WO2020079601A1

WO2020079601A1 - Lifter bar wear sensing

Info

Publication number: WO2020079601A1
Application number: PCT/IB2019/058805
Authority: WO
Inventors: Eduardo PUTZ
Original assignee: Vulco S.A.; Weir Group Ip Limited
Priority date: 2018-10-18
Filing date: 2019-10-16
Publication date: 2020-04-23
Also published as: GB2578719A; BR112021006563A2; PE20211101A1; MX2021004437A; ZA202102540B; GB2578719B; GB201816997D0; CL2021000915A1

Abstract

A lifter bar for a grinding mill is described. The lifter bar comprises: a longitudinal support bar; a plurality of inserts mounted in spaced relation on a first surface of the longitudinal support bar, where each insert comprises a channel for receiving an elongate sensor; sensing electronics mounted within the lifter bar for (i) monitoring each elongate sensor to detect any change in conductivity thereof, and (ii) transmitting a signal for each elongate sensor to an external device. The signal is indicative of the integrity of the elongate sensor. A protective covering surrounds the support bar, inserts, and sensing electronics. A method and system for detecting wear are also described.

Description

LIFTER BAR WEAR SENSING

The present invention relates generally to crushing, grinding, comminution or similar processing of materials such as mineral ores, rock and other materials, and more particularly to sensing wear on apparatus for use in such processing.

Grinding mills are one form of apparatus used for processing materials as described above. Typical grinding mills generally comprise a drum shaped shell mounted for rotation about its central axis. The axis of the shell is generally horizontally disposed or slightly inclined towards one end. The interior of the shell forms a treatment chamber into which the material to be processed is fed.

In one form of mill known as a SAG (semi autogenous grinder) a grinding medium such as balls or rods is fed to the treatment chamber (i.e. the inside of the shell) with the material to be processed. During rotation of the shell the grinding medium acts on the material to cause the crushing or grinding action. The grinding medium and material to be processed are carried up the side of the shell as a result of the centrifugal force created by rotation of the shell, and then afterwards it falls towards the bottom of the shell under the influence of gravity.

To assist in lifting the material up the side of the shell, lifter bars are often provided, which are secured to the interior surface of the shell. The lifter bars extend generally longitudinally along the shell and are circumferentially spaced apart around the inner surface. The higher the material travels up the shell the better the grinding of the material.

In one form, lifter bars for grinding mills comprise a metal bar enclosed by an elastomeric material. During operation of the grinding mill, the surface of the lifter bars is worn away by the action of the material being ground down. When the lifter bars are worn to a certain level, they should be replaced to ensure efficient continued operation of the grinding mill. However, it is difficult to detect when the lifter bars have been worn to the point where they need replaced without stopping the grinding mill. This is inefficient and expensive.

It is among the objects of an embodiment of the present invention to obviate or mitigate the above disadvantage or other disadvantages of the prior art.

The various aspects detailed hereinafter are independent of each other, except where stated otherwise. Any claim corresponding to one aspect should not be construed as incorporating any element or feature of the other aspects unless explicitly stated in that claim.

According to a first aspect there is provided a lifter bar for a grinding mill, the lifter bar comprising: a longitudinal support bar; a plurality of inserts mounted in spaced relation on a first surface of the longitudinal support bar, where each insert comprises a channel for receiving an elongate sensor; sensing electronics mounted within the lifter bar for (i) monitoring each elongate sensor to detect any change in an electrical property thereof, and (ii) transmitting a signal for each elongate sensor to an external device, where the signal is indicative of the integrity of the elongate sensor; and a protective covering surrounding the support bar, inserts, and sensing electronics.

The longitudinal support bar may comprise a steel, or other metal or alloy, bar. The support bar may comprise any convenient cross-sectional shape.

The protective covering may comprise an elastomeric coating, a non- conducting epoxy, or any other convenient (preferably not electrically conducting) covering.

The electrical property may comprise resistance (conductivity), capacitance, or the like.

The lifter bar may define an upper profiled surface and a lower surface opposite the upper profiled surface. The upper profiled surface may comprise a first portion generally parallel to the lower surface, and a second portion sloping from the first portion to a sidewall of the lifter bar.

The, or each, elongate sensor may comprise a conducting loop, a fibre optic cable, or the like.

