Under working conditions the contents of the ore box sort themselves into three fairly distinct layers. At the bottom is the separating layer, which should be maintained at a grain size and density suited to the severity with which it is to oppose penetration by particles from the feed. In jigging through the screen the concentrate must fall through this bed, which may be autogenous, but is usually composed of particles of a material chosen for its specific gravity, of a size larger than the screen openings.
Mineral Jig Sizing & Design Capacity Table
Contact me for any large duplex gold jigs listed on the table below.
The Mineral Jig is not just another gravity Separation Process. It is a highly efficient selective pulsator and concentrating machine which has the ability to treat an unclassified feed separating solids having only a slight differential in settling rates, with only a minimum addition of water.
1000s of these Mineral Jigging machines are now in operation on a “24-hour per day” basis and they are successfully used on practically every type of ore ranging from massive sulphide to others low in mineral ratio, and some which are completely oxidized. Both metallic and non-metallic ores are being handled, with equal efficiency.
The principle behind the success of the Mineral Jig focuses around its adaptability to a wide range of problems under varying operating conditions large capacity, minimum water requirements, extreme selectivity, foolproof jigging operation.
Working Principle for Effective Jigging
The Mineral Jig operates on the basic principle of hindered settling, and in order to effect a concentration it is necessary that there be a differential in the settling rate of the solids treated. As there is an accumulated differential in settling rates in the grinding mill discharge of a conventional closed grinding circuit, this is an ideal feed for the MINERAL JIG. In addition, this is an enriched product due to the settling and trapping of the higher specific gravity mineral particles in the classifier pool, and concentrate removal from the closed circuit is imperative.
The illustration at the left clearly shows why the MINERAL JIG is distinctive and differs radically from a conventional type jig and why it has been called a pulsating selector.
In the upper sectional view the rotating water valve (synchronized with the eccentric shaft) has closed and the plunger is moving the diaphragm on its downward stroke which creates an upward pulsation to the JIG bed. During this period lighter gangue particles are carried further than the heavier mineral particles which may even settle against the upward movement in the pulp. At the completion of the upward pulsation the rotating water valve has passed through a 180° arc or half of a circle.
Types of Jigging Machines
The Mineral Jig is built in two general types, simplex and duplex. The duplex type is built in all sizes while the simplex is standard in the 8″x 12″ size only.
The simplex unit consists of one screen compartment, one hutch, and one screen box, while the duplex is just double, i. e., two screen compartments, two hutches, and two screen boxes.
Each machine is furnished standard with sufficient shot for initial bedding, locking hutch cocks for each hutch, necessary screens and equipped for operation. To facilitate changing screen boxes it is recommended that a spare screen box with screens be available, although this is not necessary.
ALL JIGS are available in any of three types of drives, i. e., belt, motor and gasoline.
MOTOR DRIVE: Motor driven units may be of any standard electrical characteristics, either A.C. or D.C. Splash proof motors are recommended and furnished as standard. The drive is through V-belt to the grooved Jig flywheel. Electrical characteristics of the Jig power supply should always be given.
BELT DRIVE: All units may be belt driven from lineshaft to Jig flywheel. Except in the case of the simplex unit, a loose pulley can be furnished if desired. The Jig flywheel acts as the tight pulley.
GASOLINE DRIVE: Gasoline Engines are used to power all sizes of Jigs through V- belt to grooved flywheel. For isolated localities this makes an ideal unit. All Mineral Jigs are readily adaptable to airplane transportation due to compact nature of the various units.
Hand of the Jig
The Hand Of The Simplex Jig is interchangeable, left or right, and may be adapted to any grinding circuit.
The hand of duplex Jigs is determined by facing the rotating water valve, and with feed entering from the left and passing to the right, the Jig is right hand. A Jig is a left hand unit when facing the rotating water valve—mechanism side; the feed passes from right to left. Note the layout drawings showing the hand of Mineral Jigs. In any conventional grinding mill-classifier circuit the Mineral Jig can be installed in place of the regular launder as the flow slope over the Jig is the same as with the launder.
