Method and apparatus for leak detection and pipeline temperature modelling method and apparatus

• US 5,453,944 A
• Filed: 03/30/1994
• Issued: 09/26/1995
• Est. Priority Date: 09/22/1992
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Joseph Baumoel
• Inventors: Baumoel, Joseph
• Primary Examiner(s): Ramirez, Ellis B.
• Application Number:
  US08/220,060
• Time in Patent Office: 545 Days
• Field of Search: 364/578, 364/509, 364/558, 364/550, 364/510, 364/556, 364/477, 364/511, 73/40.5 R, 73/49.2, 73/49.1, 340/618, 340/605, 137/486
• US Class Current: 703/2
• CPC Class Codes: G01F 1/665 of the drag-type
• CPC Class Codes: G01F 1/668 Compensating or correcting for variations in velocity of sound
• CPC Class Codes: G01F 1/74 Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
• CPC Class Codes: G01F 15/024 involving digital counting
• CPC Class Codes: G01F 15/066 involving magnetic transmission devices
• CPC Class Codes: G01M 3/18 for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators
• CPC Class Codes: G01M 3/2807 for pipes G01M3/2892, G01M3/30 take precedence

Abstract

A method and apparatus of leak detection for a pipeline. The method includes dividing the pipeline into a plurality of segments, a first site station provided at the beginning of each segment and a second site station provided at the end of each segment, dividing each segment of the pipeline into a plurality of hypothetical pipeline sections, each section having the same nominal volume, measuring the liquid flow into the first section and determining a volume of liquid that has passed the first site station for a defined period, measuring the temperature of the liquid entering the first section at the first site station, measuring the liquid flow out of the last pipeline section of the segment and determining a volume of liquid that has passed the second site station for the defined period, measuring the temperature of the liquid leaving the last section at the second site station, measuring the temperature of the ambient to the pipeline at the first site station or that representative of the topography of the segment, measuring the temperature of the ambient to the pipeline at the second site station or that representative of the topography of the segment, computing the effect of the measured ambient temperatures at the first and second site stations on the sections intermediate the first and second site stations, computing the change in temperature of each section intermediate the first and second site stations due to conversion of kinetic energy into thermal energy and radiation and conduction of energy to or from the section, computing the change in volume of each section of pipeline wall and the change in volume of the liquid in each section based on the computed change in temperature of each section, determining the difference in measured volume between the volumes determined that have passed the first and second site stations for the defined period, correcting the difference in measured volume between the first and second site stations by adding or subtracting the change in the liquid and pipeline wall volume of all sections of the segment during the defined time period, comparing the corrected difference in measured volume between the first and second site stations with a threshold level, and generating an alarm signal if the difference exceeds the threshold level.

Claims

1. A method of analyzing temperature data from a first and second predetermined position in a pipeline, the first and second predetermined position defining a segment of pipeline and the segment comprising a plurality of sections, in order to model the temperature in each of the plurality of sections, the method comprising the steps of:

measuring the temperature of the liquid passing the first predetermined position, and converting the temperature to a first digital temperature representative of the measured temperature;

measuring the temperature of the liquid passing the second predetermined position, and converting the temperature to a second digital temperature representative of the measured temperature;

measuring the temperature ambient to the pipeline at the first predetermined position, and converting the temperature to a first ambient digital temperature representative of the measured temperature;

measuring the temperature ambient to the pipeline at the second predetermined position, and converting the temperature to a second ambient digital temperature representative of the measured temperature;

computing the effect of the first and second ambient digital temperatures on each of the plurality of sections intermediate to the first and second predetermined positions;

computing the change in temperature over a predetermined period of time of each section intermediate to the first and second predetermined positions due to conversion of kinetic energy into thermal energy and the radiation and conduction of energy to or from the section; and

determining a model present temperature for each section of the segment based upon the change in temperature of each section and prior temperature of the section, thereby forming a model of the temperature in each section of the segment of the pipeline, the model associating each section of the segment with the change in temperature and the model present temperature for the section.

