: 2007-08-16
Anticipated expiration: 2026-12-02
Also published as: ES2331631T3; EP1981788A1; AU2006337950B2; EP1981788B1; DE102006006468A1; CN101365637A; CN101365637B; WO2007090449A1; DE502006004765D1; PL1981788T3; ZA200806395B; ATE441608T1

Abstract

The invention relates to a method for monitoring and/or testing without destruction a transmission element having at least one magnetizable tie beam, and to a measuring arrangement for carrying out the method. The method is distinguished by the fact that a single-axis or multiple-axis measurement of the magnetic field which is disrupted by the tie beam is carried out, by at least one magnetic field sensor or an arrangement of a plurality of magnetic field sensors being guided relative to the transmission element or by the transmission element being guided relative to the measuring arrangement, and by the detected measured signals being evaluated by way of a data acquisition and evaluation device, preferably with regard to an anomaly of the detected magnetic field.

Description

Australia VERIFICATION OF TRANSLATION I, Michael Wallace Richard Turner, Bachelor of Arts, Chartered Patent Attorney, European Patent Attorney, of 1 Horsefair Mews, Romsey, Hampshire SO51 8JG, England, do hereby declare that I am the translator of the attached specification in the German language of International Application PCT/EP2006/011579 and I state that the following is a true translation to the best of my knowledge and belief. M W R Turner Signed this Z11liay of May 2008 Method of monitoring and/or non-destructive testing of a transmission element and a measuring arrangement for carrying out the method The invention concerns a method of monitoring and/or non 5 destructive testing of a transmission element comprising at least one magnetisable tensile carrier. DE 199 21 224 Al discloses a method of monitoring an endlessly circulating conveyor belt having steel cord tensile carriers. The method includes using at least one metal detector for sensing the belt movement, 10 with which a measurement signal produced by the belt is continuously detected over the entire belt length. In a first belt revolution or a first belt sensing operation over the entire length thereof, a reference signal is acquired, which is stored in the form of a belt-specific signal. Monitoring of the belt member is effected by continuously comparing the reference signal 15 to the measurement signal, in the sense of a reference/actual comparison. With that method recording and storing a reference signal over the entire length of the conveyor belt provides for the production and storage of a belt-specific induction pattern (fingerprint), from which the positional location, the signal level and the signal shape of the load-carrying elements 20 disposed in the conveyor belt, that is to say the steel cord tensile carriers, can be determined. Damage to the steel cord tensile carriers can be comparatively effectively detected on the basis of a reference/actual comparison between the reference signal stored in that fashion, and the continuously acquired measurement signal. Suitable measures can then be 25 initiated to take the belt conveyor installation out of operation and to perform maintenance operations. That method is carried out with a metal-seeking coil arrangement, wherein the magnetic field of the coil through which current flows is altered when the metallic cross-section of the enclosed conveyor belt changes. 30 In practice it has been found that such a metal-seeking coil can be used only in the lower run of the belt conveyor as the material being conveyed has an interfering influence on the measurement result. In addition only a limited level of resolution is to be achieved with such a 2 measuring arrangement as the measurement signals are integrated over the belt width. Furthermore the sensitivity of the metal-seeking coils is not homogenous in regard to the location of the damage. Thus for example damage in the edge region of the belt is not recognised or is recognised too 5 late. By virtue of the required arrangement of the metal-seeking coil in the lower run of the belt conveyor, damage caused by violent force to the belt is detected comparatively late. It would be important in that respect to detect for example holes through the belt at the locations in the upper run 10 at which material delivery thereonto is effected. Finally the measuring arrangement itself is comparatively expensive and complicated in terms of assembly, the latter for the reason that the metal-seeking coil must completely enclose the belt. Therefore, to detect individual cable cord tears, the procedure has 15 hitherto been such that a prestressed cable is passed below the belt transversely with respect to the direction of belt movement at a small spacing relative to the belt and connected to limit switches. A cable or a tongue portion which is hanging down is caught in the prestressed cable and actuates the limit switches, thereby causing the belt to be switched off. 20 The cables are stretched across the belt immediately downstream of the material delivery location in the