Arrangement for detecting the location of an electrically insulative continuous item positioned underground

Claim 1

An arrangement for detecting above the ground the location of a generally horizontally arranged gas conveying passage positioned beneath the ground, said arrangement comprising: a gas pipe positioned beneath the ground and defining a generally horizontal gas conveying passage, said gas pipe being formed of an electrically insulative synthetic resin material; an electrically conductive wire positioned along the exterior of said gas pipe, said wire comprising a flexible metallic core formed by stranding together a plurality of single wires, and an electrically conductive flexible outer coating layer applied directly over said core, said layer being formed of a combination of 100 parts by weight of chloroprene rubber or natural rubber per 50 to 60 parts by weight of acetylene carbon, and said layer having a specific resistance of approximately 100 ohm-cm; a steel pipe extending into the ground; a branch gas pipe extending from said gas pipe to said steel pipe and positioned beneath the ground, said branch gas pipe being formed of an electrically insulative synthetic resin material; an electrically conductive branch wire extending along the exterior of said branch gas pipe, said branch wire comprising a flexible metallic core formed by stranding together a plurality of single wires, and an electrically conductive flexible outer coating layer applied directly over said core, said layer being formed of a combination of 100 parts by weight of chloroprene rubber or natural rubber per 50 to 60 parts by weight of acetylene carbon, and said layer having a specific resistance of approximately 100 ohm-cm, said branch wire having a first end electrically connected to said wire and a second end wound around the exterior of said steel pipe, an end of said core of said second end of said branch wire being welded to the exterior of said steel pipe; and high frequency power source means, electrically connected to said steel pipe at a position above ground, for supplying to said steel pipe, said branch wire and said wire high frequency energy of from 2 KHz to 100 KHz at 6 volts, such that said branch wire and said wire emit electromagnetic waves which are detectable above ground.