Each insert may comprise two or more channels, with each channel being entirely contained within or entirely outside an adjacent channel. Each channel may include a sensor, such as a conducting loop. Each conducting loop may be removably mounted within its associated channel, or each conducting loop may be fabricated as part of the channel (i.e. integral with its associated channel).

Each insert may define an upper surface having a profiled surface

conforming to the upper profiled surface. Each channel may define a shape conforming to the insert’s upper profiled surface so that if the upper profiled surface is subject to even wear then the upper profiled surface approaches the channel in an even (or equidistant) manner.

Each insert may have an associated compartment mounted to the support bar in proximity thereto for storing the sensing electronics. The sensing electronics may comprise a plurality of discrete sensor boards, each sensor board being associated with a different insert, and each sensor board being stored in a different compartment. Alternatively, a single sensing board may be used to monitor a plurality of inserts.

The sensing electronics may include at least one self-contained power source for powering the sensing electronics.

The sensing electronics may include a wireless transmitter for transmitting a signal to a monitoring system. The sensing electronics may be located adjacent to a coupling (such as a bolt) used to couple the lifter bar to a grinding mill. By locating the sensing electronics (including the wireless transmitter) adjacent to a coupling, a wireless transceiver can be provided at the opposite side of the coupling (outside the grinding mill), and the wireless integrity signal can more easily be transmitted through the coupling than through the grinding mill sidewall. Where a bolt and nut arrangement is used for the coupling, the bolt may be hollow or filled with material that easily propagates electromagnetic radiation.

A self-contained power source may be provided for each sensor board. The, or each, self-contained power source may be stored in the associated compartment. Preferably, the (or each) self-contained power source includes a battery operable to power the sensing electronics for at least a year.

Each insert may comprise a steel body welded, bolted, screwed, or otherwise affixed to the support bar.

A lower surface of the lifter bar may define a cabling recess in proximity to an associated insert and compartment. The insert may define a plurality of channel apertures on a lower surface thereof for aligning with the cabling recess in the support bar, thereby defining a channel extending from the channels through the support bar and into the compartment, so that conducting loops can route from the insert through the cabling recess to the compartment and couple to the sensing electronics and self-contained power source mounted therein. By virtue of this aspect, as the protective covering wears away during operation of a grinding mill, the outer surface of the inserts become exposed. At this point, the outermost channel (and therefore the conducting loop) is intact, so the sensing electronics transmits to the external device a signal indicative of acceptable wear (for example, a green light may be presented to an operator of the external device). Further operation of the grinding mill causes the metal inserts to be worn away, eventually shearing the outermost conducting loop. This is detected by the sensing electronics, which transmits a signal indicating that a first level of wear has occurred, which may be implemented by the external device presenting an amber warning light to an operator of the external device. When the wear shears the final conducting loop the sensing electronics transmits a signal indicating that a final level of wear has occurred, which may be implemented by the external device presenting a red warning light to an operator of the external device. This indicates that the lifter bar needs replaced as soon as possible.

According to a second aspect there is provided a grinding mill comprising a plurality of lifter bars according to the first aspect and a plurality of conventional lifter bars, where at least one conventional lifter bar is mounted in the grinding mill adjacent, but in circumferentially spaced relation, to each lifter bar according to the first aspect.

The grinding mill may comprise a plurality of lifter bars according to the first aspect mounted adjacent each other so that such lifter bars are longitudinally aligned.

The grinding mill may include a liner assembly adjacent each lifter bar.

The grinding mill may include a coupling located adjacent each insert on the lifter bar. The coupling may comprise a nut and bolt arrangement. The grinding mill may include a wireless transceiver and associated power supply (such as a battery), at each coupling that is adjacent to an insert. Where a bolt and nut arrangement is used for the coupling, the bolt may be hollow or filled with material that easily propagates electromagnetic radiation.

By locating the sensing electronics (including the wireless transmitter) adjacent to a coupling, the wireless integrity signal is transmitted through the coupling (which is more reliable than being transmitted through the grinding mill sidewall), and the wireless transceiver serves as a repeater to send a stronger integrity signal to a monitoring system.

