ELECTRONICALLY DERIVING A CONCLUSION OF THE CONDITION OF SLURRY FLOW IN A NON-VERTICAL CONDUIT

Abstract

A method of deriving a conclusion of the condition of slurry flow in a non-vertical conduit includes artificially generating a first locally heated spot on an interior surface of the conduit at the invert of the conduit and artificially generating a second locally heated spot on the interior surface of the conduit at a location angularly spaced from the first heated spot at an angular spacing of at least 90. The temperatures of the heated spots are measured, obtaining first and second temperature values T1, T2. Electronically generated signals carrying the values T1, T2 are communicated to an electronic computing device. The computing device automatically calculates a first temperature difference T1 minus T2 and automatically derives a conclusion of the condition of slurry flow prevailing in the conduit based on the relationship between the value of the first temperature difference and a first reference parameter.

Claims

1. A method of electronically deriving a conclusion of a condition of slurry flow in a non-vertical conduit having a conduit wall and which contains a slurry to flow or flowing along the conduit, the method comprising: artificially generating at a first heating point on the conduit wall, which is defined at the invert of the conduit, a first locally heated spot on an interior surface of the conduit wall, using heat delivered to the conduit wall by a heating device at a first heating power level that is maintained substantially constant over time; artificially generating at a second heating point on the conduit wall, which is defined angularly spaced from the first heating point at an angular spacing of at least 90 and which is not spaced from the first heating point along the length of the conduit but which lies in the same cross-sectional plane of the conduit as the first heating point, a second locally heated spot on the interior surface of the conduit wall using heat delivered to the conduit wall by a heating device at a second heating power level that is maintained substantially constant over time; locally measuring the temperatures of the first and second locally heated spots respectively, thereby obtaining a first temperature value T1 and a second temperature value T2; communicating electronically generated signals carrying the values T1 and T2 to an electronic computing device, which operatively receives the signals and electronically: automatically calculates a first temperature difference T1 minus T2; and automatically derives a conclusion of a condition of slurry flow prevailing in the conduit based at least on a relationship between the first temperature difference and a first reference parameter for the first temperature difference.

2. The method according to claim 1, comprising: measuring, at a predetermined reference point spaced from the first and second heating points, a third reference temperature value T3; and communicating an electronically generated signal carrying the value T3 to the electronic computing device, which operatively receives the signal and automatically calculates a second temperature difference T2 minus T3, wherein automatically deriving a conclusion, using the computing device, of the condition of slurry flow prevailing in the conduit is based also on the relationship between the second temperature difference and a second reference parameter for the second temperature difference.

3. The method according to claim 2, wherein the second reference parameter is a predetermined undesired change in the second temperature difference over a predetermined time period, the method comprising: automatically determining, using the computing device, changes in the second temperature difference; and automatically concluding that the condition of slurry flow in the conduit is that there is no flow in the conduit, based on a change in the second temperature difference over the predetermined time period is equal to, or exceeds the predetermined undesired change over the predetermined time period.

4. The method according to claim 3, wherein the conclusion derived based on the second temperature difference that there is no flow in the conduit, overrides any conclusion derived based on the first temperature difference.

5. The method according to claim 4, which includes using the value of T2 minus T3 as a threshold value when the conclusion that there is no flow in the conduit has been derived, and wherein the conclusion derived based on the second temperature difference that there is no flow in the conduit continues to override any conclusion derived based on the first temperature difference, until the value of T2 minus T3 is below the threshold value of T2 minus T3.

6. The method according to claim 1, comprising: artificially generating at a third heating point along the conduit wall, which is defined between the first heating point and the second heating point at an angular spacing of less than 90 from the first heating point about the longitudinal axis, a third locally heated spot on the interior surface of the conduit wall, using heat delivered to the conduit wall by a heating device at a third heating power level that is maintained substantially constant over time; locally measuring a temperature of the third heated spot and thereby obtaining a fourth temperature value T4; communicating an electronically generated signal carrying the value T4 to the computing device, which electronically: automatically calculates a third temperature difference T4 minus T2; and automatically derives a conclusion of a condition of slurry flow prevailing in the conduit at the third heated spot, based on the relationship between the third temperature difference and a third reference parameter for the third temperature difference.

