High-precision leak detector and locator

• US 5,548,530 A
• Filed: 04/24/1995
• Issued: 08/20/1996
• Est. Priority Date: 04/24/1995
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Joseph Baumoel
• Inventors: Baumoel, Joseph
• Primary Examiner(s): TRAMMELL, JAMES P
• Application Number:
  US08/427,411
• Time in Patent Office: 484 Days
• Field of Search: 364/509 C, 364/510, 364/507, 364/558, 364/565, 364/569, 73/40.5 R, 73/40.5 A, 73/49.1, 73/49.5, 73/49.2, 73/40.7, 73/597, 73/598, 73/861.78, 73/861.31, 340/605, 367/99, 367/100, 367/125, 376/252
• US Class Current: 702/51
• CPC Class Codes: G01M 3/243 for pipes
• CPC Class Codes: G01N 2291/022 Liquids
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/105 two or more emitters, two or more receivers
• CPC Class Codes: G01N 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/50 using auto-correlation techniques or cross-correlation techniques

Abstract

A method for detecting the presence of a leak in a segment of a pipeline. The method includes providing a site station having an ultra-sonic transducer assembly at the beginning and end of the pipeline segment, each assembly having two pairs of ultrasonic transducers for determining the sonic propagation velocity V_s of ultrasonic energy emitted by the transducers through fluid in the pipeline. Each pair of ultrasonic transducers is displaced along the pipeline by a preset distance and each defines an ultrasonic energy flow path. The value of V_s for each ultrasonic energy flow path through the fluid in the pipeline is determined at each site station at predetermined time intervals. Values ΔV_s defined as the difference between sequential values of V_s at the predetermined time intervals for each flow path at each site station are formed. The ΔV_s values for each flow path are stored in a memory having a predetermined number of memory cells, where a value of ΔV_s is stored in each cell. A determination is made if there is a correlation in the stored values of ΔV_s for each flow path. If there is a correlation between the ΔV_s values for each path, a discrimination is performed between a correlation caused by zero values of ΔV_s stored in the memory for each path and a correlation of ΔV_s values reflecting that a transient in the fluid in the pipeline has arrived at each site station. Then a determination is made whether the correlation corresponds to a leak.

Claims

1. A method for detecting the presence of a leak in a segment of a pipeline comprising:

providing site stations comprising an ultrasonic transducer assembly at the beginning and end of the pipeline segment, each said assembly having two pairs of ultrasonic transducers for determining the sonic propagation velocity V_s of ultrasonic energy emitted by the transducers through fluid in the pipeline, each pair of ultrasonic transducers being displaced along the pipeline by a preset distance and each defining an ultrasonic energy flow path;

determining the value of V_s for each ultrasonic energy flow path through the fluid in the pipeline at each site station at predetermined time intervals;

forming values Δ

V_s defined as the difference between sequential values of V_s at said predetermined time intervals for each flow path at each site station;

storing said Δ

V_s values for each flow path in a memory having a predetermined number of memory cells, where a value of Δ

V_s is stored in each cell;

determining if there is a correlation in the stored values of Δ

V_s for each flow path;

discriminating, if there is a correlation between the Δ

V_s values for each path, between a correlation caused by zero values of Δ

V_s stored in the memory for each path and a correlation of Δ

V_s values reflecting that a transient in the fluid in the pipeline has arrived at each site station; and

determining, if there is a correlation wherein the Δ

V_s values reflect that a transient has arrived at each site station, whether the correlation corresponds to a leak in the segment, and if so, indicating that a leak has occurred.

2. The method recited in claim 1, further comprising determining the location of the leak in the segment by triangulation of the transient arrival time between the two site stations at the two ends of the pipeline segment.

3. The method recited in claim 1, further comprising selecting the number of cells in the memory such that substantially all Δ

V_s values from a transient caused by a leak will be stored in the memory, and substantially all Δ

V_s values from a transient not caused by a leak will not be stored in the memory because such a transient not resulting from a leak is too slow to result in substantially all the Δ

V_s values being stored in the memory.

