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Causes and Prevention of Stone Grinder Roll Explosion

Causes and Prevention of Stone Grinder Roll Explosion

Stone Grinder Roll is a common spare part for vertical mills. It can grind block, granular and powdery raw materials into required powdery materials.

AGICO CEMENT CHINA analyzes the reasons for the explosion of the Myanmar Cement Companyh roller sleeve and the preventive measures.

Mostly in the initial stage of construction and after the roller sleeve is worn to 53% of the total thickness of the large end, the material of the roller sleeve is all Cr20Mo2Ni1, the middle diameter of Rock Grinder Roll is all 1450mm, and the diameter of the grinding disc used is all 4600mm.
The thickness of the first-line UM46-4 grinding roller sleeve is 178mm at the large end and 63mm at the small end, the roller weight is 5.45 tons, and the grinding disc speed is 26.86r/min.
The thickness of the second line JLM3-46.4 grinding roller sleeve is 246mm at the large end and 147mm at the small end, the roller weight is 8.42 tons, and the grinding disc speed is 26.78r/min.
At present, the loss of roll sleeves for the first and second lines are 4g/t and 3.5g/t respectively.

The ratio of grinding materials is as follows

The easy grinding of the mixed sample is 15.65kW/t.

The company’s first-line and second-line raw meal vertical mills have 80-micron fineness controlled at 17%, 440t/h and 515t/h respectively, and power consumption of 21.5kwh/t and 20.8kwh/t.

The analysis of the reasons for the explosion of the grinding roller and the preventive measures are as follows

1. In the process of heating and cooling, the step is too fast to burst.
The temperature inside and outside the grinding roller rises or drops sharply, causing the roller sleeve to expand or shrink rapidly. Excessive thermal stress causes the roller sleeve to burst. When the material density and wear are uneven, it is more likely to cause multiple roller sleeves to burst at the same time.
The explosion caused by the temperature rise is not easy to be found after the operation, but the generation and expansion of the crack is inevitable because the roller sleeve has burst.
Therefore, the Stone Grinder Roll will definitely slide relatively abnormally with the roller shaft, and finally there will be slight abnormal vibration between the grinding disc, grinding roller and grinding roller shaft, and the return oil temperature of the grinding roller will also have a certain degree. rise.
When the explosion is caused by cooling, generally the frying seam will not exceed 2mm, and the frying seam width will not exceed 30mm. The discovery and judgment are more intuitive.
The above situation is mainly due to the fact that the air temperature at the entrance and exit of the mill is adjusted too quickly before and after the mill is turned on and off, or the on-site personnel are eager to enter the mill.

Preventive measures to strengthen the operation and grasp the stepping time
The temperature rise and fall is generally based on the outlet temperature of 80°C, and the step of 0.4-0.6°C per minute in summer is the most suitable.
Due to the relatively high ambient temperature in summer, the mill can enter the mill below 50 °C, and it can be turned on when the temperature rises above 80 °C. The process takes about 1 hour.
The step of heating and cooling in winter cannot be greater than 0.5°C per minute.
Due to the low ambient temperature in winter, although the surface temperature of the grinding roller has decreased, the internal temperature of the grinding roller has not dropped to the temperature of the measuring point, so the outlet can only enter the mill below 20°C.
It can be turned on only when the temperature rises above 80 °C. The process takes about 1.5-2 hours. If necessary, the holding time can be increased.
Try to install a curtain with a thickness of more than 10mm at the observation door of the vertical mill to reduce the incorporation of cold air when entering the mill.
Before and after starting and stopping the mill, it is necessary to carefully confirm the effectiveness of the valves of each spray pump, whether there is water leakage into the mill, and the water discharge valve must be set on the spray pipe and can be opened in time.

2. The foreign matter entering the mill will be crushed and burst. When the metal material with greater hardness enters the mill or the internal parts of the mill fall off, and the thickness before the shearing of the grinding roller is greater than the thickness of the material layer, it is possible to fry the roller sleeve.
There is also a kind of rolling explosion that is difficult to find, that is, the metal enters the mill and is not discharged in time after rolling, but is stuck on the inner ring or base of the retaining ring. If the grinding inspection cannot be removed in time, this This situation is quite dangerous. During operation, there will be periodic abnormal vibration of the mill. Finally, after the superposition of various stresses on the grinding roller is greater than the mechanical stress it can withstand, the roller sleeve will burst.
Secondly, there is another kind of crushing and bursting, which is caused by the excessive particle size of the grinding material. When the material whose diameter is greater than 5.51% of the middle diameter of the grinding roller is more than 20%, the grinding efficiency will be greatly reduced, and the mill will also produce large vibrations. , causing the roller sleeve to burst over and over again.
In addition to the material reasons, the blasted roller sleeve will have obvious corner drop or scratches on the big end of the blasted roller, and the scratches are relatively new.

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