7. The method of claim 6, comprising artificially generating a fourth heating point and, optionally, further heating points along the conduit wall, defined between the first and second heating points, to generate a fourth heated spot and, optionally, further locally heated spots on the interior surface of the conduit, the method comprising: obtaining a fifth and, optionally, further temperature values T5 . . . Tn by local measurement of the temperatures of the fourth and optional further heated spots; communicating an electronically generated signal carrying the fifth and, optionally, further temperature values T5 . . . Tn to the computing device, which electronically: automatically calculates a fourth and, optionally, further temperature differences T5 minus T2 . . . Tn minus T2; and automatically derives one or more further conclusions of a conditions of slurry flow prevailing in the conduit at the fourth and optional further heated spots, based on the relationship between the fourth and optional further temperature differences and fourth and optional further reference parameters for each of the fourth and optional further temperature differences respectively.

8. (canceled)

9. (canceled)

10. (canceled)

11. The method according to claim 1, comprising transmitting, using the computing device, an electronic response to at least the following conclusions, when derived by the computing device: that there is no flow in the conduit; and that a settled particle bed has formed in the conduit at the first or second locally heated spot.

12. The method according to claim 11, wherein the electronic response is or causes at least one of a visual or audio indication that the conclusion causing the electronic response has been derived by the computing device.

13. The method according to claim 2, wherein the first and second heating points both lie in the same cross-sectional plane of the conduit, wherein the reference point is defined on the conduit wall and lies in a same cross-sectional plane of the conduit as the first and second heating points.

14. (canceled)

15. (canceled)

16. A slurry flow condition monitoring system for electronically deriving a conclusion of a condition of slurry flow in a non-vertical conduit having a conduit wall and which contains a slurry to flow or flowing along the conduit, the system including at least one heating device that is arranged to deliver heat to the conduit wall at: a first heating point on the conduit wall, which is defined at the invert of the conduit, thereby artificially to generate a first locally heated spot on an interior surface of the conduit wall by delivering heat to the conduit wall at a first heating power level that is maintained substantially constant over time; and a second heating point on the conduit wall, which is defined angularly spaced from the first heating point at an angular spacing of at least 90 and which is not spaced from the first heating point along the length of the conduit but which lies in the same cross-sectional plane of the conduit as the first heating point, thereby artificially to generate, in use, a second locally heated spot on an interior surface of the conduit wall by delivering heat to the conduit wall at a second heating power level that is maintained substantially constant over time, first and second temperature sensors that are arranged locally to measure the temperatures of the first and second heated spots respectively, thereby to obtain a first temperature value T1 and a second temperature values value T2; electronic signal generating means capable of electronically generating signals carrying the values T1 and T2; and a computing device that is in communication with the electronic signal generating means operatively to receive the signals carrying the values T1 and T2, the computing device being programmed electronically to: automatically calculate a first temperature difference T1 minus T2; and automatically derive a conclusion of slurry flow conditions prevailing in the conduit, based at least on the relationship between the first temperature difference and a first reference parameter for the first temperature difference.

17. The system according to claim 16, further comprising: a third temperature sensor that is arranged to measure a third reference temperature at a reference point spaced away from the first and second heating points, thereby to obtain a third reference temperature value T3; and electronic signal generating means capable of electronically generating a signal carrying the value T3, wherein the computing device is in communication with the electronic signal generating means operatively to receive the signal carrying the value T3 and is programmed electronically to: automatically calculate a second temperature difference T3 minus T2; and automatically derive a conclusion of slurry flow conditions prevailing in the conduit based on the relationship between the second temperature difference and a second reference parameter for the second temperature difference.

18. The system according to claim 17, wherein the second reference parameter is a predetermined undesired change in the second temperature difference over a predetermined time period, and the computing device is programmed electronically to: automatically note changes in the second temperature difference; and automatically conclude that the condition of slurry flow in the conduit is that there is no flow in the conduit, based on a change in the second temperature difference over the predetermined time period is equal to, or exceeds the predetermined undesired change over the predetermined time period.

19. The system according to claim 18, wherein the computing device is programmed such that the conclusion derived based on the second temperature difference that there is no flow in the conduit, overrides any conclusion derived based on the first temperature difference.

20. The system according to claim 19, wherein the computing device is electronically programmed automatically to use the value of T2 minus T3 as a threshold value when the conclusion that there is no flow in the conduit has been derived, and such that the conclusion derived based on the second temperature difference that there is no flow in the conduit, continues to override any conclusion based on the first temperature difference until the value of T2 minus T3 is below the threshold value of T2 minus T3.