According to a third aspect there is provided a method of manufacturing a lifter bar, the method comprising: providing a longitudinal support bar; mounting a plurality of inserts in spaced relation on a first surface of the longitudinal support bar, where each insert comprises a channel housing an elongate sensor; mounting on the support bar (i) sensing electronics and (ii) at least one self-contained power source for powering the sensing electronics thereby creating a featurised support bar; mounting the featurised support bar in a mould including pre-vulcanised elastomer, and surrounding the featurised support bar with pre-vulcanised

elastomer; curing the pre-vulcanised elastomer using conventional heat treatment to create a lifter bar comprising elastomeric material encapsulating the featurised support bar; and removing the featurised support bar from the mould.

According to a fourth aspect there is provided a method of detecting wear of a lifter bar according to the first aspect, the method comprising: detecting an electrical property on a first conducting loop; ascertaining if the electrical property is associated with a wear condition; in the event that the electrical property is not associated with a wear condition transmitting a first wear indication signal to a remote device; and in the event that the electrical property is associated with a wear condition transmitting a second wear indication signal to the remote device.

According to a fifth aspect there is provided a system for detecting in situ wear of a lifter bar, the system comprising: a lifter bar according to the first aspect; a receiver operable to receive signals from sensing electronics in the lifter bar; a controller operable to ascertain a level of wear corresponding to a received signal; and a user interface device operable to provide a sensory indication of wear based on the ascertained level of wear.

The user interface device may comprise one or more of: a display, a loudspeaker, or the like. The user interface may be provided by a pc, a cellular telephone, or any other convenient computing device, preferably with access to a web browser.

According to a sixth aspect there is provided a lifter bar for a grinding mill, the lifter bar comprising: a longitudinal support bar; a plurality of inserts mounted in spaced relation on a first surface of the longitudinal support bar, where each insert comprises a channel for receiving an elongate sensor; sensing electronics mounted within the lifter bar for (i) monitoring each elongate sensor to detect any change in a property thereof, and (ii) transmitting a signal from each elongate sensor to an external device, where the signal is indicative of the integrity of the elongate sensor; and a protective covering surrounding the support bar, inserts, and sensing electronics.

The property may comprise an electrical or optical property.

The elongate sensor may comprise a loop of wire, cable (including a fibre optic cable), or any other convenient sensor. The loop may comprise a conducting loop; which may be encased by an insulating sheath.

By virtue of one or more of these aspects, a simple system is provided that enables in situ monitoring of wear in a lifter bar.

These and other aspects will be apparent from the following specific description, given by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of a lifter bar according to a first embodiment of the present invention;

Fig. 2 is a schematic diagram of a part (an insert) of the lifter bar of Fig. 1 ;

Fig. 3 is a schematic diagram of other parts (conducting loops) located in the insert of Fig. 2;

Fig. 4 is a pictorial view of additional parts (a support bar, the inserts, and associated compartments) of Fig. 1 ;

Fig. 5 is a pictorial view of an underside of part of the support bar of Fig. 4;

Fig. 6 is a pictorial view of a mould containing the components of Fig. 4 during manufacture of the lifter bar of Fig. 1 ;

Fig. 7 is a pictorial view of the lifter bar of Fig. 1 removed from the mould of

Fig. 5;

Fig. 8 is a pictorial view of the underside of the lifter bar of Fig. 1 illustrating three electronic control boards;

Fig. 9 is a pictorial view of one of the electronic control boards of Fig. 8;

Fig. 10a is a simplified, schematic side view of a shell of a grinding mill including a plurality of lifter bars of the type shown in Fig. 1 and Fig 10b is a plan view of two of those lifter bars aligned at their ends; Fig. 11 is a simplified schematic cross-sectional diagram showing the insert of Fig. 2 mounted in the lifter bar of Fig. 1 and coupled to the grinding mill of Fig. 10a; and

Fig. 12 is a schematic diagram of a system for monitoring wear of a lifter bar of the type shown in Figs. 1 and 10.

Reference is first made to Fig. 1 , which is a schematic diagram of a lifter bar 10 suitable for use in a grinding mill. The lifter bar 10 comprises a longitudinal steel support bar 12 enclosed in a protective covering 14 and extending from a first end 16 of the lifter bar 10 to a second end 18, opposite the first end 16, and

longitudinally spaced therefrom. The support bar 12 defines a rectangular cross section in this embodiment, but other embodiments may comprise a support bar having a different cross-sectional shape.

