Ball mill contorl

we use HASLER SOUND1 controller for controling the ball mill level.( grinds coke material) what is the optimum position to keep the microphone? secodly how to find the predominant frequency which hasler is using.( I want to cross check the sound signal using oscilloscope to evaluate the failure of controller)
thanks.

Tough one

Hello siv, As far as my experience is concerned I've come to the conclution that the ball mill level sensor of the microphone type is not as simple as any other level control. In my previous company that I was working with we had the microphone placed less than 2 cm away from the rotating mill. also the most important thing in this case is the angle at which the microphone is mounted. it should be at the 4 o'clock position. This is because the impact of the material spinning in the mill will be at this position.

Hope this helps.

Regards,

rex

Exactly the same. that means the position we placed is okay. now the problem is The production is complainig about poor throughput or production say. Now the variables are the sound quality and the steelballs. if the steel ball size become less it is going to grind less, or if we put less balls the same. the situation is i would like to record the sound signal in mostly empty mode and fill the mill fully and take another set of recording (using the oscilloscope of course) but how to co-relate the signal i record and the controller output?
regards,
siv

My opinion

I dont think taking a recording of empty and full mill will help much. What u have to do is take recording while constantly increasing the feed rate to the mill while keeping the output constant. when u reach the max feed rate possible( within Safe limit) then u hold that feed rate and start increasing the output rate. by this the level of the mill will first increase and later decrease. U should get a graph on oscciloscope similar to your pattern of feeding that u did in the exercise.

This way u have a good reference for the actual level fopr any other readings u make later on in running plant.

But it will be more helpful for me in suggesting something if u can give the details of the exact problem u r facine.

What we faced in our case was that the level would fluctuate rapidly. The best we could do was adjust thye distance of the microphone on hit and trial basis. Since our mill was not a continuously running equipment we had chance to adjust the distance everytime the mill stopped.

The problem is that the production is complaining the level remain closer to high and the output is low (less grinding). The blame is that since the output is low the feed rate is low. (they argue that the volume of balls inside the mill is ok according to the chart provided by the manufacturer). so blame the maintenance. We can not find why the mill is grinding less , and we are trying to eliminate the controller problem. so how to cross check the actual level and the continous level subsequently?

hope this works

Then i guess the excercise i suggested wil help.

Empty the mill first and then start feeding the mill all the time recording the microphone output on oscilliscope. keep the output closed. then once the level is almost full start opening the outfeed while the infeed is closed. then carry on till the low level is reached.

compare this grapf to the normally running mills graph. U will find whether the mill output according to the graph is normal or not.

If the graph of normally running mill is showing normal operation on comparison with the excercise graph but the outfeed is low then We can pretty safely say the level sensing is wrong.

else u can concentrate on other factors.

thanks, i will post my encounters after the excersice, hope it will help some one. anyway thanks for the help.
siv

pls tell me how many compartments your ball mill have. I have worked with 3 compartment ball mill & we used to place the microphone at 1/3 rd of the total length of the ball mill ( material input side ) at 4'O Clock position as mentioned by Rexy. The distance we used to keep is somewhere between 5 to 10 mm.
The another question I would like to ask is whether the ball mill is stand alone or is there any other ball mill nearby. The chances of interferance becomes very high if any other mill or sound source is in near vicinity.