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

• US 5,343,737 A
• Filed: 09/22/1992
• Issued: 09/06/1994
• 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): Williams, Hezron E.
• Assistant Examiner(s): ROSKOS, JOSEPH
• Application Number:
  US07/949,076
• Time in Patent Office: 714 Days
• Field of Search: 73/40.5 R, 73/40.5 A, 73/861.28
• US Class Current: 73/40.50R
• 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. Apparatus for detecting a leak in an elongated fluid conducting pipe, said apparatus comprising at least first and second flowmeter means for measuring an amount of fluid per unit time flowing within said pipe;

said first and second flowmeter means coupled to said pipe at axially spaced locations with said second flowmeter means being downstream of said first flowmeter means;

measurement means for determining a total amount of fluid flowing through said pipe at each of said locations for equivalent periods of time;

comparison means coupled to said measurement means for comparing the total flow amounts at said first and second locations for said equivalent periods of time and for producing a volume difference value; and

output means operable in response to a predetermined volume difference value from said comparison means, and further comprising means for determining the temperature of fluid at said first and second flowmeter means, and means for correcting the flow amount determined at said second location to compensate said difference value for effects of temperature on the entire pipeline.

2. The apparatus recited in claim 1, wherein said flowmeter means comprises clamp-on transducers clamped onto the outer surface of said pipe for measuring the transit time for ultrasonic energy to traverse the fluid in said pipe.

3. Apparatus for detecting a leak in an elongated fluid conducting pipe, said apparatus comprising at least first and second flowmeter means for measuring an amount of fluid per unit time flowing within said pipe;

said first and second flowmeter means coupled to said pipe at axially spaced locations with said second flowmeter means being downstream of said first flowmeter means;

measurement means for determining a total amount of fluid flowing through said pipe at each of said locations for equivalent periods of time;

comparison means coupled to said measurement means for comparing the total flow amounts at said first and second locations for said equivalent periods of time and for producing a volume difference value;

output means operable in response to a predetermined volume difference value from said comparison means, and further comprising means for determining the temperature of fluid at said first and second flowmeter means, and further including a plurality of additional flowmeter means disposed along the length of said pipe;

each of said plurality of flowmeter means having outputs which are provided to said measurement means for measuring the total amount of fluid in said pipe at each of said locations for equivalent periods of time;

said comparison means being coupled to said measurement means for comparing the total flow amounts at any two locations for said equivalent periods of time and for producing a volume difference value, and said output means being operable in response to exceeding a predetermined volume difference value from any two locations from said comparison means.

4. The apparatus recited in claim 3, wherein said flowmeter means are clamp-on transducers clamped onto the outer surface of said pipe for measuring the transit time for ultrasonic energy to traverse the fluid in said pipe.

5. The apparatus recited in claim 3, further comprising means for determining the temperature of fluid at each of said flowmeter means, and means for measuring the ambient temperature at each of said flowmeter means, and further comprising means for correcting the flow amount determined at each of said locations to compensate said volume difference value for effects of temperature.

6. The apparatus recited in claim 3, wherein said measurement means comprise integration means for accumulating flow amount totals for fluid flow past each location for a preset period of time.

7. The apparatus recited in claim 6, wherein said preset period of time comprises a group of preset periods of time.

8. The apparatus recited in claim 7, wherein said group of preset periods of time comprise one minute, five minute, fifteen minute and one hour periods.

9. The apparatus recited in claim 6, wherein said integration means comprises means for updating said totals periodically.

10. The apparatus recited in claim 9, wherein said totals are updated every minute, with the oldest data being deleted in favor of new data.

11. The apparatus recited in claim 3, wherein said total flow amounts comprise mass amounts.

12. A method for detecting a leak in an elongated fluid conducting pipe, said method comprising measuring an amount of flow of fluid per unit time flowing within said pipe at axially spaced locations with a second location being downstream of a first location;

determining the total flow amount of said fluid in said pipe at each of said locations for equivalent periods of time;

comparing the total flow amounts at said first and second locations for said equivalent periods of time and producing a volume difference value; and

generating an output in response to a predetermined volume difference value; and

further comprising measuring the temperature of fluid at said first and second locations and correcting the flow amount determined at the second location to compensate said volume difference value for effects of temperature on the entire pipeline.

