METHOD AND APPARATUS FOR APPLYING POWDER PAINTING TO INSIDE OF CAST IRON PIPE

PURPOSE:To reduce the generation of inferiority, film blistering or a pinhole in the powder painting due to an epoxy resin to the inner surface of a cast iron pipe to a large extent by inserting one high frequency heating process on the way of a usual powder painting process. CONSTITUTION:The inner surface of a cast iron pipe 1 after a water pressure test is ground by a grindstone and a high frequency coil 4 is inserted in the cast iron pipe inside the stepped part 8 of the receiving port 3 of the pipe over at least the thick wall part A thereof so as to advance and recede. The inner surface of the pipe 1 rapidly receives high frequency heating by the actions of a high frequency oscillator 5 and the coil 4 to remove the moisture remaining after the water pressure test by evaporation. Next, buff grinding is applied to the inner surface of the pipe 1 and low temp. heating and the spraying of an epoxy resin are applied thereto according to procedure. In conventional powder painting due to an epoxy resin to the inner surface of the cast iron pipe, the inferiority such as film blistering or a pinhole of powder painting generated after painting is developed in a ratio of 30-60% of the whole, and the painted inner surface of the pipe requires frequent repairing but said inferiority is drastically reduced to 5-0% by this method.