Sugar Mill Roller Grooves

SUGAR MILL ROLLER GROOVING

    The three rolls of a conventional mill are arranged in a triangle so that the fiber is squeezed twice between the top roll and the feed roll and the top roll and the discharge roll. The rolls have cast iron, grooved shells mounted on steel shafts. Fiber passing between the top and feed roll is conducted over a turner plate to the discharge roll. The rolls are pinion driven from the top roll which is driven at a speed of 3 to 6 rpm by a gear reduction system. The feed and discharge rolls are fixed, while the top roll is free to move up and down by means of a hydraulic pressure system. Cane is moved between mills by means of intermediate conveyors. They are generally rake or drag-slat type, which carry the fiber to a fixed chute leading to the next mill.

1)      Circumferential Grooves

a)      Cutting grooves around the roll gives a corrugated surface of increased area which has better gripping action because of the compression of the fiber against the walls of the V-shaped grooves. Since the bagasse at the bottom of the groove is not so highly compressed, a drainage channel for juice is formed.

b)      The surface area changes with the angle of the groove, the sharper the angle the greater the surface. Larger pitch increases the speed differential between the tip and the channel. This gives a grinding action which will open up cells.

c)      Sharper grooves give more surface, the effective surface is not much affected by very sharp grooves (30-35°) since little pressure reaches the bottom of the channel.

d)      Normally, 45° is most practicable where damage potential is severe.

e)      Juice extraction decreases with increase in pitch of grooving.

Sugar Mill Roller Grooving

f)       As preparation increases down the milling tandem, finer grooving is used. Good standard practice on the last mill is 1.25 cm (1/2 in.) pitch. With a good shredder, such grooving can be used throughout. With poor preparation, 2.5 cm (1 in.) pitch is effective. In the absence of a shredder, 5 cm (2 in.) pitch is common in the beginning mills.

2)      Juice (Messchaert) Grooves

a)      Juice grooves are narrow channels cut deeper than the circumferential grooves to give better drainage.

b)      They are normally not over 0.6 cm (1/4 in.) wide to prevent much fiber being compressed into them, and are of a depth sufficient to carry away the juice. This averages about 2.5 cm (1 in.). The pitch is also a function of the volume of juice and is normally 7.5 cm (3 in.).

c)      Juice grooves are most effective on the feed roll where juice flow is greater.

3)      Chevron Grooves

a)      Chevron-shaped grooves are cut lengthwise through the circumferential grooving as an aid to feeding.

b)      They are nominally cut to one half the depth of the grooving and at a pitch of 25 cm (10 in.).

c)      Chevron grooves are effective only on the feed and top rolls.

d)      Such grooving decreases the effective pressure surface of the rolls and causes excessive baggasse in mixed juice, more efficient operation of a mill is obtained without chevron grooves by arcing maintenance of the circumferential grooving.