AU2016202263A1 - Belt wear profile measurement - Google Patents

Abstract

An apparatus and associated method is disclosed for assessing remaining carry cover thickness of a steel cord conveyor belt (1) without interrupting normal operations. The apparatus is positioned adjacent to a tail pulley (2) at an unloaded point. The apparatus uses ultrasonic or inductive sensors (9) for measuring remaining cover thickness as claimed in Australian Patent Application No. 2012 216 769. The sensors (9) are mounted on a carriage (7) that is driven along a linear slide (3) by a servo motor (16), and scan in a direction transverse to the operating belt (1), the scan sweeping out a zig-zag path along the belt due to lateral belt wander and longitudinal motion. The carriage (7) is controlled by a microprocessor (20), which receives and records signals from the remaining cover thickness sensors (9), a carriage absolute displacement sensor (14), a belt lateral position indicator (21), a belt speed tachometer (22), a splice detector (23), and a belt section RFID reader (35). The recorded signals are analysed to correlate sensor readings with lateral and longitudinal positions on the belt (1) and its constituent belt sections. Related readings are then averaged into representative profiles of remaining cover thickness, and used, inter alia, for forecasting serviceable belt life. 5004N-AU 2/d 0-

Description

1

BELT WEAR PROFILE MEASUREMENT

Field of the Invention

The present invention relates to conveyor belts and, in particular, to conveyor belts having rubber covers either side of steel reinforcing cords. Such steel reinforced conveyor belts are widely used in bulk materials handling.

Background Art

In hard rock mining, in particular, such steel reinforced conveyor belts have a relatively short life compared, for example, with the operating life where such belts are used to transport coal. The reason for this is that hard rock materials such as iron ore, copper ore and bauxite are particularly dense and abrasive and thus the carry cover of the belt is worn in use. However, it is virtually impossible for the carry cover of a belt to wear uniformly across the full belt width. Certain lateral locations may not wear at all since typically the extreme outer edge or side regions of the belt never carry any product or load. Typically covers that do wear take on a characteristic transverse “wear profile” depending upon the nature of their duty.

It is very desirable for operational and budgetary reasons to be able to effectively predict when a steel reinforced conveyor belt will reach the end of its operational life.

Genesis of the Invention

The Genesis of the present invention is a desire to increase the accuracy of such predictions.

For many conveyor belts, the belt is used in the same way day in and day out and thus the rate of wear, and the location of the maximum wear, is substantially predictable. However, particularly in port facilities, many conveyor belts are used in different ways on different occasions. This may involve blending of different materials, loading materials from different sources to different destinations, using multiple load points on the same conveyor which necessitates side loading and other complex loading geometries, and the like. Under these circumstances, a hypothesis upon which the present invention is to some extent founded, is that the rate of wear and the location of

5004N-AU 2 the maximum wear are not fixed but can vary. As a consequence, the prediction of expected belt life under these circumstances is much more complicated.

For many years attempts have been made to measure various conveyor belt parameters. These measurement activities can be divided into two distinct groups. The first group requires that the belt be stopped in order for the measurement to take place. This is highly undesirable since most belts run 24 hours per day, 7 days a week, apart from scheduled maintenance shutdowns of short duration and all downtime represents a significant financial loss to the belt operator. The second group enables measurements to be taken whilst the belt is in normal operation and such measurements are infinitely more desirable than those of the first group.

Prior art first group measurements involve manual measurement of the belt cover thickness, for example, which is the distance between the surface of the cover and the upper surface of the steel reinforcing cords. These measurements are done manually using hand-held instruments.

Prior art second group measurements involve directing a laser or ultrasonic probe at the unloaded surface of the cover as the belt passes over an idler roller or pulley. This measurement measures the overall thickness of the belt. Such measurements do not measure the remaining thickness of the cover which is the distance between the upper surface of the cover and the upper surface of the steel reinforcing cords.

Just recently a measurement technique which enables the remaining cover thickness of the carry or “working” cover, for example, to be measured at a given lateral location, with the belt running, has been discovered. This measurement technique is described in Australian Patent Application No 2012 216 769 the contents of which are incorporated into the present specification for all purposes. The applicant in respect of the above-mentioned patent applicant is also the applicant of the present application. As at the priority date of this application, there have been no sales of the apparatus disclosed in the above-mentioned patent application in Australia, nor has there been any commercial use in Australia of the methods disclosed in the above-mentioned patent application.

