Grinding & Classification Circuits

Grinding & Classification Circuits 2017-03-23T09:46:37+00:00
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SAG Mill Shell Liners Spacing (18 replies)

Rahil Khan
1 year ago
Rahil Khan 1 year ago

What is your idea about space between SAG mill shell liners? How much space would be appropriate?

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

An interesting question! Unfortunately, the answer begs other questions such as:

Mill size, shape, et al. - Length, Diameter, Cone types et al., Liner shape, Liner Material,
Product size distribution
Ball size range from feed to grate opening
Grate Size
Recycle size
Power
Critical Speed – range
High and low pattern;
Reversing or single direction?
Other factors not mentioned.

Note: too close and you get all large material and balls thrown to far liners; too far and you get too much wear and not enough grind rate.

OberstGruppen
1 year ago
OberstGruppen 1 year ago

10mm max - backfill with Sikaflex.

John Koenig
1 year ago
John Koenig 1 year ago

I agree will you, although I would use another type of material similar to the sikaflex.

Marshal Dienes
1 year ago
Marshal Dienes 1 year ago

For a conventional rubber lined ball mill, based on the amount of gold behind the liners: The distance is about 0.05mm (800oz in an 8x12ft mill), but much higher in steel lined mills. If you eliminate the flex space completely then the impact acts on the mill shell causing damage, the can crack the feed end panel or shell to panel joint when welded.

Obergruppenfuhrer
1 year ago

The type of liner material will have an effect on the amount of spacing. For instance manganese steel liners prone to spreading would require more spacing than chrome moly (medium spread) and high chrome (minimal spread). Could range from 12mm to 8mm.

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

8-10mm is typical in both steel lined and rubber lined mills. Modern casting technology provides for dimensionally stable steel liners, usually they are slightly undersize. A good quality rubber "widget" placed in between each liner eliminates most gaps. Any remaining gaps can be filled with a Sikaflex type product - we have used Sika TANK with good results. If the gaps are too small, then you have the risk that the liners will not fit. NB: we stay away from Manganese liners due to tendency to spread.

For rubber liners, similar 8-10mm gaps again can be filled by a suitable rubber "widget" and remaining gaps with a suitable silastic. We have found rubber liners vary more in dimensions that steel liners.

Rahil Khan
1 year ago
Rahil Khan 1 year ago

Excellent ideas! Because of some casting process considerations and also negative tolerance which is necessary (I think), sometimes it is created more than 20 mm space between SAG mill shell liners but I believe that this space will be filled by ball scats.

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

These spaces should be evened out amongst the liners when installing. 20mm seems a bit on the large side. The rubber widgets need to be there, as ball scats will act as wedges driving the liners apart. Plus, as scats do not seal around the liners, they allow water / slurry to get in behind the liners and cause all sorts of problems.

Tarun Karakoti
1 year ago
Tarun Karakoti 1 year ago

For sure 20 mm gap between shell lifters is quite high as even though the scats fill in eventually , the risk of slurry ingress always remain which may affect the shell mother plate.

Rubber widget is highly recommended.
In the Rubber liners, we generally prefer to have 0 mm gap so as to make the lining 100% leak proof. This being a feature unique to rubber compared to steel lining.
For rubber it’s better and easier to have tight fit using a PortaPower.

If gaps are left between lifter, during the wear life cycle they may become weak spots and at times tend to determine the reline time affecting the overall life.

Sachin Prakash
1 year ago
Sachin Prakash 1 year ago

Advisable tolerance by up to 3 mm in between lifters and plates, prior to ease of installations, as well as, allowance for expansions and contractions of rubber liners during mill operations.

Gruppen
1 year ago
Gruppen 1 year ago

No gaps for rubber lining system are preferable; however, small gaps of up to 5mm normally fill up with scats etc. Good quality rubber widgets to fill 10-20mm gaps in steel lining systems.

Bob Mathias
1 year ago
Bob Mathias 1 year ago

We use 14mm in the shell liners. This measure will also depend on the measures of the filler strip.

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

Don't you use a layer of rubber behind the liners to protect the shell? Here for steel liners in a SAG mill, 10 to 15 mm (1/2 inch). Here on primary mills the liners aren't in there long enough to need filling in the gaps and I can't imagine any filler material that would last anyway. The gaps fill with ball chips. We use a jackhammer on either a forklift or positioned to knock out the first liner and first row. Any rubber damage is repaired before the new liners are put in.

Sachin Prakash
1 year ago
Sachin Prakash 1 year ago

Usually using of inner rubber layers are unnecessary for Rubber lined Ball mills in general, unless the shore hardness is high from the particular rubber supply.

Kumar Choudhry
1 year ago
Kumar Choudhry 1 year ago

I am comfortable with 10-12mm spacing between steel shell liners. It’s advisable to have a 6mm rubber lined shell prior to relining in order to prevent any form of slurry ingress during operation.

Oberstorm
1 year ago
Oberstorm 1 year ago

We generally find that our customers prefer no gaps in both rubber and composite liners. As noted (above) the use of a porta power and good lining design ensures this is possible. Gaps between lifter bars can increase racing and premature wear in that area. When designing a lining we ensure that there is adequate compression in the lining to allow easy, yet effective fitment.

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

In my view that is all OK for rubber or composite liners, and in fact no gaps is preferred to effectively "seal" the liners in place - exactly as states. However, for cast steel liners, a gap is required to ensure that all liners can be fitted, and removed at the end of their wear life. Rubber wedges in between and rubber lagging on the shell behind the liners provide protection to the mill shell. In our mills we specify steel liners with geometry to prevent slurry racing circumferentially, and minimise longitudinal gaps to prevent wedging by scats and slurry. In my experience, consistent gaps of between 10 and 12mm are the norm.

Alan Carter
1 year ago
Alan Carter 1 year ago

From an installers point of view! Most steel liner suppliers supply rubber widgets or void filling segments to prevent liner movement or creeping to a degree with the initial installation and prevent smaller balls locking up wedging liners apart. As mentioned additional tools as jackhammers will be needed to remove these liners and can increase relining times. We had a client that experienced this problem by not using the rubber void segments and has since changed with great results. These rubber filling segments do not close the entire gaps on the impact side and wear with the liner, so rubber lining your shell can only be a positive. These rubber segments assist with preventing shell burn or wash, and making stripping the liners when it comes to relining your mill easier. Speak to your suppliers as these rubber void filling segment do work and can eliminate unnecessary downtime when relining your shell. As for rubber composite liners/ lifters no gaps under compression is ideal.

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