13. The method recited in claim 12, wherein said step of measuring the amount of flow per unit time comprises providing clamp-on transducers on the outer surface of said pipe and measuring the transit time for ultrasonic energy to traverse the fluid in said pipe.

14. A method for detecting a leak in an elongated fluid conducting pipe, said method comprising measuring an amount of flow of fluid per unit time flowing within said pipe at axially spaced locations with a second location being downstream of a first location;

determining the total flow amount of said fluid in said pipe at each of said locations for equivalent periods of time;

comparing the total flow amounts at said first and second locations for said equivalent periods of time and producing a volume difference value;

generating an output in response to a predetermined volume difference value; and

further including providing a plurality of additional locations along the length of said pipe;

measuring the amount of said fluid flow per unit time in said pipe at each of said locations;

determining the total flow amounts at each of said locations for equivalent periods of time;

comparing the flow amounts at said first and second locations for said equivalent periods of time and producing a volume difference value; and

providing an output in response to exceeding a predetermined volume difference value.

15. The method recited in claim 14, wherein said step of measuring the amount of flow per unit time comprises providing clamp-on transducers on the outer surface of said pipe and measuring the transit time for ultrasonic energy to traverse the fluid in said pipe.

16. The method recited in claim 14, further comprising determining the temperature of fluid at each of said locations and measuring the ambient temperature at each of said locations, and further comprising correcting the flow amount determined at each of the locations to compensate said volume difference value for effects of temperature.

17. The method recited in claim 14, wherein said step of determining the total flow amount comprises integrating flow amount totals for fluid flow past each location for a preset period of time.

18. The method recited in claim 17, wherein said preset period of time comprises a group of preset periods of time.

19. The method recited in claim 18, wherein said group of preset periods of time comprise one minute, five minute, fifteen minute and one hour periods.

20. The method recited in claim 17, wherein said step of integrating comprises updating said totals periodically.

21. The method recited in claim 20, wherein said totals are updated every minute, with the oldest data being deleted in favor of new data.

22. The method recited in claim 14, wherein said total flow amounts comprise mass amounts.

23. A method of leak detection for a pipeline, comprising the steps of:

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 said threshold level.

24. The method recited in claim 23, wherein the steps of measuring the liquid flow at the first and second site stations 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 site station non-intrusively.

25. The method recited in claim 24, wherein the step of providing a clamp-on ultrasonic flowmeter comprises providing a wide-beam flowmeter.

26. The method recited in claim 24, further comprising the step of identifying the presence of free gas or water in the liquid at each site station, and providing an indication of the presence of said free gas or water.

27. The method recited in claim 26, 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 the site station.

28. The method recited in claim 26, 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 the site station.

29. The method recited in claim 28, 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.

30. The method recited in claim 24, further comprising the step of identifying an interface between liquids of two different types at a site station.

31. The method recited in claim 30, wherein the step of identifying an interface comprises measuring the temperature and the sonic propagation velocity of the liquid at the site station during a time period when an interface between liquids is passing through the pipeline at the site station.

32. The method recited in claim 31, 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.

33. The method recited in claim 32, further comprising computing mass flow through the pipeline at a plurality of site stations and comparing the determined mass flow at each of the site stations from the passage of a first interface to the passage of a second interface to determine if a leak has occurred.

34. The method recited in claim 24, 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.

35. The method recited in claim 24, further comprising identifying the presence of a pig in the pipeline at a site station by 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.

36. The method recited in claim 24, further comprising identifying the presence of water in the liquid at a site station by measuring a defined change in sonic propagation velocity from that of the liquid to that of water at the site station.

37. The method recited in claim 24, further comprising measuring the sonic propagation velocity of the liquid in the pipeline at each site station, determining if a change in sonic propagation velocity has occurred at least two site stations and recording the time of such change at said two site stations, and using a difference in the recorded times at said two site stations to determine the location of a leak.

38. The method recited in claim 23, wherein the steps of measuring the liquid temperature at the first and second site stations comprise providing a clamp-on temperature sensor at the respective site station to measure the liquid temperature.

