Abstract: A coating fault locating technique transmits a base electric signal from a power source to a buried metal pipe. A location of a coating fault in the buried pipe is detected by detecting a gradient of a changing magnetic field between two points spaced along the buried pipe. The gradient is detected based upon the output differential of at least one pair of search coils. The gradient is caused by a leakage of current that occurs at the coating fault. In particular, the at least one pair of search coils are provided in a mobile unit that is located above ground. The at least one pair of search coils are spaced apart from one another and have their axes arranged so as to have a low sensitivity to a magnetic field generated by the base electric signal running through the buried pipe. The at least one pair of coils are spaced apart from each other such that a line drawn between midpoints of the search coils' axes crosses a plane normal to the axis of the buried pipe.

Abstract: A buried pipe laying method of additionally coupling a new pipe with the extreme end of a buried pipe laid underground involves flatly deforming a cylindrical pipe having a pipe length smaller than the inside diameter of the buried pipe, conveying the deformed cylindrical pipe to the extreme end of the buried pipe laid underground through the interior thereof, and then returning the deformed shape of the cylindrical pipe to its original circular shape and coupling it with the extreme end of the buried pipe.

Abstract: A control method for controlling the screwing down pressure provided in a reeling mill where the reels are controlled by a combination of signals continuously monitored by a computer. The signals include the temperature of the pipe entering the reeling mill, the voltage and current supplied to the reeling motor and the speed of the reeling motor. A calculation is then performed which gives the actual reduction of wall thickness based upon a predetermined relationship of the temperature of the pipe entering the reeling mill and the torque of the rolling motor. The torque is calculated based upon the speed, current and voltage of the rolling motor. The pressure supplied to the rolling reels is then altered based on this signal.