21. The system according to claim 16, which includes comprising: a heating device arranged to deliver heat to the conduit wall at a third heating point along the conduit wall, which is defined between the first heating point and the second heating point at an angular spacing of less than 90 from the first heating point about a longitudinal axis, thereby artificially to generate a third locally heated spot on the interior surface of the conduit wall at a third heating power level that is maintained substantially constant over time; a fourth temperature sensor that is arranged locally to measure a temperature of the third heated spot, thereby to obtain a fourth temperature value T4; electronic signal generating means capable of electronically generating a signal carrying the value T4 and of communicating the signal to the computing device, the computing device being in communication with the electronic signal generating means operatively to receive the electronically generated signal carrying the value T4 and being programmed electronically to: automatically calculate a third temperature difference T4 minus T2; and automatically derive a conclusion of slurry flow conditions prevailing in the conduit at the third heated spot, based at least on a relationship between the third temperature difference and a third reference parameter for the third temperature difference.

22. The system according to claim 21, further comprising: one or more heating devices arranged to deliver heat to the conduit wall at a fourth and, optionally, further heating points along the conduit wall, between the first heating point and the second heating point, thereby artificially to generate fourth and, optionally, further locally heated spots on the interior surface of the conduit; one or more temperature sensors arranged locally to measure, in use, the temperatures of the fourth and optionally further heated spots respectively, thereby to obtain fifth and, optionally, further temperature values T5 . . . Tn; electronic signal generating means capable of electronically generating, in use, a signal carrying the values T5 . . . Tn and of communicating the signal to the computing device, the computing device being in communication with the electronic signal generating means operatively to receive the electronically generated signal carrying the values T5 . . . Tn and being programmed electronically to: automatically calculate fourth and optionally further temperature differences T5 minus T2 . . . Tn minus T2; and automatically derive a conclusion of slurry flow conditions prevailing in the conduit at the fourth and optionally further heated spots, based at least on a relationship between the value of (a) the fourth and optionally further temperature differences, and (b) fourth and optionally further reference parameter/s for the fourth and optionally further temperature differences, respectively.

23. (canceled)

24. (canceled)

25. (canceled)

26. (canceled)

27. (canceled)

28. The system according to claim 17, wherein the first and second heating points both lie in the same cross-sectional plane of the conduit, wherein the reference point is defined on the conduit wall and lies in the same cross-sectional plane of the conduit as the first and second heating points.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0124] The invention will now be described by way of illustrative example only, with reference to the accompanying diagrammatic drawings in which

[0125] FIG. 1 shows, in cross sectional view, a system in accordance with the second aspect of the invention in conjunction with a conduit in the form of a pipe;

[0126] FIG. 2 shows a block diagram of operations performed according to the method of the first aspect of the invention by/under direction of the computing means/device of the system of the second aspect of the invention; and

[0127] FIG. 3 shows a screenshot of electronically generated signals obtained and used in the system of the second aspect of the invention in implementing the method of the first aspect of the invention, to derive conclusions and provide visible indications of slurry flow conditions prevailing in a conduit.

DETAILED DESCRIPTION OF THE INVENTION

[0128] Exemplary embodiment of a system according to the second aspect of the invention, implementing a method according to the first aspect of the invention

[0129] Referring to the drawings, and particularly to FIG. 1, reference numeral 10 generally indicates a slurry flow condition monitoring system in accordance with the second aspect of the invention.

[0130] The system 10 includes a conduit in the form of a pipe 12. The pipe 12 has a conduit wall which is a pipe wall 14, having a thickness of between about 2 and about 20 mm, both values inclusive. The pipe 12 is circular cylindrical.

[0131] A first heating device 16 is mounted on an exterior surface of the pipe wall 14 at the invert of the pipe. The first heating device 16 has a heated working surface that is in contact with the exterior surface of the pipe wall 14 at a first heating point 17 along the exterior surface of the pipe wall 14, and delivers heat to the pipe wall 14 at the first heating point 17. It will be appreciated that the first heating point 17 is at the invert of the pipe 12. The first heating device 16 delivers heat to the pipe wall 14 at a first heating power level that is maintained substantially constant over time. The delivery of heat to the exterior surface of the pipe wall 14 by the first heating device 16 at the first heating point 17 results in a first locally heated spot 18 being artificially generated on an interior surface of the pipe wall 14 due to conductive heat transfer through the pipe wall 14.

