Abstract: A method for reducing voltages required by in-place proximity-effect circuits includes providing uninsulated conductors which extend from a main transformer station to remote feed-node locations for connection to insulated conductors within a heat-tracing pipe.

Abstract: A proximity effect heat-tracing system in which proximity effect heat-tracing circuits are fed in either direction from a plurality of feed points connected to a single main transformer to increase the length of pipeline supplied by a single main transformer. A secondary transformer interposed between a main transformer and a plurality of feed points reduces the voltage required to be applied to a proximity effect heat-tracing system of a given length. Two or more proximity effect heat-tracing systems used along the same length of pipeline, employ neutral conductors having approximately the same diameter as "hot" conductors where the secondary of the main transformer in each system is 180.degree. electrically out of phase with the secondary of the main transformer in the other system.

Abstract: Methods and apparatus for detecting abnormalities in proximity effect pipeline tracing circuits by coupling conductive elements carrying proximity effect circuit currents and having opposite polarities. These conductive elements are coupled to an additional conductive element which is in turn connected to a system for detecting current so that when the difference between the proximity effect circuit currents is non-zero, the current flows through the additional conductive element and is detected by a relay or ammeter.

Abstract: An improvement in a heat-generating pipe made up of a ferromagnetic pipe having an insulated conductor extending through it to a given point so that both the pipe and conductor may be connected in series with a power source of alternating current. The invention is directed to both a method and nonferromagnetic means for reducing the heat output over a desired segment of the pipe by reducing the magnetic field created by the alternating current flowing in the insulated conductor and that segment of the pipe.The nonferromagnetic means comprises a portion of the insulated conductor that is exterior to the ferromagnetic pipe along the segment of reduced heat output so that it is magnetically decoupled from the pipe.

Abstract: An improvement in a heat-generating pipe made up of a ferromagnetic pipe having an insulated conductor extending through it to a given point so that both the pipe and conductor may be connected in series with a power source of alternating current. The invention is directed to both a method and nonferromagnetic means for reducing the heat output over a desired segment of the pipe by reducing the magnetic field created by the alternating current flowing in the insulated conductor and that segment of the pipe.The nonferromagnetic means comprises an electrically nonconductive, nonferromagnetic section of pipe connected in place of the segment of the ferromagnetic pipe and shunted by a second conductor connected at each end of the nonferromagnetic pipe to the ferromagnetic pipe.

Abstract: The heat output over a segment of a heat generating pipe of the type comprising an elongated ferromagnetic pipe having an insulated conductor extending therethrough up to a given point with both the pipe and the conductor connected in series with a source of alternating current is reduced by making the pipe segment of a non-ferromagnetic material, e.g., aluminum. Dielectric unions can be used to couple the non-ferromagnetic pipe segment into the ferromagnetic pipe, in which case means are provided to electrically bypass the dielectric unions in order to maintain the series circuit through the conductor, ferromagnetic pipe and the non-ferromagnetic segment. Alternatively, the non-ferromagnetic segment can be connected directly is series with the ferromagnetic pipe.

Abstract: A heat-generating pipe is made up of a ferromagnetic pipe having an electrically insulated wire extending through the pipe to a given point so that the pipe and first wire may be electrically connected in series with an alternating current supply to generate heat in the pipe. A second electrically insulated wire is provided parallel to the first wire in that portion of the pipe wherein increased heat output is desired. The second wire is connected to the alternating current supply and the first and second insulated wires are simultaneously energized. The power supply may comprise separate alternating current sources for energizing each of the first and second wires. Alternatively the second wire can be energized from the secondary of a transformer having its primary in series with the first wire. The first and second insulated wires can comprise a single wire looped back along the heat-increase section to provide two series connected wire segments.