| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique capable of shortening time required for replacing the inside of a tank with gas.SOLUTION: A gas replacement method includes: a step (a) for performing several times a supply/exhaust step including a supply step for supplying second-class gas into the tank so that pressure in the tank becomes a predetermined value or more and an exhaust step for exhausting the gas in the tank to the outside after the supply step; and a step (b) for reducing pressure in the tank to a level less than the predetermined value after the step (a). In the step (a), the exhaust step is switched to the supply step at a point of time when an inflection point appears in a graph expressing the pressure in the tank by a vertical axis and lapsed time by a horizontal axis to express a change of the pressure in the tank during execution of the exhaust step. |
