Method and apparatus for electromagnetic testing of pipes

1. An apparatus for testing within a metal pipe, comprising:

an exciter for generating an electromagnetic (EM) field for exciting a wall of the metal pipe;

an extendable and retractable sensor assembly comprising a plurality of sensor bars for sensing residue EM field on the wall of the pipe, each sensor bar comprising a plurality of sensors, and having a first axis arranged in an angled manner with respect to a second axis of the pipe,

the sensors in each sensor bar being arranged in such a manner that an axis of a sensor forms an angle with respect to the first axis of the sensor bar, the angle being in a range from about 20° to 70°;

a plurality of guide wheel assemblies for supporting and moving the apparatus along the second axis of the pipe; and

a control unit for processing the sensed residue EM field from the sensor assembly.

2. The apparatus of claim 1 , wherein each of the sensors comprises coils.

3. The apparatus of claim 1 , wherein the sensor assembly includes a plurality of expandable and retractable arms, and each arm has a sensor bar.

4. The apparatus of claim 3 , wherein the each arm is made of graphite composites.

5. The apparatus of claim 1 , wherein the sensor bars are substantially parallel to a surface of the wall of the pipe when the apparatus advances along the pipe.

6. The apparatus of claim 1 , wherein the sensor bars are configured to be in contact with the wall of the pipe when a diameter of the pipe changes.

7. The apparatus of claim 1 , wherein the sensor bars include bristles.

8. The apparatus of claim 1 , wherein the guide wheel assemblies are extendable and retractable.

9. The apparatus of claim 1 , wherein each of the guide wheel assemblies includes a brake.

10. The apparatus of claim 1 , further comprising a handle for manually moving the apparatus through the pipe.

11. The apparatus of claim 1 , wherein the control unit includes a battery for supplying a current to a processor, and wherein the processor modulates the current and supplies the modulated current to the exciter to generate the EM field.

12. The apparatus of claim 1 , wherein the exciter comprises a plurality of conductive coils.

13. The apparatus of claim 12 , wherein exciter further comprises a support structure and the plurality of conductive coils are mounted on an external surface of the support structure.

14. The apparatus of claim 13 , wherein the support structure is collapsible to fit through a manhole.

15. The apparatus of claim 12 , wherein the plurality of conductive coils are detachable from each other.

16. The apparatus of claim 12 , wherein each of the plurality of conductive coils has a connector for receiving current input.

17. The apparatus of claim 12 , wherein the exciter comprises at least one spacer for binding the plurality of conducive coils on an external surface of a support structure.

18. The apparatus of claim 1 , further comprising an attachment mounted at a front end and/or a rear end of the apparatus.

19. The apparatus of claim 18 , wherein the attachment is a tow ring attachment.

20. The apparatus of claim 1 , further comprising a flex joint mounted between the exciter and the sensor assembly.

21. The apparatus of claim 1 , wherein the apparatus comprises a first guide wheel assembly mounted at a first end of the sensor assembly, and a second guide wheel assembly mounted at a second end of the sensor assembly.

22. The apparatus of claim 21 , wherein the apparatus comprises a third guide wheel assembly mounted between the exciter and the second guide wheel assembly.

23. A method for testing a metal pipe, comprising:

generating an electromagnetic (EM) field;

exciting a wall of the metal pipe with the EM field;

providing an extendable and retractable sensor assembly comprising a plurality of sensor bars for sensing the EM field on a wall of a pipe, each sensor bar comprising a plurality of sensors, and having a first axis arranged in an angled manner with a second axis of the metal pipe the sensors in each sensor bar being arranged in such a manner that an axis of a sensor forms an angle with respect to the first axis of the sensor bar, the angle being in a range from about 20° to 70°;

moving the sensor assembly along the second axis of the pipe; and

sensing, by the sensor assembly, residue EM field on the wall of the pipe.

24. The method of claim 23 , further comprising:

outputting sensed data to a control unit; and

detecting defects on the metal pipe.

25. An apparatus for testing within a metal pipe, comprising:

an exciter for generating an electromagnetic (EM) field for exciting a wall of the metal pipe;

a sensor assembly comprising a plurality of sensor supports for sensing residue EM field on the wall of the pipe, each sensor support having a first longitudinal axis, each sensor support including a plurality of sensors, each sensor having a second longitudinal axis that intersects the first longitudinal axis at an angle from 20° to 70°;

a plurality of guide wheel assemblies for supporting and moving the apparatus along the pipe; and

a control unit for processing the sensed residue EM field from the sensor assembly.

26. The apparatus of claim 25 , wherein the sensor assembly includes a plurality of expandable and retractable arms, each arm having one of the plurality of sensor supports mounted thereon.

27. The apparatus of claim 25 , wherein the sensor supports are substantially parallel to a surface of the wall of the pipe.

28. The apparatus of claim 25 , wherein the sensor supports are configured to be in contact with the wall of the pipe when a diameter of the pipe changes.

29. The apparatus of claim 25 , wherein the sensors include coils.