2. The method recited in claim 1, further comprising the steps of:

measuring the liquid flow past the first predetermined position over the period and converting the measurement to a digital value;

determining a first digital volume representative of the volume of liquid that has passed the first predetermined position for a defined period;

measuring the liquid flow past the second predetermined position over the period and converting the measurement to a digital value;

determining a second digital volume representative of the volume of liquid that has passed the second predetermined position for the defined period;

computing a digital representation of a change in volume of each section of pipeline and a digital representation of a change in volume of the liquid in each section based on the change in temperature of each section;

determining a difference in measured volume between the first digital volume and the second digital volume;

correcting the difference in measured volume by accounting for the change in volume of each section of pipeline and the change in volume of the liquid in each section;

comparing the corrected difference in measured volume with a threshold level; and

generating an alarm signal if the difference exceeds said threshold level.

3. The method recited in claim 2, wherein the steps of measuring the liquid flow at the first and second predetermined positions comprises providing a clamp-on ultrasonic transit-time flowmeter at each site station for injecting a sonic beam into the liquid for measuring the liquid flow in the pipeline at each respective predetermined position non-intrusively.

4. The method recited in claim 3, wherein the step of providing a clamp-on ultrasonic flowmeter comprises providing a wide-beam flowmeter.

5. The method recited in claim 1, wherein the steps of measuring the liquid temperature at the first and second predetermined positions each comprise providing a clamp-on temperature sensor at the respective site station to measure the liquid temperature.

6. The method recited in claim 1, wherein the step of computing the effect of the ambient digital temperature on each of the plurality of sections comprises interpolating the ambient temperature at each section from the first and second ambient digital temperatures.

7. The method recited in claim 6, wherein the step of computing the effect of ambient digital temperature at the first and second predetermined positions on each section comprises determining the topography of the segment.

8. The method recited in claim 7, wherein the step of determining the topography of the segment comprises determining if each section of the segment is disposed in air, water or soil.

9. The method recited in claim 8, further comprising the step of determining the effect of prior temperature history of each section on current and future ambient temperatures.

10. The method recited in claim 2, wherein said step of computing a digital representation of a change in volume comprises performing said step of computing for a defined period of time.

11. The method recited in claim 10, wherein said steps of computing and correcting are performed periodically for said defined period of time, with results of said step of correcting being accumulated over multiple ones of said period of time.

12. The method recited in claim 11, further comprising comparing said results to threshold values assigned to said multiple periods of time, and generating an alarm if the result exceeds the threshold for any one of the periods.

13. The method recited in claim 12, further comprising the step of performing said steps of computing and correcting for a plurality of different defined periods of time.

14. The method recited in claim 13, further comprising providing threshold values for each of said different defined periods of time, comparing results of said step of correcting to said threshold values, and generating an alarm if the results exceed the threshold value for any one of the periods.

15. The method recited in claim 14, wherein the plurality of different periods of time comprise one minute, five minute, fifteen minute and one hour periods of time.

16. The method recited in claim 2, further comprising the step of identifying the presence of free gas or water in the liquid at at least one of the first and second predetermined positions, and providing an indication of the presence of said free gas or water.

17. The method recited in claim 16, wherein the step of identifying the presence of free gas comprises measuring the variation of sonic propagation velocity due to scattering of the sonic beam caused by included free gas in the liquid at at least one of the first and second predetermined positions.

18. The method recited in claim 16, wherein the step of identifying the presence of free gas comprises measuring a received signal strength of the sonic beam and comparing the received signal to a reference value for the liquid at at least one of the first and second predetermined positions.

19. The method recited in claim 18, further comprising measuring variation in amplitude over time of said sonic beam to determine the presence of free gas in the liquid at the site station.

20. The method recited in claim 2, further comprising the step of identifying an interface between liquids of two different types at at least one of the first and second predetermined positions.

21. The method recited in claim 20, wherein the step of identifying an interface comprises measuring the temperature and the sonic propagation velocity of the liquid at at least one of the first and second predetermined positions during a time period when an interface between liquids is passing through the pipeline at the at least one of the first and second predetermined positions.

