| 摘要 |
PROBLEM TO BE SOLVED: To prevent degradation in air-tightness of a valve and to prevent dusts in a chamber. SOLUTION: Related to a vacuum chamber device 2, a butterfly valve 6, a main valve 8, a slow valve 10, a bent point 14 of a piping 4, a bent line 118, and a valve 12 connected to the bent line 118 are heated by a heating means at vacuation. So, even if a product such as ammonium chloride remains in a vacuum chamber 104, it does not coagulates and stick to such point as the valve 12, preventing degradation in air-tightness of the valve 12. Thus, a fact that dusts flow backward due to valve leak to raise occurrence coefficient of defective product is avoided while the life of the valve 12 is extended. The main valve 8 is closed and the slow valve 10 is opened at the initial stage of vacuation for depression to 1 TORR or below, and then the main valve 8 is released for further depressurizing, resulting in prevented dusts due to rapid pressure change.
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