Originally Posted by R Ward

I'm wondering about the practicality of suspending a Magnetic Separator

over a very large Belt Conveyor i.e. 84" or 96" wide used in the Oil Sand Industry.

This Magnet would be required to pick up large tramp metal e.g. teeth from

large Mining equipment etc.

It would have to be located above the horizontal section or sloping portion of the belt

not the head end.

The blt would be carrying primary crushed ore with a maximum size of 400 x 400 x 600mm.

Would this magnet be capable of picking the metal through the pile on a fully loaded belt?

It would operate in very harsh conditions i.e down to -40 degrees C in winter.

This seems to be a problem in this industry because of the size of metal to

be removed and magnets required.

Why on earth would you want to install this magnet on a sloped belt?????,

it is self defeating as the magnet would have to be mounted on the level to:

(If your losing bucket teeth your shovel operators are not paying attention well enough

to flag the load for dumping off to dig out the shovel teeth)

1. provide enough clearance for the magnetic field to work properly as the magnet has the

potential to pull at the idlers and belt stands while under power.

2. permit it to be slid back for servicing anyway?????!!

3. An electro magent will generate a huge amount of heat depending on the size needed

as determined by the magnet distributor.

If your locating the magnet at the wrong placement on the conveyor your always going to

have problems.

If your not using an electromagnet............ that may be most if not all of your problem as an

electromagent will generate mor emagnetism than a permamanent magnet and Eriez in but

one example has a scraper conveyor that utilises a a system where a rubber conveyor belt

rotates around the entire electro magnet and scrapes the metal of while under power

In most cases the magnet is located at the head pulley or directly over the flat portion of the belt flight

where it can do the most good as the material is passing under the entire magentic field or falling out

of the ore stream.

THE other very important thing you have to remember is anyone with a pacemaker cannot be anywhere

near an electromagnet unless it it is turned off!!!!!!!!!!!!!!!!!!!!!!!!!!

You can purchase very powerfull electromagnets for belt conveyor use so thats not an issue,

but wanting to spend the money to solve it is what the actual issue is.

If your losing a lot of teeth -Assuming they are ESCO ther is problem with wear that you may not be

addressing or simply an issue of controlling the crowding function where the winch speed is too fast

or too much hydraulic power is is being used at the open face of the pit.

If you do not have spot lights pointing at the dipper at all times on the dipper boom versus just

mercury vapor lights on the upper boom it is also self defeating as you cannot see if you have

full compliment of teeth and then have the truck driver dump the load off to be dug through

with a loader or grader with a permanent magnet mounted on a boom or a truck crane

when needed.

If your using a WRStamler Feeder Breaker you could install the magnet at the discharge pulley end and

accomplish the most good providing the shovel operator is also vigilant in watching the dipper also. ■

If you can pick up a stray tooth from under lumps of the size quoted then you can probably pick up the carrying roller when the lumps are not so large. That would not be such a good idea. As stated - Prevention is better than cure. ■

Hi,

We here in South Africa deal with very large conveyor belts for the coal industry, these conveyors have very large burden depths which require correctly sized belt magnets to remove unwanted tramp iron. We have recently supplied a large self air cooled electromagnet for an overland conveyor system feeding one of our new power stations. Here is a video of this magnet in operation - http://www.youtube.com/watch?v=UbIchxTaNjs

This magnet was able to extract a 22kg bucket tooth from a coal burden of 400mm, the magnet was susepnded at 700mm (distance from bottom of magnet to bottom of conveyor). The magnet is a self air cooled design which requires no oil (environmentally friendly) and uses half the kW power consumption of an equivalent oil cooled magnet (energy efficient).

Im sure we could offer you a solution, please could you give us more information on your conveyor system so that we may suggest the best magnet for your application.

Regards,

MAGQUIPrsa ■

Hello R Ward,

You have mentioned the belt width around 2400 mm (96 inch). Please also mention the troughing idler profile that is 3 rollers length and troughing angle, for one to judge the probable operational depth. Equally important is the belt speed. What is the name of ore?

If the crusher is capable to crush some 400 x 600 mm size lumps, then whether it really matters tit bit iron pieces going into this massive crusher? So what size of tramp iron you are expecting to extract?

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Hello R Ward,

Removing the tramp iron deeply buried under the material burden and again by cross belt magnetic separator alone, in direction perpendicular to belt travel, is most inefficient (costly) solution. As far as removal action is concerned, it goes by engineering rules. To get the feel about the problem, here is some information:

1) Assume certain size (width) of magnetic separator. The magnetic separator width is the dimension along conveyor length.

2) The aforesaid width divided by belt velocity will give total time available for tramp iron extraction (this is the time during which tramp iron will be under magnet).

3) Now assume certain size and shape of tramp iron to be extracted. Again this is to be analysed in varied orientation of the tramp iron.

4) Find out (calculate) the force to be applied to such tramp iron for its release from entanglement and to pierce through material burden, as you are intending to get it extracted from bottom. The force should be capable to lift up material column weight plus friction to this column by surrounding material plus self weight of the tramp iron.

5) Force is to overcome resistance as per sr. no. 4 and also to accelerate the tramp iron to stuck the magnet bottom (its belt) in allotted time.

6) Study electrical engineering book on magnetism which will enable to calculate flux density gauss, its gradient, etc. to achieve calculated force at maximum distance that is burden bottom.

7) Generally the magnetic force increases in proportion to square of the closeness. So, once the tramp irons move, the subsequent action will be fast.

8) The 2400 mm wide belt you are mentioning is likely to have high speed. People have found such arrangement and solution commercially not attractive and technically not best. I do not suggest it.

9) However there are maker of powerful magnets in the world for need other than conveyor also (ship container lifting, possibly scientific research for sub atomic particles, railway moving (flying) on rail track and so on). So nothing is impossible. It depends on money power !

10) The practical solution is as below:

A) Create a fixed tripper arrangement in the conveyor and install an inline magnetic separator at the head pulley of fixed tripper.

B) Make the conveyor in two pieces. The first piece is to discharge material on small length and wide belt width conveyor, picking type idler and slow speed, 1 mps etc. This conveyor belt width may become double etc. but such belt is available (Germany Rheinbraun mine has 6400 mm wide belt feeder). The cross belt magnetic separator on this conveyor which has widelt spread material, will definitely remove most of the tramp irons. In addition the small conveyor head pulley will be magnetic type which will certainly remove any left over tramp iron in bottom zone. This small length conveyor feeds to the second piece of conveyor taking the material to destination.

In case you do not want to make the conveyor in two piece, then introduce aforesaid small conveyor (with cross belt magnetic separator and magnetic pulley), either at the beginning of the conveyor or at the end of conveyor.

Regards,

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■