[0132] A second heating device 20 is also mounted on the exterior surface of the pipe wall 14. The second heating device 20 also has a heated working surface that is in contact with the exterior surface of the pipe wall 14 at a second heating point 21 along the exterior surface of the pipe wall 14, and delivers heat to the pipe wall 14 at the second heating point 21. The second heating device delivers heat to the pipe wall 14 at a second heating power level that is equal to the first heating power level and is also maintained substantially constant over time. As in the case of the first heating device 16, the delivery of heat to the exterior surface of the pipe wall 14 by the second heating device 20 artificially generates a second locally heated spot 22 on the interior surface of the pipe wall 14 due to conductive heat transfer through the pipe wall 14.

[0133] The first and second heating points 17, 21 are angularly spaced from each other about a central longitudinally extending axis A of the pipe 12. Relative mounting of the first heating device 16 and the second heating device 20 about the axis A is therefore also such that the first and second heated spots 18, 22 are generated at locations that are equally angularly spaced from each other about the axis A. The angular spacing is, in accordance with the invention, at least 90. It is, however, preferred that the angular spacing is greater than 90.

[0134] Most preferably, and as illustrated in FIG. 1, the angular spacing is 120.

[0135] The system 10 also includes first and second temperature sensors 16A, 20A that are arranged locally to measure the temperature of each of the first and second heated spots 18, 22 respectively, thereby to obtain first and second temperature values T1, T2. This measurement is independent of the first and second heating devices 16, 20. Since the first and second temperature sensors 16A, 20A operate in close proximity to the heating devices 16, 20, however, the first and second temperature sensors 16A, 20A are illustrated as being included in the heating devices 16, 20. This is merely to simplify the drawing and would not necessarily hold true in practice.

[0136] The temperatures of the first and second heated spots 18, 22 are measured at the respective heating points 17, 21 in substantially the same plane, or in a plane slightly upstream of the plane in which the heating points 17, 21 and heating spots 18, 22 are located, e.g. 15 mm upstream therefrom. The temperature measurement is preferably continuous or at predetermined intervals over time.

[0137] In a particular embodiment of the invention, all of the heating devices and their associated temperature sensors are mounted a distance of 15 mm from each other (centre to centre) on an aluminium base plate. This base plate is then water-tightly screwed to a head, which also provides a cable gland. Cable ends are soldered onto contact points on the base plate. 3 cores are needed to control of heat created by the transistor, and two cores for the sensor, which is desirably a Pt100 sensor. The heads should be mounted such that their cable glands point downstream of the flow in the pipe 12, so that the Pt100 is 15 mm upstream of the heating device. Then the heating devices are on exactly the same cross sectional plane, whereas all three temperature sensors are in their own plane, which is however still functionally speaking in the same plane as the heating devices, also depending on how thick the plane is defined to be. The base plate is typically 3 mm thick.

[0138] The system 10 further includes a reference temperature sensor 24. While the inclusion of this reference temperature sensor 24 is optional in accordance with the invention, it is preferred that it is included. The reference temperature sensor 24 is provided at a reference point 25, which is a point along the pipe wall 14, and measures a reference temperature to obtain a reference temperature value T3. The reference temperature is therefore a temperature of the pipe wall 14. No artificial heating is supplied at the reference point. Preferably, the reference sensor is also a Pt100 sensor.

[0139] The reference point 25 is angularly spaced as far as possible from each of the first and second heating points 17, 21. When defined on the pipe wall 14, as is presently the case, the reference point is therefore equidistally spaced along the pipe wall 14 from both of the first and second heated spots 18, 22. Angular spacings between the reference point 25 and each of the first and second heating points 17, 21 are therefore also equal, being 120 in the illustrated embodiment. It will be appreciated that, in the illustrated embodiment, the first and second heating points 17, 21 and the reference point 25 are therefore equiangularly spaced from each other about the axis A.

[0140] The first and second heating points 17, 21 and the reference point 25 all lie in the same cross-sectional plane of the conduit. The first and second heated spots 18, 22 therefore also lie in this plane.