4. The method recited in claim 1, where the step of discriminating comprises generating a correlation factor which indicates the relative strength and arrival time of a transient pulse as reflected in the Δ

V_s values for each path in the memory, and using said correlation factor to determine whether there is a leak in the pipeline or some other condition which is not a leak.

5. The method recited in claim 4, wherein the step of storing comprises storing said Δ

V_s values in a FIFO memory for each flow path.

6. The method recited in claim 5, wherein the step of storing in a FIFO memory for each flow path comprises storing in a shift register.

7. The method recited in claim 5, further comprising providing a number of cells in each FIFO memory sufficient to allow correlation of Δ

V_s values in each FIFO memory for a transient arising from a leak in the pipeline and substantially preventing correlation of Δ

V_s value in each FIFO memory for a transient arising from a condition in the pipeline that is not a leak.

8. The method recited in claim 5, further comprising determining the direction of a transient pulse in the fluid in the pipeline from the direction of a cell shift of correlating values in each of the FIFO memories.

9. The method recited in claim 8, wherein the step of generating the correlation factor comprises forming the following value CF:

space="preserve" listing-type="equation">CF=FIFO sum/(Displaced FIFO Difference+X)

where FIFO sum=the sum of all correlated values for either FIFO;

Displaced FIFO Difference=the difference between the sums of the correlated values for each FIFO; and

X=a small fixed number to prevent a zero denominator.

10. Apparatus for detecting the presence of a leak in a segment of a pipeline comprising:

two site stations each having an ultra-sonic transducer assembly provided respectively at the beginning and end of the pipeline segment, each said assembly having two pairs of ultrasonic transducers for determining the sonic propagation velocity V_s of ultrasonic energy emitted by the transducers through fluid in the pipeline, each pair of ultrasonic transducers being displaced along the pipeline by a preset distance and each defining an ultrasonic energy flow path;

a computer for determining the value of V_s for each ultrasonic energy flow path through the fluid in the pipeline at each site station at predetermined time intervals, the computer further forming values Δ

V_s defined as the difference between sequential values of V_s at said predetermined time intervals for each flow path at each site station;

a memory wherein said Δ

V_s values are stored for each flow path having a predetermined number of memory cells, where a value of Δ

V_s is stored in each cell;

the computer further determining if there is a correlation in the stored values of Δ

V_s for each flow path and discriminating, if there is a correlation between the Δ

V_s values for each path, between a correlation caused by zero values of Δ

V_s stored in the memory for each path and a correlation of Δ

V_s values reflecting that a transient in the fluid in the pipeline has arrived at each site station; and

the computer further determining, if there is a correlation wherein the Δ

V_s values reflect that a transient has arrived at each site station, whether the correlation corresponds to a leak in the segment, and if so, indicating that a leak has occurred.

11. The apparatus recited in claim 10, wherein the computer further determines the location of the leak in the segment by triangulation of the transient arrival time between the two site stations at the two ends of the pipeline segment.

12. The apparatus recited in claim 10, wherein the number of cells in the memory is such that substantially all Δ

V_s values from a transient caused by a leak will be stored in the memory, and substantially all Δ

V_s values from a transient not caused by a leak will not be stored in the memory because such a transient not resulting from a leak is too slow to result in substantially all the Δ

V_s values being stored in the memory.

13. The apparatus recited in claim 10, wherein the computer generates a correlation factor which indicates the relative strength and arrival time of a transient pulse as reflected in the Δ

V_s values for each path in the memory, said correlation factor determining whether there is a leak in the pipeline or some other condition which is not a leak.

14. The apparatus recited in claim 13, wherein the memory comprises a FIFO memory for storing said Δ

V_s values for each flow path.

15. The apparatus recited in claim 14, wherein the FIFO memory for each flow path comprises a shift register.

16. The apparatus recited in claim 14, wherein a number of cells in each FIFO memory is sufficient to allow correlation of Δ

V_s values in each FIFO memory for a transient arising from a leak in the pipeline and substantially preventing correlation of Δ

V_s values in each FIFO memory for a transient arising from a condition in the pipeline that is not a leak.