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However, the above-mentioned measurement technique enables the remaining cover thickness to be measured across a very small portion of the width of the belt, typically 80-90mm compared to a total belt width of up to 2 metres, and more.

In theory, it would be possible to duplicate the apparatus of the above-mentioned patent application approximately 20-25 times and thereby be able to measure the remaining carry cover thickness across the entire width of the belt. However, since the ultrasonic and inductive sensors used in the above-mentioned apparatus are not inexpensive, such a duplication or replication is prohibitively expensive.

Summary of the Invention

In accordance with a first aspect of the present invention there is disclosed a method of determining remaining carry cover thickness in a steel cord conveyor belt whilst the belt is moving, said method comprising the steps of: mounting an apparatus as claimed in any one of claims 4-8 of Australian Patent Application No. 2012 216 769 to be moveable transversely across the carry cover at an unloaded location on said belt, moving said apparatus from one side of said belt to the other whilst taking a series of remaining cover thickness measurements to thereby measure remaining cover thickness at a first plurality of locations spaced apart along a diagonal line notionally drawn across said belt.

In accordance with a second aspect of the present invention there is disclosed a method of predicting the expected date at which the carry cover of a steel cord conveyor belt will reach the end of its working life, said method comprising the steps of: determining an average belt cover profile on a plurality of occasions in order to determine the change in average belt cover profile with time, and extrapolating said change to predict when a predetermined minimum acceptable belt cover thickness will be reached.

According to another aspect of the present invention there is provided an apparatus for determining remaining carry cover thickness of a moving steel cord conveyor belt extending between a tail pulley and a discharge pulley, said apparatus comprising:

5004N-AU 4 the apparatus as claimed in any one of claims 4-8 of Australian Patent Application No. 2012 216 769 mounted for transverse movement from one side of said belt to the other side of said belt at a location where said belt is unloaded.

Brief Description of the Drawings A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is an end elevation of the tail pulley which supports a steel cord conveyor belt,

Fig. 2 is a side elevation of the apparatus of Fig. 1,

Fig. 3 is a plan view of the linear slide illustrated in Figs. 1 and 2,

Fig. 4 is a side elevation of the linear slide of Fig. 3,

Fig. 5 is a schematic block diagram of the processor controller,

Fig. 6 is a schematic representation of measurement locations,

Fig. 7 is a sequence of three graphs each illustrating an average remaining cover profile, and

Fig. 8 is a transverse average cover wear profile.

Detailed Description

The method and apparatus of the preferred embodiment to be described hereafter are based upon a realisation that if a transverse remaining cover thickness profile can be determined, then the location of the thinnest carry cover across the belt can be ascertained. Once this location is known, the single apparatus described in the above-mentioned patent application can then be positioned at this location. Thereafter the resulting measurements of the remaining carry cover thickness at the location of minimum remaining carry cover thickness, can be used to accurately predict the remainder of the belt life, where loss of cover is the deciding factor. This is because the belt will wear out when the thinnest remaining carry cover thickness reaches the minimum operational thickness. In practice this minimum operational thickness is approximately zero and will become apparent when the steel cords of the belt become visible through the carry cover.

Turning now to Figs. 1 and 2, a conveyor belt 1 passes over a tail pulley 2. In operation, the conveyor belt 1 can wander from left to right and right to left across the

5004N-AU 5 tail pulley 2. Mounted above the tail pulley 2 is a linear slide 3 which includes a cross bar 4 mounted between a pair of supports 5. The longitudinal axis of the crossbar 4 is mounted so as to be parallel to the axis of the tail pulley 2. In this way the crossbar 4 is in a plane which is parallel to the plane containing the reinforcing cords (not illustrated) of the conveyor belt 1. In addition, the crossbar 4 is perpendicular to the reinforcing cords.

The linear slide 3 includes a carriage 7 upon which is mounted the remaining cover thickness (RCT) sensor 9 being the apparatus disclosed in the above-mentioned Australian patent application. As seen in Fig. 3, the carriage 7 is mounted between a pair of concertina rubber boots 11, 12 and includes an absolute displacement sensor 14. Such a sensor can be fabricated using barcodes arranged in strips or an optical shaft encoder which detects pulses generated by the rotation of a shaft driven by a servo motor 16 and a reduction gearbox 17. The absolute displacement sensor 14 enables the instantaneous position of the carriage 7 on the slide to be known precisely.