[0141] The system 10 also includes an electronically programmable computing device 26. The first and second temperature sensors 16A, 20A and the reference temperature sensor 24 are in communication with the computing device 26 along respective electronic communication lines 28, 30 and 32. The first and second temperature sensors 16A, 20A and the reference sensor 25 are also operatively associated with one or more electronic signal generating means (not illustrated) which are capable of electronically generating signals carrying the values of T1, T2 and T3, which are to be communicated to the computing device 26 along the communication lines 28, 30 and 32 respectively. By operatively associated is meant that the electronic signal generating means can receive the measured values T1, T2 and T3 in order electronically to generate the signals carrying these values.

[0142] The computing device 26 is configured and programmed operatively to receive the electronically generated signals and derive a conclusion of the condition of slurry flow conditions prevailing in the pipe 12 from a first temperature difference, which is T1 minus T2, and a second temperature difference, which is T2 minus T3. The computing device is also programmed to calculate these temperature differences from the temperature values communicated to it in the respective signals. By operatively receive is meant that the computing device 26 receives the signals carrying the values T1, T2 and T3, and interprets or decodes the signals in whichever manner necessary in order to calculate the abovementioned temperature differences. With respect to the signals, it will be appreciated that embodiments can exist in which a single combined signal carrying all of the values of T1, T2 and T3 is communicated, rather than respective signals for each value.

[0143] The computing device 26 includes or is in controlling communication with visual and/or audio indicating means, or indicators, which provide visible and/or audible indications of selected conditions of slurry flow in the pipe 14, when concluded by the computing device. These are not illustrated. The indicators are configured to provide respective visible and/or audible indications on the basis of an output conclusion derived by the computing means, indicating that the output conclusion has been derived, which output conclusion is one of at least [0144] (i) that a settled particle bed has formed at the invert of the conduit, i.e. at the first heated spot; and [0145] (ii) that there is no flow in the conduit.

[0146] The computing device 26 is programmed electronically to automatically derive a conclusion that a settled particle bed has formed at the invert of the conduit on the basis of the relationship between the first temperature difference and a first reference parameter, which is a reference parameter for the first temperature difference. More particularly, the first reference parameter is a desired value of the first temperature difference and has a value of 0 (zero). A conclusion that a settled particle bed has formed at the invert of the conduit is derived by the computing device 26 on the basis that the first temperature difference is greater than 0.

[0147] The computing device 26 is programmed electronically to automatically derive a conclusion of no flow in the conduit on the basis of the relationship between the second temperature difference and a second reference parameter, which is a reference parameter for the second temperature difference. More particularly, the second reference parameter is a predetermined undesired change in the second temperature difference over a predetermined time period. Specifically, the predetermined undesired change in the second temperature difference is 0.25 C. and the predetermined time period is 10 seconds. A conclusion that there is no flow in the conduit is therefore derived on the basis that the second temperature difference has increased with 0.25 C. or more within a time period of 10 seconds. The computing device 26 is therefore programmed electronically to automatically note changes in the second temperature difference, and to automatically conclude that the condition of slurry flow in the pipe 12 is that there is no flow, on the basis that a change in the second temperature difference over the predetermined time period is equal to, or exceeds the predetermined undesired change over the predetermined time period.

[0148] The computing device 26 is programmed such that a conclusion derived on the basis of the second temperature difference that there is no flow in the pipe 12 automatically overrides any other conclusion derived on the basis of the first or any other temperature differences. The conclusion that there is no flow in the pipe 12 is therefore always the output conclusion when it is derived by the computing device 26. In all other circumstances, the conclusion/s derived on the basis of the first and/or any other temperature differences that a settled bed has formed in the conduit is the output conclusion, or provides a group of output conclusions. The computing device 26 is also programmed electronically to automatically note, as a threshold value, the value of T2 minus T3 when a conclusion that there is no flow in the conduit has been derived, and such that the conclusion that there is no flow in the conduit continues to override any conclusion derived on the basis of the first or any other temperature differences until the value of T2 minus T3 is again below the threshold value of T2 minus T3.

[0149] The system 10 further includes, between the first heating point 17 and the second heating point 21, at angular spacings of less than 90 from the first heating point, third and fourth heating device/temperature sensor combinations 34/34A, 36/36A operable to generate, by delivering heat to third and fourth heating points (not illustrated) along the exterior surface of the pipe wall 14, third and fourth locally heated spots (also not indicated on the drawing) on the interior surface of the pipe wall 14. This is achieved in the same manner in which generation of the first and second heated spots 18, 22 is achieved. Heating power levels of the third and fourth heating devices 34, 36 are the same as the heating power levels of the first and second heating devices 12, 20.

