| 摘要 |
A system for controlling fluid flow between a first point and a second point on a fluid line is disclosed. The system includes the first valve located at the first point on the fluid line to permit forward fluid flow from the first point to the second point on the fluid line and for closing to prevent such forward fluid flow. The system also includes flow sensors for detecting forward fluid flow at the second point and opening the first valve when such forward fluid flow is detected. The flow sensors also close the first valve when fluid flow at the second point stops. The system further includes a second valve located at the second point for opening and closing to control forward fluid flow at the second point. The system prevents forward fluid flow if a break in the fluid line occurs between the first and second points by preventing the first valve from opening. The first valve is prevented from opening since forward fluid flow cannot occur at the second point when the second valve is opened if a depressurizing break in the fluid line has occurred.
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