WATER SUPPLY 349
used, and this operation has been proved, when carefully attended to, to double
the length of life of the machine wire. In this case, formerly only about half
the water-required at the stuff box was recovered water, the other half being
'fresh' and very hard. It was found that after a week the machine wire was
so filled up with a white limy deposit that it was necessary to remove it with
a strong solution of vitriol. This, of course, ruined the wire in about 4 to 6
weeks, or even less.
When, however, use was made of all the water which could be recovered
and no fresh water was added, no vitriol was required to clean the wires, and
they lasted from 8 to 12 weeks without any special cleaning other than an
occasional blow with the force jet.
It had also been found expedient to have a spray-pipe on all the wire rolls,
whereas, after the back water only was used, no sprays were used except on
the wash and breast rolls.
In mills making printings and newsprint there is no recoverable water
except at the machines, and every drop of this should be carefully caught and
returned to the beaters, stuff box and machine service system, either direct or
after passing through some sort of save-all. This water is generally termed
'white water', and it comes from the wire and suction boxes at the machine.
It is collected in the pit below the machine, and contains large quantities of
clay and fibre from the deckle edges which are cut off, and also from the water
which passes through the meshes of the wire, carrying clay and fibres with it.
The water is kept agitated by means of paddles in the pit, and is pumped
to huge tanks above the breakers or beaters, whence it is run to the latter when
furnishing.
There should be no dirty effluent at all from a news or printing mill, except
floor washings, containing oil from bearings, etc., and the only fresh water
which should usually be necessary will be for the sprays at the slices and guard
board, for the spray damper at the reel end, and for the edge cutters.
Other mills making different grades of paper should be able to recover
varying amounts of water, according to the conditions under which they work,
and if it is found impossible to use all the water it should in any case be filtered
to remove the valuable fibres and clay, which can be used again either in the
same paper or in lower grades.