Wear gauges and methods to electrically monitor the wear extent of a wear surface

A wear gauge 10 comprises an elongate substrate 12 having a proximal end 14 and a distal end 16. At least a first row 18 of spaced electronic components 22.1, 22.3 . . . 22.n and a juxtaposed second row 20 of spaced electronic components 22.2, 22.4 . . . 22.n−1 are provided on the substrate. The first and second rows extend in a direction from the proximal end towards the distal end of the substrate. The electronic components 22.2 to 22.n−1 in the second row are spatially interposed between adjacent electronic components 22.1 to 22.n in the first row. The electronic components of the first and second rows are electrically connected in parallel by conductive tracks 19. An electrical parameter relating to the parallel connection as measured at a port 24 of the parallel connection towards the proximal end, changes as electronic components are removed from the connection from the distal end, to provide an indication of the extent of wear, as indicated by the arrow A.

A WEAR GAUGE

This application claims priority to ZA Patent Application No. 2017/03419 filed 17 May 2017, the entire contents of which is hereby incorporated by reference.

INTRODUCTION AND BACKGROUND

This invention relates to a wear gauge, a system for monitoring wear and a method of monitoring wear of a body.

Grinding of bulky raw material is typically performed by utilizing a mill, such as a ball, Semi-Autogenous Grinding (SAG) or autogenous mill comprising a drum comprising a shell having a feed end and a discharge end. The shell is internally lined with a liner. The liner resists abrasion and protects the shell against wear.

In order to prevent damage to the shell, the liner needs to be replaced when the liner has worn down to a predetermined remaining thickness. Devices for providing early warning that the liner thickness is approaching the predetermined thickness are known in the art. However, the wear measurement resolution of the known devices may not be suitable for at least some applications.

OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to provide a wear gauge, a system for monitoring wear and a method of monitoring wear of a body with which the applicant believes the aforementioned problems may at least be alleviated or which may provide a useful alternative for the known devices, systems and methods.

SUMMARY OF THE INVENTION

According to the invention there is provided a wear gauge comprising:an elongate substrate having a proximal end and a distal end;at least a first row of spaced electronic components and a juxtaposed second row of spaced electronic components provided on the substrate, the first and second rows extending in a direction from the proximal end towards the distal end of the substrate; andthe electronic components in the second row being at least partially interposed between the electronic components in the first row and the electronic components of the first and second rows being electrically connected to one another in an electrical connection having a port,
the arrangement being such that an electrical parameter relating to the connection as measured at the port changes as electronic components are removed from the connection from the distal end of the substrate.

The connection may be a parallel connection, the port may be located towards the proximal end and the arrangement may be such that an electrical parameter relating to the parallel connection as measured at the port of the parallel connection changes as electronic components are removed from the parallel connection from the distal end of the substrate.

The electronic components may comprise resistors.

The electrical parameter relating to the parallel connection may be the parallel resistance of the resistors as measured at the port.

The resistors may all have the same resistance value. Any suitable value may be used, for example about 100 kΩ.

The wear gauge may be provided in an elongate housing comprising a head and a shank extending from the head.

The shank may comprise an external thread towards an end thereof remote from the head.

According to a second aspect of the invention there is provided a system for monitoring wear, the system comprising:a wear gauge comprising:an elongate substrate having a proximal end and a distal end;at least a first row and a juxtaposed second row of spaced electronic components provided on the substrate, the first and second rows extending in a direction from the proximal end towards the distal end of the substrate; andthe electronic components in the second row being at least partially interposed between the electronic components in the first row and the electronic components of the first and second rows being electrically connected in parallel,the arrangement being such that an electrical parameter relating to the parallel connection as measured at a port of the parallel connection towards the proximal end of the substrate changes as electronic components of the connection are removed from the connection from the distal end of the substrate; andelectronic circuitry which is connected to the port for repetitively measuring the parameter.

