WO2001006207A1

WO2001006207A1 - Monitoring arrangement for a wear part

Info

Publication number: WO2001006207A1
Application number: PCT/IB2000/000987
Authority: WO
Inventors: Hendrik Van Zyl Smit; Michael Glen Blenkinsop; Jorge Omar Rodriguez; Pravin Sewsanker
Original assignee: Eskom
Priority date: 1999-07-19
Filing date: 2000-07-19
Publication date: 2001-01-25
Also published as: AU5701700A

Abstract

A monitoring device (10) for monitoring a parameter of a wear part (42) which is embeddable in the wear part includes a monitor for monitoring the parameter of the wear part and for providing a parameter signal representative thereof and an internal transmitter for transmitting the parameter signal externally of the wear part. The invention further includes an internal receiver for receiving a power signal from an external transmitter and a transducer for converting energy inherent into electrical energy.

Description

MONITORING ARRANGEMENT FOR A WEAR PART

This invention relates to an arrangement for monitoring a wear part, a

method of monitoring a wear part, and a monitoring device for monitoring the wear

part. In particular, the wear part may be a millball.

According to a first aspect of the invention there is provided a monitoring

device for monitoring a parameter of a wear part and which is embeddable in the wear

part, which includes a monitor for monitoring the parameter of the wear part and for

providing a parameter signal representative thereof; and an internal transmitter for

transmitting the parameter signal externally of the wear part.

The device may be electrically operable and may be externally or internally

powered. Thus, it may include an internal receiver for receiving a power signal from

an external transmitter and a transducer for converting energy inherent in the power

signal into electrical energy. An energy storage component may also be provided .

Instead, the device may include an internal generator.

The device may include an antenna for transmitting the parameter signal.

If the device is externally powered, the antenna for transmitting the parameter signal

may also be operable to receive the power signal.

CONFIRMATION COPT The parameter being monitored may be the size of the wear part or its

temperature.

Conveniently, the device may be receivable in a cavity in the wear part.

The device may include a sensor for sensing variations in the parameter

being monitored. The antenna and the sensor may be the same component.

The device may further include a cylindrical casing and the said

component may be located in the casing. In one embodiment the component may be

comprised of two parts that are spaced apart in the casing. In the case where the size

of the wear part is being monitored, the sensor may be arranged such that it wears

away as the part wears.

The device may have a frequency variable oscillator, the frequency of

oscillation being representative of the value of the parameter being monitored. The

frequency may be varied by variations in the resistance of the sensor caused by

variations in its length, in the case where the size of the wear part is being monitored,

or as a result of temperature variations, in the case where temperature is being

monitored. In another embodiment, in which the size of the wear part is being

monitored and in which the sensor and the antenna are the same component, the

frequency may be determined by the length of the component, the component being worn shorter as the wear part wears.

As indicated above, the wear part may, in particular, be a millball.

According to a second aspect of the invention there is provided an

arrangement for monitoring a parameter of a wear part, which comprises a monitoring

device as described above and an external unit which includes an external receiver for

receiving the parameter signal from the internal transmitter.

As described above, the monitoring device may be embedded in the wear

part.

The external unit may also include an external transmitter for supplying

a power signal to the monitoring device, if the monitoring device is externally

powered.

According to a third aspect of the invention there is provided a wear part

with a monitoring device as described above embedded therein. As indicated above,

the wear part may, in particular, be a millball.

According to a fourth aspect of the invention there is provided a mill

which includes an external receiver for receiving the parameter signal from the internal 75 transmitter of a monitoring device embedded in millballs to be used therewith. The

mill may also include at least one millball.

According to a fifth aspect of the invention there is provided a method

of monitoring a parameter of a wear part, which includes

so monitoring the parameter of the wear part by means of a monitor embedded in

the wear part;

transmitting a parameter signal representative of the parameter by means of an

internal transmitter embedded in the wear part; and

receiving the transmitted parameter signal externally of the wear part.

85

As indicated above, the monitoring device may be supplied with power

from an external source or from an internal generator.

Further as indicated above, the frequency of the parameter signal may be

90 varied in accordance with variations in the parameter.

The invention is now described in more detail with reference to the

accompanying drawings, in which:

Figure 1 is an exploded view of a first embodiment of a monitoring device for

95 monitoring a parameter of a wear part according to the invention;

Figure 2 is a schematic representation of a monitoring arrangement according to the invention; and

Figure 3 is a sectioned side view of a second embodiment of a monitoring

device for monitoring a parameter of a wear part according to the invention.

In Figure 1 , a first embodiment of a monitoring device 1 0 for monitoring

the diameter of a millball according to the invention is shown to include a rubber plug

1 2 which houses three T-shaped ferrite antennae 14. The plug 1 2 locates within a

holder 1 6 which includes longitudinally opposed slots 1 8 and 20 respectively.

The holder 1 6 includes key formations 1 7 which key into circumferential

grooves 1 9, formed in the plug 1 2 to retain the plug firmly located in the holder 1 6.

Two elongate resistive sensors 22 and 24 locate in slots 1 6 and 1 8 in the sides of the

holder 1 6.