It will be apparent to those skilled in the mechanical arts that the above-mentioned arrangement enables the servo motor 16 to be driven so as to move the RCT sensor 9 from left to right across the conveyor belt 1 and back again. The linear slide 3 produces very smooth uniform single plane movement of the carriage 7 and its RCT sensor 9. Various mechanisms are available to achieve this including a toothed belt and sprocket, a screw feeder, or a dial cord. Such mechanisms are located within the rubber boots 11, 12.

The linear slide 3 preferably over spans the conveyor belt 1 which therefore caters for belt wander. The linear slide 3 is orientated parallel to the plane of the conveyor belt and at right angles to the direction of travel of the conveyor belt and is securely mounted on the conveyor belt structure itself, by two supports 5 which allow for very precise and stable positioning above the belt surface being measured. If it is the carry cover of the belt 1 which is to be measured, as is usually the case, the linear slide 3 is ideally positioned just after, and close to, the tail pulley 2. At this location the belt 1 is substantially in a single plane and substantially free from vibration and flapping.

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The movement of the carriage 7 is controlled by a microprocessor 20 as illustrated in Fig. 5. The microprocessor 20 receives inputs from a number of different devices including a lateral position indicator (LPI) 21, a tachometer 22, a splice detector 23 and a high resolution surveillance camera 24. As schematically illustrated in Fig. 2, the lateral position indicator 21 is fitted to the conveyor structure and determines the lateral position of the conveyor belt 1 on the conveyor structure. The tachometer 22 is fitted to, and is driven by, the conveyor belt 1 and consequently measures belt speed and longitudinal position along the belt path.

The splice detector 23 is located in the belt return strand and outputs a signal when a splice passes it. This detector is needed to eliminate measurement anomalies occurring in the data as splice cover thickness is measured, as opposed to the desired measurement of the thickness of the “parent” belt cover.

The camera 24 is attached to the conveyor structure and is framed to view the scanning location and the belt being measured. Images from the camera are available in real time over the Internet utilising either a modem 26 incorporated into the microprocessor 20 and an associated aerial 27, or a site network 29 which incorporates a Ethernet port, for example. A number of measurement voltages are generated. The first of these (VI) is generated by the RCT sensor 9 and represents the finite cover thickness in mm. The second measurement voltage (V2) is generated by the absolute displacement sensor 14 and represents the location in mm of the RCT sensor 9 on the linear slide 3. This is always a positive value beyond a home base position, which is designated as zero. The third measurement voltage (V3) is generated by the lateral position indicator 21 and represents the lateral position in mm of the conveyor belt 1 on its structure. This voltage can be either positive or negative depending upon whether the belt 1 is wandering to the left or to the right, for example. This voltage is set to zero when the belt 1 is centred on the tail pulley 2. A fourth voltage (V4), in the form of a sequence of pulses, is generated by the tachometer 22 and is used to determine the longitudinal position in mm of the belt in the belt path. All these measurement voltages are delivered to the microprocessor 20 which incorporates non-volatile memory 33.

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Preferably before a measurement is commenced, the image being streamed by the surveillance camera 24 is reviewed to ensure the conveyor belt 1 upstream of the RCT sensor 9 is clean. Any carry back of product will give rise to noisy data so it is desirable to know that the belt 1 is reasonably clean before initiating a scan. In this connection rain falling on the conveyor belt 1 is one way of cleaning the belt. Another way of cleaning the belt 1 is to apply a high-pressure water or air hose to the conveyor belt 1 prior to and in the vicinity of the tail pulley 2.

Prior to commencing a scan, the RCT sensor 9 is located in its fully left or “home base” position. The sensor is located vertically so that when it executes its lateral travel above the belt, the sensor will be 30-40mm above the tops of the steel cords.

When the sensor 9 is parked in its home base location, it is positioned above a small rectangular sample of the belting being scanned. This sample is permanently fixed to the supporting structure of the conveyor belt and has a known cover thickness. This thickness has previously been established using a hand-held device, or by other means, and does not change since the sample does not experience any wear. The sample allows the RCT sensor 9 to verify that it is producing a correct cover thickness value prior to a scan. In this way, the sensor 9 can be calibrated and can be remotely known to be calibrated.

With a clean conveyor belt 1 and with the conveyor belt 1 running, the carriage 7 is driven from left to right and then from right to left for its full travel across the linear slide 3. This movement over spans the belt 1 on both sides. This produces a continuous sequence of zigs and zags as illustrated in Fig. 6. As a consequence, a measurement is taken at each of a series of spaced apart locations Ml, M2, M3, etc. spaced along a diagonal line D1 notionally drawn across the conveyor belt 1. As the carriage 7 reverses, a second sequence of measurements is taken at each of a series of spaced apart locations M7 - M12. Then the procedure is repeated resulting in measurements being taken at each of locations M13 - M18, and then at location M19, and so on.

