17 Signs of Problems with Ball Mills: Quickly Remove Hidden Troubles
2025/2/14 14:54:00 Other23205
The failure of the ball mill in the grinding process will affect the output and efficiency. So, what abnormal signs will occur before the machine going to malfunction?
Here we list 17 signs to mention you that the ball mill is running and needs to be checked in.
Find the abnormal signs early is very important to prolong the ball mill service life.
1. The sign of "swollen belly"
Just like a bloated stomach, if the amount of grinding exceeds the maximum capacity and discharge capacity, it will cause the mill shell to loses its grinding capacity, and thats why we call it "swollen belly".
3Tips for mentioning you whether it is "swollen belly"
Digital clamp-on meter indicates that the current is decreasing.
The ball mill starts to discharge a great amount of ore blocks.
The machine operation sound is dull, and there is no sounds of steel ball impacting.
What causes the sign of "swollen belly"
Feeding volume is too large to exceed the maximum passing capacity of the mill.
The granularity becomes coarse, which prolongs the time grinding the material to get the standard of discharging particle size.
Steel balls are not added on time, which means the filling rate is low.
Reduces water pressure at the feed opening and inefficient feed water will cause the flow velocity of the ore pulp in the ball mill slow, the ore drainage not smooth, and the more ore sand accumulating.
What should we do to solve those problems?
1First of all, it is necessary to do analyses including changes of nature of the ore, whether the amount of ore, water, sand and overflow size are normal. Then do the measures to deal with them.
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2Reduce the amount of feed to the mill until the working state of the ball mill returns to normal.
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3Appropriately reduce the amount of volume of rinse to the returned sand so that we can increase the concentration of the ore and the discharge amount.
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4Reasonable addition of grinding media. Ball filling rate- the ratio of grinding media to the volume of the mill, is so important to the mill rotation rate. The following shows their relations:
We should put proper steel balls
5Necessary inspections of the mill: such as whether the feeder is loose, the screws are cut, and other components are damaged.
2. More and more coarse materials final products
1It refers to the abnormal phenomenon that the fineness of the grinding product is significantly coarse and difficult to control.
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2It generally appears on the double-cylinder open-circuit mill with a relatively small diameter.
The reasons for more coarse material
When processing materials with small particle size and low hardness, the mentioned situation will happen if the ratio of small ball is small.
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The capacity of coarse grinding silo is over strong while the capacity of fine grinding silo is over weak.
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The amount of feeding material suddenly increases.
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The gap of the partition board is too large.
Partition board maintaining is key to stop the coarse material genetating
Solutions
1Properly add more small balls to adapt to the nature of ores and get better product fineness.
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2So, we must strictly follow the standard ratio to prevent the imbalance of large and small balls.
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3If the loading capacity of the grinding medium in the coarse chamber is too small, or the diameter of the steel ball is not large enough, we should enlarge the loading capacity to adjust the grinding grade.
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4Keep the amount of feeding material compatible with the crushing capacity to avoid the increasing amount of feed.
3.There is a large amount of ball wear in the ball mill
In the grinding operation, the consumption of the steel ball accounts for more than 10 times of the liner of the ball mill.
Here are the reasons for it:
The quality of the steel ball has a greater relation to ball consumption. The wear resistance of the surface layer of steel ball is quite different from that of internal, leading to the uneven speed of diameter reduction and the gradation deviation.
The above situations result in higher ball consumption, lower grinding efficiency, and less-ideal product fineness.
If there are too many useless balls, the broken ball rate will increase, and the load of the ball mill will also increase.
Too much large-diameter steel ball would cause wear problems
2 Ways to avoid the steel balls consumption
1Use medium with high quality and strong wear resistance. Commonly used grinding media include steel balls, alumina balls, zirconia balls, etc.
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2Reduce the numbers of the large-diameter steel ball to less than 70%. Ensure that when the grinding medium moves in the disperser, the void ratio of the medium is not less than 40%.
The common three grinding media in the ball mill
4. Output is getting lower and lower
If we find the amount of feed too much, the hardness of the material to be ground becomes harder and the particle size larger, you get the output problems. Besides, output decrease also follows other factors.
for example, the moisture of the material to be ground is too high, the partition board or the caster joints is blocked by debris, or grinding balls and liners pasted.
Why the output production is lower than before?
"Full grinding" of ball mills
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When the output of ball mills is getting lower and lower, the first thing to consider is whether "full grinding" occurs.
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The working time of the ball mill is too long.
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Failure to add steel balls in time
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The temperature in the ball mill shell increases
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The moisture content of the material is too high
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The proportion of grinding aid added is unreasonable.
4 Ways to improve the output production
1When the temperature of the ball mill exceeds 100 ℃, a layer of air film isolated from the surface of the small particles will be destroyed, which will cause adhesion.
So, to reduce the temperature inside the mill and improve the efficiency of the milling, you can Spray a small amount of mist water into the milling bin to reduce the temperature inside the mill to below 50 ℃.
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2The amount of grinding aid add amount in the general cement production process should not exceed 1%.
High temperature of the ball mill will affact the efficiency
3For every 1% increase in moisture, the output of the ball mill will be reduced by 8% -10%.
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4 when the moisture is greater than 5%, the ball mill will be unable to perform the grinding operation.
5. The bearing of the ball mill is overheated and the motor is overloaded
Reasons
High-quality bearing lubrication
The lubricating oil grade is inconsistent with the manual or is deteriorated.
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The lubricating pipeline is blocked, resulting in the lubricating oil cannot enter the lubricating point.
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The bearing or coupling is not installed correctly.
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The gap between the journal and the bush is unreasonable, which causes poor contact.
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The oil groove is damaged.
Correct ways to solve the overheated bearing and overloaded motor
Use the correct grade of lubricating oil and replace the deteriorated lubricating oil.
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Add enough oil according to the regulations, and generally, 1/3 to 1/2 of the bearing gap is more appropriate.
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Dredge the lubrication pipeline.
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Install bearings or couplings correctly.
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Adjust the gap between the journal and the bush.
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Check the oil tank in time.
6. There are regular and loud knocking sounds during operation
Some liner bolts are not tightened, which makes the liner strikes the ball mill barrel when the ball mill rotates.
Correct ways to deal with the abnormal knocking sound
Find the exact part of the ball mill according to the sound position, then tighten the loose bolts.
