Precautions for operation of the vertical grinding mill

Precautions for operation of the vertical grinding mill:

(1)The vertical grinding mill grinds with a material bed. Therefore the stability of the material layer is essential to the safe operation of the grinding mill. Under normal circumstances when the thickness of grinding material layer is about 20 to 30mm, the grinding mill runs smoothly, making soft sound and the outer circulation material is basically maintained the same. If no outer circulation, the discharge opening may discharge small debris only such as iron block and gangue. If the material layer is too thin, the grinding mill vibrates; if it is too thick, the grinding mill load is too large and grinding efficiency is reduced, or may vibrate vigorously if thicker.

(2) Analysis from the perspective of material balance can effectively guide operation of the vertical grinding mill. During running of the vertical grinding mill, feeding rate, grinding capacity, air flow (output of finished product), slag discharge or the amount of outer circulation shall be in balance. In the case of a fixed amount of feed, the lack of grinding capacity will cause great slag discharge, which will increase; it is necessary to appropriately increase the working pressure of high-pressure station to enhance the grinding capacity or appropriately reduce the feed rate. On the contrary, if the grinding capacity is too large, the material layer may be gradually thinner and eventually cause grinding mill vibration; it is necessary to reduce the working pressure of high-pressure station or appropriately increase the feed rate. Another situation is that if the grinding capacity is appropriate but lack of air capacity, the same situation of great slag discharge will be caused; however, it has a large amount of fine powders. Therefore it is necessary to increase the air volume and enhance the transport capacity. Therefore, during operation of the vertical grinding mill, problems shall be identified in advance by making use of material balance principle, so appropriate measures may be taken to prevent unnecessary downtime.

(3) The vertical grinding mill is operated with negative pressure. Material transport and classification require a large amount of air. The air volume shall meet the requirements of material transport first. Small air flow will result in failure to send a large amount of qualified fine powder out in time; too much air flow is not only a waste, but also results in coarser products.

(4) The classifier motor is adjusted with frequency control. Adjust its controller knob, you can get different speeds. Users shall select an appropriate speed according to the particle size of finished product. The faster the classifier, the finer the finished products will be.

(5) Check bearings at regular intervals. Shut down the equipment if the temperature rise exceeds  400 ℃ or there is abnormal noise.

Shutdown of the grinding mill:

First stop feeding, then carefully observe the distance between the limit screw and the limit elastic head; switch on the bypass unloading valve of the high-pressure station immediately if they contact each other. Then stop the main unit motor, and finally reduce the classifier slowly to zero to shut down the classifier. Pull the handle on the reversing valve to allow the roller in the lifted state, start the motor of the high-pressure blower pump (during normal operation, the high-pressure cutoff valves in the oil inlet and return tubes are fully switch on). Note: make sure the rollers are lifted at the same time, and then switch the high-pressure cutoff valves upon lifting of the rollers, and finally turn off the lubrication station motor.

Shutdown must be conducted in the following sequence:

1)        Stop feeding to the crusher and turn it off when the crushing chamber is fully discharged.

2)        Turn off the hoist when materials in it are fully discharged.

3)        Stop feeding. Carefully observe the distance between the limit screw and the limit elastic head; switch on the bypass unloading valve of the high-pressure station immediately if they contact each other.

4)        Turn off the main unit motor, do not stop the lubrication station immediately after the motor stops. Allow it to continue to run fast. It is not necessary to stop it if a second start is to be proceeded.

5)        Turn off the blower in half a minute after shutdown of the main unit.

6)        Turn off the pulse controller.

7)        Turn off the classifier.

8)        Lift the rollers of the vertical grinding mill.

9)        Stop the motor of the lubrication station.