39. The method recited in claim 23, wherein the step of computing the effects of the ambient temperature at each section comprises interpolating the ambient temperature at each section from the respective ambient temperatures at each site station.

40. The method recited in claim 39, wherein the step of computing the effect of ambient temperature of the first and second site stations on each section comprises determining the topography of the segment.

41. The method recited in claim 40, wherein the step of determining the topography of a segment comprises determining if each section of the segment is disposed in air, water or soil.

42. The method recited in claim 41, further comprising the step of determining the effect of prior temperature history of each section, if the section is disposed in soil, on current and future ambient temperatures.

43. The method recited in claim 23, wherein said step of computing the change in volume of the liquid and the pipe comprises performing said step of computing for a defined period of time.

44. The method recited in claim 43, 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.

45. The method recited in claim 44, 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 time periods.

46. The method recited in claim 45, further comprising the step of performing said steps of computing and correcting for a plurality of different defined periods of time.

47. The method recited in claim 46, 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.

48. The method recited in claim 46, wherein the plurality of different periods of time comprise one minute, five minute, fifteen minute and one hour periods of time.

49. The method recited in claim 23, further comprising computing an expected absolute temperature of each section intermediate the first and second site stations using the computed change in temperature of each section and comparing the measured liquid temperature at the second site station with the computed temperature at the second site station, and correcting the temperature computed at each of the sections based on a difference between the computed temperature and the measured temperature of the liquid at the second site station.

50. The method recited in claim 49, further comprising optimizing thermodynamic equations defining liquid temperature change for each section in accordance with said step of comparing the measured and computed liquid temperatures at the second site station.

51. The method recited in claim 23, further comprising transferring data from each site station to a master station via a high speed data communications link.

52. The method recited in claim 51, further comprising polling the site station from the master station.

53. The method recited in claim 23, further comprising identifying the liquid at each site station by determining sonic propagation velocity of the liquid and the temperature of the liquid at each site station, 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.

54. The method recited in claim 53, 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.

55. The method recited in claim 54, further comprising determining that section which each type of liquid in the pipeline has reached, so that the appropriate liquid expansion coefficient can be used to determine the change of liquid volume in each section due to the change in section temperature.

56. The method recited in claim 53, further comprising storing in advance parameters relating to a plurality of different liquids carried by said pipeline, and using said prestored parameters to identify the liquid in the pipeline by comparing said prestored parameters to actual measured parameters.

57. The method recited in claim 56, wherein the measured and prestored parameters include sonic propagation velocity versus temperature.

58. The method recited in claim 57, wherein the prestored parameters include density and/or viscosity versus temperature.

59. Leak detection apparatus for a pipeline, comprising:

means dividing the pipeline into a plurality of segments, said dividing means comprising a first site station provided at the beginning of each segment and a second site station provided at the end of each segment;

each segment of the pipeline being divided into a plurality of hypothetical pipeline sections, each section having the same nominal volume;

means for measuring the liquid flow into the first section and for determining a volume of liquid that has passed the first site station for a defined period;

means for measuring the temperature of the liquid entering the first section at the first site station;

means for measuring the liquid flow out of the last pipeline section of the segment and for determining a volume of liquid that has passed the second site station for the defined period;

means for measuring the temperature of the liquid leaving the last section at the second site station;

means for measuring the temperature of the ambient to the pipeline at the first site station or that representative of the topography of the segment;

means for measuring the temperature of the ambient to the pipeline at the second site station or that representative of the topography of the segment;

means for computing the effect of the measured ambient temperatures at the first and second site stations on each of the sections intermediate the first and second site stations;

means for 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;

means for 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;

means for determining the difference in measured volume between the volumes determined that have passed the first and second site stations for the defined period;

means for 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;

means for comparing the corrected difference in volume between the first and second site stations with a threshold level; and

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

60. The apparatus recited in claim 59, wherein the means for measuring the liquid flow at the first and second site stations 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 site station nonintrusively.

61. The apparatus recited in claim 60, wherein the clamp-on ultrasonic flowmeter comprises a wide-beam flowmeter.

62. The apparatus recited in claim 60, wherein said means for computing the change in volume of the liquid and the pipeline wall comprise means for computing for a defined period of time.