The system may comprise a wireless transmitter, such as an RF transmitter, connected to the circuitry to transmit data relating to the measured parameter to a remote location for further processing.

The wear gauge may be provided in an elongate housing comprising a head and a shank extending from the head.

The shank may comprise an external thread at an end thereof remote from the head.

The wear gauge may be utilized to measure the extent of wear in a mill such as a grinding mill. The mill may comprise a cylindrical drum having a central axis. The drum may comprise a shell and an internal liner for the shell and the wear gauge may be used to measure the extent of wear of the liner.

In use, the housing with internal gauge may extend radially into the liner with the head retained in the liner preferably by one of counter-sinking and a counter-bore in the liner.

The housing may be fastened to the shell of the drum. The head of the housing may terminate flush with a wear surface of the liner.

The wear surface of the liner may be exposed to abrasion and may wear in a radial direction relative to the central axis of the drum. The housing and electronic components may wear away sequentially with the liner, thereby changing the measured parameter for indicating the extent of wear of the liner.

The port may comprise first and second terminals.

The electronic circuitry may comprise a voltage divider network between first and second poles of a voltage source, the voltage divider network comprising a serial connection of a measurement resistor and said parallel connection of electronic components.

The electronic circuitry may further comprise an amplifier, an analog to digital converter and a processor.

The first terminal of the port may be connected to the first pole of the voltage source and the second terminal of the port may be connected via the measurement resistor to the second pole of the voltage source.

An input of the amplifier may be connected over the measurement resistor and an output of the amplifier may be connected to an input of the analog to digital converter.

An output of the analog to digital converter may be connected to the processor.

Also included within the scope of the invention there is provided a method of monitoring wear of a body having a wear surface, the method comprising the steps of:utilizing an elongate substrate having a proximal end and a distal end; at least a first row of spaced electronic components and a juxtaposed second row of spaced electronic components provided on the substrate, the first and second rows extending in a direction from the proximal end towards the distal end of the substrate; the electronic components in the second row being at least partially interposed between the electronic components in the first row and the electronic components of the first and second rows being electrically connected to one another in an electrical connection having a port, the arrangement being such that an electrical parameter relating to the connection as measured at the port changes as electronic components are removed from the connection in a direction from the distal end of the substrate;embedding the substrate in the body with the distal end adjacent the wear surface of the body and allowing electronic components to be removed from the connection as the body wears; andrepeatedly measuring the parameter, thereby to determine the extent of the wear of the body.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

An example embodiment of a wear gauge is generally designated by the reference numeral10inFIG. 1.

The wear gauge10comprises an elongate substrate12having a proximal end14and a distal end16. At least a first row18of spaced electronic components22.1,22.3. . .22.nand a juxtaposed second row20of spaced electronic components22.2,22.4. . .22.n−1 are provided on the substrate12. The first and second rows18,20extend in a direction from the proximal end14towards the distal end16of the substrate12. The electronic components22.2to22.n−1 in the second row20are spatially interposed between adjacent electronic components22.1to22.nin the first row18. The electronic components of the first and second rows18,20are electrically connected in parallel by conductive tracks19. An electrical parameter relating to the parallel connection as measured at a port24of the parallel connection towards the proximal end14, changes as electronic components of the connection are removed from the connection from the distal end and is therefore indicative of the extent of wear from the distal end16, as indicated by the arrow A.

The electronic components22.1to22.npreferably comprise resistors. The electrical parameter measured at the port24is the parallel resistance of the parallel connection. The port24comprises a first terminal24.1and a second terminal24.2. The resistors24.1to24.npreferably all have the same resistance value. A suitable value, for example about 100 kΩ is utilized. The resistors are provided at respective pre-selected distances from the distal end16.

