hi; Our raw mill is 200 t/h vertical mill, and it was running with high efficiency till few months back when the damring start damaging from time to time by the mill rollers(damaged 2 time). Is there any one can share me his experience in this subject?

Thanks  

Function of damring is to maintain material bed height in grinding table.It is unlikely that rollers could damage the damring.There is possibility of damage of damring by some foreign hard material.You may check functioning of your metal detector or magnetic separator in upstream of VRM.

Regards,

R.M.Sahu

Hey;

i don't agree  with you mr. Sahu because the main reason of damaging the damring is the mill rollers, when the roller touch the damring it cause damaging of it. The roller may touch the ring when it bend from its position and cause high vibration due to:

1. Fine material

2. Sudden cut of material due to several reasons and problems

3. Non maintained material bed ( especially starting up of the mil)

4. Operating the mill in bad way ( it is the main reason of high vibration in my opinion)

Best Regard

Dear Mr.Nael,

I strongly disagree with your answer.Any comments from other technical forum viewer.

Hi all

there can not any dispute in basic. The roller can not touch the dam ring during operation. Only in case of any break down( tie rod failure), it may touch. But  by that time, the mill will be tripped either by the proxmity switches or vibration.

Normally, the dam is used to get damaged by foreign material from rawmaterial or the mill roller itself may break due to fatigue and the samll piese may struck in between roller and dam ring.

Coming back to the original question,

when the dam ring height is very less, it will lead to mill vibration.when it too high, it lead to high mill power, lesser drying rate and too high bed.

hence, it sholud be balncd between the vibration and mill KW.After a period of operation it is normal to have the wear on the table liner and hence the mill KW will go up. So we should periodically reduce the dam ring height( around 5 to10 mm for 2 months) to maintiin the same bed height.

If the dam ring is damaged, it is better to replace the dam ring so that there will be uniform bed and hence output will be improved and vibration will be lesser.

Hey to All;

The roller can move from its original position (few centimeters) and can touch the dam ring, several times I have seen this fenomena in our 200 tph vertical mill, alot of time  we have opened the mill door (after tripping due to vibration)  and found one roller not in postion and in touch postion with the dam ring. adusting the roller position can be done be removing part of the material under the roller ( if excess material) and then start the auxilary motor for few minutes (experienced alot of times).

Regards 

Dear Mr.Nael,

Could you please tell who are the original supplier of your VRM? We never experienced such problem in Loesche & Atox mill.

gebr.pfeifferag kaiserslautern

Dear Nael,

Similar problem of Roller touching with dam ring  in our VRM 2250 supplied by Pfeiffer experienced several times. By similar metohd describe in your message to remove the material and run on AUX the problem is set right.

 Regards

R P Soni

Hi!

This problem exists for all MPS-type mills.

In my opinion, the reason is in the unit of fastening of roller to the frame. The gap is too big...