Use an electro magnet as close as possible to the source of the bolts. HangHthe magnet in a tower that allows the magnet to straddle the belt. The magnet needs to be strong enough to pull the material up through the product in the belt. Run the magnet on a motorized trolley and when the conveyor shuts down it automatically moves out from the conveyor, trips a travel switch that deenergizes the magnet and drops the metal into a collection bin. The trolley can also be set at specific time intervals to ensure the magnet does not get too full.

You also should have a metal detector downstream of the magnet that will trip and stop the belt if any metal gets by the magnet. This will require someone to lock out the conveyor and go to the downstream side of the metal detector and remove the metal. To test how far the belt travels after stopping, place a piece of metal on the belt and let the metal detector trip the conveyor, then paint a strip on the conveyor or place a sign at the spot the material has stopped at. This allows you to go directly to the metal. Sometimes a hand held metal detector helps to locate the metal under the product.

The conveyor components below the magnet should be as non metallic as possible. Then your transfer chute can be of a normal design and metal free. ■

Is this reinforcing bar(rebar) that you are dealing with?

Would it be at all possible for the material to be crushed or broken smaller by a crawler mounted hydraulic breaker claw

and employing an electromagnet used on the material on a second crawler excavator before it is dumped into the conveyor

transfer system??

Short of that if you what you are doing is reclaiming concrete to make new aggregate you have very few options. ■

Four metre long by 20 dia. roof bolts are quite a hazard for conveying purposes.

In one breath the magnet is described as a 'clear and simple thing' and in the next sentence the severe belt damage is acknowledged.

Belt magnets are, of necessity, violent gadgets. In earlier days I spotted a brand new shovel on the belt. I could have used that discarded tool myself except for it having had the handle worn away before I could shut down and retrieve the shovel. If you have roof bolts exposed to a belt magnet your downtime will be very frustrating.

Your post is excellent because it highlights the intermittent operation of some conveyor belts which are supposed to be continuously operated. Consider an examination of the crusher. It is probably a Blake (Jaw) type: otherwise the crusher would also experience downtime when the wire became wrapped around rotating surfaces. Crusher exit would be a more convenient site for a very strong fixed magnet like the one Gary mentions. At the crusher exit the nip has reduced the opening, that's what nips do, to the limit size of any, rarely, attached rock. This would make it possible to extract the bolt in less active, nearly said calm, airflow.

The occurrence of discarded roof bolts was never quoted in texts covering comminution. That is because roof bolts where unheard of until the latter half of the 20th century. Are you crushing underground? ■

Four metre long by 20 dia. roof bolts are quite a hazard for conveying purposes.

In one breath the magnet is described as a 'clear and simple thing' and in the next sentence the severe belt damage is acknowledged.

Belt magnets are, of necessity, violent gadgets. In earlier days I spotted a brand new shovel on the belt. I could have used that discarded tool myself except for it having had the handle worn away before I could shut down and retrieve the shovel. If you have roof bolts exposed to a belt magnet your downtime will be very frustrating.

Your post is excellent because it highlights the intermittent operation of some conveyor belts which are supposed to be continuously operated. Consider an examination of the crusher. It is probably a Blake (Jaw) type: otherwise the crusher would also experience downtime when the wire became wrapped around rotating surfaces. Crusher exit would be a more convenient site for a very strong fixed magnet like the one Gary mentions. At the crusher exit the nip has reduced the opening, that's what nips do, to the limit size of any, rarely, attached rock. This would make it possible to extract the bolt in less active, nearly said calm, airflow.

The occurrence of discarded roof bolts was never quoted in texts covering comminution. That is because roof bolts where unheard of until the latter half of the 20th century. Are you crushing underground? ■

As this thread develops there are underlying contradictions which must be acknowledged.

If the tramp iron removal is simple and straightforward, belt skirt damage is insignificant & tramp iron can be removed from the silo I cannot understand the rationale of the thread. Further, what is the functional way of removing the clogged wires from the crusher.

You are already sitting the belt magnet on top of the high chute walls which is already the best solution. You don't need any skirt there, the magnet can be arranged to sit directly on top of the chute sides.

Upstream removal of the roof bolts & mesh, as suggest by Izaharis, is the only worthwhile improvement you can make. This is because if there is inadequate airflow in an otherwise very good installation the only way to correct this would be to enlarge the airflow. (This assumes that a rubber curtain is already fitted at the feeder exit & the working envelope of the crusher is able to withstand the whiplash.) ■