upper run (transfer) or downstream of the discharge drum. Response on the part of that system requires that the damage has already assumed a certain level so that the prestressed cable is engaged 25 thereby. A hanging cable or a tongue portion is further stressed at each support roller station, and that leads to an ongoing increase in the amount of damage. If, between two such monitoring devices, the damage develops to such a pitch that the tongue portion or the hanging cable hooks on a support roller station or other elements of the structure, that can result in 30 an extended longitudinal tear, in spite of the monitoring device. Therefore, in spite of the monitoring devices already described above, there is still the aim of reliably detecting belt damage when already at an early time, that is to say in the damage-originating phase in order to 3 be able to switch off the installation in good time. Hitherto there is to date no system which sufficiently satisfactorily automatically detects the state of the belt in order to be able to repair or replace the belt at the optimum moment. 5 Therefore the object of the invention is to provide a method of monitoring and/or non-destructive testing of a transmission element such as for example a belt or the like, which does not suffer from the above mentioned disadvantages. A further object of the invention is to provide a measuring 10 arrangement for carrying out such a method. That object is attained by a method of monitoring and/or non destructive testing of a transmission element having at least one magnetisable tensile carrier, wherein a single-axis or multi-axis measurement of the magnetic field disturbed by the tensile carrier is 15 carried out by a procedure wherein at least one magnetic field sensor or an arrangement of a plurality of magnetic field sensors is guided relative to the transmission element or the transmission element is guided relative to the measuring arrangement and the detected measurement signals are evaluated with a data acquisition device, preferably in regard to anomalies 20 in the detected magnetic field. As the method according to the invention manages without a coil arrangement but only provides for the use of magnetic field sensors, it is possible to carry out a measurement operation at any location on the belt circulation, for example when monitoring a circulating belt of a bulk 25 material conveyor. There is no need for the conveyor belt to be embraced with the measuring arrangement. The measurement signal is not disturbed by the material being conveyed as long as no ferromagnetic material is being conveyed. The measurement signal is independent of the direction of travel and speed. 30 Preferably the measurement operation is carried out without magnetisation of the tensile carrier, that is to say without separate external magnetisation. The magnetic field sensors register disturbances in the natural magnetic field of the earth by virtue of the presence of 4 ferromagnetic substances. Such sensors are extremely compact and can be arranged in mutually juxtaposed relationship in virtually any number. Preferably the measurement operation is carried out in a measurement range (sensitivity range) of up to 200 T, preferably up to 5 100 T. The signal strength of the signals to be measured is about +/- 50 4T. In a preferred variant of the method according to the invention the measurement operation is carried out on a belt of a belt conveyor of rubber-elastic material with steel cables embedded therein as the tensile 10 carrier. The method according to the invention however is to be interpreted in such a way that monitoring and/or testing of any circulating or oscillating transmission element with or comprising magnetisable tensile carriers is possible. By way of example it is possible to implement non destructive cable testing of a steel cable by means of magnetic field 15 detection instead of the previously known radiological inspection or inductive detection of damage. Any damage to individual cable strands causes a change in the magnetic field lines which are detected by magnetic field sensors. The measurement operation is preferably effected in a three axis mode and can be carried out for example by means of one or more 20 Forster probes. Detection of the magnetic field produced by the article to be measured can be effected both dynamically and also statically. It will be appreciated that it is possible for the signal which is to be measured to be boosted by separate external magnetisation. Such 25 separate external magnetisation however is not absolutely necessary. In accordance with the invention it is provided that the reference position of the tensile carriers in the belt is tested by way of the magnetic field measurement operation. In that way it is possible to implement quality testing of the belt used, possibly already at a time prior to 30 installation thereof in the belt conveyor apparatus. By virtue of the signal produced by each tensile carrier it is possible to detect the position or the tensile carriers of a belt relative to each other comparatively precisely.