[0150] The third and fourth heating device/temperature sensor combinations 34/34A, 36/36A operate in the same manner as the first and second heating device/temperature sensor combinations 16/16A, 18/18A to obtain temperature values, calculate temperature differences and derive conclusions of the conditions of slurry flow at the third and fourth heated spots. More specifically, fourth and fifth temperature values T4, T5 of the third and fourth heated spots are measured and communicated to the computing device 26. The computing device 26 then calculates third and fourth temperature differences T4 minus T2 and T5 minus T2. On the basis of the relationship between the third and fourth temperature differences and respective third and fourth reference parameters therefor, respective conclusions are derived by the computing device 26 of the condition of slurry flow prevailing at the third and fourth heated spots. The third and fourth reference parameters are desired values of the third and fourth temperature differences, each being zero. The computing device 26 is programmed to derive a conclusion that a settled particle bed has formed at the third and fourth heated spots, respectively on the basis that the third and fourth temperature differences are greater than 0. It will be appreciated that the use of such third and fourth heating device/temperature sensor combinations 34/34A, 36/36A and the information obtained therefrom, allows the computing device 26 to derive a conclusion of the profile of a settled particle bed, since the development of the settled particle bed can then be monitored as the third and fourth temperature differences are noted as becoming greater than 0. While the second temperature difference is not the output conclusion, the first, third, fourth and further temperature differences, when individually greater than zero, may therefore be a group of output conclusions. In this manner, not only is a conclusion of the formation of a bed derived, but also a conclusion of profile characteristics of the bed.

[0151] Discussion

[0152] While there is unrestricted and free flow of slurry in the pipe 12, heat is removed from the first and second heated spots 18, 22 due to convective heat transfer. Since the rate of heat removal from the first and second heated spots 18, 22 will be more or less equal in such a case, the difference between the first and second temperature values (T1 minus T2, i.e. the first temperature difference) would, when the same constant level of heating power is delivered by each of the heating devices 16, 20 with the temperatures of the first and second heated spots 18, 22 also being equal, approximate zero. A zero differential between the first and second temperature values T1, T2 (i.e. a zero value of the first temperature difference) should, and does depending on the circumstances, therefore cause a conclusion of unrestricted and free flow conditions in the conduit being derived. While this holds true when a settled bed forms while there is still flow in the conduit, it does not necessarily remain true if flow conditions deteriorate and eventually result in a condition of no flow.

[0153] When flow conditions in the pipe 12 deteriorate starting from a condition of full flow, for example as a result of loss of pumping power that drives flow in the conduit and/or as a result of a change in slurry properties, thereby causing the formation of a settled particle bed at the invert of the pipe 12, flow at the invert becomes restricted. Initially, such a settled particle bed may still be in motion, being in the form of a sliding bed. Later, the bed may become completely stationary if solid particles continue to settle from suspension in the event that flow conditions do not improve.

[0154] While the bed is relatively shallow, flow above the bed may continue. In such a case the rate of heat removal from the first heated spot 18 would be perceivably less than the rate of heat removal from the second heated spot 22, due to the difference in flow conditions. Consequently, a difference between the first and second temperature values T1, T2 would be observed, with the result that the first temperature difference is no longer zero. Observing such a difference therefore requires a conclusion to be derived that a settled particle bed has formed at the invert of the pipe 12.

[0155] If flow conditions still do not improve when a bed of sediment has formed at the invert of the pipe 12, the bed may continue to grow. This would necessarily impact on flow above the bed, which would become progressively more restricted, flowing slower and slower, potentially eventually coming to a complete standstill. As flow above the bed slows, the rate of heat removal at the second heated spot 22 also slows. It will be appreciated that this will cause the second temperature value T2 progressively to increase until, when there is no flow in the pipe, it is again equal to the first temperature value T1. This increase in the second temperature value T2 necessarily affects the value of the first temperature difference (between the first and second temperature values), eventually erasing it when the first and second temperature values are again equal. In such a case, the abovementioned conclusion of free and unrestricted slurry flow when there is no difference between the first and second temperature values would not hold true and would therefore be misleading to an operator, who might assume, incorrectly, that flow has recommenced. It is in this scenario in which the second temperature difference comes into play, since slowing of the flow rate above the settled bed and consequent slowing of heat removal from the second heated spot 22 also causes the value of the second temperature difference to change. When the magnitude of this change is such that it is equal to or exceeds the second reference parameter as hereinbefore defined, an overriding conclusion of no flow is drawn despite the fact that the value of the first temperature difference is again moving toward or approximating zero.