Jig Sizes and Jigging Capacity
How does a Jig Work
It is often hard for people to understand exactly how jigs work. For what it’s worth, I will put forth my understanding of the principles.
Simply stated a jig is a device which has a couple of basic advantages over a sluice box.
- It is continuous and only needs occasional clean up (its biggest drawing card to hard rock mills).
- It maintains, if properly balanced, an intermittent fluidized bed capable of retaining finer gold than a sluice box.
- If not properly balanced it can be more disastrous than a sluice box.
A properly functioning jig is dependent upon a number of factors; feed flow density, feed flow rate, pulse rate, hutch water input, hutch concentrate delivery flow and of course the make up of the gangue and specifically the particle shape and size of the gold.
My opinion is that the balance of all those factors is well beyond the capabilities of most operators. However, lets look at what we are attempting to do in a jig.
- Create a cross flow on the top that:
a] is fast enough so that only the desired product and as little as possible worthless gangue accompanies it into the jig hutch and
b] is slow enough to allow the desired product to settle into the ragging without being rushed right over the top to tails for, once trapped in the ragging, capture of a particle is reasonably certain as all forward motion should now be defeated.
- Put enough hutch water in to make sure that:
a] the negative pull of the diaphram or pulsing device does not create a sucking effect on the jig bed and
b] it’s not so much that all settling rate is defeated.
- Draw off enough water with the hutch product to:
a] flow it to whatever point of delivery and
b] at same time balance this with the incoming hutch water to accomplish the aims of 2) above.
If we analyze the foregoing statements, we must realize that if the incoming hutch water rate is too large, then the upward thrust during the positive stroke will be too severe and will push fine gold particles upwards and not allow them to settle out and if the incoming rate of feed and water is too large, then forward motion will be too fast and again not allow fine gold particles to settle out. Most of us know from experience that the settling rate of fine gold is quite slow so we can assume that the settling rate on the negative pulse of the jig mist overcame the forward movement turbulence of the gangue; for on the positive pulse, no fine sized gold particles will settle out. We can be quite certain that forward motion takes place on both negative and positive strokes albeit at different speeds depending on the portion of the pulse cycle it is in and depending on where the particle is in relation to the feed entrance and tails exit of the jig cell – for the flow rate speeds up the closer you get to the tails exit and in the same manner as a sluice box at same point the speed of the gangue destroys recovery of fine gold. One assumes that forward motion will be much reduced in the very last portion of the negative pulse but that settling rate is ranging from positive to negative in the positive pulse of the jig, and if there is the slightest bit too much hutch take up water the settling rate will go to the negative side sufficiently to stop all fine gold recovery and in the writer’s experience, some quite coarse gold recovery (up to 10 mesh in size).
Interstitial trickling is the redeeming feature of jigs for fine particle recovery. At the end of each settling cycle, coarse particles will bridge together first, and cone to rest. Finer particles will then trickle through the interstices of the larger one, and came to rest much later.
Flaky particles are generally not well recovered by jigs. Firstly, their terminal velocity is much lower than that of a spherical particle of equal mass. Secondly, their shape restricts their motion during the trickling phase.
Jigs are often used in gold concentration. Their effectiveness, however, rapidly decreases below 300 µm (50 Mesh). This seriously limits their use as sole recovery unit.
An interesting configuration is the placing of two identical sized jig cells, one behind the other. One of those jig cells absolutely has to be out of sync. If the first one is balanced, it will have sufficient hutch water added that the following combination will be in effect. In jig #2 solids will be correct but liquid content will be far too large, thus the forward speed of the total will be too fast for effective settling. Conversely, if volume and flow are correct for the second jig, then forward motion will be too slow in the first unit and either too much product will go to the hutch or blinding of the ragging and jig bed will take place. In essence, the same can be said of jigs as of sluice boxes. The large and dense particles will almost immediately drop out of flow and become part of the ragging. Like all 1 g systems the finer the gold and larger the aspect ratio the less likely you are to catch it. Jigs are not a fine gold recovery unit. Simply stated, unless you can find a, way to change the laws of the settling rate in relation to the laws of the flow rate you cannot improve the recovery beyond some fairly definite limits. The laws governing settling and laminar flow are quite absolute.