A plurality of inserts 20a, b,c (three in this embodiment, although a greater or smaller number may be used in other embodiments) are upstanding from the support bar 12. In this embodiment the inserts comprise metal, such as steel, and are coupled to the support bar 12 by welding joins, although other connection methods, such as bolts, screws, or rivets may be used instead or in addition.

The protective covering 14 is in the form of elastomeric material completely surrounding the support bar 12 and inserts 20. The protective covering 14 provides protection from balls used in a grinding mill (not shown) in which the lifter bar 10 may be installed.

The lifter bar 10 comprises a profiled upper surface 22 comprising a first portion 24, generally parallel to an underside (not shown in Fig. 1 ) of the lifter bar 10, and a second portion 26 at a slope to the first portion 24 and rising from a front edge 28 thereto.

Reference will now also be made to Figs. 2 and 3, which show one of the inserts 20 in more detail. In this embodiment, each of the inserts 20 is identical in shape.

The insert 20 comprises a body 30 defining two channels: an outer channel 32 and an inner channel 34. The inner channel 34 is located entirely within the outer channel 32. Each channel 32,34 terminates at a pair of outlet apertures 36, 38 respectively. Each channel 32,34 accommodates a conducting loop 40,42 located therein, in the form of insulated wire. The ends of each conducting loop 40,42 protrude through the respective outlet apertures 36,38.

Fig. 4 illustrates the conducting loops 40,42 mounted in the inserts 20, and compartments 46a, b,c associated with each insert 20a, b,c and mounted on top of the support bar 12.

Fig. 5 is a pictorial view of an underside of the support bar of Fig. 4 illustrating a cabling recess 48 in the support bar 12 beneath the insert 20 and associated compartment 46 in which wiring from the conducting loops 40,42 is routed from the insert 20 to the compartment 46. In Figure 5, a cavity enclosed by the compartment 46 is visible through the cabling recess 48 so that the cabling recess 48 and compartment 46 together define a cavity (or chamber) in which sensing electronics, cabling, and a power source can be located and stored, as described in more detail below.

Reference is now made to Fig. 6, which illustrates a stage in the

manufacturing process for the lifter bar 10. To manufacture the lifter bar 10, a mould 50 is provided defining, at a lower portion 52 thereof, a profiled surface corresponding to the profiled upper surface 22. The mould 50 is part-filled with pre- vulcanised elastomer, then a featurised bar 60, which is coupled to a mould lid 54 (but with pre-vulcanised elastomer therebetween), is pushed into the mould 50 as the lid 54 is closed. The featurised bar 60 comprises the support bar 12, inserts 20a, b,c (each including the conducting loops 40,42), and associated compartments 46a, b,c. The pre-vulcanised elastomer is then heated and treated until it solidifies. This elastomer covering manufacturing process (that is heating pre-vulcanised elastomer in a mould) is conventional.

Fig. 7 shows the lifter bar 10 after it has been removed from the mould 50 and Fig. 8 shows an underside 62 of the lifter bar 10, which defines a generally central, longitudinal channel 64 and three cabling recesses 48a, b,c in the channel 64. Each cabling recess 48 allows an electronic control board 70, illustrated in Fig. 9, to be accommodated therein.

The electronic control board 70 comprises a pair of batteries 72 and a sensor controller 74 for (i) detecting a short circuit in one or both of the conducting loops 40,42, and (ii) transmitting a signal indicative of the conductivity of the conducting loops 40,42 to an external device (not shown in Fig. 9). The electronic control board 70 includes a unique identifier so that a single external device can ascertain which conducting loop 40 or 42 has been short circuited.

The electronic control board 70 functions as both sensing electronics and a self-contained power source.

Fig. 10a is an end view of a portion of a rotatable shell 80 of a grinding mill 84

(Fig. 12), and Fig. 10b is an elevation view of a smaller portion of the shell 80.

Alternate lifter bars 10 and conventional liner assemblies 82 are mounted

circumferentially around an inner surface of the shell 80, with the longitudinal axis of the lifter bars 10 parallel to the axis of rotation of the shell 80. In larger grinding mills, lifter bars 10 may be mounted adjacent each other along the axis of rotation, as shown in Fig. 10b, to form lifter bar lengths.

