Grid ball mill is a grinding mill with discharging grid and will grind the big size ore into small or fine. It is usually used in the first stage grinding to produce coarse particle product and can work at wet or dry way. Grid ball mill is widely used for electric power, ferrous metal and nonferrous metal, chemical industry and building materials etc.
Structure of grid ball mill
The structure of the ball mill of all kinds of specifications is basically the same.Now we describe the structure through the model 2700x3600mm grid ball mill which manufacturered by sinonine. Fig 1 is the general layout of 2700x3600mm grid ball mill manufacturered by sinonine
Figure 1.2700x3600 grid ball mill
(1) Barrel, (2)Flanges,(3)Liner,(4)Bolt, (5)Human hole cover, (7)Hollow shaft neck end cover, (8)Joint feeder, (9)End liner, (10)Bearing inner sleeve, (11)Dustproof cover, (12)Hollow shaft neck end cover,(13)Grid type liner, (16)Center liner,(17) Bearing inner sleeve, (18)Big gear, (19)Pinion , (20)Drive shaft, (21)Coupling
The barrel（1） of a ball mill is welded by a steel plate with a thickness of about 18-36 millimeters, Its ends are welded with steel flanges(2). The end cover (7)and the hollow shaft neck end cover(12) are connected to the flange plate, the two must be precision processing and coordination, because the shaft neck of the weight of the mill is welded on the end cover. A manhole for repairing and replacing the liner is opened on the barrel. The lining of the barrel is fitted with liners which are made by manganese steel, chrome steel, Wear-resistant cast iron or rubber etc, Of which high manganese steel is widely used. The thickness of the liner is about 50-130 mm, and there is a gap of 10-14mm between the shell and the cylinder. It is made of plywood, asbestos pad, plastic board or rubber shop, which is used to slow down the impact of the steel ball on the barrel. The liner(3) is fixed on the barrel with bolt (4)and rubber ring and metal washer under the nut in order to prevent the leakage of the pulp.
Liner of grid ball mill
The shape of the liner shown as figure2 is divided into two types, such as the smooth and the unsmooth.The smooth liner can be used for fine grinding because of the larger sliding of the steel ball and strong grinding and stripping，The unsmooth liner can cause the ball to fall from higher place and it has strong agitation for both steel ball and mineral material, so it is suitable for coarse grinding. At present, it has the tendency of long strip liner, because it is simple to manufacture, no or less bolt fixation, and it only needs to be pressed by the end cover liner or wedge layering. It is easy to install, and it also reduces the leakage of slurry along the bolt hole and improves the strength of the barrel.
Fig2 The shape of the liners
The liners is a vulnerable part of the ball mill. It is damaged by the impact and grinding of the steel ball and ore, and the corrosion of the pulp during the work. The service life of the liners depends on the type of ore and the way of grinding, usually about half a year to about one year. In order to improve the time limit for the use of the lining, many studies have been carried out at home and abroad. The test results showed that life can reach 3-4 times the steel liner rubber lining the (more than twice as high as hard nickel alloy), and has low noise, light weight, easy replacement.
A flat fan-shaped manganese steel liner is laid on the inner side of the end cover at the end of the ore. The hollow shaft is equipped with a shaft neck inner sleeve with an inner surface which is a spiral blade. The inner sleeve can not only protect the axle neck from being damaged by ore, but also send ore into the ball mill.The ore feeder is fixed to the end of the inner sleeve of the shaft neck.
