Method for inspecting the elements of piping systems by electromagnetic waves

• US 6,008,657 A
• Filed: 08/15/1996
• Issued: 12/28/1999
• Est. Priority Date: 12/16/1994
• Status: Expired due to Fees

• Current Assignee: Tokyo Gas Company Limited
• Original Assignee: Tokyo Gas Company Limited
• Inventors: Imaoka, Takashi, Suyama, Kiichi
• Primary Examiner(s): REGAN, MAURA K
• Application Number:
  US08/687,450
• Time in Patent Office: 1,230 Days
• Field of Search: 324/528, 324/529, 324/530, 324/536, 324/537, 324/639, 324/637
• US Class Current: 324/639
• CPC Class Codes: G01N 22/02 Investigating the presence of flaws

Abstract

Electromagnetic waves are driven in the pipe to be inspected in the piping system by a transmitting antenna of a transmitter, to be propagated in the pipe; while a receiving antenna of a receiver is moved outside the pipe along the pipe, to receive leaking electromagnetic waves for inspecting elements of the piping system, and the location concerned of each element of the piping system to be inspected is detected in reference to the location of the receiving antenna where the level of electromagnetic waves received by the receiver becomes a peak. The locations to be inspected are the damaged portions such as holes formed by corrosion, cracks, etc. in the pipes, and the locations of joints, etc. It is also possible to move the transmitting antenna outside along the pipe, while arranging the receiving antenna at proper place in the pipe. Furthermore, it is also possible to move both the transmitting antenna and the receiving antenna in synchronization to effect the above inspection. When either the transmitting antenna or the receiving antenna is moved, the frequency of electromagnetic waves can be a frequency propagated in the pipe or can also be lower than the cut-off frequency. On the other hand, the antenna can be made long and kept in the pipe, to use a frequency lower than the cut-off frequency without moving the antenna.

Claims

1. A method for inspecting elements of a piping system by electromagnetic waves comprising the steps of forming an opening in a wall of the pipe to be inspected, said opening being formed by installing a Tee in the pipe to be inspected, inserting a probe inside a cover closing a central branch opening of a Tee installed in the pipe to be inspected, connecting said probe and an electromagnetic wave oscillator by a coaxial cable;

said probe being located in the Tee with a cover installed at a central branch opening, to constitute a transmitting antenna driving electromagnetic waves by said transmitting antenna of a transmitter, to propagate electromagnetic waves in the pipe;

moving a receiving antenna of a receiver outside the pipe along the pipe, to receive leaking electromagnetic waves for inspecting elements of the piping system; and

detecting a location concerned with each element of the piping system to be inspected, in reference to the location of the receiving antenna where the level of electromagnetic waves received by the receiver becomes a peak.

2. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 1, wherein the frequency of the electromagnetic waves is changed over time.

3. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 2, wherein the frequency of electromagnetic waves is continuously changed by sweep.

4. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 2, wherein the frequency of electromagnetic waves is stepwise changed.

5. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 1, wherein the electromagnetic waves propagated by the transmitter in the piping system inspected are modulated.

6. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 5, wherein the electromagnetic waves are modulated by human recognizable information signals.

7. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 1, wherein the electromagnetic waves driven by the transmitter in the pipe of the piping system inspected are modulated;

the electromagnetic waves received by the receiver are compared with the electromagnetic waves transmitted by the transmitter as modulated signals, to obtain the time difference; and

the propagation time corresponding to the distance corresponding to the propagation distance from the driving point to the leak point is subtracted from the time difference, to measure the propagation time of electromagnetic waves from the driving point to the leak point, for obtaining the distance of the piping system from the driving point to the leak point.

8. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 7, wherein the time difference is measured in reference to the phase difference between the electromagnetic waves detected by the receiver and the electromagnetic waves transmitted by the transmitter in terms of modulated signals.

9. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 1, wherein the transmitter is provided with a device for adjusting the intensity of the electromagnetic waves transmitted by it.

10. A method for inspecting elements of a piping system by electromagnetic waves, according to claim 9, wherein the adjusting device is adjusted in response to the level of electromagnetic waves received by the receiver.

11. The method for inspecting elements of a piping system by electromagnetic waves, according to claim 1 wherein the electromagnetic waves driven by the transmitter in the pipe of the piping system inspected are modulated;

the electromagnetic waves received by the receiver are compared with the electromagnetic waves transmitted by the transmitter as modulated signals, to obtain the time difference; and

the propagation time corresponding to the distance corresponding to the propagation distance from the driving point to the leak point is subtracted from the time difference, to measure the propagation time of electromagnetic waves from the driving point to the leak point, for obtaining the distance of the piping system from the driving point to the leak point, wherein in the transmission of electromagnetic waves by the transmitter and in the receiving of electromagnetic waves by the receiver, pulse compression technic is applied.

12. A method for inspecting elements of a piping system by electromagnetic waves, comprising the steps of driving electromagnetic waves at a properly point of the pipe to be inspected in the piping system, by a transmitting antenna of a transmitter, to propagate them in the pipe;

moving a receiving antenna of a receiver outside the pipe along the pipe, to receive leaking electromagnetic waves for inspecting elements of the piping system; and

detecting the location concerned of each element of the piping system to be inspected, in reference to the location of the receiving antenna where the level of electromagnetic waves received by the receiver becomes a peak wherein the receiving of leaking electromagnetic waves by the receiver is effected when the drive of electromagnetic waves by the transmitter is in ON state, and is effected also when the drive of electromagnetic waves by the transmitter is temporarily in OFF state, and the signals received in OFF state are compared with the signals received in ON state, to distinguish the electromagnetic waves caused by leaking.

13. A method for inspecting elements of a piping system by electromagnetic waves, comprising the steps of driving electromagnetic waves at a properly point of the pipe to be inspected in the piping system, by a transmitting antenna of a transmitter, to propagate them in the pipe;

moving a receiving antenna of a receiver outside the pipe alone the pipe, to receive leaking electromagnetic waves for inspecting elements of the piping system; and

detecting the location concerned of each element of the piping system to be inspected, in reference to the location of the receiving antenna where the level of electromagnetic waves received by the receiver becomes a peak wherein the receiving of leaking electromagnetic waves by the receiver is effected when the drive of electromagnetic waves by the transmitter is in ON state, and is effected also when the drive of electromagnetic waves by the transmitter is temporarily in OFF state, and the signals received in OFF state are compared with the signals received in ON state, to distinguish the electromagnetic waves caused by leaking wherein the transmitter is provided with an electromagnetic wave drive ON-OFF control means, to effect ON-OFF control by itself, and signals synchronous with the ON-OFF actions are transmitted to the receiver, to allow the receiver to detect the ON-OFF states.