To enable sound fusion even if water exists in an electrofusion coupling.
Application of an electric current to a heating wire of an electrofusion coupling is started from the time t10, and when it reaches a water evaporation temperature at the time t12, the temperature is kept within the range above the water evaporation temperature and less than the fusion start temperature of polyethylene until the time t13. The time A is taken as the time when quantity of heat enough for evaporating water of a volume of a clearance between an electrofusion coupling and a polyethylene pipe can be given, and previously set on a timer. From the time t13 and on after enough time elapses, application of an electric current under the specified condition of the electrofuslon coupling is started and after temperature rising is stopped at the time 14, cooling is performed.
FURUKAWA JOJI
MIYAKI SEIJI
NISHIMURA HIROYUKI
HIGUCHI HIROSHI