[0156] Referring to FIG. 2, the abovementioned functionality is illustrated by way of a block diagram. The values T1, T2, T3 and T4 (as represented in column 1 of FIG. 2) are communicated to the computing device 26 by means of the electronically generated signals. The computing device 26 then calculates the first, second and third temperature differences (respectively T1, T2, and T3). For each temperature difference, a reference parameter is programmed into the computing device 26 (respectively being designated as T1ref, T2ref, and T3ref). As will be appreciated from the foregoing discussion, T1ref and T3ref are discrete values of zero, while T2ref is defined and set to be the actual T2 value at that very point in time, when a predetermined undesired change in the value of T2 over a predetermined time period occurred. T2ref is therefore set only when the predetermined undesired change in the value of T2 occurs. Before it occurs, T2 is naturally below what T2ref would be when it is set.

[0157] The computing device 26 is also programmed to determine the relationship between T1, T2, and T3 and AT1ref, T2ref, and T3ref respectively. As is represented in column 3 of FIG. 2, the computing device 26 derives certain conclusions of the conditions of slurry flow in the pipe 12, based on the relationship of the T1, T2, and T3 and T1ref, T2ref, and T3ref respectively, as set out in column 2 of FIG. 2. These relationships and the conclusions that they necessitate speak for themselves from the drawing, and no further detail is provided. Based on the conclusions, each of which is an output conclusion for the relationship grouping in column 2 that requires it, visible and/or audible outputs are provided by the visual and/or audio indicating means included in the system 10. These indicating means may, in one embodiment, include green, orange and red lights. The computing device is programmed such that a conclusion of full flow, no bed would provide an illuminated green light, that conclusions of constrained flow, bed at T1, no bed at T3 and constrained flow, bed at T1, bed at T3 would provide an illuminated yellow light, and that a conclusion of no flout would provide an illuminated red light. The latter conclusion overrides all other conclusions. Note that in column 3 of FIGS. 2, T1 and T4 are used to represent the respective heated spots for which conclusions of the condition of slurry flow are being derived by the computing means.

[0158] Against the background provided above, deriving an indication of slurry flow conditions in accordance with the method of the invention is on the basis of the first temperature difference while any changes in the second temperature difference are below the second reference parameter. When a change in the second temperature difference exceeds the predetermined reference parameter, deriving a conclusion of slurry flow conditions in accordance with the method of the invention is based on the relationship between the second temperature difference and the second reference parameter.

[0159] Results of an Experimental Test of the Efficacy of the System of the Invention, Implementing the Method of the Invention, Except the Use of T4

[0160] Seven signals and 2 thresholds are shown in FIG. 3, which was created during a test of the overall logic of the method of the invention and its computing algorithms.

[0161] The ambient temperature and the reference temperature T3, which were measured, gradually increased during the test run. The values of these are not shown to minimize the clutter in the chart. It will be appreciated that the computing algorithms of the method of the invention use temperature differences, which in any event eliminate ambient temperature effects. Thus, T1 and T2 essentially float on the changing T3 reference temperature.

[0162] The test results show the performance of the system and the method of the invention in response to a ramping down of the flow rate to zero from a condition of full flow of slurry in the pipeline. After about 10 minutes at zero flow rate, the flow rate was again ramped up. Thus, the test represents a complete cycle from full flow to no flow and back to full flow.

[0163] An online output signal (PLC controlled) provides distinct voltage levels to communicate the computed flow conditions to either an operator by means of acoustic and/or visual alarms, or to a PLC for predefined responses in according to options available at specific operations.

[0164] Key steps shown in FIG. 3 are as follows:

[0165] 1) initial auto-calibration, including switching on the heating power during full flow

[0166] 2) automatically setting a threshold (first reference parameter) for (T1-T2) at 0.4 Deg C. above (T1-T2)

[0167] 3) computing signals to trigger a settled bed indication

[0168] 4) computing signals to trigger a no flow indication

[0169] 5) computing signals to remove the no flow condition

[0170] 6) computing signals to remove the settled bed condition after all settled particles have been re-suspended into full flow.