Reference is now also made to Fig. 11 , which is a simplified schematic cross- sectional diagram showing the insert 20 mounted in the lifter bar 10 and coupled to the rotatable shell 80 of the grinding mill 84. It should be noted that the lifter bar 10 is mounted to the shell 80 using couplings 90, in the form of bolts 92 and

corresponding threaded nuts 94. These couplings 90 engage with the steel support bar 12 and are positioned adjacent to the inserts 20. This has the advantage that it is easy to locate the position of the inserts from outside the grinding mill 84 because they correspond to the locations of the bolts 92 protruding therethough.

A signal booster (or repeater) 100 is mounted on each bolt 92 (at least each bolt that is located adjacent to an insert 20, as there may be more bolts 92 than inserts 20). The function of the signal repeater 100 is to receive the siginal transmitted by sensor controller 74 and to re-transmit that signal to a receiver in a monitoring system (described in more detail below with reference to Fig. 12). To implement this, the signal repeater 100 comprises a housing 102 having a screw thread mount for coupling to the bolt 92 and enclosing a wireless transceiver 106 in communication with the sensor controller 74 (as illustrated by broken arrow 107) and operable to boost and transmit that signal (as illustrated by arrow 108). A battery 109, similar to battery 72, is provided to power the wireless transceiver 106.

Fig. 12 illustrates a wireless system 110 for detecting in situ wear of lifter bars

10. The system 110 comprises four lifter bars 10 mounted circumferentially equi- spaced on the inner surface of a rotatable shell 80 of a grinding mill 84.

Conventional liner assemblies are located between the lifter bars 10 but are not shown for clarity. In addition, the system 110 includes a user console 112 including a display 114, a receiver 116 operable to receive signals from sensing electronics (the electronic control board 70 in Fig. 9) in the lifter bars 10 (re-transmitted via the repeater 100 of Fig. 11 ), and a controller 118 operable to ascertain a level of wear corresponding to a received signal. The user console 112 also includes an alarm 120 that sounds in response to receipt of a signal indicating that the highest level of wear has been detected.

During operation of the grinding mill 84, balls and/or aggregate in the rotating shell 80 erode or otherwise wear the elastomeric protective covering 14. After a period of time, the outer surface of the inserts 20 become exposed. At this point, the outermost channel 40 remains intact, so the electronic control board 70 transmits to the user console 112 (which is an external device) a signal indicative of acceptable wear (for example, a green light may be presented to an operator on the display 114). Further operation of the grinding mill 84 causes the metal inserts 20 to be worn away, eventually shearing the outermost conducting loop 40. This is detected by the electronic control board 70, which transmits a signal indicating that a first level of wear has occurred, which may be implemented by the user console 112 presenting an amber warning light on the display 114. When the wear shears the final conducting loop 42 the electronic control board 70 transmits a signal indicating that a final level of wear has occurred, which may be implemented by the display 114 presenting a red warning light and text indicating that immediate replacement of the lifter bar 10 is required. The user console 112 may include a cellular transmitter to send a critical wear signal (which may be a text message) to an mobile telephone of an operator responsible for the grinding mill 84.

In a simple embodiment, the sensing electronics detects the resistance of each of the conducting loops 40,42. If the resistance is low then this indicates that the conducting loops 40,42 have retained their structural integrity (i.e. they have not sheared or been worn down); however, as each conducting loop becomes worn the resistance increases, and when they are sheared the resistance becomes effectively infinite (very high).

Various modifications may be made to the above described embodiments within the scope of the present invention. The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. For example, more than two conducting loops may be provided.

Multiple levels of wear may be indicated for each conducting loop instead of just unsheared and sheared. Other electrical or even optical properties may be used for the sensors mounted in the channels.

The terms“comprising”,“including”,“incorporating”, and“having” are used herein to recite an open-ended list of one or more elements or steps, not a closed list. When such terms are used, those elements or steps recited in the list are not exclusive of other elements or steps that may be added to the list.

Unless otherwise indicated by the context, the terms“a” and“an” are used herein to denote at least one of the elements, integers, steps, features, operations, or components mentioned thereafter, but do not exclude additional elements, integers, steps, features, operations, or components.