5 In that way it is possible not only to identify the reference position of the tensile carriers relative to each other, but rather it is also possible to detect any skewed running of the belt, whereby it is possible in good time to prevent the belt running into the structural components of the belt 5 conveyor as a consequence of skewed running. Calibration of the measuring arrangement can be effected by detecting a reference signal of the transmission element in question or another transmission element in a defined condition. Alternatively or additionally to material testing with the above 10 described method it is provided that the measurement operation is effected during operation of the belt conveyor for the purposes of monitoring thereof. In addition the measurement operation can be used for ascertaining the speed of the belt. The step of ascertaining the speed of the belt can be 15 effected for example by continuous comparison of one or more reference signals detected in a first belt circulation with one or more measurement signals. Desirably the width of the belt is sensed in a plurality of belt circulations. That means that the measuring arrangement can be of a 20 comparatively simple configuration. The aforementioned object is further attained by a measuring arrangement for monitoring and/or non-destructive testing of a transmission element having at least one magnetisable tensile carrier, wherein the measuring arrangement includes one or more, preferably 25 multi-axis magnetic field sensors which are arranged at a spacing relative to the transmission element in such a way that the magnetic field which is disturbed by the tensile carrier can be detected as a measurement signal. A preferred embodiment of the measuring arrangement can further include at least one data acquisition and evaluation device. 30 The measuring arrangement can be stationarily provided on a belt conveyor. Preferably provided over the width of the belt is a number of n sensors at a spacing from each other which approximately corresponds to 6 the spacing of the tensile carriers of the belt from each other. In that way a measurement operation affords information about the condition of each tensile carrier in the belt. In a variant of the measuring arrangement according to the 5 invention it is provided that the sensors are arranged beneath the belt in the upper run of the belt conveyor. They can and should all be arranged at the same spacing relative to the belt. It is particularly desirable if the sensors are arranged to follow the 10 contour (trough configuration) of the belt. They can be disposed for example in the form of a per se known garland at the underside of the belt. As already mentioned hereinbefore the overall width of the belt does not have to be covered by sensors, rather it may be desirable if a number 15 of n-sensors is arranged on a support structure displaceable over the width of the belt. The support structure can then be respectively displaced for one or more belt revolutions over the width of the belt so that the overall cross-section of the belt can be detected for a measuring process in a plurality of revolutions of the belt. That arrangement also has the 20 advantage that it is possible to set any desired tracking position for the sensors. For carrying out material testing operations prior to installation or prior to vulcanisation of belts it may be desirable to mount the measuring arrangement on a hand truck with which then a stationarily arranged or 25 spread-out belt can be movably negotiated and sensed. For punctiform inspection of a belt it may be desirable for the measuring arrangement to be in the form of a portable measuring and detection device (hand scanner). The invention is described hereinafter by means of an embodiment 30 by way of example as illustrated in the drawings, more specifically using the example of monitoring a belt conveyor. In the drawings: 7 Figure 1 shows a diagrammatic, greatly simplified view of a belt conveyor with a measuring arrangement according to the invention, Figure 2 shows a part of the measuring arrangement mounted in the top run of the belt conveyor, 5 Figure 3 shows a view of a measuring arrangement provided for stationary mounting to a belt conveyor, Figure 4 shows a view from below of the top run of the belt conveyor with a measuring arrangement according to the invention, Figure 5 shows a perspective view of the Figure 4 measuring 10 arrangement on a belt conveyor, and Figure 6 shows a diagrammatic measurement record of a measurement operation on a belt in accordance with the method of the invention. As already mentioned hereinbefore the method and the measuring 15 arrangement according to the invention are described hereinafter only by way of example for monitoring a belt conveyor for the transport of bulk material. Such a belt conveyor 1 includes a circulating belt 2 of rubber-elastic material with steel cables embedded therein as a tensile carrier. The belts 20 2 which are frequently used in belt installations in brown coal open-cast mines comprise rubber and are approximately of a width of 2800 mm. Steel