The speed of the carriage 7 can be controlled so that preferably at least one complete pass (i.e. left to right or right to left) is achieved in every belt section between

5004N-AU 8 adjacent belt splices. Such belt sections can typically vary in length between 15 m and 750 m. Preferably, a number of radiofrequency identity (RFID) tags 32 are implanted into the body of the conveyor belt 1 at the location of each splice. The tags 32 are detected by an RFID reader 35 as the tags 32 pass the reader 35. The belt path distance in mm between the RFID reader 35 and the RCT sensor 9 is noted as a longitudinal offset. The output of the RFID reader 35 is delivered to the microprocessor 20. Each RFID tag 32 is assigned a unique identification number during its manufacture. Detection and identification of any RFID tag 32 allows the microprocessor 20 to establish what location along the endless belt length, within each section of the belt, is being recorded as the voltage VIis produced.

The voltages VI, V2, V3, and V4 and the output from the RFID reader 35 are input into the microprocessor 20 and stored in its non-volatile memory 33 as a series of substantially simultaneous records. Preferably each record contains a timestamp and the time between adjacent records is preferably 20mS. Preferably measurements are taken from at least two belt revolutions, at which time the RCT sensor 9 and the carriage 7 are returned to “home base”.

The microprocessor 20 is able to be remotely controlled by means of the modem 26 and aerial 27 in conjunction with the local mobile telephone (cell phone) service. Alternatively, the microprocessor 20 is able to be remotely controlled via the site network 29 via its Ethernet connection. This enables the stored data to be downloaded and processed either off-site, or if preferred, on-site.

As schematically illustrated in Fig. 6, for every measurement Ml, M2, etc. there is both a value for the voltage V1 and a lateral coordinate which is the result of the formula V2 minus the lateral offset of the home base (eg 250mm) minus V3. For every measurement, the values of voltage V1 and the lateral coordinates are recorded.

In Fig. 7, for each of the three graphs, the Y axis is the voltage VI and the X axis is the lateral coordinate (ie the result of V2 - 250 - V3). The locations of skirt wear are clearly visible and it will be seen that the carry cover thickness is actually thicker in the centre of the belt than to either side of centre. Each of the graphs of Fig. 7 is a result of a corresponding pass of the belt at three different positions along the belt. At

5004N-AU 9 the time of the pass which resulted in graph A, the belt was centred on the structure. At the time of the pass which resulted in graph B the belt had wandered 170mm to the left, and at the time of the pass which resulted in graph C the belt had wandered 75mm to the right.

For a 2000 mm wide belt travelling at 6000mm/sec the full travel of the carriage 9 is preferably 2500mm. A suitable lateral speed of the carriage 9 is in the range of 100 -200mm/sec and a suitable sample logging rate is 20mS (50Hz) which results in a sample being logged in the range of from every 2mm to every 4mm of belt width. As a consequence, a full sweep takes between 12.5 and 25 seconds and produces a total number of between 625 and 1250 samples of which between 500 and 1000 samples are from the actual belt. The spatial location of the samples which are from the actual belt will vary with belt wander.

For those measurements, such as M6, M7, M18, M19, etc., where the lateral coordinates are found to be the same, the values of VI are summed so as to produce a total EVl which is then divided by n, being the number of measurements with the same lateral coordinate. This gives an average cover thickness (EVl/n) along the belt for each lateral coordinate at which measurements were taken. This enables the graph of Fig. 8 to be produced which is a transverse average cover profile across the belt, which can also be termed a lateral average cover wear profile. This does not necessarily have a U or V shape as might be anticipated because materials are not necessarily symmetrically loaded onto a belt, and wear can be caused by other activities such as material turbulence during the material being conveyed from one location to another, belt scraping and cleaning, actions to restrict belt wandering, etc.

At those locations in the endless belt where there is a splice, this is recorded as an artificially thin cover thickness because of the extra steel present in the splice zone. Accordingly, the data from such splice locations are preferably ignored.

Measurements which include part of a spice can be readily identified by reference to the output of the RFID reader 35 in conjunction with the longitudinal offset.

