GB2169702A - A method for detecting the onset of splice failure in a conveyor belt - Google Patents

Abstract

A method of detecting the onset of splice failure in a conveyor belt (7), which comprises monitoring the temperature of the conveyor belt (7) with temperature sensors (6) and identifying any hot spots on the belt (7). Once the hot spots have been identified their position relative to the spliced joints are ascertained to determine if they coincide thereby indicating splice failure. A metal tag may be provided on the belt in the vicinity of a spliced joint and a metal detector 12 connected to a timing device 13 enables the relative position of the joint to be determined. <IMAGE>

Description

SPECIFICATION A method for detecting the onset of splice failure in a conveyor belt The present invention relates to a method of detecting the onset of splice failure in a conveyor belt, and in particular to a method which relies upon detecting hot spots in a conveyor belt as an indication of the onset of splice failure in the conveyor belt. The present invention also relates to a conveyor belt monitoring apparatus for use in detecting the onset of splice failure in a conveyor belt.

Endless conveyor belts are widely used in industry, and particularly the coal industry where they are used to transport many tonnes of coal along their length from one part of a mine to another. These endless conveyor belts are usually formed by securing together several individual sections of belting. Several methods are known for securing the ends of the sections together into an endless loop but the present invention is primarily concerned with belts where the ends of the sections are spliced together; that is where the ends of adjacent sections are pared away or profiled so as to fit together and the two ends bonded together.

Should a spliced joint between two adjacent sections of belting fail whilst the conveyor is in use and operating under load it can have disastrous consequences. The risk of injury to any person standing near the conveyor is high and also there may be many hours of lost production during the period that the conveyor is out of use.

In order to avoid splice failure frequent periodic inspection of the belt takes place. Conventionally, this inspection is done manually by an operator who looks for deterioration in the belt in the region of the splice. Unfortunately, visual deterioration may only become apparent in the final stages of failure, when surface irregularities appear as the internal layers separate from the external belt covering. Of course, by the time this stage is reached failure may occur in a matter of hours, before the next inspection takes place.

Moreover, where very long conveyor runs are involved, it may be prohibitively expensive and unreliable to have continuous manual examination of the conveyor for spliced joints likely to fail and therefore in need of replacement. Accordingly, a compromise is achieved in which the joints are renewed periodically as a matter of course. However, in the very nature of these things it is impossible to predict exactly when a joint requires renewal and as a result there will often be occasions when joints with many hours of useful life are replaced and occasions when a joint in need of renewal fails before it is renewed.

It is an object of the present invention to provide a method of detecting the onset of splice failure in a conveyor belt which obviates or substantially mitigates the problems referred to herein above.

It is a further object of the present invention to provide a conveyor belt monitoring system which operates in accordance with the aforementioned method.

According to a first aspect of the present invention there is provided a method of detecting the onset of splice failure in a conveyor belt, which comprises monitoring the temperature of the conveyor belt and identifying any hot spots on the belt, and ascertaining whether the hot spots coincide with any spliced joints in the belt thereby indicating splice failure.

Hot spots are areas of the belt where the temperature is some 5"C to 7"C above the ambient belt temperature. There are a number of circumstances in which hot spots can arise in the belt. However, where the hot spots arise in the vicinity of a spliced joint it can usually be attributed to splice failure. In this context as a spliced joint fails the internal breakdown of the belt gives rise to friction in the belt as the belt tension varies and generates a hot spot. Once a hot spot is detected at a spliced joint an alarm may be triggered and the conveyor operation may be automatically stopped.

Preferably, the temperature of the belt is monitored across the width of the belt, but at the very least it is monitored at the centre of the belt.

A recognition marker may be employed to identify a particular reference point on the belt so that the position of hot spots on the belt can be calculated. Knowing the velocity of the belt and the elapsed time between the reference and the hot spot, its position on the belt can be identified and if it coincides with a spliced joint appropriate action can be taken to have the splice renewed.

The effects of random hot spots occurring in the belt may be eliminated by monitoring the temperature of the belt during several passes of the conveyor belt.

According to a second aspect of the present invention there is provided conveyor belt monitoring apparatus for use in detecting the onset of splice failure in a conveyor belt comprising temperature sensing means positioned to sense the temperature of a conveyor belt, and control means which identifies hot spots on the belt coinciding with a spliced joint in the belt.

Preferably, the temperature sensing means comprises an infra-red radiation sensor, and in particular a long-wavelength pyro-electric infrared sensor.

In order to ascertain whether the hot spot coincides with a spliced joint, a recognition marker may be provided in association with each splice. Conveniently, this may be in the form of a metallic disc which can be detected using an inductive sensor.

Preferably, the control means comprises an alarm which generates a warning signal when a hot spot at a spliced joint is detected, and conveniently this causes operation of the conveyor to be stopped automatically.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a much simplified view of a spliced joint between two adjacent sections of belt, and, Fig. 2 shows a part schematic and part block circuit diagram of a conveyor belt monitoring apparatus in accordance with the present invention.

Referring to Fig. 1 there is shown a much simplified view of a spliced joint 1 between two adjacent sections 2, 3 of belt. The ends of the sections 2, 3 are provided with interlocking fingers 4 so as to fit together and the edges of these interlocking fingers 4 are bonded together. A metal tag 5 is provided in the vicinity of the spliced joint 1 to allow its position to be detected automatically, as will be elaborated upon in greater detail with reference to Fig. 2 of the drawings. Although not actually shown in the drawings each section 2, 3 comprises a number of plies, including internal fabric layers and an external coating.