22. The method recited in claim 21, further comprising using the identified interface to determine the end of a first liquid product batch and the beginning of a second liquid product batch in the pipeline.

23. The method recited in claim 22 further comprising computing mass flow through the pipeline at a plurality of predetermined positions and comparing the determined mass flow at each of the predetermined positions from the passage of a first interface to the passage of a second interface to determine if a leak has occurred.

24. The method recited in claim 1, further comprising the step of computing an expected absolute temperature of each section intermediate to the first and second predetermined positions using the computed change in temperature of each section and comparing the second digital temperature with the computed temperature at the second predetermined position, and correcting the model temperatures computed for each of the sections based on a difference between the computed temperature and the second digital temperature.

25. The method recited in claim 24, further comprising optimizing thermodynamic equations defining liquid temperature change for each section in accordance with said step of comparing the second digital temperature and computed liquid temperatures at the second predetermined position.

26. The method recited in claim 3, wherein the step of providing a clamp-on flowmeter comprises providing a multi-path sonic meter to minimize flow profile effects due to bends in the pipeline.

27. The method recited in claim 1, further comprising transferring data from each predetermined position to a master station via a high speed data communications link.

28. The method recited in claim 27, further comprising polling the predetermined location from the master station.

29. The method recited in claim 1, further comprising identifying the liquid at at least one of the first and second predetermined positions by determining sonic propagation velocity of the liquid and the temperature of the liquid at the at least one of the predetermined positions, said sonic propagation velocity and temperature defining a unique curve for each liquid allowing identification of the liquid, and identifying the liquid based on the unique curve corresponding to the determined sonic propagation velocity and temperature.

30. The method recited in claim 29, further comprising determining an appropriate liquid expansion coefficient once the liquid is identified for determining the change in liquid volume based on the change in temperature of each section.

31. The method recited in claim 29, further comprising storing in advance parameters relating to a plurality of different liquids caused by said pipeline, and using said prestored parameters to identify the liquid in the pipeline by comparing said prestored parameters to actual measured parameters.

32. The method recited in claim 31, wherein the measured and prestored parameters include sonic propagation velocity versus temperature.

33. The method recited in claim 32, wherein the prestored parameters include density and/or viscosity versus temperature.

34. The method recited in claim 3, further comprising identifying the presence of a pig in the pipeline at one of the predetermined positions by identifying the interruption of the sonic beam for a period of time defined by a dimension of the pig in the longitudinal extent of the pipeline.

35. The method recited in claim 3, further comprising identifying the presence of water in the liquid at one of the predetermined positions by measuring a defined change in sonic propagation velocity from that of the liquid to that of water at the site station.

36. The method recited in claim 3, further comprising measuring the sonic propagation velocity of the liquid in the pipeline at the first and second predetermined positions, determining if a change in sonic propagation velocity has occurred at between the first and second predetermined positions and recording the time of such change at the first and second predetermined position, and using a difference in recorded times determine the location of a leak.

37. The method recited in claim 8, further comprising the step of determining the effect of prior temperature history of each section disposed in soil on current and future ambient temperatures.

38. The apparatus recited in claim 29, wherein the a clamp-on ultrasonic flowmeter comprises a wide-beam flowmeter.

39. Apparatus for analyzing temperature data from a first and second predetermined position in a pipeline, the first and second predetermined position defining a segment of pipeline and the segment comprising a plurality of sections, in order to model the temperature in each of the plurality of sections, the method comprising:

means for measuring the temperature of the liquid passing the first predetermined position, and means for converting the temperature to a first digital temperature representative of the measured temperature;

means for measuring the temperature of the liquid passing the second predetermined position, and converting the temperature to a second digital temperature representative of the measured temperature;

means for measuring the temperature ambient to the pipeline at the first predetermined position, and converting the temperature to a first ambient digital temperature representative of the measured temperature;

means for measuring the temperature ambient to the pipeline at the second predetermined position, and converting the temperature to a second ambient digital temperature representative of the measured temperature;

means for computing the effect of the first and second ambient digital temperatures on each of the plurality of sections intermediate to the first and second;

means for computing the change in temperature over a predetermined period of time of each section intermediate to the first and second predetermined positions due to conversion of kinetic energy into thermal energy and the radiation and conduction of energy to or from the section; and

means for determining a model present temperature for each section of the segment based upon the change in temperature of each section and prior temperature of the section, thereby forming a model of the temperature in each section of the segment of the pipeline, the model associating each section of the segment with the change in temperature and the model present temperature for the section.

