Modern pulp and paper making; a practical treatise by Witham G. S. (George Strong) 1860-1939

Author:Witham, G. S. (George Strong), 1860-1939
Language: eng
Format: epub
Tags: Wood-pulp, Papermaking
Publisher: New York, Book Department, The Chemical Catalog Co.
Published: 1920-03-25T05:00:00+00:00

running constantly 600 feet a minute or more, the wire may be raised at the breast roll end as much as 16 or 18 inches to give the necessary speed to the stuff. If the stuff were moving

slower than the Wire, the sheet would be rough and not properly felted and if the stuff should run faster than the wire it would accumulate in puddles causing streaks.

It will be noticed that when a wire after running, sometimes becomes slack on either of the edges, it is generally the back side, if the water for the wash roll enters at the front side, and vice versa if the water enters from the back. The reason for this is that the small holes in the water pipes are apt to become choked at the end farthest from the inflow, and the wire owing to its being much more dry is strained in its passage over the roils. Apart from this the wash roll should have a suitable doctor and a good strong shower in order that any pulp, which would become lodged in the meshes, may be washed out.

Attention to this and also to thoroughly washing the wire, when shut down for any length of time, will keep the meshes clear, lessen the strain on the suction boxes, and improve the appearance of the sheet, in addition to prolonging the life of the wire.

Having the wire too slack is another very frequent source of "snap-offs" or crackings and breakings in the sheet between the dryers and calenders. When the wire is too slack the seam of it is apt to crease the paper when passing under the couch roll, but in such a way that it is scarcely noticeable, unless the ma-xrhine tender knows where to look for it. ' This is most liable to happen when making a narrow sheet of heavy paper, and the first thing a machine tender should do when he is at a loss to account for such breaks, is to hold a light under the web between the under couch roll and the wet felt roll, so that he may make sure if any creases are there. If the wire is causing creases they will appear like small black streaks running a little way in from the edge. Tightening up the wire a few turns and putting more weight on the couch roll will cure this.

Causes of Wire Deterioration.

(i) The destructive action of the couch roll through actual wear,

(2) The pitch pressed into the wire.

(3) Foreign substances passing through.

(4) Cleaning the wire with acids.

(5) Breaking of jackets.

(6) Accumulation of stock on the wire, breast rolls and carrying rolls through ^the use of imperfect deckle straps and carelessness and above all the operation of imperfect shower pipes with inadequate pressure. This may be corrected by concave deckles and installation of shower pipes delivering a continuous and unbroken spray of water at from twenty to thirty pounds pressure.

(7) Improper bearings on rolls and unbalanced rolls.

(8) Rolls out of alignment.

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