Mag Screen

The Gekko Mag-Screen is a high quality product that combines a magnet and screen in a two in one unit, resulting in a low head height, cost effective solution for feed preparation. The unit is specifically designed to improve downstream gravity separation by classifying the feed and removing magnetics in one step. Onsite research has indicated significant recovery benefits associated with removing heavies prior to gravity separation.

The Gekko Mag-Screen is almost entirely fabricated of stainless steel, has zero water consumption and boasts a unique alternating tapered magnet designed to minimise gold entrainment and provide the cleanest magnetics recovery. The screen component features automated screen rotation allowing finer cut points and non blinding operation.

 

 

  

 

Theory of Operation

The Mag-Screen incorporates a high-powered permanent wet drum magnetic separator with an automated sieve bend style screen. The sieve bend is a high capacity screen capable of classifying solids down to fine sizes at very high capacities over small surface areas. The unit has been specifically designed for application in any circuit where magnetics and coarse product are combined in one stream (such as cyclone underflow in a milling circuit). The Mag-Screen produces three products that can all be kept separate.

The feed stream flows to the distributor at the top of the magnet, which spreads the feed across the width of the drum. The feed flows onto the top of the drum and is directed down one face of the drum. The magnetic element is fixed inside the drum and is held static whilst the drum rotates around the magnet. The fixed magnet is constructed in such a way as to have the maximum power (Gauss) where the feed flow hits the drum (recovery section). This immediately ensures the magnetics are attached to the drum in a thin film situation where the bed thickness is limited and drag on magnetic particles is minimised.

Once the particles are fixed to the drum it is possible that other non-mag material can be entrained in the mags fraction. The magnet is designed with another section below the recovery section, where the polarity of the magnet field is swapped 4 times to “flick” the material over and release the non-mags from the drum surface whilst retaining the mags.

Gekko have developed a tapered magnetic field that allows a slow release of the mags to the discharge point where they literally fall away from the drum. Prior to the Gekko Mag-Screen, detachment has been an issue in strong magnetic separation. Traditionally a high-powered magnet ensures recovery of mags but it is difficult to ensure their release from the drum if the power is too high. The mags tend to stick or hold to the last edge of the magnetic element and slide on the drum surface, which in turn causes a high wear zone. A step change in power also creates the same effect. The alternating tapered magnetic field design has resolved this problem.

The screen unit is a high capacity sieve bend style screen capable of treating very high tonnage per area of screen at high feed densities (up to 80% solids). The screen panels can be made of wedge wire, poly or rubber. The screen unit is automated to allow for screen rotation on a regular basis. This in turn reduces screen blinding and maximises screen wear life. The material that has passed the magnetic drum flows onto the screen at relatively high velocity in line with best practice in sieve bend technology.

The screen incorporates a feed diversion mechanism that allows the feed to be diverted to the coarse fraction launder or to another launder. The unit then shuts down and a pair of pneumatic rams opens the back panel that supports the screen support frame. The screen frame is then rotated which subsequently reverses the direction of flow on the screen panel. To remove and change the screen cloth the back panel is simply opened up automatically, whilst in maintenance mode, and the screen removed by knocking out 4 wedges. The new cloth is fitted and the start button pressed for the unit to return to operation. The unit is also fitted with a complete safety lockout system whilst in maintenance mode.

 
Gekko Mag-Screen Specifications

		Model
	Units	Mag-Screen 1000
Length	mm	2430
Height	mm	2491
Width	mm	1946
Mass	Kg	1828
Total sandable volume	M3	1.7
Total sanded mass @ S.G. 3.6	Kg	4100
Maximum feed rate	M3/Hr	200
Maximum particle size	mm	15
Screen size	mm	4
Screen type		Stainless steel wedge wire
Gausse, magnetic strength	Gauss	>2500
Outlet options, u/s, o/s + magnetics		2 or 3
Construction material		Full stainless steel
Instrument air supply		Instrument air @ 600 kPa
Instrument air consumption @ 600 kPa	L/hr	10
Drum rpm		20
Drum width	mm	910
Drum diameter	mm	646
Feed chute width	mm	800
Installed power	kW	1.1
Supply voltage	V	3 phase

Click here for a printable version of the Gekko Mag-Screen specifications list
 

Click here for the Gekko Mag-Screen brochure  

Further technical information on the Gekko products and services are available in the form of technical papers. To view the list of Gekko technical papers click here