Electronically deriving a conclusion of the condition of slurry flow in a non-vertical conduit
11268842 · 2022-03-08
Assignee
Inventors
Cpc classification
G01F1/6847
PHYSICS
International classification
G01F1/74
PHYSICS
G01F1/684
PHYSICS
Abstract
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 is provided.
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 first heating device at a first variable heating power level W1 that is 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 second heating device at a second variable heating power level W2 that is 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; measuring, at a predetermined reference point spaced from the first and second heating points, a third reference temperature value T3; communicating electronically generated signals carrying the values W1, W2, T1, T2, and T3 to one or more electronic computing devices, which operatively receives the signals and electronically: automatically calculates a first temperature difference dT1 between T1 and T3 and compares dT1 to a reference value for dT1, being dT1ref, automatically causes the first heating device to change the heating power level W1 delivered to the conduit wall at the first heating point if dT1 is not equal to dT1ref, or not within an allowable deviation of dT1ref, sufficiently to change T1 such that dT1 is equal to dT1ref, or within an allowable deviation of dT1ref, automatically calculates a second temperature difference dT2 between T2 and T3 and compares dT2 to a reference value for dT2, being dT2ref, automatically causes the second heating device to change the heating power level W2 delivered to the conduit wall at the second heating point if dT2 is not equal to dT2ref, or not within an allowable deviation of dT2ref, sufficiently to change T2 such that dT2 is equal to dT2ref, or within an allowable deviation of dT2ref; automatically calculates a power difference dW between W1 and W2 and compares dW to a reference value for dW, being dWref, automatically compares W2 to a reference value for W2, being W2ref, and automatically derives a conclusion of a condition of slurry flow prevailing in the conduit based at least on a relationship between dW and dWref and between W2 and W2ref, that if an absolute value of dW is smaller than an absolute value of dWref and an absolute value of W2 is greater than an absolute value of W2ref, there is unrestricted flow in the conduit, in that no flow restricting bed of solid material has formed at the invert of the conduit, if an absolute value of dW is greater than an absolute value of dWref and an absolute value of W2 is greater than an absolute value of W2ref, there is partially restricted flow in the conduit, in that a flow restricting bed of solid material has formed at the invert of the conduit, and if an absolute value of W2 is smaller than an absolute value of W2ref, there is restricted flow in the conduit, in that flow in the conduit has ceased.
2. The method according to claim 1, wherein W2ref>0 W2ref>dWref>0 W2>W2ref at unrestricted flow W1=W2 at unrestricted flow.
3. 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: a first heating device that is arranged and configured 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 to artificially generate a first locally heated spot on an interior surface of the conduit wall by delivering heat to the conduit wall at a first variable heating power level W1 that is substantially constant over time, and a second heating device that is arranged and configured to deliver heat to the conduit wall 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, to thereby artificially generate a second locally heated spot on an interior surface of the conduit wall by delivering heat to the conduit wall at a second variable heating power level W2 that is substantially constant over time; first and second temperature sensors that are arranged locally and configured to measure the temperatures of the first and second heated spots respectively, thereby to obtain a first temperature value T1 and a second temperature value T2; a third temperature sensor that is arranged and configured 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; electronic signal generating means capable of electronically generating signals carrying the values W1, W2, T1, T2 and T3; and one or more computing devices in communication with the electronic signal generating means operatively configured to receive the signals carrying the values W1, W2, T1, T2 and T3, the one or more computing devices being programmed electronically and configured to: automatically calculate a first temperature difference dT1 between T1 and T3 and compare dT1 to a reference value for dT1, being dT1ref, automatically cause the first heating device to change the heating power level W1 delivered to the conduit wall at the first heating point if dT1 is not equal to dT1ref, or not within an allowable deviation of dT1ref, sufficiently to change T1 such that dT1 is equal to dT1ref, or within an allowable deviation of dT1ref, automatically calculate a second temperature difference dT2 between T2 and T3 and compare dT2 to a reference value for dT2, being dT2ref, automatically cause the second heating device to change the heating power level W2 delivered to the conduit wall at the second heating point if dT2 is not equal to dT2ref, or not within an allowable deviation of dT2ref, sufficiently to change T2 such that dT2 is equal to dT2ref, or within an allowable deviation of dT2ref, automatically calculate a power difference dW between W1 and W2 and compare dW to a reference value for dW, being dWref, automatically compare W2 to a reference value for W2, being W2ref, and automatically derive a conclusion of a condition of slurry flow prevailing in the conduit based at least on a relationship between dW and dWref and between W2 and W2ref, that if an absolute value of dW is smaller than an absolute value of dWref and an absolute value of W2 is greater than an absolute value of W2ref, there is unrestricted flow in the conduit, in that no flow restricting bed of solid material has formed at the invert of the conduit, if an absolute value of dW is greater than an absolute value of dWref and an absolute value of W2 is greater than an absolute value of W2ref, there is partially restricted flow in the conduit, in that a flow restricting bed of solid material has formed at the invert of the conduit, and if an absolute value of W2 is smaller than an absolute value of W2ref, there is restricted flow in the conduit, in that flow in the conduit has ceased.