InFIG. 2is shown a sectional view of a mill26comprising a cylindrical drum27having a central axis X. The mill26may be grinding mill such as a ball mill. The drum27comprises a cylindrical shell28and an internal liner30. The liner30comprises a first part30.1(shown inFIGS. 2 and 4) abutting the shell and a second part30.2(shown inFIGS. 2 to 4) also abutting the shell, but protruding beyond the first part. The protruding part30.2is commonly referred to as a lifting bar. In use, the wear gauge10is housed in an elongate housing32which is shown in more detail inFIG. 3.

InFIG. 3is shown an enlarged view of a portion designated /// inFIG. 2, illustrating the housing32and the gauge10located in the housing. The housing32is preferably made of steel and comprises a head34and a tubular shank36extending from the head. Hence, the housing32preferably has a hammer-head shape. The shank36comprises an external thread38at an end remote from the head34. The external thread cooperates with an internal thread of a nut40, to fasten the housing32to the shell28. In use, the housing32extends radially into the liner30with the head34retained in the liner30preferably via counter-sinking or by a counter-bore33in the liner. The housing32and the distal end16of the wear gauge10preferably terminate flush with a wear surface42of the liner30. The gauge10may be embedded in a filler35(shown inFIG. 4) such as an adhesive, epoxy resin or the like in the housing.

InFIG. 4is shown a diagrammatic representation illustrating a sectional view on line IV-IV′ inFIG. 3and a high-level block diagram illustrating a system100for monitoring wear. The system100comprises the wear gauge10and a measuring unit102comprising electronic circuitry110which is connected to the port24for repetitively measuring the parameter. A transmitter112is connected to the circuitry110to transmit data relating to the measured parameter to remote locations114,116for further processing. The circuitry110comprises a battery118which is provided as voltage source for the remainder of the circuitry, which includes a processor120. At the remote locations, there may be provided at least one of a gateway114and a backend116. The gateway114comprises a receiver115connected to a gateway processor117which is connected to a transmitter, preferably in the form of a Global System for Mobile Communications (GSM) modem119. The backend116comprises at least a server and a database122, which are in data communication with the gateway in known manner.

InFIG. 5is shown a block diagram illustrating the gauge10connected to the electronic circuitry110. The circuitry110comprises a voltage divider network124connected between first and second poles126.1,126.2of the voltage source. The voltage divider network124comprises a serial connection of a measurement resistor134and the parallel connection22.1to22.n. The electronic circuitry110further comprises an amplifier130, an analog to digital converter132and the processor120. The first terminal24.1of the port24is connected to the first pole126.1of the voltage source, whereas the second terminal24.2of the port24is connected via the measurement resistor134to the second pole126.2of the voltage source. An input of the amplifier130is connected over the measurement resistor134and an output of the amplifier130is connected to an input of the analog to digital converter (ADC)132. An output of the ADC132is connected to the processor120in known manner.

Referring toFIGS. 1 to 5, in use, the housing32(with the gauge10located in the housing) is secured to the drum27of the mill26as described above. The wear surface42of the liner30is in use exposed to abrasion and wears in a generally radial direction (as indicated by the arrow A inFIGS. 1 and 3) relative to the central axis X of the drum27, as material is ground by the mill. Hence, the resistors22.nto22.1are sequentially worn away in a direction from the distal end16towards the proximal end14, which causes the parallel resistance to change, indicating the extent of wear of the liner30.

Referring toFIGS. 4 and 5, a signal at the output of the amplifier130is indicative of a voltage drop over the measurement resistor134. From the ADC132, the processor120receives data relating to the voltage drop. The output voltage of the battery118is measured in real time at the measuring unit102. The data relating to the voltage drop and other data such as the data relating to the output voltage of battery118are transmitted by transmitter112to local gateway114and via GSM modem119to backend116for further processing.

InFIG. 6is shown a flow diagram illustrating steps of a method for monitoring wear as performed at processor120on board measuring unit102. At121, data relating to the voltage drop and data relating to the battery voltage are received. At123, the data may be encrypted. At125, the data is transmitted to the gateway114. At127, the measuring unit102is put to sleep for example for a period of 30 seconds, before returning to step121. The data may be encoded by the gateway114before being transmitted via GSM to backend116.

