Locating method of and the locating unit for leaks on piping

• US 4,704,897 A
• Filed: 09/24/1986
• Issued: 11/10/1987
• Est. Priority Date: 09/30/1985
• Status: Expired due to Fees

• Current Assignee: Tokyo Gas Company Limited
• Original Assignee: Tokyo Gas Company Limited
• Inventors: Kawase, Akira, Imamura, Minoru
• Primary Examiner(s): Levy, Stewart J.
• Assistant Examiner(s): ROSKOS, JOSEPH
• Application Number:
  US06/911,256
• Time in Patent Office: 412 Days
• Field of Search: 73/40.5 R
• US Class Current: 73/40.50R
• CPC Class Codes: G01M 3/22 for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators

Abstract

A method of locating a leak in a block of pipes comprises the filling of the pipe with inert gas and the sealing of the pipe. Thereafter, suction is applied to the pipe for drawing air or atmospheric gas into the pipe through the leak. Care is taken to insure that the block of pipes is sealed, except for the suction port and the leak position. Once a layer of air or atmospheric gas is established in the pipe near the leak position, inert gas is drawn from the pipe by the pump, in a direction toward an oxygen or atmospheric gas sensor. By doing this, the layer of air or atmospheric gas is moved along in the pipe from the leak position toward the oxygen sensor. A measurement is taken of the volume of gas being drawn while the layer of air or atmospheric gas is being moved along the pipe. The oxygen or atmospheric sensor indicates when the layer of air or atmospheric gas has arrived. This measurement is used in conjunction with a measurment of the volume that has been drawn from the block of pipes to give an accurate measurement of the position of the leak in the block of pipes.

Claims

1. A method for locating the position of a leak in a pipe, comprising, filling the pipe with an inert gas, sealing the pipe with inert gas therein, drawing gas from a first end of pipe to reduce the pressure of gas in the pipe and to draw air into the pipe through a leak in the pipe to form an air layer in the pipe in the vicinity of the leak, opening an opposite end of the pipe, sucking the inert gas and the air layer from the first end of the pipe, in a direction toward the first-mentioned end of the pipe for moving the air layer toward the one end of the pipe away from the leak, continuously measuring the air density of gas leaving the one end of the pipe using a sensor at a known location, measuring the volume of inert gas being supplied to the opposite end of the pipe, the pipe having a known sectional area, and calculating the distance between the leak and the known location of the sensor by dividing the volume by the sectional area of the pipe, the volume of inert gas being measured from the time drawing begins until the detection of air at the sensor indicating the presence of air layer at the sensor after it has moved from the leak.

2. A method according to claim 1, including filling the pipe with air before the pipe is filled with inert gas, cause an overflow and storage of air through the leak in the neighborhood of the pipe.

3. A method according to claim 1, including drawing the inert gas into the opposite end of the pipe while sucking gas from the one end of the pipe so as to prevent the air layer from being disturbed.

4. A method according to claim 1, including supplying the inert gas into the opposite end of the pipe by feeding pressurized inert gas to the opposite end of the pipe so as to move the air layer in the pipe.

5. A method according to claim 1, including filling the pipe with inert gas by connecting a dummy pipe which is initially filled with inert gas and sealed, to the opposite end of the pipe, and opening communication between the pipe with the leak and the dummy pipe.

6. An apparatus for locating the position of the leak in a pipe which is between first and second opposite ends of the pipe, comprising:

a suction line connected to the first end of the pipe;

a flow meter in said suction line for measuring the flow of gas through the suction line;

an oxygen sensor connected to the suction line for detecting a concentration of oxygen density in the gas of the suction line;

an infusion line for inert gas connected to said second end of the pipe;

an inert gas cylinder for containing an inert gas connected to said infusion line;

gas suction means connected to said suction line for drawing gas from the pipe,

a computing element connected to receive signals from said sensor and from said flow meter for calculating a volume of inert gas being sucked from the inside of into the pipe by said suction means as a funtion of the cross-sectional area of the pipe and as a function of an indication from said sensor indicating the presence of an oxygen-containing layer of gas from the pipe from the vicinity of the leak in the pipe between said first and second ends thereof, said calculating unit operating to calculate the distance between the sensor and the position of the leak; and

a display connected to said computing element for displaying the distance between the sensor and the position of the leak.

7. An apparatus according to claim 6, including an air inlet valve connected to the infusion line which is openable to admit air into said infusion line and through said second end into said pipe.

8. An apparatus according to claim 7, including a dummy pipe which is filled with inert gas and sealed, connected between said infusion line and said second end of the pipe, and valve means for establishing communication between said dummy pipe and said pipe with the leak.