the pulp mat 3 through first wash liquor nozzle 71 this wash liquor 70 fills the space outside the first compaction baffle 6 and the excluder baffle 8 it passes through the slot between the compaction baffle 6 and the excluder baffle 8 to wash the pulp mat 3 on the deck 2 in the first wash zone following the first wash zone 30 is the second wash zone 40 in this zone the second wash liquor 60 is fed through the second wash liquor nozzle 61 from which it flows beneath the excluder baffle 8 and second compaction baffle 7 in the circled region labeled a an interface 75 as shown enlarged in fig1 a exists between the two wash liquors at the boundary of the wash zones 30 and 40 this is merely a liquid interface and does not include any mechanical separation features this interface is possible because both the first wash liquor 70 and the second wash liquor 60 are fed by separate pumps which maintain a pressure equality between the two wash zones there is therefore no tendency for either wash liquor to flow into the neighboring wash zone provision of a separate wash liquor supply pump for each wash zone permits operation of the multiphase washer without seals between the wash zones because both zones are maintained at equal pressure there is no driving force for inter zone flow the only mechanical separation required is provided by an excluder baffle which does not touch the.