Grate discharge ball mill

Assembly drawing of Grate discharge ball mill

The structure of various specifications of ball mill is basically the same, the following is an example of 2700x3600mm grate ball mill produced by Henan Deya Machinery Co., Ltd.

The following figure shows the assembly drawing of 2700x3600mm grate ball mill produced by Henan Deya Machinery Co., Ltd.

2700x3600mm grate ball mill
1.Drum 2. Flange 4. Screw 5. Manhole 7. Quill shaft end cover 8. Combination drum-scoop feeder 9. End cover liner 10. Bearing inner sleeve 11 Dust Cover 12 Quill shaft end cover 13 Grate liners 16 Central liners 17 Bearing inner sleeve 18 Ring gear 19 Pinion 20 Transmission shaft 21 Coupling Joint

1. The ball mill drum 1 is rolled and welded by steel plates with thickness about 18-36 mm, there are welded casting steel flanges 2 at both ends of it, the end cover 7 and 12 are connected to the flanges, both of which must be precisely machined and matched, because the quill shafts are welded on the end covers which bear the weight of the mill. There is a manhole 5 on the drum for maintenance and liner replacement.

2. The drum is equipped with liners, which are made of manganese steel, chromium steel, wear-resistant cast iron or rubber and other materials, of which high manganese steel is widely used, the use of rubber liner is still in the trial stage. The liner plate is about 50-130 mm thick, with a gap of 10-14 mm between the drum shell, with plywood, asbestos pad, or plastic sheet or rubber laid in it, used to slow down the impact of the steel ball on the drum. The liner plate 3 is fixed to the drum shell with screws 4, with rubber rings and metal washers under the nuts to prevent the slurry from leaking out.

Liners of grate ball mill

1. The shape of the liner plate has several kinds as indicated in the following figure, which are divided into two categories: smooth and unsmooth. Smooth liner is suitable for fine grinding because the steel ball slides more and the abrasive stripping effect is stronger, it is suitable for fine grinding, unsmooth liner can make the steel ball fall from a higher place and has a strong stirring to both the steel ball and the ore, thus it is suitable for coarse grinding. At present, there is a trend of using long liners, because they are simple to manufacture, without or less screws for fastening, only the end cover liner or wedge-shaped pressure bar, easy to install, and reduce the slurry leakage along the screw hole, it also improves the strength of the drum.

Different shapes of liners

2. The liners are wearing parts of the ball mill, which are constantly damaged by the impact and abrasion of steel balls and ore materials, as well as the corrosion of the ore slurry when the ball mill is working. The service life depends on the type of ore and grinding method, generally about half a year to one year. In order to improve the service life of the liner, at present, Henan Deya Machinery Co., Ltd. has made a lot testing and researches. Deya machinery pays attention to the research on the formula of rubber liner, the structural parameters of liner and the influence of mill operation on the life of liner. The trial results show that the rubber liner service life can reach 3-4 times that of steel liner (twice as high as that of hard nickel alloy), and has the advantages of low working noise, light weight and easy replacement. In addition, other wear-resistant materials are being trialed and progress is being made.

3. There is a flat fan-shaped manganese steel liner 9 on the inner side of the end cover of the ore feeder, and there is a quill shaft sleeve 10 with spiral blades on the inner surface inside the quill shaft, which can protect the journal from being worn out by the ore and also has the function of feeding the ore into the ball mill. The ore feeder 8 is fixed at the end of the inner sleeve of the shaft neck.

4. In the end cover 12 with hollow journal at the discharge end, there is a bearing inner sleeve and a discharge grate. The discharge grate is composed of central liners, grate liners and skip-shaped liners. In the inner wall of the end cover there are eight casting radial bars, the end cover is divided into eight fan-shaped chamber, each chamber is installed with skip-shaped liner and grate liner. The skip liner is fixed to the end cover with screws. The grate liner currently has two structural forms: one is a composite group of two pieces, pressed by the wedge iron, the wedge iron is fastened to the end cover with screws through the bars, the center part with the center liner to hold, so that they do not tilt and fall off; the other is to change the two pieces into one, fixed with screws. The holes on the grate liner are tilted and arranged, and the width of the holes is gradually expanded toward the discharge end, which can prevent the backflow of slurry and coarse particles from blocking. The center liner is star-shaped, which consists of two pieces and is fixed to the bars with screws. The slurry flows into the fan chamber through the aperture on the grate liner at the lower part of the discharge end, and then turns to the upper part with the drum and discharges along the aperture. The hollow journal is set with wear-resistant inner sleeve, and one end of the journal is made into a flared blade, which is convenient to guide the ore slurry to flow out along the blade.

Grate ball mill discharge side cover
1.Grate liner 2.Bearing inner sleeve 3.Quill shaft 4.Skip-shape liner 5.Central liner 6.Steel bars 7.Drill key

Different of feeding device of grate ball mill

1. The feeders of ball mill are: drum type, worm type and combined type, and their structures are shown as (a), (b) and (c) in the figure. Drum type feeder is made of pig iron casting or steel plate welding. It has a truncated conical shape. Its inner wall is inlaid with spiral, and the end connected with the truncated conical lid, and a partition plate with fan-shaped hole is installed between the drum shell and the lid, through which the ore is fed into the ball mill through the spiral. The ore is fed into the ball mill through the spiral. It is used for open circuit grinding.

Structure of ore feeder
(a)Drum feeder(b)Worm feeder(c)Combined Mineral Feeder

2. The worm feeder is a spiral scoop with an interchangeable spoon nozzle. In order to feed the scooped ore into the ball mill, a circular hole is cut in the center of its side wall, from which the ore is fed into the ball mill through the inner sleeve of the hollow journal. The worm feeder is available in the form of single scoop, double scoop, etc. and is used in the second stage of the two-stage grinding mill.

3. The combined feeder is a combination of two types of feeders, drum and worm, which is used in the first section of the closed circuit grinding ball mill.

Main bearing of the grate ball mill

1. The main bearing of the ball mill adopts self-locating spherical plain bearing, the bearing seat is concave spherical, the inner surface of the lower bearing bush is cast with babbit alloy, the outer surface is made into a convex spherical surface, the two become spherical contact, avoiding the formation of partial contact between the hollow journal and the bearing bush. In order to prevent the bearing bush from slipping out of the seat, a cylindrical pin is placed in the center of the spherical surface of the seat and the bearing bush. The bearings are lubricated by thin oil centralized oil station, and the oil flow is pressed into the main bearing and transmission bearing in four ways by the pump, and then discharged to the oil discharge pipe at the bottom of the bearing, and then flow back to the oil tank. If necessary, cooling pipes are installed on the bearings. For small or medium-sized mills, oil cup dripping or oil ring self-lubrication is used.

Grate ball mill main bearing

2. The transmission method of the ball mill uses a low-speed synchronous motor to rotate the pinion 19 through the coupling 21, and engages the ring gear 18 fixed on the drum to rotate the ball mill. To prevent dust from falling into the gear, it is sealed with dust cover. For small ball mill, asynchronous motor and reducer drive are available.