METHOD FOR LINING INNER WALL SURFACE OF REDUCING DUCT

摘要

PURPOSE:To form a uniform film at the same thickness on the inner wall of a deformed duct by using a pig made of a thin film which is expanded to the prescribed outer diameter dimension by filling gas and is freely extensible and contractible and smoothly advancing the pig even in the deformed duct and allowing paint filled in the duct to proceed. CONSTITUTION:Pressure P1 of the rear space of a pig 7 and pressure P2 of the front space of paint 6 are held at constant value respectively and both the pig 7 and paint 6 are integrally pressed and transferred forward at constant velocity and a film 6a is formed on the inner wall surface of a duct in a large diameter part. When this pig 7 reaches the terminal of the large diameter part 5a, pressure P1' of the rear space of the pig 7 and pressure P2' of the front space of paint 6 are raised respectively and the pig 7 is contracted as a whole and its outer diameter becomes the dimension suitable to the narrow diameter part 5b of the duct. Successively the pig 7 is advanced through the narrow diameter part 5b of the duct at constant velocity and a film 6b having thickness nearly equal to the film 6a of the large diameter part 5a is formed on the inner wall of the narrow diameter part 5b.