PURPOSE: To obtain durability usable over a long period by preventing a blister from being generated even when used for a long period user a flow water environment of repeating cooling and heating, in a synthetic resin coated metal pipe.
CONSTITUTION: In an outer layer forming sheet-shaped fiber compound unit 10 used in a two-layer pipe laminated to be inserted into a metal pipe, a recessed part 24, caused by scraping off a resin composition, is formed. In the metal pipe of coating the internal surface with the two-layer pipe of using this compound unit, many cavities 24 are formed in the lengthwise direction, and since steam, even when generated, is escaped in this cavity and prevented from staying in a generated spot, a diametric direction of a pipe unit is prevented from compression, accordingly to prevent a blister (swelling phenomenon) from being generated.
FUJII KIYOYASU
SUGAWARA HIROSHI
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