| 摘要 |
PROBLEM TO BE SOLVED: To produce a synthetic resin lining pipe wherein air does not remain between a metal pipe and a synthetic resin pipe by adjusting the synthetic resin pipe after preheating to constant temp. and properly expanding the synthetic resin pipe by final heating. SOLUTION: The temp. of a synthetic resin pipe 1 expansible in its diameter by heating is measured before or after preheating to adjust preheating temp. so that the synthetic resin pipe 1 after preheating becomes predetermined temp. Thereafter, the metal pipe 2 into which the synthetic resin pipe 1 is inserted is introduced into a heating furnace 5 to successively heat the metal pipe from the central part thereof to the pipe end part thereof or from the pipe end thereof to the other pipe end thereof and the synthetic resin pipe 1 is expanded in its diameter to be closely bonded to the inner surface of the metal pipe 2. |