17. The apparatus recited in claim 14, wherein the computer further determines the direction of a transient pulse in the fluid in the pipeline from the direction of a cell shift of correlating values in each of the FIFO memories.

18. The apparatus recited in claim 17, wherein the means for generating the correlation factor comprises forming the following value CF:

space="preserve" listing-type="equation">CF=FIFO sum/(Displaced FIFO Difference+X)

where FIFO sum=the sum of all correlated values for either FIFO;

Displaced FIFO Difference=the difference between the sums of the correlated values for each FIFO; and

X=a small fixed number to prevent a zero denominator.

19. Apparatus for detecting the presence of a leak in a segment of a pipeline comprising:

two site stations each having an ultra-sonic transducer assembly provided respectively at the beginning and end of the pipeline segment, each said assembly having two pairs of ultrasonic transducers for determining the sonic propagation velocity V_s of ultrasonic energy emitted by the transducers through fluid in the pipeline, each pair of ultrasonic transducers being displaced along the pipeline by a preset distance and each defining an ultrasonic energy flow path;

means for determining the value of V_s for each ultrasonic energy flow path through the fluid in the pipeline at each site station at predetermined time intervals;

means for forming values Δ

V_s defined as the difference between sequential values of V_s at said predetermined time intervals for each flow path at each site station;

a memory for storing said Δ

V_s values for each flow path having a predetermined number of memory cells, where a value of Δ

V_s is stored in each cell;

means for determining if there is a correlation in the stored values of Δ

V_s for each flow path;

means for discriminating, if there is a correlation between the Δ

V_s values for each path, between a correlation caused by zero values of Δ

V_s stored in the memory for each path and a correlation of Δ

V_s values reflecting that a transient in the fluid in the pipeline has arrived at each site station; and

means for determining, if there is a correlation wherein the Δ

V_s values reflect that a transient has arrived at each site station, whether the correlation corresponds to a leak in the segment, and if so, indicating that a leak has occurred.

20. The apparatus recited in claim 19, further comprising means for determining the location of the leak in the segment by triangulation between the two site stations at the two ends of the pipeline segment.

21. The apparatus recited in claim 19, wherein the number of cells in the memory is such that substantially all Δ

V_s values from a transient caused by a leak will be stored in the memory, and substantially all Δ

V_s values from a transient not caused by a leak will not be stored in the memory because such a transient not resulting from a leak is too slow to result in substantially all the Δ

V_s values being stored in the memory.

22. The apparatus recited in claim 19, wherein the means for discriminating comprises means for generating a correlation factor which indicates the relative strength of a transient pulse as reflected in the Δ

V_s values for each path in the memory, said correlation factor determining whether there is a leak in the pipeline or some other condition which is not a leak.

23. The apparatus recited in claim 22, wherein the memory comprises a FIFO memory for storing said Δ

V_s values for each flow path.

24. The apparatus recited in claim 23, wherein the FIFO memory for each flow path comprises a shift register.

25. The apparatus recited in claim 23, wherein a number of cells in each FIFO memory is sufficient to allow correlation of Δ

V_s values in each FIFO memory for a transient arising from a leak in the pipeline and substantially preventing correlation of Δ

V_s values in each FIFO memory for a transient arising from a condition in the pipeline that is not a leak.

26. The apparatus recited in claim 23, further comprising means for determining the direction of a transient pulse in the fluid in the pipeline from the direction of a cell shift of correlating values in each of the FIFO memories.

27. The apparatus recited in claim 26, wherein the means for generating the correlation factor comprises forming the following value CF:

space="preserve" listing-type="equation">CF=FIFO sum/(Displaced FIFO Difference+X)

where FIFO sum=the sum of all correlated values for either FIFO;

Displaced FIFO Difference=the difference between the sums of the correlated values for each FIFO; and

X=a small fixed number to prevent a zero denominator.