cables of a diameter of 9.2 mm are vulcanised into the rubber, at a pitch of 15 mm. A belt of the width of 2800 mm contains 165 steel cables. Such a steel cable conveyor belt has a nominal strength St 4500. The 25 service life of the belt is on average between about 6 and 7 years. Service life-determining factors are damage to the belt due to material impinging thereon at the transfer location, the belt running into structural components as a consequence of skewed running thereof, overstretching of the steel cables by virtue of material being caked on the drums as well as 30 frictional wear at the longitudinal seals. A belt conveyor 1 is shown in greatly simplified diagrammatic form in Figure 1. It includes the endlessly circulating belt 2 of rubber with steel cables which are vulcanised thereinto, a drive drum 3 and one or more 8 guide drums 4, between which the belt 2 is tensioned. The belt 2 forms a top run 5 (load run) and a lower run 6 (idle run), wherein the belt 2 is held by support rollers 7 both in the top run and also in the lower run. The support rollers 7 are suspended on a support frame structure (not shown). 5 Reference 8 denotes a delivery chute, by way of which the bulk material is delivered onto the belt 2. It will be appreciated that the trough configuration of the belt 2 is greater in the top run than in the lower run 6. In addition the spacing of the support rollers 7 relative to each other is shorter at least in the region of the chute 8 than in the lower run 6. 10 In the embodiment shown in Figure 1 the circulatory belt travel is in the clockwise direction. A measuring arrangement 9 according to the invention is arranged in the top run 5 beneath the belt 2 immediately downstream of the chute 8 in the direction of circulatory movement of the belt. The measuring arrangement 9 includes a number of magnetic field 15 sensors 10 which are positioned in mutually juxtaposed relationship and which are fixed relative to each other and which in the described arrangement are in the form of F6rster probes. As can be seen in particular from Figure 2, the embodiment illustrated therein provides that the magnetic field sensors 10 are combined 20 to form a sensor packet. The sensor packet 11 includes a predetermined number of magnetic field sensors arranged in mutually juxtaposed relationship at equal spacings. The sensor packet can be arranged for example in the tubular guide passage 12 shown in Figure 2 beneath the belt, protected from dirt and weather influences. The length of the sensor 25 packet 11 is different from the belt width, the sensor packet is displaced for a respective one or more belt circulations in the guide passage 12 so that the width of the belt 2 is sensed in a plurality of measurement cycles. In the illustrated embodiment 6 magnetic field sensors 10 are combined to form a sensor packet 11, the spacing of the magnetic field sensors 10 from 30 each other being about 70 mm, which is wider than the spacing of the steel cables in the belt 2 from each other. By virtue of displacement of the sensor packet 11 in the guide passage 12 however it will be noted that it is possible to achieve any desired resolution in the measurement operation for 9 it is desirable to acquire a measurement signal for each steel cable in the belt 2. The sensor packet 11 can be arranged on a carriage which is displaceable with a linear drive. Alternatively it is possible, at a location beneath the belt, to arrange a plurality of sensor packets in mutually 5 juxtaposed relationship in order to be able to arrange the sensors at a spacing which is as uniform as possible relative to the belt even when the belt is of a severely trough-shaped configuration. The sensor packet 11 and each individual magnetic field sensor 10 within the sensor packet 11 are connected to a data acquisition and 10 evaluation device 13 only diagrammatically shown in the Figures. In the simplest case this can be a PC with a corresponding number of analog signal inputs. In the embodiment shown in Figures 4 and 5 a total of three sensor packets 11 of different sizes are suspended in the manner of a garland 15 beneath the belt 2 in the top run 5 of the belt conveyor 1, wherein the sensor packet 11 is held by means of guide rollers 14 against the belt 2 to achieve a uniform spacing of the magnetic field sensors 10 relative to the belt 2. That permits precise sensing of the belt 2 over the entire width thereof, up to the edges. A uniform spacing in relation to the belt 2 can be 20 maintained, even when the belt 2 is of a severely trough-shaped configuration, by virtue of the particular arrangement of the sensor packets. Figure 6 shows a measurement of a belt portion, in which the belt width is plotted on the ordinate and the belt length on the abscissa. The 25 individual signals are approximately straight when undisturbed, deflections are to be seen where the tensile carriers of the belt 2 are damaged. The measuring method according to the invention is highly sensitive so that tensile carriers suffering from incipient corrosion already produce a comparatively marked change in the measurement signal.