An external, hardened steel casing 26 with a serrated outer surface 26.1

is provided to enclose the plug 1 2 and plug holder 1 6.

A steel electronics housing 27 is attachable by way of a screw thread

arrangement 28 to the end of the casing 26 as shown in the drawing. The housing

27 houses electronic circuitry on PC boards 30. The electronic circuitry includes a

transducer (not shown) for receiving a power signal from an external transmitter, as

is explained below, a storage capacitor (also not shown) for storing energy supplied via the external transmitter, and a frequency variable oscillator (also not shown) for

supplying a parameter signal to the antennae 14. The oscillation frequency of the oscillator is determined by the resistance of the sensors 22 and 24, and is in the order

of 200 kHz.

When assembled, the rubber plug 1 2 locates within the plug holder 1 6,

which in turn locates within the casing 26 with the sensors 22 and 24 sandwiched

between the outer surface of the plug holder 1 6 and the inner surface of the casing

26. The antennae 1 4 and the sensors 22 and 24 are connected to the PC boards 30

by way of electrical conductors, schematically represented as lines 32 and 34

respectively. A bolt 36 and nut 38 arrangement holds the monitoring device in its

assembled configuration.

In Figure 2, a monitoring arrangement 40 for a millball 42 is shown

schematically. In the drawing, a coal mill 44 is shown to include a plurality of millballs

42 comprising hollow, spherical steel balls having walls 46 of measurable thicknesses.

In use, the balls 42 rotate in a horizontal plane along troughs 48 to mill coal (not

shown).

Monitoring devices 10, in their assembled configuration, are located

within pre-drilled, radially orientated cavities in the walls 46 of balls 42 as shown in

the drawing. An external unit 50 according to the invention includes an external

145 transmitter 50.1 and an external receiver 50.2. An antenna 52 is provided for the unit

50.

In use, the unit 50 powers the monitoring devices 1 0 continuously by

transmitting a power signal at a suitable frequency. This power signal is received by

150 the antennae 1 4 and directed to the transducer located on the PC boards 30 in the

housing 27 (see Figure 1 ) . The capacitor is provided which is charged by the power

signal from the unit 50 to provide power, in use.

Referring now to Figures 1 and 2 generally, the outer ends 1 0.1 of the

155 monitoring devices 1 0 are located flush with the outer surfaces of the millballs 42.

As the balls 42 wear down, the monitoring devices wear down with them, effectively

reducing the lengths of the sensors 22 and 24 as this process takes place. The

sensors 22 and 24 continuously determine the oscillation frequency of the oscillator

on the PC boards 30. The oscillator then generates a parameter signal at a frequency

i6o determined by the resistance of the sensors 22 and 24. As the lengths of the sensors

22 and 24 are reduced as a result of wear, their resistance changes and the frequency

of the parameter signal changes accordingly. The antennae 1 4 of the monitoring

device are supplied with the parameter signal which is transmitted to the external

receiver 50.2. In use, the antennae 1 4 also wear down, hence the necessity of

165 providing a plurality (three in this embodiment) of antennae for the monitoring device. g

The external unit 50 is connected to a microprocessor and database (not

shown) wherein the minimum wall thickness values of the millballs to be monitored are electronically stored. The wall thicknesses of the millballs are incrementally

o associated with pre-determined frequencies of the parameter signals anticipated from

the monitoring device. Accordingly, it is possible to determine and continuously

monitor the millball wall thicknesses as a function of the frequency of the parameter

signals received from the monitoring device 1 0.

175 A second embodiment of a monitoring device 1 0 for monitoring the size

of a millball is shown in Figure 3. Like parts in Figure 3 are given like numbers as

shown in Figures 1 and 2.

The monitoring device 10 in Figure 3 is shown to include a rubber plug

180 1 2 in which an antenna 14 is located. The antenna 14 is made of steel and also acts

as the sensor, as the frequency of oscillation is determined by the length of the

antenna 14.

The plug 1 2 locates within a steel housing 54. An outer portion of the

185 housing 54 is provided with external screw threading 72 which locates the monitoring

device 10 in the wall 46 of the millball 42.

The housing 54 extends past the wall 46 into the millball 54 as shown 190 in Figure 3. The electronic circuitry on a PC board 30, a section of co-axial cable 56

and a generator 58 are also housed in the housing 54.

The antenna 1 4 is connected to the PC board 30 by way of the co-axial

cable 56 and the generator 58 is connected to the PC board 30 by way of wires 60.

195 The PC board 30 is held in place by spacers 62 and the rubber plug 1 2 is held in place

in the housing 54 by a bolt 64. A teflon disc 66 is located between the rubber plug

1 2 and the bolt 64.

The generator 58 has a counterweight 68 attached by an arm 67. The

2oo counterweight 68 moves under the influence of gravitational force when the millball

42 turns, in use. This movement causes the arm 67 to rotate, which in turn causes

the generator 58 to produce electrical energy. The generator 58 then powers the PC

circuitry.

