Выражение встречается в следующем контексте:

The demi water package will treat the filtered water to a quality suitable for
use in steam generation. The preliminary design of the package consists of
four trains with 3 operating and 1 spare. Each train contains a cation
exchanger, degasser, anion exchanger and a mixed cation/anion bed. The
demineralised water is sent to the demi water storage tank and from here is
pumped using demi water pumps (1 operating and 1 spare) to the demi water
distribution for use in Boiler Feed Water (BFW) make-up and various
process uses.

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