[0171] Table 1 below provides a description of the signals and the relevant axes to which they refer.

[0172] The units of the thresholds are also delta temperatures in Deg C. Thus they are also shown in the Delta Temps scale.

TABLE-US-00001 TABLE 1 Signals and axes Signal Marker Axis Label Flow rate in m.sup.3/h with dashed line none Flow m.sup.3/h for zero Heating power none Heat % T1temperature at invert Real Temps T2temperature at top Real Temps T2-T3 Delta Temps T1-T2 Delta Temps Threshold top (TH.sub.top) dashed line and Delta Temps Threshold invert (TH.sub.inv) dashed line and Delta Temps Computed online output in Volts for none PLC CTRL indicators

[0173] Table 2 that follows explains the initiated processes and the computed conditions.

TABLE-US-00002 TABLE 2 Initiated processes and computed conditions LED status and Output transition Direct Derived Signal of Time Action/process Consequence Conclusion (PLC Ctrl) indicators 13:31:00 Full flow at 65 m.sup.3/h No settled Full flow Baseline at Green is particles at the 1.6 V ON invert of the pipe 13:31:35 In response to an Both real Baseline at Green is external calibration temperatures T1 1.6 V ON command: Heating and T2 increase power changes from zero to 100% for both sensors 13:33:00 (T1-T2) and (T2-T3) are A threshold of 0.4 Baseline at Green is stabilized Deg C. above the 1.6 V ON stabilised (T1-T2) is noted for future use. 13:33:30 Ramping down of flow Baseline at Green is rate commences 1.6 V ON 13:34:45 At 46 m.sup.3/h, particles Sudden increase Settled bed Increase to Yellow settle and become in T1-T2. 2.4 V goes ON stationary, thus reducing Threshold for Green goes the heat removal from invert is now OFF T1 transgressed by T1-T2 moving upwards. 13:37:10 As flow approaches T1-T2 starts to Increase to zero, T2 heats up drop back 2.4 V towards its threshold 13:37:30 The rate of rise of T2- At this point in No flow Increase to Red goes T3 exceeds a preset time, the T2-T3 3.2 V ON value (e.g. 0.25 Deg C. value is noted (i.e. Yellow in 10 seconds) 3.7 Deg C.) and goes OFF stored as a reference parameter (TH.sub.top). Threshold for T2-T3 is transgressed upwards 13:40:40 T1-T2 drops below its No effect, as T2- Increase to NB: When reference parameter T3 is higher than 3.2 V T1-T2 is (TH.sub.invert) TH.sub.top. below TH.sub.invert, this would indicate false green, but is overridden by red LED 13:46:00 Pump starts and some Minor cooling of Increase to NB: When minor movement of T2 reduces T2- 3.2 V T1-T2 is supernatant water T3, and thus below TH.sub.invert, occurs, but the flow is increases T1-T2. this still too small to be would recognized by the flow indicate meter. false green, but is overridden by red LED 13:47:50 Meaningful flow T2-T3 is dropping Increase to NB: When commences and flow towards its 3.2 V T1-T2 is meter starts to provide threshold. The below TH.sub.invert, an output. T2 is now thermal inertia this being rapidly cooled by delays the would the flow of supernatant passing of the indicate water. TH.sub.top by about 1 false Solids are being minute. green, but gradually picked from is the top of the settled overridden bed. by red LED 13:48:50 Further cooling down of T2-T3 passes its Settled bed Decrease Red goes T2. reference to 2.4 V OFF T1-T3 is reaching a parameter TH.sub.top Yellow saturation level even of 3.7 Deg C. goes ON while the bed is eroded from the top due to increasing flow rate. 13:50:20 Rapid decrease in T1 T1-T2 decreases due to slurry flow at the rapidly. Again, invert, after all settled some thermal solids were removed. inertia delays the transgressing of the TH.sub.inv downwards by one minute. 13:51:15 Further cooling of T1 T1-T2 passes Full flow Decrease Yellow after solids are all re- TH.sub.inv downwards. to 1.6 V goes OFF suspended into the Green goes slurry ON

[0174] The applicant believes that the invention as described provides an elegant and effective approach to monitoring and determining the undesired occurrence as well as the vertical extent of sedimentation at the pipe invert in a pipeline. The invention is in this regard not limited to pipelines, but could also find application in open conduits which are not visually monitored.