Method and apparatus for detecting leaks in pipelines using cross-correlation techniques

• US 5,205,173 A
• Filed: 06/21/1991
• Issued: 04/27/1993
• Est. Priority Date: 06/21/1991
• Status: Expired due to Fees

• Current Assignee: Palmer Environmental Services
• Original Assignee: Palmer Environmental Services
• Inventors: Allen, Trevor J.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): FAYYAZ, NASHMIYA SAQIB
• Application Number:
  US07/718,746
• Time in Patent Office: 676 Days
• Field of Search: 73/40.5 A, 73/592, 340/605, 376/252
• US Class Current: 73/592
• CPC Class Codes: G01M 3/243 for pipes

Abstract

An improved method and apparatus for detecting leaks in pipelines using cross-correlation techniques including improved correlating circuitry featuring a pair of circulating delay lines for respectively receiving, temporarily storing and processing in a revolving sequence samples of input data obtained from a pair of remotely positioned sensors, a multiplying circuit for causing samples input to each channel to be multiplied by each sample stored in the circulating delay line associated with the other channel, an adder and accumulator memory for accumulating the multiplication results, and a display for displaying the correlation results.

Claims

1. Apparatus for detecting a leak position in a pipeline comprising:

first sensor means for disposition at a first position on one side of a pipeline leak to detect sounds generated by the leak and operative to develop a first analog electrical signal corresponding to such sounds;

second sensor means for disposition at a second position on the opposite side of the leak at a known distance from said first sensor means to detect sound generated by the leak and operative to develop a second analog electrical signal corresponding to such sounds;

analog-to-digital converter means for converting said first analog signal to a digital signal including a series of first digital signal samples, and for converting said second analog signal to a digital signal including a series of second digital signal samples;

first latch means for temporarily storing each said first signal sample;

second latch means for temporarily storing each said second signal sample;

memory means having a first sample storage channel coupled to said first latch means and operative to store the "n" most recent first signal samples each previously temporarily stored in said first latch means, and a second sample storage channel coupled to said second latch means and operative to store the "n" most recent second signal samples each previously temporarily stored in said second latch means, where "n" is a predetermined nonzero integer;

multiplier means having a first input coupled to said first latch means and said first sample storage channel, and a second input coupled to said second latch means and said second sample storage channel;

control means for causing said multiplier means to alternately multiply each first signal sample temporarily stored in said first latch means with each of the "n" samples stored in said second storage channel, and each second signal sample temporarily stored in said second latch means with each of the "n" samples stored in said first storage channel;

accumulator means for accumulating the results of each said multiplication; and

display means for displaying the accumulated results to indicate the position of said leak relative to the positions of said first and second sensor means.

2. Apparatus for detecting a leak in a piperline as recited in claim 1 wherein said memory means includes a random access memory device and associated latch means configured to operate as a first circulating delay forming said first sample storage channel and a second circulating delay forming said second sample storage channel.

3. Apparatus for detecting a leak in a piperline as recited in claim 1 wherein said multiplier means is a read-only memory device programmed to output a digital signal corresponding to the product of first and second digital signals input thereto.

4. Apparatus for detecting a leak in a piperline as recited in claim 1 wherein said accumulator means includes a random access memory, adder means having a first input coupled to the output of said multiplier means, a second input coupled to said random access memory, and an output coupled to said random access memory and to said display means.

5. Apparatus for detecting a leak in a piperline as recited in claim 4 wherein said control means includes address signal generating means for developing address signals for determining the memory locations within said random access memory and said memory means from which data is to be read and to which data is to be written.

6. Apparatus for detecting a leak in a piperline as recited in claim 2 wherein said multiplier means is a read-only memory device programmed to output a digital signal corresponding to the product of first and second digital signals input thereto.

7. Apparatus for detecting a leak in a piperline as recited in claim 7 wherein said accumulator means includes a random access memory, adder means having a first input coupled to the output of said multiplier means, a second input coupled to said random access memory, and an output coupled to said random access memory and to said display means.

8. Apparatus for detecting a leak in a piperline as recited in claim 7 wherein said control means includes address signal generating means for developing address signals for determining the memory locations within said random access memory and said memory means from which data is to be read and to which data is to be written.

9. A method for detecting a deal in a piperline comprising the steps of:

positioning a first sensor means at a first position on one side of a piperline leak for detecting sounds generated by the leak and for developing a first analog electrical signal corresponding to such sounds;

positioning a second sensor means at a second position on the opposite side of the leak at a known distance from the first sensor means for detecting sound generated by the leak and for developing a second analog electrical signal corresponding to such sounds;

converting said first analog signal to a digital signal including a series of first digital signal samples, and for converting said second analog signal to a digital signal including a series of second digital signal samples;

temporarily storing each said first signal sample and each said second signal sample in first and second latch means respectively;

storing the "n" most recent first signal samples each previously temporarily stored in the first latch means in a first sample storage channel of a memory means, and storing the "n" most recent second signal samples each previously temporarily stored in the second latch means in a second sample storage channel of a memory means, where "n" is a predetermined nonzero integer;

alternately multiplying each temporarily stored first signal sample by each of the "n" samples stored in the second storage channel, and each temporarily stored second signal sample with each of the "n" samples stored in said first storage channel;

accumulating the results of each said multiplication; and

displaying the accumulated results to indicate the position of the leak relative to the positions of the first and second sensor means.