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Method and apparatus for online switching between supply vessels

  • US 6,640,996 B2
  • Filed: 12/21/2001
  • Issued: 11/04/2003
  • Est. Priority Date: 12/21/2001
  • Status: Expired due to Fees
First Claim
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1. An apparatus for continuously supplying a liquid composition to a downstream process, comprising:

  • (a) a first vessel containing a first batch of the liquid composition and having a first vessel isolation valve;

    (b) a second vessel containing a second batch of the liquid composition and having a second vessel isolation valve;

    (c) a vessel selection valve including a first switch valve and a second switch valve;

    (d) a first outlet conduit from the first vessel isolation valve to the first switch valve;

    (e) a second outlet conduit from the second vessel isolation valve to the second switch valve;

    (f) a first conductivity sensor located in the first outlet conduit at a first known distance from the first switch valve for measuring electrical conductivity of the composition in the first outlet conduit;

    (g) a second conductivity sensor located in the second outlet conduit at a second known distance from the second switch valve for measuring electrical conductivity of the composition in the second outlet conduit;

    (h) a delivery conduit connected to the vessel selection valve for transmitting fluid therethrough downstream of the vessel selection valve;

    (i) a process control computer receiving input from the first and second conductivity sensors and controlling actuation of the first and second switch valves in response thereto, the computer opening the second switch valve and closing the first switch valve when the conductivity in the first outlet conduit is outside a predetermined range, the computer delaying closing the first switch valve for a period time to allow for liquid in the first outlet conduit below the first conductivity sensor to reach the first switch valve before closing the first switch valve.

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