4. The system according to claim 3, wherein W2ref>0 W2ref>dWref>0 W2>W2ref at unrestricted flow W1=W2 at unrestricted flow.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention will now be described by way of illustrative example only, with reference to the accompanying diagrammatic drawings in which
(2)
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DETAILED DESCRIPTION OF THE INVENTION
(6) Referring to the drawings, and particularly to
(7) 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.
(8) 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.
(9) 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.
(10) 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°. Most preferably, and as illustrated in
(11) 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.
(12) 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.
(13) 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.
(14) 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.
(15) 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.
(16) 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.
(17) 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.
(18) 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.
(19) 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 (i) that a settled particle bed has formed at the invert of the conduit, i.e. at the first heated spot; and (ii) that there is no flow in the conduit.
(20) 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.
(21) 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 or for T2. More particularly, the second reference parameter is a predetermined undesired change in the second temperature difference over a predetermined time period or a threshold value for the second temperature difference, or a threshold value for T2. Only the first option is further discussed, but it may equally be the second or third options, as described in accordance with the invention.
(22) 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.
(23) 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.
(24) 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.
(25) 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.
DISCUSSION
(26) 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.
(27) 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.
(28) 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.
(29) 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.
(30) Referring to
(31) The computing device 26 is also programmed to determine the relationship between ΔT1, ΔT2, and ΔT3 and ΔT1ref, ΔT2ref, and ΔT3ref respectively. As is represented in column 3 of
(32) 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.
(33) Results of an experimental test of the efficacy of a system as taught herein, implementing a method taught herein, except the use of T4.
(34) Seven signals and 2 thresholds are shown in
(35) 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.
(36) 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.
(37) 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.
(38) Key steps shown in
(39) 1) initial auto-calibration, including switching on the heating power during full flow
(40) 2) automatically setting a threshold (first reference parameter) for (T1-T2) at 0.4 Deg C. above (T1-T2)
(41) 3) computing signals to trigger a “settled bed” indication
(42) 4) computing signals to trigger a “no flow” indication
(43) 5) computing signals to remove the “no flow” condition
(44) 6) computing signals to remove the “settled bed” condition after all settled particles have been re-suspended into full flow.
(45) Table 1 below provides a description of the signals and the relevant axes to which they refer. The units of the thresholds are also delta temperatures in Deg C. Thus they are also shown in the Delta Temps scale.
(46) TABLE-US-00001 TABLE 1 Signals and axes Signal Marker Axis Label Flow rate in m.sup.3/h with dashed line for zero none Flow m.sup.3/h Heating power none Heat % T1 − temperature at invert ◯ Real Temps T2 − temperature at top Δ 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
(47) Table 2 that follows explains the initiated processes and the computed conditions.