10 List of references 1 belt conveyor 2 belt 3 drive drum 5 4 guide drum 5 top run 6 lower run 7 support rollers 8 chute 10 9 measuring arrangement 10 magnetic field sensors 11 sensor packet 12 guide passage 13 data acquisition and evaluation device 15 14 guide rollers

Claims

1. A method of monitoring and/or non-destructive testing of a transmission element having at least one magnetisable tensile carrier, wherein a single-axis or multi-axis measurement of the magnetic field disturbed by the tensile carrier is carried out by a procedure wherein at least one magnetic field sensor or an arrangement of a plurality of magnetic field sensors is guided relative to the transmission element or the transmission element is guided relative to the measuring arrangement and the detected measurement signals are evaluated with a data acquisition device, preferably in regard to anomalies in the detected magnetic field.

2. A method according to claim 1 characterised in that the measurement operation is carried out without magnetisation (separate external magnetisation) of the tensile carrier.

3. A method according to one of claims 1 and 2 characterised in that the measurement operation is carried out in a measurement range of up to 200 iT, preferably up to 100 pT.

4. A method according to one of claims 1 to 3 characterised in that the measurement operation is carried out on a belt of a belt conveyor of rubber-elastic material with steel cables embedded therein as the tensile carrier.

5. A method according to claim 4 characterised in that the reference position of the tensile carriers in the belt is tested by way of the magnetic field measurement operation.

6. A method according to one of claims 1 to 5 characterised in that calibration of the measuring arrangement is effected by detecting a reference measurement signal of the transmission element in question or another transmission element in a defined condition.

7. A method according to claim 5 characterised in that the measurement operation is effected during operation of the belt conveyor. 12

8. A method according to one of claims 5 and 7 characterised in that the measurement operation is used for ascertaining the speed of the belt.

9. A method according to claim 1 characterised in that the speed is ascertained by continuous comparison of one or more reference signals detected in a first belt circulation with one or more measurement signals.

10. A method according to one of claims 5 to 9 characterised in that the width of the belt is sensed in a plurality of belt circulations.

11. A measuring arrangement for monitoring and/or non-destructive testing of a transmission element having at least one magnetisable tensile carrier, wherein the measuring arrangement includes one or more, preferably multi-axis magnetic field sensors (10) which are arranged at a spacing relative to the transmission element in such a way that the magnetic field which is disturbed by the tensile carrier can be detected as a measurement signal.

12. A measuring arrangement according to claim 11 characterised in that it further includes at least one data acquisition and evaluation device (13).

13. A measuring arrangement according to one of claims 11 and 12 characterised in that it is stationarily provided on a belt conveyor (1).

14. A measuring arrangement according to claim 13 characterised in that over the width of the belt (2) it has a number of n-sensors at a spacing from each other which approximately corresponds to the spacing of the tensile carriers of the belt (2) from each other.

15. A measuring arrangement according to one of claims 11 to 14 characterised in that the sensors are arranged beneath the belt (2) in the upper run (5) of the belt conveyor (1).

16. A measuring arrangement according to one of claims 13 to 15 characterised in that the sensors are arranged at an equal spacing relative to the belt (2). 13

17. A measuring arrangement according to one of claims 15 and 16 characterised in that the sensors are arranged to follow the contour (trough configuration) of the belt (2).

18. A measuring arrangement according to one of claims 11 to 17 characterised in that a number of n-sensors is arranged on a support structure or a carriage displaceable over the width of the belt (2).

19. A measuring arrangement according to one of claims 11 and 12 characterised in that it is arranged on a hand truck.

20. A measuring arrangement according to claim 11 characterised in that it is in the form of a portable measuring and detection device (hand scanner).