63. The apparatus recited in claim 62, wherein the means for computing and correcting comprise means for periodically computing for said defined periods of time, with results from said means for correcting being accumulated over multiple ones of said period of time.

64. The apparatus recited in claim 63, 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 one of the periods of time.

65. The apparatus recited in claim 64, further comprising means for performing said steps of computing and correcting for a plurality of different periods of time.

66. The apparatus recited in claim 65, 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 generating an alarm if the results exceed the threshold value for any one of the periods.

67. The apparatus recited in claim 65, wherein the plurality of different periods of time comprise one minute, five minute, fifteen minute and one hour periods of time.

68. The apparatus recited in claim 63, 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.

69. The apparatus recited in claim 68, 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 the site station.

70. The apparatus recited in claim 69, 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.

71. The apparatus recited in claim 63, 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.

72. The apparatus recited in claim 60, wherein the clamp-on flowmeter comprises a multi-path sonic meter to minimize flow profile effects due to bends in the pipeline.

73. The apparatus recited in claim 72, further comprising means for polling the site station from the master station.

74. The apparatus recited in claim 60, further comprising means for measuring the sonic propagation velocity of the liquid in the pipeline at each site station, means for determining if a change in sonic propagation velocity has occurred at least two site stations and means for recording the time of such change at said two site stations, and means for using a difference in the recorded times at said two site stations to determine the location of a leak.

75. The apparatus recited in claim 59, wherein the means for measuring the liquid temperature at the first and second site stations each comprise a clamp-on temperature sensor at the respective site station to measure the liquid temperature.

76. The apparatus recited in claim 59, wherein the means for computing the effect of the ambient temperature at each section comprises means for interpolating the ambient temperature at each section from the respective ambient temperatures at each site station.

77. The apparatus recited in claim 76, wherein the means for computing the effect of ambient temperature at the first and second site stations on each section comprises means for determining the topography of the segment.

78. The apparatus recited in claim 77, wherein the means for determining the topography of the segment comprises means for determining if each section of the segment is disposed in air, water or soil.

79. The apparatus recited in claim 78, 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.

80. The apparatus recited in claim 59, further comprising means for identifying an interface between liquids of two different types at a site station.

81. The apparatus recited in claim 80, wherein the means for identifying an interface comprises means for measuring the temperature and the sonic propagation velocity of the liquid at the site station during a time period when an interface between liquids is passing through the pipeline at the site station.

82. The apparatus recited in claim 81, 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.

83. The apparatus recited in claim 82, further comprising means for computing the mass flow through the pipeline at a plurality of site stations and means for comparing the determined mass flow at each of the site stations from the passage of a first interface to the passage of a second interface to determine if a leak has occurred.

84. The apparatus recited in claim 59, further comprising means for computing an absolute temperature of each section intermediate the first and second site stations using the computed change in temperature of each section and means for comparing the measured liquid temperature at the second site station with the computed temperature at the second site station, and means for correcting the temperature computed at each of the sections based on a difference between the computed temperature and the measured temperature of the liquid at the second site station.

85. The apparatus recited in claim 84, further comprising means for optimizing thermodynamic equations defining the liquid temperature change for each section in accordance with said means for comparing the measured and computed liquid temperature at the second site station.

86. The apparatus recited in claim 59, further comprising means for transferring data from each site station to a master station via a high speed data communications link.

87. The apparatus recited in claim 59, further comprising means for identifying the liquid at each site station by determining the sonic propagation velocity of the liquid and the temperature of the liquid at each site station, 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.

88. The apparatus recited in claim 87, 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.

89. The apparatus recited in claim 88, wherein the measured and prestored parameters include sonic propagation velocity versus temperature.

90. The apparatus recited in claim 89, wherein the prestored parameters include density and/or viscosity versus temperature.

91. The apparatus recited in claim 59, further comprising means for identifying the presence of a pig in the pipeline at a site station comprising means for determining 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.

92. The apparatus recited in claim 59, further comprising means for identifying the presence of water in the liquid at a site station comprising means for measuring a defined change in sonic propagation velocity from that of the liquid to that of water at the site station.