(48) TABLE-US-00002 TABLE 2 Initiated processes and computed conditions LED Output status and Direct Derived Signal transition 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 Full flow 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 A threshold of Full flow Baseline at Green is (T2 − T3) 0.4 Deg C. above 1.6 V ON are stabilized the stabilised (T1 − T2) is noted for future use. 13:33:30 Ramping down of Full flow Baseline at Green is flow 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 Threshold for Green reducing the heat invert is now goes OFF removal from T1 transgressed by T1 − T2 moving upwards. 13:37:10 As flow approaches T1 − T2 starts to Settled bed Increase to zero, T2 heats up drop back 2.4 V towards its threshold 13:37:30 The ‘rate of rise’ of At this point in No flow Increase to Red goes T2 − T3 exceeds a time, the T2 − T3 3.2 V ON preset value (e.g. 0.25 value is noted Yellow Deg C. in 10 seconds) (i.e. 3.7 Deg C.) goes OFF and 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, No flow Increase to NB: When reference parameter as T2 − T3 3.2 V T1 − T2 is (TH.sub.invert) is higher below TH.sub.invert, than TH.sub.top. this would indicate “false green”, but is overridden by red LED 13:46:00 Pump starts and some Minor cooling No flow Increase to NB: When minor movement of of T2 reduces 3.2 V T1 − T2 is supernatant water T2 − T3, and thus below TH.sub.invert, occurs, but the flow is increases T1 − T2. this would indicate still too small to be “false green”, recognized by the but is flow meter. overridden by red LED 13:47:50 Meaningful flow T2 − T3 is No flow Increase to NB: When commences and flow dropping 3.2 V T1 − T2 is meter starts to provide towards its below TH.sub.invert, an output. T2 is now threshold. The this would indicate being rapidly cooled thermal inertia “false green”, by the flow of delays the but is supernatant water. passing of the overridden Solids are being TH.sub.top by about 1 by red LED gradually picked from minute. the top of the settled bed. 13:48:50 Further cooling down T2 − T3 passes its Settled bed Decrease Red goes of 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 rapidly. Again, the invert, after all some thermal settled solids were inertia delays removed. 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 to 1.6 V goes OFF suspended into the downwards. Green slurry goes ON
(49) 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.
(50) Exemplary embodiment of a system taught herein, implementing a method taught herein.
(51) Referring again to
(52) In the alternative embodiment of the system 10, the sensors 16A, 20A may be incorporated in their associated heating devices 16, 20, e.g. being in the form of heated sensor heads.
(53) Further, in the alternative embodiment of the system 10, the electronic programming and configuration of the computing device 26 is different to that hereinbefore described. More specifically, the computing device 26 is electronically programmed and configured to automatically calculate a first temperature difference dT1 between T1 and T3 and compare dT1 to a reference value for dT1, dT1ref, or compare T1 to a desired value for T1, T3″, that is T3 plus a predetermined value T3′, automatically cause the first heating device to change the heating power level W1 delivered to the conduit wall at the first heating point if dT1 is not equal to dT1ref, optionally not within an allowable deviation of dT1ref, sufficiently to change T1 such that dT1 is equal to dT1ref, optionally within an allowable deviation of dT1ref, or T1 is not equal to T3″, optionally within an allowable deviation of T3″, sufficiently to change T1 such that T1 is equal to T3″, optionally within an allowable deviation of T3″ automatically calculate a second temperature difference dT2 between T2 and T3 and compare dT2 to a reference value for dT2, dT2ref, or compare T2 to a desired value for T2, T3″″, that is T3 plus a predetermined value T3′″; automatically cause the second heating device to change the heating power level W2 delivered to the conduit wall at the second heating point if dT2 is not equal to dT2ref, optionally not within an allowable deviation of dT2ref, sufficiently to change T2 such that dT2 is equal to dT2ref, optionally within an allowable deviation of dT2ref, or; T2 is not equal to T3″″, optionally within an allowable deviation of T3″″, sufficiently to change T1 such that T1 is equal to T3″″, optionally within an allowable deviation of T3″″; automatically calculate a power difference dW between W1 and W2 and compare dW to a reference value for dW, dWref; automatically compare W2 to a reference value for W2, W2ref, and automatically derive a conclusion of a condition of slurry flow prevailing in the conduit based at least on a relationship between dW and dWref and between W2 and W2ref.