40. The apparatus recited in claim 39, further comprising:

means for measuring the liquid flow past the first predetermined position over the period and converting the measurement to a digital value;

means for determining a first digital volume representative of the volume of liquid that has passed the first predetermined position for a defined period;

means for measuring the liquid flow past the second predetermined position over the period and converting the measurement to a digital value;

means for determining a second digital volume representative of the volume of liquid that has passed the second predetermined position for the defined period;

means for computing a digital representation of a change in volume of each section of pipeline and a digital representation of a change in volume of the liquid in each section based on the change in temperature of each section;

means for determining a difference in measured volume between the first digital volume and the second digital volume;

means for correcting the difference in measured volume by accounting for the change in volume of each section of pipeline and the change in volume of the liquid in each section;

means for comparing the corrected difference in volume with a threshold level; and

means for generating an alarm signal if the difference exceeds said threshold level.

41. The apparatus recited in claim 40, wherein the means for measuring the liquid flow at the first and second predetermined positions comprises a clamp-on ultrasonic transit-time flowmeter at each site station for injecting a sonic beam into the liquid for measuring the liquid flow in the pipeline at each respective predetermined position non-intrusively.

42. The apparatus recited in claim 39, wherein the means for measuring the liquid temperature at the first and second predetermined positions each comprise a clamp-on temperature sensor at the respective site station to measure the liquid temperature.

43. The apparatus recited in claim 39, wherein the means for computing the ambient digital temperature on each of the plurality of sections comprises means for interpolating the ambient temperature at each section from the first and second ambient digital temperatures.

44. The apparatus recited in claim 43, wherein the means for computing the effect of the measured ambient temperatures at the first and second site stations on each section comprises means for determining the topography of the segment.

45. The method recited in claim 44, wherein the means for determining the topography of a segment comprises means for determining if each section of the segment is disposed in air, water or soil.

46. The apparatus recited in claim 45 further comprising means for determining the effect of prior temperature history of each section, if the section is disposed in soil, on current and future ambient temperatures.

47. The apparatus recited in claim 39, wherein said means for computing comprise means for computing for a defined period of time.

48. The apparatus recited in claim 47, wherein said means for computing and correcting comprise means for periodically computing and correcting for said defined periods of time, with results of said means for correcting being accumulated over multiple ones of said period of time.

49. The apparatus recited in claim 48, further comprising means for comparing said results to threshold values assigned to said multiple periods of time, and means for generating an alarm if the result exceeds the threshold for any of the periods.

50. The apparatus recited in claim 49, further comprising means for performing said steps of computing and correcting for a plurality of different periods of time.

51. The apparatus recited in claim 50, further comprising means for providing threshold values for each of said different defined periods of time, said means for comparing comprising means for comparing said difference to said threshold values, and means for generating an alarm if the results exceed the threshold value for any one of the periods.

52. The apparatus recited in claim 51, wherein the plurality of different periods of time comprise one minute, five minute, fifteen minute and one hour periods of time.

53. The apparatus recited in claim 40, further comprising means for identifying the presence of free gas or water in the liquid at each site station, and means for providing an indication of the presence of said free gas or water.

54. The apparatus recited in claim 53, wherein the means for identifying the presence of free gas comprises means for measuring variation of sonic propagation velocity due to scattering of the sonic beam caused by included free gas in the liquid at the site station.

