BACKWATER

143

and the mixture of stuff and water is run to the wire. As soon as the wire is
moving, and the water begins to drain through it and fill up the low-level box
through the save-all trays and shutes, the fresh water may be partly shut off.
Sufficient overflow is left for a few minutes to compensate for any change the
machineman may make. As soon as he has got the correct proportion of the
stuff and water, the water valve may be closed, so as to leave little more than
the surface froth going down the overflow from the high-level box. This
will have the effect of overflowing the low-level box, and the fresh wrater
may be turned off to reduce the overflow in the same way. If the adjustments
are correctly made, it will be found that no fresh water will be required.

FIG. 40.—THE ROTOR WHTTEWATES CIRCULATION SYSTEM [Rete Engineering Co.
The Whitewater from the save-all tray and the back-water from the suction boxes are both collected in pit *A\ By means
of pump *B* this water is conducted through the supply pipes *a* to the Rotors *C*, and is used as spray water. The
trays *D* collect this Whitewater again and conduct it through the supply pipes 'V to die existing pump for diluting
the stuff in the mixing box. Fresh water, which is necessary during the starting of the machine, is automatically
added by the floating valve '£'. *F is the turbine which causes the water to spin.
The back water will gradually attain to its full saturation of size, loading,
colour, etc., and the stuff coming from the chest will get all the benefit of
these things returned over and over again. It is an advantage to have a con-
nection from the suction pump which deals with the suction boxes. The fine
fibres, loadings, starch, colour, etc,, may then be led back to the low-level
box and any overflow pumped to a tank in the beater room to be used in
furnishing the beaters. Some 'fine' mills, however, prefer to lose the suction-
box water rather than risk having in the paper dirt and bits from the suction-box
packing. Still, as the machine may have a run of engine-sized or printing
paper, these otherwise wasted materials could be used.
Rotor Whitewater Circulation System (Kg. 40).—A new method of recovering
fibre and loading from excess whitewater has recently been introduced, and
quite a large number of the plants have been installed on paper imcbines.