(54) In deriving a conclusion of the condition of slurry flow prevailing in the conduit, if an absolute value of dW is smaller than an absolute value of dWref and an absolute value of W2 is greater than an absolute value of W2ref, the computing device concludes that there is unrestricted flow in the conduit, in that no flow restricting bed of solid material has formed at the invert of the conduit, if an absolute value of dW is greater than an absolute value of dWref and an absolute value of W2 is greater than an absolute value of W2ref, the computing device concludes that here is partially restricted flow in the conduit, in that a flow restricting bed of solid material has formed at the invert of the conduit, and if an absolute value of W2 is smaller than an absolute value of W2ref, the computing device concludes that there is restricted flow in the conduit, in that flow in the conduit has virtually ceased.
(55) Thus, the computing device 26 is in controlling communication with the first and second heating devices 16, 20 respectively, to control the first and second heating devices 16, 20 respectively by selectively causing the first and second heating devices 16, 20 respectively to change the first and second heating power levels W1, W2 respectively, in the circumstances discussed above.
Example 1 of a System of the Sixth Aspect of the Invention in Operation
(56) The following parameters are provided: W1 (supplied by first heating device 16) T1 (supplied by W1 and measured by temperature sensor 16A) W2 (supplied by second heating device 20) T2 (supplied by W2 and measured by temperature sensor 20A) W2ref (predetermined constant reference value for W2) dW=W2−W1 dWref (predetermined constant reference value for dW) T3=measured by temperature sensor 24 (T3 is a floating reference value for T1 and T2 respectively) dT1=T1-T3 dT2=T2-T3
(57) For the example W2ref=8 W1 at unrestricted flow is 10 W2 at unrestricted flow is 10 dWref=2 T3=24 T1 and T2=32 at full flow It is desired for dT1 and dT2, respectively, to approximate a desired constant, which is 8° C. in the example, alternatively meaning that predetermined values T3′ and T3′″ are equal to 8, with T3″ and T3″″ respectively being T3+8.
(58) At full flow dW=W2−W1=10−10=0<2 (dWref) W2=10>8 (W2ref) dT1=8° C. dT2=8° C. Thus, dW<dWref and W2>W2ref which are the conditions for a conclusion of full flow
(59) A bed forms at the invert, with flow above the bed T1 increases dT1 increases
(60) Controller for W1 responds decreases power to W1 to 4 dT1 restored dW=W2−W1=10−4=6>2 (dWref) W2=10>8 (W2ref) Thus, dW>dWref and W2>W2ref which are the conditions for a conclusion of bed formation, i.e. partially restricted flow.
(61) Flow deteriorates and ultimately gets fully restricted T1 increases T2 increases dT1 increases dT2 increases
(62) Controllers for W1 and W2 respond further decreases power to W1 to 2 decreases power to W2 to 5<8 (W2ref) dT1 restored dT2 restored dW=W2-W1=5−2=3>2 (dWref) Thus, dW>dWref, but since W2<W2ref, a conclusion of no flow is drawn (it may be that under no flow dW<dWref, but the overriding factor (rule) is W2<W2ref)
Example 2 of a System of the Sixth Aspect of the Invention in Operation
(63) Referring now to
(64) Changing the Process Condition: Flow Rate, which was set to zero flow (restricted flow) at the start, then to a flow rate with a bed (partially restricted flow), and then to a high flow rate with no bed (unrestricted flow). Thus, the three flow rates create the three distinct process conditions to be identified by the instrumentation.
(65) Sensing the Temperature Responses to Variable Flow and/or Bed Conditions: T1Bot is T1, provided and measured by the heated bottom heating device/sensor 16, 16A at pipe invert, automatically controlled to be about 8° C. above the reference temperature. T2Top is T2, provided ad measured by the heated top heating device/sensor 20, 20A, automatically controlled to be also about 8° C. above the reference temperature. T3Ref is T3, measured by the unheated reference sensor 24 to provide a set point, based on slurry temperature.
(66) Controlling to Maintain the Set Points: W1Bot is W1, the variable heat supplied to the bottom sensor 16A to maintain the desired set point under all process conditions. For this test, the set point for both heating devices 16, 20, as mentioned above, is 8° C. above T3 (i.e. the desired values for dT1 and dT2 are 8, alternatively that T3′ and T3′″ are each 8, and T3″ and T3″ ″ are each T3+8). It varies naturally, as the slurry temperature changes, e.g. from the energy supplied by the centrifugal pump in the recirculating pipe loop. W2Top is W2, the variable heat supplied to the top sensor 20A to maintain the desired set point under all process conditions.