InFIG. 7is shown a flow diagram illustrating steps of the method for monitoring wear as performed at the backend116. At129, the encoded and encrypted data is received. At131, the data is decrypted and decoded. At133, a calculation is performed to calculate the parallel resistance of the gauge10. The calculation further comprises determining a current length of the gauge10. The calculated parallel resistance and the pre-selected distances of the resistors22.1to22.nare utilized in the calculation to indicate the extent of wear of the liner30. At135, the database is updated with data relating to the calculation.

InFIG. 8is shown an example graph140of parallel resistance value (0) against number of gauge resistors22.1to22.n, for the case of n=300. InFIG. 9is shown an example graph150of number of gauge resistors against voltage measured (V) over the measurement resistor134and at the output of the amplifier130. The data relating to the measured battery voltage is utilized to derive an equation of number of parallel gauge resistors22.1to22.nagainst the voltage over the measurement resistor134. One example of such an equation is represented by the graph150inFIG. 9. The measured voltage over the measurement resistor134is then used in the equation to yield a number of remaining gauge resistors22.1to22.n. Utilizing the known pre-selected distances of the resistors22.1to22.nfrom the distal end16of the substrate12, backend116is enabled to calculate the extent of wear in the liner30, in real time while the mill is running.

Referring toFIG. 1, when the wear surface42has reached a first level A.1(shown in the enlarged part ofFIG. 1) on the gauge, resistor22.nis removed from and no longer forms part of the parallel connection. The voltage drop over the measurement resistor134changes accordingly. The axially spaced center lines (not shown) of resistors22.1to22.nare spaced at about 0.5 mm from one another. Resistor22.nis also spaced 0.5 mm from the distal end16. Hence, the first level A.1is between 0.5 mm and 1 mm from the distal end16, whereas a second level A.2is between 1 mm and 1.5 mm from the distal end. Hence, when only resistor22.nis worn away, an amount of wear of more than 0.5 mm, but less than 1 mm can be inferred when backend116determines that the change in the voltage drop corresponds to resistors22.1to22.n−1 only being left on the substrate12. Similar inferences are drawn for further wear levels A.2, A.3etc

Referring toFIG. 9, in an example case of a measured voltage drop of 1 V on graph150, approximately 150 gauge resistors would be left on the gauge, which corresponds to 150×0.5=approximately 75 mm of wear of the liner in direction of the arrow A inFIGS. 1 and 3. As described above, the resistors22.2to22.n−1 in the second row20are spatially interposed between the resistors22.1to22.nin the first row18. Hence, the resolution of the measured data is better than in the case of only one row of resistors being utilized.

It will be appreciated that by utilizing the gauge10, the system100is enabled to provide continuous wear readings during operation of the mill26.

It will further be appreciated that there are many variations in detail on the invention as herein defined and/or described without departing from the scope and spirit of the appended claims.

For example, data relating to a unique identifier of the monitoring unit102and/or the gauge10may be included with the data transmitted by the monitoring unit102. This data relating to the unique identifier may also be stored in the database122at the backend116.

Referring toFIG. 4, it will be appreciated that the gauge is provided to measure the wear level in the second protruding part30.2or lifting bar of the liner30. However, other parts, such as the first part30.1of the liner30may also be monitored, by providing the housing32in the first part30.1. Liners provided in other regions of the mill26for example at the outlet, may also be measured with the gauge10. For example, the gauge may be utilized to measure wear in liners which extend axially into the mill at the outlet, or to measure wear in liners which extend at an acute angle relative to the central axis X. Other liners such as substantially flat liners may also be monitored utilizing the gauge10. The housing32may even be omitted by providing or embedding the substrate12with components22.1to22.nin the liner.

The gauge10may furthermore be utilized to measure wear of any surface and this specification is not limited in scope to measuring wear of internal liners of mills.