CHAPTER XI
THE FOURDRINIER MACHINE
THE modern paper-making machine is a very complicated affair. We will
not in this chapter go into the subject of any specially built machine, such as
the huge machines that are designed to make newsprint at 1500 feet or more
per minute (see Chapter XVI). We will confine our remarks to the usual
type of Fourdrinier capable of making a wide range of papers, from wood
pulp alone, wood pulp and rags, wood pulp and esparto, or those fibres in any
combination (cf. Fig. 37).
The machine actually begins at the stuff chest. These are constructed in
sizes varying according to the output of the beaters and the machine itself. For
a general purpose machine, say 92 inches wide, and running the above furnishes
at speeds up to 150 feet per minute, a chest holding i\ tons of stuff (dry weight)
is a very convenient size. Two such chests will be necessary. They should
be set so that the bottoms are well above flood level. The waste valves will
then be safe from being dislodged by pressure from outside, and it will be
possible to wash out at all seasons of die year. Their dimensions may be such
as are most convenient—deep and narrow, or shallow and wide, but the latter
are best.
The bottoms should be concave, with all edges bevelled, the pipe to the
stuff pump connected to the lowest part, and the waste valve in a similar
position. This ensures that, when a chest is to be emptied and washed out,
no stuff will be left where the pump cannot get it. It is very important that
the last pound of stuff be taken up and over the machine. Where there are
many changes of colour, etc., a very great loss may easily occur if this point
is neglected. Both chests ought to be lined with glazed tiles, but copper or
well-glazed cement will do very well. A connecting pipe and valve between
the two chests are very useful. When the machine is stopped longer than usual
for any reason, both chests may be filled with stuff and circulated by the pump
through the connecting pipe, thus ensuring a large quantity of stuff of the same
consistency and shade. Where the chests are capable of containing not less
than i ton of stuff, the best plan is to run from one while the beaters are filling
the other. Then shade, weight, etc., remain constant while the whole quantity
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