| 摘要 |
A method and apparatus for switching a supply to a process from a first vessel to a second vessel. Liquid is flowed from the first vessel through a first outlet conduit through a vessel selection valve, including first and second switch valves, to the process. A conductivity sensor measures the conductivity level of the liquid in the first outlet conduit at a point upstream of the selection valve and a computer compares the conductivity level to a predetermined range. The computer signals an isolation valve, in a second outlet conduit from the second vessel, to open and allow liquid to displace air in the second outlet conduit from the second vessel to the selection valve. The computer determines a delay to allow liquid below the first conductivity sensor to reach the first switch valve, then closes the first switch valve and opens the second switch valve.
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