End cover of grid ball mill
The end cover with a hollow shaft neck at the end of the mine is equipped with a bearing inner sleeve and a grille. Discharge lattice by lattice center liner, liner and dustpan shaped lining board etc. Cast ribs with eight radial wall in the end cover, the end cover is divided into eight fan rooms, each room equipped with dustpan shaped lining plate and grid lining board. Dustpan shaped liner with screws fixed on the end cover. Grid lining board currently has two kinds of structure forms: one is the synthesis of a two block group, by wedge pressing, wedge iron screw through the fastening ribs on the end cover, a center of center liner spigot holds so they tilt and fall off. The other is to change the two pieces into one piece and fix it with a screw. The holes on the lining of the grid are tilted, and the width of the holes expands gradually to the end of the ore, which can prevent the reflow of the pulp and the clogging of the coarse grain. The center liner is star shaped, which consists of two blocks and is fixed on the bar with screws. The pulp flows into the fan chamber through the pores on the lining plate at the bottom of the row of ore. Then the slurry is transferred to the upper part and discharged along the channel. The hollow shaft neck is inlaid with a wear-resistant inner sleeve and a horn shaped blade is made at one end of the neck of the shaft to guide the flow of the pulp to the blade.
Figure 3 Discharge end cover of ball mill
1.grid liner 2.bearing sleeve 3.hollow shaft 4.dustpan shaped liner 5.center liner 6.ribs 7.wedge
Feeder of grid ball mill
The ore feeder of a ball mill has (a)drum type, (b)worm type and (c)combined type, and its structure is like fig 4
The drum type ore feeder is cast by raw iron or welded by steel plate. Conical. The inner wall of a spiral end connected with the conical cover, baffle with fan-shaped holes is arranged between the shell and the lid, aggregate through the baffle through the spiral into the ball inside. It is used for open grinding.
The worm type feeder is a spiral spoon with a replaceable spoon mouth. In order to put the scooping ore material into the ball mill, a circular hole is opened at the center of its side wall, and the ore is then sent through the hollow shaft neck inner sleeve to the ball mill. The worm type ore feeder has a single spoon and double spoon form, which is used for the second stage grinding machine of two section grinding.
The joint feeder is composed of two kinds of ore feeder with drum type and worm type. It is used in the first stage of the ball mill with closed grinding.
Main bearing of grid ball mill
The main bearing of ball mill by self aligning sliding bearing, the bearing seat is a concave spherical surface, Vanessa cast shaft Babbitt, outer surface made of convex spherical, two spherical contact, avoid the hollow axle neck and bearing formation of local contact. A cylindrical pin is placed in the center of the sphere of the bearing seat and the axle bush to prevent the slippery displacement from being too large to slip out of the bearing seat. The bearing is lubricated by the thin oil centralized oil station. The oil flows through the pump into four main parts and then enters the main bearing and the transmission bearing. Then it goes to the oil drain pipe at the bottom of the bearing and flows back to the oil tank. If necessary, the cooling pipe is mounted on the bearing. For small or medium-sized mill, using oil cup oil or self lubricating oil ring.
Figure5. main bearing structure
1.Bearing seat; 2.Bearing cover; 3.Bearing bush; 4.Babbitt alloy layer; 5.Cylindrical pin; 6.Bolt;7.Discharge pipe; 8.Dustproof sealing ring; 9.Felt pan
Drive the ball mill, with low speed synchronous motor through the coupling to rotate the pinion gear, the gear meshing and fixed in the shell and rotate the cylinder. To prevent dust from falling into the gear pair, it is sealed with a dustproof cover. The small ball mill can be driven by asynchronous motor and gear box.
Specification of grid ball mill
1.Advanced sealing technology, to ensure good working environment.
2.The use of advanced design means, to ensure safe and reliable mill.
3.Mature and strict processing and detection means, to ensure the quality and accuracy.
4.With a strong brand manufacturers at home and abroad, to ensure the quality of the machine running.
5.The machine is equipped with a complete turning, jacking device and tool installation and maintenance.
The main part of grid ball mill is a rotation cylinder rotating slowly by the transmission device. The material is fed from the cylinder inlet and grinded by the impact of steel ball and ore and self-grinding. Due to the continuously feeding material, the pressure pushes material to the outlet and the grinded material is discharged from the cylinder outlet. In wet grinding, material is taken out by water; in dry grinding, the material is taken out by air. The grid installed in the outlet of mill is relied for forced discharge. Low pulp surface in cylinder reduces the ore over-grinding, and prevent the steel ball out. Under the same production conditions, production capacity of grid mill is larger than overflow ball mill’s.