Brief introduction of overflow ball mill
Overflow type ball mill It is mainly composed of barrel, end cover, main bearing, hollow journal, transmission gear and feeder. The ball mill is divided into grid type ball mill and overflow type ball mill according to different discharging methods, which is the most common mill used in concentrator. The cone type ball mill has been eliminated because of its low productivity, many types of lining plates and difficult maintenance. It is still used in some old concentrators.
The main bearing is a key part of overflow type ball mill, so we must pay attention to its lubrication. Generally, the concentrated circulating lubrication of thin oil is adopted. The oil flows through the pump and is pressed into the main bearing and transmission bearing in four ways, and then it is discharged to the oil drain pipe at the bottom of the bearing, and then flows back to the oil tank. For medium and small ball mills, oil ring automatic lubrication, oil cup drip lubrication or solid lubricant are used. Some concentrators are equipped with oil cut-off automatic alarm device to ensure the reliability of lubrication.
The overflow type ball mill is supported on the main bearing by hollow shafts at both ends. One of the two hollow shafts can be axially retracted on the main bearing, and the other is fixed. Because the gear transmission of ball mill will produce the direction force, in the design, a hollow journal has two shoulders, the distance between the shoulders is exactly equal to the length of the bearing bush, so as to prevent axial movement. The other hollow journal has no shoulder, and its length is 5-25 mm longer than that of the bearing bush. When the cylinder is heated and extended or the cylinder is flexed due to load, it can freely expand and expand within a certain range. Generally, the journal close to the transmission ring gear is selected as the fixed hollow journal.
The hollow journal is equipped with tapered bushing and bearing bush, and the fit between the hollow journal and the inner sleeve is required to be tight, and necessary sealing shall be carried out. In order to make the pulp surface in the ball mill have a certain inclination, the inner diameter of the hollow journal at the discharge end is slightly larger than that at the feeding end. The inner surface of the hollow journal can be a smooth surface or with spiral blades. The forward spiral blade in the hollow journal at the feeding end is used to transport materials; the reverse spiral blade in the hollow journal at the discharge end can make the coarse material return and prevent the small ball from running out. The driving gear ring is fixed on the cylinder body at the ore discharging end and meshed with the small gear. The motor drives the cylinder body through the small gear and big gear ring.
The discharge of the mill depends on the fact that the hollow shaft diameter at the discharge end is slightly larger than that at the feeding end, resulting in a certain inclination of the pulp in the mill towards the discharge end. When the pulp surface height is higher than the minimum bus bar of discharge port inner diameter, pulp will overflow and discharge from the mill. This is a non forced high level ore discharge, and the discharging speed is slow. Therefore, the ore material remains in the mill for a long time, and the effective role of the medium is also low. Therefore, the overflow type ball mill is seriously over grinded and its treatment capacity is lower than that of the grid type of the same specification. It is generally applicable to the second stage grinding in fine grinding or two-stage grinding.
According to the mill specifications, the transmission modes of domestic ball mills are as follows: (1) synchronous motor drive. Large ball mill adopts low-speed synchronous motor to directly drive the small gear of ball mill, and the small gear drives the big gear ring to make the ball mill rotate. It has the advantages of high transmission efficiency, small floor area, convenient maintenance and improvement of power factor of power grid. However, the price of synchronous motor is higher and it needs DC power supply. (2) Asynchronous motor gear reducer drive. Large and medium-sized ball mills adopt asynchronous transmission, and the gear reducer drives the small gear and big gear ring to drive the ball mill. The advantage is that the asynchronous motor is cheap, but it uses a large set of large reducer. (3) Asynchronous motor V-belt drive. Small ball mill uses asynchronous motor to drive small gear and big gear ring through triangle belt to drive ball mill. Its disadvantages are low transmission efficiency, large floor area and complex maintenance.
matters needing attention
1. The equipment shall be installed on the horizontal concrete foundation and fixed with anchor bolts.
2. Pay attention to the verticality of the main body and the horizontal during installation.
3. After installation, check whether the bolts at all parts are loose and whether the door of the main engine compartment is tight. If so, please tighten it.
4. The power line and control switch are configured according to the power of the equipment.
5. After the inspection, carry out the no-load test run. If the test run is normal, the production can be carried out.
Model and specification
（ r/min ）
（ t ）
（ mm ）
Discharge particle size
（ mm ）
（ t/h ）
（ kw ）
（ t ）
Φ ninety 0×2100
one point five
three point nine
Φ ninety 0×2400
one point eight
eighteen point five
four point five
Φ ninety 0×3000
two point five one
Φ one thousand and two hundred ×2400
three point eight
nine point two
Φ one thousand and two hundred ×2800
nine point five
Φ one thousand and two hundred ×3000
four point five
eleven point five
Φ one thousand and two hundred ×4500
five point five
thirteen point six