As a spliced joint starts to fail the various plies separate from each other. This internal breakdown gives rise to friction in the belt as the belt tension varies and this in turn generates a hot spot in the belt. The heat generated in such a hot spot is fairly low, being typically of the order of 5"C to 7"C above the ambient temperature of the belt when failure is imminent. However, despite being low it can be detected.

Referring now to Fig. 2 there is shown a part schematic and part block diagram of a conveyor belt monitoring apparatus. The apparatus comprises "n" sensors 6 which are spaced along the return run of a conveyor belt 7, adjacent to its surface. Failure of a spliced joint in a conveyor belt tends to occur at the centre of the belt, so the sensors 6 are positioned at least at the centre of the belt 7.

However, a number of sensors will usually be arranged across the width of the belt. Each sensor 6 is comprised of a long-wavelength pyro-electric infra-red sensor which is able to sense the localised temperature of the belt 7 as it passes immediately adjacent to it. Hot spots in the belt can be identified as those areas of the belt which have a temperature which is higher than the ambient temperature of the belt, by a predetermined amount. In order to detect this predetermined increase in temperature the output of each sensor 6 is connected to a comparator 8, via a preampBi- fier 9 and an amplifier 10 Within the compare- tor 8 the output of the amplifier 10 is com- pared with a predetermined value equalling the ambient temperature plus the temperature above ambient of a hot spot.If the output of the amplifier 10 exceeds the predetermined value a hot spot is present, and if it coincides in position with a spliced joint an alarm signal control 11 is operated.

In order to detect whether the position of a hot spot coincides with that of a spliced joint a metal detector 12 is located adjacent to the surface of the conveyor belt 7. This detects the metal tag 5 provided in the vicinity of each spliced joint 1 (see Fig. 1) and enables the position of a hot spot in the belt 7 relative to a spliced joint to be determined. In this respect, the output of the metal detector 11 is connected to a timing device 13. Since the velocity of the belt 7 is known, or can at least be determined using, for example, a length tranducer roller (not shown), the position of the spliced joints in the belt at any instant in time can always be determined.

Should a hot spot be detected by each of the sensors 6 at the very instant in time when a spliced joint is expected to pass the sensor 6 it can be assumed that the hot spot coincides with the spliced joint. When this occurs the alarm signal generator 11 will be operated, indicating the potential failure and stopping the belt 7. A specific check can then be made on the spliced joint, and if necessary the spliced joint can be renewed.

It will be appreciated that the method and apparatus of the present invention allow the condition of the spliced joints in a conveyor belt to be monitored continuously and automatically. Only in the event of a hot spot coinciding in position with a spliced joint will it be necessary for the condition of thespliced joint to be inspected by an operative.

Claims (14)

1. A method of detecting the onset of splice failure in a conveyor belt, which comprises monitoring the temperature of the conveyor belt and identifying any hot spots on the belt, and ascertaining whether the hot spots coincide with any spliced joints in the belt thereby indicating splice failure.

2. A method according to claim 1, characterised in that the temperature of the belt is monitored at least at the centre of the belt.

3. A method according to claim 1 or 2, characterised in that once a hot spot is detected at a spliced joint an alarm may be triggered and the conveyor operation may be automatically stopped.

4. A method according to claim 1, 2 or 3, characterised in that a recognition marker is employed to identify a particular reference point on the belt so that the position of hot spots on the belt can be calculated.

5. A method according to claim 4, characterised in that the recognition marker is provided in the vicinity of each spliced joint.

6. A method according to claim 5, characterised in that the velocity of the belt is determined and the position of a hot spot relative to the recognition marker is calculated from the elapsed time between a recognition marker being detected and a hot spot on the belt being detected.

7. A method according to any preceding claim, characterised in that the effects of random hot spots occurring in the belt may be eliminated by monitoring the temperature of the belt during several passes of the conveyor belt.

8. A conveyor belt monitoring apparatus for use in detecting the onset of splice failure in a conveyor belt comprising temperature sensing means positioned to sense the temperature of a conveyor belt, and control means which identifies hot spots on the belt coinciding with a spliced joint in the belt.

9. A conveyor belt monitoring apparatus according to claim 8, characterised in that the temperature sensing means comprises an infra-red radiation sensor.

10. A conveyor belt monitoring apparatus according to claim 9, characterised in that the infra-red radiation sensor comprises a longwavelength pyro-electric infra-red sensor.

11. A conveyor belt monitoring apparatus according to any of claims 8 to 10, characterised in that a recognition marker is associated with each spliced joint and detector means are provided for detecting the recognition marker.

12. A conveyor belt monitoring apparatus according to claim 11, characterised in that the recognition marker comprises a metal tag provided in the conveyor belt adjacent each spliced joint and the detector means comprises an inductive sensor.

13. A conveyor belt monitoring apparatus according to any of claims 8 to 12, characterised in that the control means comprises an alarm which generates a warning signal when a hot spot at a spliced joint is detected.

14. A method of detecting the onset of splice failure in a conveyor belt substantially as hereinbefore described with reference to the accompanying drawings.

1 5. A conveyor belt monitoring apparatus for use in detecting the onset of splice failure in a conveyor belt substantially as hereinbefore described with reference to the accompanying drawings.