(67) Computing to Derive at a Conclusion and its Visualisation: dW is the difference between the heat supplied to the two sensors. TH NeF is W2ref, the threshold for ‘Not enough Flow’, which is set to trigger the condition of ‘no flow’ (restricted flow), as well as the condition of re-commencing the flow, by using W2 Top. TH Bed is dWref, the threshold for a settled bed (partially restricted flow) at the bottom of the pipeline, and in turn for bed erosion. Visualisation of computed conditions: This has been done in practice with a set of 3 different LEDs (red, yellow and green). The ON condition of the relevant LED is shown at the bottom of the chart. E.g. the solid red line represents the period of ‘Not enough Flow’, i.e ‘No Flow’. The yellow line represents the settled ‘Bed’ condition (with flow). The green line represents flow with ‘No Bed’. The LEDs are triggered by the various algorithms/rules, as well as applicable over-riding rules, as mentioned in the original specifications.
(68) TABLE-US-00003 TABLE 3 Example 2 of the system of the sixth aspect of the invention, with reference to FIG. 4 Comments/Flow Rate Time Sensing/Condition Responses/Explanations Changes 4 Stable temperatures The settled bed ‘acts’ like an Pipe loop has been standing and stable, but unequal insulator and thus less heat is for a while with a settled bed. heat is supplied to both needed to maintain the set point for sensors. the bottom sensor, when compared to the top sensor. Top sensor ‘sees’ clear water, which takes more heat away than the settled bed, even during no flow conditions. 5 T2Top drops more than Controller detects the drop of Only a low flow rate is T1Bot due to cold T2Top and thus increases gradually initiated to avoid erosion of water flowing past the the heat to the top sensor. the bed. sensor, thereby cooling the hot spot. 6 W2Top increases and The red LED for ‘Not enough Flow’ This output is the key insight 7 passes upwards through turns OFF, and the yellow LED which the patented 8 the threshold for ‘Not goes ON to indicate a bed condition, technology provides to the enough Flow’, TH with some flow above. operator/pump control. NeF. 14 The temperature T1Bot The controller detects the Flow rate is increased to 15 drops rapidly due to the temperature drop and reacts by significantly above the 16 erosion of the increasing the heat W1Bot. Thus deposition velocity, thus the insulating bed, while T1Bot increases until it reaches the bed is completely eroded. the heat supply is still set point again, being 8° C. above the low. slurry temperature, T3Ref. 17 dW drops below System calculates that both criteria The system response could threshold for No Bed. are met to qualify for a green LED be improved to be faster than for flow with no bed: 3 Minutes, but that could W2 > TH NeF, as well as dW < TH Bed. result in an undesired under- swing of dW when a bed develops, i.e. at 55 Minutes in upper chart. 22-37 Stable and equal heat dW is zero and clearly below the This is regarded as the supply to both sensors, threshold for no bed. normal operation without a as both sensors are bed. cooled by the moving slurry. 38 T1Bot increases rapidly The sudden bed reduces the heat Flow rate is reduced to create due to high heat supply removal from the bottom of the a sudden stationary bed. to the bottom sensor pipe. before flow reduction. The controller reacts to the rapid I.e. heat is stored in the temperature increase and reduces sensor. the heat supply accordingly. 39 dW increases and The green LED changes to the The bed detection happens passes upwards through yellow LED indicating a bed, while within 1 Minute, which is the threshold. the slurry is still flowing. much faster than the detection of bed erosion, which was about 3 Minutes 53 T2 increases rapidly W2 is reduced automatically by the Flow rate is stopped to zero. due to stored heat in controller. the sensing head. 54 W2Top passes The yellow LED changes to the red T1Bot only reacts mildly to downwards through the LED for No Flow conclusion. the flow stoppage, as the threshold for ‘Not sensor is already covered enough Flow’. with a settled bed. 55 The under-swing of Control parameters and thresholds The correct setting of the two dW does not pass are suitably set for this test thresholds is important to downward through the configuration. ensure that during flow threshold for no bed. reduction, TH NeF is passed by W2, i.e at 54 minutes in above test, before dW would potentially passing through TH Bed, i.e. at 55 minutes in above test.