The cover wear profile of Fig. 8 is then reviewed which enables the lateral location of the thinnest cover across the belt 1 to be established. In this particular embodiment,

5004N-AU 10 this location happens to be to the left of the centre of the belt. This then becomes the location where the RCT sensor of the above-mentioned Australian patent application is to be positioned for future longitudinal cover thickness measurements.

Whilst in most circumstances, it is usual for a cover profile, once established, to be constant for the life of the belt cover, in some instances the cover profile changes. In particular, in certain applications where the conveyed material is very dense and abrasive, and the operating conditions of the belt change with time, variations in the cover profile shape can occur relatively quickly. It is important to be aware if this is occurring since this will require that the belt be re-measured or scanned as described above, on a regular basis, a revised cover profile thereby established, and the lateral position of the RCT sensor moved to the new lateral location of thinnest belt cover. Comparing consecutive scans as described above in Fig. 7 enables the change in profile shape to be easily detected.

It will be apparent to those skilled in the art that the cover wear profile produced by the method described above is a true measurement of the profile of the cover thickness. This is to be contrasted with the overall belt thickness profile produced by the prior art, such as the above-mentioned laser or ultrasonic probe methods, which do not sense the actual position of the tops of the steel cords.

The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the conveyor belt arts, can be made thereto without departing from the scope of the present invention. For example, the RCT sensor 9 can be raised or lowered in a vertical direction so as to ensure there is no impact between the belt and the RCT sensor 9. However, it is simpler not to raise or lower the RCT sensor but merely to move the carriage 7 to its “home base” and thus to one side of the belt where it is also safe from collision with the belt.

The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of’.

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Claims (14)

1. A method of determining remaining carry cover thickness in a steel cord conveyor belt whilst the belt is moving, said method comprising the steps of: mounting an apparatus as claimed in any one of claims 4-8 of Australian Patent Application No. 2012 216 769 to be moveable transversely across the carry cover at an unloaded location on said belt, moving said apparatus from one side of said belt to the other whilst taking a series of remaining cover thickness measurements to thereby measure remaining cover thickness at a first plurality of locations spaced apart along a diagonal line notionally drawn across said belt.

2. The method as claimed in claim 1 wherein said apparatus is moved from said one side to said other side and back again to thereby measure remaining cover thickness at a second plurality of locations spaced apart along a V-shaped line notionally drawn across said belt.

3. The method as claimed in claim 2 including the further steps of: repeating the measurement of claim 2 for at least a plurality of complete belt resolutions, and for each measured transverse location on said belt determining an average belt cover thickness at that location by summing those measurements having the same transverse location and dividing the total thickness by the number of those measurements.

4. The method as claimed in any one of claims 1-3 including the step of: measuring lateral wander of said belt and determining the position of said transverse location with reference to a known belt position.

5. The method as claimed in claim 4 wherein said known belt position is the position of said belt when centred on its supporting structure.

6. The method as claimed in claim 3, or claims 4 and 5 when dependent upon claim 3, including the further step of: for each measured transverse location across said belt, determining said average belt cover thickness to thereby form an average belt cover thickness profile.

7. A method of predicting the expected date at which the carry cover of a steel cord conveyor belt will reach the end of its working life, said method comprising the steps of: determining said average belt cover profile by carrying out the method as claimed in claim 6 on a plurality of occasions in order to determine the change in average belt cover profile with time, and extrapolating said change to predict when a predetermined minimum belt cover thickness will be reached.

8. Apparatus for determining remaining carry cover thickness of a moving steel cord conveyor belt extending between a tail pulley and a discharge pulley, said apparatus comprising: the apparatus as claimed in any one of claims 4-8 of Australian Patent Application No. 2012 216 769 mounted for transverse movement from one side of said belt to the other side of said belt at a location where said belt is unloaded.

9. The apparatus as claimed in claim 8 wherein said location is downstream from, but closely adjacent to, the tail pulley of said belt.

10. The apparatus as claimed in claim 8 or 9 and including lateral belt measurement means to measure the lateral movement, if any, of said belt from a predetermined belt position.

11. The apparatus as claimed in claim 10 wherein said predetermined belt position is the position of said belt when centred on its supporting structure.

12. The apparatus as claimed in any one of claims 8-11 and including longitudinal belt position measuring means.

13. The apparatus as claimed in claim 12 wherein said longitudinal belt position measuring means comprise a multiplicity of longitudinally spaced apart RFID devices.

14. The apparatus as claimed in claim 13 wherein each adjacent pair of said RFID devices corresponds to, and is spaced apart in accordance with the spacing between, adjacent belt splices.