174 MODERN PAPER-MAKING
the wire if ordinary care is taken in putting through the breast and other
rolls.
The wire must be supported by two poles when putting "in the 'tube rolls'.
These poles must be held at the same height and tension, and when moved
forward as the tubes are placed in position it should be done slowly and in the
same parallel, or the wire may be buckled or wrinkled. When all the rolls
are in position and the suction boxes are levelled, the stretch roll should be
allowed to tighten the wire by its own weight only.
Then the machinemen should examine all the arrangements and see that
no pieces of wood from the save-alls or suction boxes, etc., have fallen on the
inside of the wire. The wire rolls will, of course, have been cleaned and
washed before being put in, but the hose-pipe should be freely used again.
A very wise precaution is to start the machine slowly and run the wire round
a few turns to allow it to straighten itself out, all watching carefully for any
defect or damage.
No attempt should be made to straighten the seam if it is out of square
with the edge of the wire. A slight slope is an inherent feature in some forms
of twill-woven wires and causes no trouble or difficulties in running.
If there is a top couch roll which has the effect of tightening the wire, the
stretch roll has to be freed to keep no more tension than its own weight until
the machineman finally tensions it.
Care of the Wire.—It is necessary at all times to keep a close watch, on the
wire, and more especially when starting up. The wash roll under the wire,
which is cleaned by a doctor board, does not always start if the wire is not very
tight, and this may be the cause of stuff getting on to the next roll and making
a ridge in the wire. A very sharp spray of water is essential here; it should
strike the wire from the inside and impinge on the roll itself, or, better still,
two sprays are more effective, one spraying through the wire a few inches
before it reaches the wash roll, and the other after it passes the roll and impinging
on the roll at the contact point of the doctor board.
The breast roll also is a source of danger if the doctor board is not true
all across, since a very small piece of pulp or foreign substance may pass, or
even a layer of scale form, from the water getting through* Water passing
the doctor at a part where the latter fits badly will cause a ridge in the wire, if
the speed of the roll is high enough to carry the water round and under the
wire. Where wood pulp is used a very stiff and close-fitting doctor board is
required to scrape off sulphite pitch.
Before he starts the wire, the machineman ought to have a good hose-pipe
handy, with the water turned full on, ready to wash off the.wire rolls as soon
as the paper is on the felt If the stuff should run up the top couch roll, this