55. The apparatus recited in claim 54, wherein the means for identifying the presence of free gas comprises means for measuring a received signal strength of the sonic beam and means for comparing the received signal to a reference value for the liquid at at least one of the first and second predetermined positions.

56. The apparatus recited in claim 55, further comprising means for measuring variation in amplitude over time of said sonic beam to determine the presence of free gas in the liquid at the site station.

57. The apparatus recited in claim 40, further comprising means for identifying an interface between liquids of two different types at at least one of the first and second predetermined positions.

58. The apparatus recited in claim 57, wherein the means for identifying an interface comprises means for measuring the temperature and the sonic propagation velocity of the liquid at at least one of the first and second predetermined positions during a time period when an interface between liquids is passing through the pipeline at the at least one of the first and second predetermined positions.

59. The apparatus recited in claim 58, further comprising means for using the identified interface to determine the end of a first liquid product batch and the beginning of a second liquid product batch.

60. The apparatus recited in claim 59, further comprising means for computing the mass flow through the pipeline at a plurality of predetermined positions and means for comparing the determined mass flow at each of the predetermined positions from the passage of a first interface to the passage of a second interface to determine if a leak has occurred.

61. The apparatus recited in claim 39, further comprising means for computing an expected absolute temperature of each section intermediate to the first and second predetermined positions using the computed change in temperature of each section and means for comparing the second digital temperature with the computed temperature at the second predetermined position, and means for correcting the model temperatures computed for each of the sections based on a difference between the computed temperature and the second digital temperature.

62. The apparatus recited in claim 61, further comprising means for optimizing thermodynamic equations defining the liquid temperature change for each section in accordance with said means for comparing the second digital temperature and computed liquid temperature at the second predetermined position.

63. The apparatus recited in claim 50, wherein the clamp-on flowmeter comprises a multi-path sonic meter to minimize flow profile effects due to bends in the pipeline.

64. The apparatus recited in claim 40, further comprising means for transferring data from each predetermined position to a master station via a high speed data communications link.

65. The apparatus recited in claim 64, further comprising means for polling the predetermined location from the master station.

66. The apparatus recited in claim 40, further comprising means for identifying the liquid at at least one of the first and second predetermined positions by determining the sonic propagation velocity of the liquid and the temperature of the liquid at the at least one of the predetermined positions, said sonic propagation velocity and temperature defining a unique curve for each liquid allowing identification of the liquid, said means for identifying comprising means identifying the liquid based on the unique curve corresponding to the determined sonic propagation velocity and temperature.

67. The apparatus recited in claim 66, further comprising means for determining an appropriate liquid expansion coefficient once the liquid is identified for determining the change in liquid volume based on the change in temperature of each section.

68. The apparatus recited in claim 66, further comprising means for storing in advance parameters relating to a plurality of different liquids carried by said pipeline, and means using said prestored parameters to identify the liquid in the pipeline by comparing said prestored parameters to actuate measured parameters.

69. The apparatus recited in claim 68, wherein the measured and prestored parameters include sonic propagation velocity versus temperature.

70. The apparatus recited in claim 68, wherein the prestored parameters include density and/or viscosity versus temperature.

71. The apparatus recited in claim 41, further comprising means for identifying the presence of a pig in the pipeline at one of the predetermined positions comprising means for identifying the interruption of the sonic beam for a period of time defined by a dimension of the pig in the longitudinal extent of the pipeline.

72. The apparatus recited in claim 41, further comprising means for identifying the presence of water in the liquid at one of the predetermined positions comprising means for measuring a defined change in sonic propagation velocity from that of the liquid to that of water at the site station.

73. The apparatus recited in claim 41, further comprising means for measuring the sonic propagation velocity of the liquid in the pipeline at the first and second predetermined positions, means for determining if a change in sonic propagation velocity has occurred at between the first and second predetermined positions and means for recording the time of such change at the first and second predetermined position, and means for using a difference in the recorded times determine the location of a leak.

74. The apparatus recited in claim 45 further comprising means for determining the effect of prior temperature history of each section disposed in soil on current and future ambient temperatures.