It depends on what type of crusher and how it is fed. If you are using a large crusher direct fed from a dump pocket, there is not much you can do besides having a very observant operator watching the pit.

If you are using a dump pit that uses a conveyor to feed the crusher, then a metal detector and tramp magnet might work.

Experienced similar problem at Barrick Porgera Mining Operations. Need Spotter(s) when loading dump truck and discharging into the gyratory crusher?

Spotters are cheaper at Porgera but very hard to spot a broken tooth, tramp magnets are great with a belt feed but obviously have issues if there is much magnetite in the ore, probably no need for detectors as a good magnet will find most of it. If the loader and excavator tooth is common - that needs to be addressed on its own with the vendor. Operator care can eliminate most of the drill bit occurrence as well. Loader feed directly into the crusher works well with only "clean" feed. I have seen tramp magnets that can pull a 10lb piece of steel from over 2 feet above the belt.

Mines either have direct dumping into a coarse crusher with a tramp iron recovery system following it, or a tramp iron recovery system on a conveyor feeding a close/narrow gapped primary crusher. Both are usually followed by.

It sounds like you have more than one problem if you are dumping rejects from mill discharge into crusher you need to install magnets on the reject chute. When the loader operator does inspections he must report to his supervisor at once. This gives everyone a heads up.

As far as drill bits are concerned I have found that if the driller reports that he has lost a bit right away that is really all you can do. If not reported. A policy must be put in place that states the driller will lose x amount of dollars off his bonus.

I think it was pre mill, ROM ex pit material. Agree on the drill.

Thanks to you all for your invaluable contributions and advice. They are well appreciated.

To clarify a few things, we use a gyratory crusher and we do direct dumping into the crusher for crushing. So I think that the spotters issue will b looked at immediately for remedy of the problem and such sanctions will conscientize operators and supervisors in the pits.

At the downstream there are magnets both self cleaning ones and static ones to get rid of magnets that pass through the gyratory crusher because of their sizes and hence do not hurt the downstream circuits.

Have you tried to see if you can pick them up using a powerful magnet?

Can you guess the source of this material?

We are currently about to explore the usage of hand held detectors. We hope that can help us to hand pick these metals.

Some of the metals that have caused serious problems are from the mining operations. Digger and loader teeth, drill bits and other heavy mine equipment parts.

By the way many of those parts are none or low ferrous, meaning magnets have little effect. Try having the operations people be more careful. As to the loader teeth and other moving equipment parts, perhaps a better preventative maintenance program would be easier to emplace, such as checking the parts early and often and replacing them before they break off. As to drill steel and bits, have the drillers do a better job of cleaning up after themselves.

A little care ahead saves a lot of problems later.

It is the responsibility of the shovel operator to watch the teeth and to immediately notify the shift boss that a tooth may be heading to the crusher. The trucks in transit along with the next few loads from the same spot could be diverted to a dump where smaller equipment could be used to check it, a dozer comes to mind. If that pile is spread out a drill bit should be easy to find electronically.

Someone, either a mechanic, shift boss, or someone else should be inspecting the teeth of all machines at the beginning of the shift. If one is loose either it or the pin must be replaced unless the pin can be tightened. A new pin is cheap compared to a mantle. Surely they have a tool to retrieve one.

What is the CSS of your primary crusher? It is hard to imagine a crushing circuit that was designed without provision for either picking tramp out of the feed or planning on it passing a relatively large CSS then being picked up later.

That is why one has to start from the mining operations and tries to find the source (main culprit) and try to stop there before the crushing units get damaged.

We have our css to be 130mm for the primary crusher.

Most of the tramp iron is normally removed by using suspended magnets/magnetic pulleys and metal detectors that stop the belt conveyors for its physical removal.

Thank you all for your contributions. We have taken all your suggestions and experiences on board and we are currently drafting an idea on how to combat and manage the situation brilliantly to avoid future damages to our crusher and its parts.

I am trying to co relate the problems at your end.

•You have heavy duty drilling machines, shovels, loaders and dumpers whose broken and damaged Manganese steel, hard phased, ni hard ( low fe steels ) steel parts are being transported along with the ore boulders and directly unloaded to the primary crusher's (gyratory or jaw crusher) receiving chute.

•The tramp iron magnet and metal detector will not work effectively on low fe steels and it needs proper surface exposure. Which can’t be accommodated in dumper transportation but.certainly on conveyor and very successfully on passing 150 mm material?

•If the above facts are coinciding then you may try photo imaging and alarming systems at the unloading and loading points (certainly will be a dusty atmosphere) of dumpers.

•Notifying the healthy fitments of these parts at the end of every shift by respective operators with un postponed corrective measure will certainly reduce the frequency of damages incurring by them. (Loader buckets teeth, pins, drilling couplings, rods and etc).