205 An external receiver 50.2 is provided in a wall 70 of the mill 44. As the

length of the antenna 1 4 is reduced as a result of wear, the frequency of the

parameter signal that is transmitted to the external receiver 50.2 varies.

Similarly, the external receiver 50.2 is connected to a microprocessor and

2io database (not shown) and it is thereby possible to determine and continuously monitor

the millball wall thicknesses as a function of the frequency of the parameter signals received from the monitoring device 1 0.

215 It will be appreciated that many variations and modifications of the

invention are possible without departing from the spirit of the disclosure. For example,

with little modification, the arrangement as described with reference to the drawings

can monitor other parameters such as temperature.

220 The applicant believes that with the arrangement as described with

reference to the drawings, the disadvantages associated with the conventional

methods of monitoring millball sizes are to a large extent minimised. The conventional

methods involve stopping the mill and physically measuring the circumference of the

balls with large callipers or by way of ultrasonic equipment or the like. Accordingly,

225 unnecessary mill down-time (to measure millball sizes) can be eliminated with a

resultant reduction in operating costs.

Claims

CLAIMS:

1 . A monitoring device for monitoring a parameter of a wear part and which 230 is embeddable in the wear part, which includes

a monitor for monitoring the parameter of the wear part and for providing a

parameter signal representative thereof; and

an internal transmitter for transmitting the parameter signal externally of the

wear part.

235

2. The device as claimed in Claim 1 , which includes an internal receiver for

receiving a power signal from an external transmitter and a transducer for converting

energy inherent in the power signal into electrical energy.

240 3. The device as claimed in Claim 2, which includes an energy storage

component.

4. The device as claimed in Claim 1 , which includes an internal generator.

245 5. The device as claimed in any one of the preceding claims, which includes

an antenna for transmitting the parameter signal.

6. The device as claimed in Claim 3, which includes an antenna for

transmitting the parameter signal and which is also operable to receive the power 250

signal.

7. The device as claimed in any one of the preceding claims, in which the

parameter being monitored is the size of the wear part.

255

8. The device as claimed in any one of Claims 1 to 6, in which the

parameter being monitored is the temperature of the wear part.

9. The device as claimed in any one of the preceding claims, which is

260 receivable in a cavity in the wear part.

10. The device as claimed in Claim 5, which includes a sensor for sensing

variations in the parameter being monitored.

265 1 1 . The device as claimed in Claim 10, in which the antenna and the sensor

are the same component.

1 2. The device as claimed in Claim 1 1 , which further includes a cylindrical

casing and the said component is located in the casing.

270

1 3. The device as claimed in Claim 1 2, in which the said component is

comprised of two parts.

1 4. The device as claimed in any one of the preceding claims, in which the

monitor has a frequency variable oscillator, the frequency of oscillation being representative of the value of the parameter being monitored.

1 5. The device as claimed in any one of the preceding claims, in which the

wear part is a millball.

1 6. An arrangement for monitoring a parameter of a wear part, which

comprises a monitoring device as claimed in any one of Claims 1 to 14 and an external

unit which includes an external receiver for receiving the parameter signal from the

internal transmitter.

1 7. An arrangement as claimed in Claim 1 6, in which the monitoring device

is embedded in the wear part.

1 8. An arrangement for monitoring a parameter of a wear part, which

comprises a monitoring device as claimed in Claim 2 and an external unit which

includes an external receiver for receiving the parameter signal from the internal

transmitter and an external transmitter for supplying a power signal to the monitoring

device.

1 9. A wear part with a monitoring device as claimed in any one of Claims 1 to 14, embedded therein.

20. A millball which has a monitoring device as claimed in any one of Claims 1 to

14 embedded therein.

21 . A mill which includes at least one millball as claimed in Claim 20 and an

external unit which has an external receiver for receiving the parameter signal from the

internal transmitter of the monitoring device.

22. A mill which includes an external receiver for receiving a parameter signal

from the internal transmitter of a monitoring device of a millball as claimed in Claim

20.

23. A method of monitoring a parameter of a wear part, which includes

monitoring the parameter of the wear part by means of a monitor embedded in

the wear part;

transmitting a parameter signal representative of the parameter by means of an

internal transmitter embedded in the wear part; and

receiving the transmitted parameter signal externally of the wear part.

24. The method as claimed in Claim 23, in which the monitoring device is

supplied with power from an external source.

320 25. The method as claimed in Claim 23, in which the monitoring device is supplied with power from an internal generator.

26. The method as claimed in any one of Claims 23 to 25, in which the

parameter being monitored is the size of the wear part.

325

27. The method as claimed in any one of Claims 23 to 25, in which the

parameter being monitored is the temperature of the wear part.

28. The method as claimed in any one of Claims 23 to 27, in which the

330 frequency of the parameter signal is varied in accordance with variations in the

parameter.

29. The method as claimed in any one of Claims 23 to 28, in which the wear

part is a millball.

335

30. A monitoring device substantially as herein described with reference to

the accompanying drawings.

31 . A method of monitoring a wear part substantially as herein described with

340 reference to the accompanying drawings.