| 摘要 |
PURPOSE:To prevent counterflow reliably by forming sub-flow path and pressure path in parallel with main flow path while arranging a solenoid valve and restricting mechanism in series in sub-flow path thereby interrupting the flow path quickly and reliably on the basis of the differential pressure variation in the flow path. CONSTITUTION:Sub-flow path 4 and pressure detection path 5 are arranged in parallel with main flow path 3 where a solenoid valve 6 and a check valve 7 are arranged in series. While a differential pressure switch 10 functionable through detection of the differential pressure between the upstream side and the downstream side is arranged in the pressure detection path 5 where the solenoid valves 6, 8 in main and sub-flow paths 3, 4 are coupled with a differential pressure switch 10 to function said valves 6, 8 simultaneously. With such arrangement, counterflow can be prevented reliably.
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