| US 7,466,134 B2 | ||
| Method and apparatus for locating underground cast iron pipe joints | ||
| Joe W. McCarty, Wauconda, Ill. (US) | ||
| Assigned to Gas Technology Institute, Des Plaines, Ill. (US) | ||
| Filed on Aug. 04, 2006, as Appl. No. 11/499,379. | ||
| Prior Publication US 2008/0030189 A1, Feb. 07, 2008 | ||
| Int. Cl. G01V 3/11 (2006.01) | ||
| U.S. Cl. 324—327 [324/326] | 4 Claims |
| 1. A method for locating underground cast iron pipe joints comprising the steps of:
determining the location and orientation of an underground cast iron pipe;
passing an oscillating electrical current through an electrically driven resonant coil disposed substantially vertically above
said underground cast iron pipe, forming an oscillating magnetic field;
inducing an electrical current in each of two resonant sensor coils disposed within said oscillating magnetic field;
measuring a magnetic reluctance between said electrically driven resonant coil and each of said resonant sensor coils, producing
an initial magnetic reluctance; and
measuring said magnetic reluctance while moving said coils above and parallel to said cast iron pipe, whereby measured magnetic
reluctances substantially different from said initial magnetic reluctance constitutes proximity to a cast iron pipe joint.
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