• To participate in the 911Metallurgist Forums, be sure to JOINLOGIN
  • Use Add New Topic to ask a New Question/Discussion about Grinding.
  • OR Select a Topic that Interests you.
  • Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent).
    Using Add Reply allows you to Attach Images or PDF files and provide a more complete input.
  • Use Add Comment = to comment on someone else’s Reply in an already active Topic/Discussion.

SAG Mill Discharge Scats – Ball Chips (14 replies)

10 months ago
Standartenfurer 10 months ago

I’m looking for ideas to process the discarded material of a SAG mill. We have huge material stocks of this process that contains ore contaminated with metal balls and some scrap elements that makes it hard to process it on a crusher. I have seen a small company that almost manually clean up the discarded material separating the ore from the other elements, once we send this kind of material to a sulphide leach pad so we can recover some of the ore, but sending ore that has around 1% of copper grade to a metallurgical process that recovers around 35% versus the concentration plants that recovers nearly 80-85% then you would understand my concern to search for a better destiny to the material. I would like to know if any of you has experience processing this type of material or any success history that you can share with me.

Ace Levy
10 months ago
Ace Levy 10 months ago

During the Metplant 2015 conference held in Perth during September there was a paper presenting "The Benefits of Applying Modern Coal Plant Design Principles to Base Metal Heavy Medium Separation”.

This presentation included a small modular Heavy Medium Plant specifically designed for treating SAG mill pebbles. Depending on your ore types and host material this process can reject the waste rock and remove the steel so the ore can be recovered, crushed and re-processed.

Alan Carter
10 months ago
Alan Carter 10 months ago

Sounds like a magnetic separation process, VFD conveyor for reject materials with a self cleaning magnet/belt with appropriate capacity.

10 months ago
OberstGruppen 10 months ago

I truly believe my teammates of Metso Chile could help you on that, designing a smart solution with a very fair cost.

Bill Fraser
10 months ago
Bill Fraser 10 months ago

You could use a ball separator that we have used in other mines. It's like a screen deck and the balls sorry through and land in barrels. The oversize rock would screen off the end and the metal balls and smaller metals could be dispersed into bins. You could also fabricate a small grizzly screen as a trial. You can dump on the screen with the loader and smaller rock and material can sort through this as well.

Bill Rico
10 months ago
Bill Rico 10 months ago

Eriez Trunnion magnet separator.

10 months ago
Unterstarm 10 months ago

Classifying material inside the mill using classifying liners can be a possibility.

Carmen Ibanz
10 months ago
Carmen Ibanz 10 months ago

The use of trash metal removers such as magnets or belt magnets over the SAG mill discharge receiving conveyor is the most common separating method I have worked with.

Bob Mathias
10 months ago
Bob Mathias 10 months ago

I agree with you, we successfully installed and commissioned a metal detector across the by-pass conveyor between the SAG Mill1 that conveyed rejected oversize materials and the Jaw Crusher for further crushing at Porgera Mine in 2003...The metal detector performed very well in processing metals by removing any traces of metals from the materials on the conveyor prior to entry in the Jaw Crusher! But what kind of discarded material from SAG mill for this particular case are we trying to process? Is it oversize materials, metals or whatever that has been stockpiled as rejects from SAG mill?

If this is the case (i.e. from stockpile) and you do not have a by-pass conveying system, a metal detector and Jaw/Cone Crusher as a separate system for processing discarded material from SAG mill and recycle back to SAG mill via the feed conveyor then I can see that you now have a technically viable project for someone to design this process and make some good money! This may solve your problem in managing your stockpile effectively with some good return and long term benefits...

10 months ago
Obergruppenfuhrer 10 months ago

Keep us updated with the solution you decided on.

Carl Jenkins
10 months ago
Carl Jenkins 10 months ago

Or you could consider another way. Target the product and ignore the tramp and barren material. Test work shows a very strong case for you to consider.

David Kano
10 months ago
David Kano 10 months ago

I have posted a comprehensive collection of photos and videos of this application on the following link where you can review and download them if required.


The magnets are about 98% effective. One of the initial problems we had was the Stainless steel cladding was only as wide as the magnets themselves, cause the mill balls to 'stick' to the side of the conveyor. This was easily fixed by extending the length of every 4th cladding; I don't have up-dated pictures of that.

The metal detector was then fitted to the conveyor feeding the mobile cone. Only using the Mobile cone crusher metal detector meant the whole plant had to be shut out for removal of the mill balls. With the metal detector on the feed conveyor, we only had to shut out the feeder and once conveyor, considerably improving up time.

You can also consider using the metal detector to activate a by-pass conveyor to remove the tramp metal.

10 months ago
Oberstorm 10 months ago

Use magnetic separators or belt magnets.

Dizzy Flores
10 months ago
Dizzy Flores 10 months ago

Use magnetic at the mill trammel to pick as much metal scars and recycle back the reject to mill feed.

John Koenig
10 months ago
John Koenig 10 months ago

You may find more information regarding the SAG discharge if you search them as "scats" (broken ball chips). Safety Notes; they result from internal stresses in the balls impact and heat energy in the SAG mill causing a Martensite transformation in the ball (Crystals form in the metal) and they have a potential to rupture with very sharp edges. Please pay careful attention to the balls rolling back especially on empty conveyors! Good to have the pile where it is easy to remove with a loader. Also, if you have not been recovering the material as part of the circuit design you may be running a very tight SAG grate resulting in pebble loading of the mill. If this is the case you could look at installing a magnet, pebble crusher, screen, SAG feed size control and re-circulating system back to your SAG feed then running a wider opening on your grates. A project I worked on saw a 30% increase in SAG throughput. ROI < 90 days.

Please join and login to participate and leave a comment.