PURPOSE: To surely detect the position of joint and pipe externally by connecting a heater wire used for an electronic melt contacting pipe joint and lead wires laid along the pipe in series for supplying electronic power and generating a large electromagnetic field around the joint part.
CONSTITUTION: In soil 31, pipes 12, 13 made of thermal plastic synthetic resin are embeded and these are thermally melt contacted airtight with a thermal melt contact joint 1. At the joint 1, heater wires 5, 6 to thermally melt contact are provided and they are connected with locating wires 32, 33 are connected to vertical pipes 34, 35 made of steel. By connecting a power source 38 (direct or indirect current) in between these vertical pipes 34 and 35 for generating electromagnetic field, the electromagnetic field is detected from the ground with a detection means 40 having an antenna 39. Since the heater wires 5, 6 on the joint 1 are especially wound large like eddy or coil, the magnitude of generated electro magnetic field is large and thus the position of the joint 1 is detected surely from the ground.
TSUNASAKI MASARU
SUYAMA MASAMI
