| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for surely preventing the discoloration of the activated inside surface of a copper pipe from which oil-components are removed by a heating and blasting method, etc. SOLUTION: Caps consisting of a material having a steam permeation rate of <=30×10<-9> are used as the caps in the method for preventing the discoloration of the inside surface of the copper pipe by removing the oil-components from the inside surface of the copper pipe by means, such as blasting of air into the copper pipe held at a high temp., then putting the caps into the apertures of the copper pipe to close the inside of the copper pipe. The steam permeation rate is the value measured by a differential pressure method (JIS K 7126). Namely, this value is the rate (cm<3> ) of the steam which passes the sample of a unit thickness (cm) and unit area (cm<2> ) in unit time (sec) under a unit steam pressure difference (cmHg). As a result, the steam permeation rate of the caps to be put into the apertures of the copper pipe is low and, therefore, the steam hardly infiltrates the inside of the copper pipe. Then, the oil-components are removed by the heating and blasting method, etc., and the discoloration of even the activated inside surface of copper pipe is surely prevented.
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