The presence of broadening words and phrases such as "one or more," "at least," "but not limited to" or other similar phrases in some instances does not mean, and should not be construed as meaning, that the narrower case is intended or required in instances where such broadening phrases are not used.

Claims

1. A lifter bar for a grinding mill, the lifter bar comprising:

a longitudinal support bar;

a plurality of inserts mounted in spaced relation on a first surface of the longitudinal support bar, where each insert comprises a channel for receiving an elongate sensor;

sensing electronics mounted within the lifter bar for (i) monitoring each elongate sensor to detect any change in an electrical property thereof, and (ii) transmitting a signal for each elongate sensor to an external device, where the signal is indicative of the integrity of the elongate sensor; and

a protective covering surrounding the support bar, inserts, and sensing electronics.

2. A lifter bar according to claim 1 , wherein the protective covering

comprises an elastomeric coating.

3. A lifter bar according to claim 1 or 2, wherein the lifter bar defines an

upper profiled surface and a lower surface opposite the upper profiled surface, the upper profiled surface comprising a first portion generally parallel to the lower surface, and a second portion sloping from the first portion to a sidewall of the lifter bar.

4. A lifter bar according to any preceding claim, wherein each insert

comprises two or more channels, each channel being entirely contained within or entirely outside an adjacent channel.

5. A lifter bar according to claim 4, wherein each channel includes a sensor comprising a conducting loop.

6. A lifter bar according to claim 3, wherein each insert defines an upper surface having a profiled surface conforming to the upper profiled surface so that if the upper profiled surface is subject to even wear then the upper profiled surface approaches the channel in an equidistant manner.

7. A lifter bar according to any preceding claim, wherein each insert has an associated compartment mounted to the support bar in proximity thereto for storing the sensing electronics.

8. A lifter bar according to claim 7, wherein the sensing electronics comprises a plurality of discrete sensor boards, each sensor board being associated with a different insert, and each sensor board being stored in a different compartment.

9. A lifter bar according to claim 7 or 8, wherein the sensing electronics

includes at least one self-contained power source for powering the sensing electronics.

10. A grinding mill comprising a plurality of lifter bars according to any

preceding claim, further comprising a plurality of conventional lifter bars, mounted adjacent, but in circumferentially spaced relation, to each lifter bar.

11. A grinding mill according to claim 10, further comprising a coupling for mounting a lifter bar to a sidewall of the grinding mill, and a repeater mounted on the coupling, the repeater including a wireless transceiver for receiving the transm itted integrity signal from the sensing electronics in the lifter bar, and re-transmitting the integrity signal to the external device.

12. A grinding mill according to claim 11 , wherein the repeater further

comprises a power source for the wireless transceiver.

13. A grinding mill according to claim 11 or 12, wherein the coupling

comprises a bolt and nut arrangement, and the repeater is screwed onto an end of the bolt.

14. A method of manufacturing a lifter bar, the method comprising:

providing a longitudinal support bar;

mounting a plurality of inserts in spaced relation on a first surface of the longitudinal support bar, where each insert comprises a channel housing an elongate sensor;

mounting on the support bar (i) sensing electronics and (ii) at least one self-contained power source for powering the sensing electronics, thereby creating a featurised support bar; mounting the featurised support bar in a mould including pre- vulcanised elastomer, and surrounding the featurised support bar with pre- vulcanised elastomer;

curing the pre-vulcanised elastomer using conventional heat treatment to create a lifter bar comprising elastomeric material encapsulating the featurised support bar; and

removing the featurised support bar from the mould..

15. A method of detecting wear of a lifter bar according to any of claims 1 to

9, the method comprising:

detecting an electrical property of a first elongate sensor; ascertaining if the electrical property is associated with a wear condition;

in the event that the electrical property is not associated with a wear condition transmitting a first wear indication signal to a remote device; and

in the event that the electrical property is associated with a wear condition transmitting a second wear indication signal to the remote device.

16. A system for detecting in situ wear of a lifter bar, the system comprising:

a lifter bar according to any of claims 1 to 9;

a receiver operable to receive signals from sensing electronics in the lifter bar;

a controller operable to ascertain a level of wear corresponding to a received signal;

a user interface device operable to provide a sensory indication of wear based on the ascertained level of wear.