Using Trommels in Mining

A trommel is mining equipment comprising of a cylindrical drum that has many holes of a given size. The holes help in classification, and when the drum rotates it only lets the material smaller than the holes fall through while the rest of the material flows out of the other end. They are widely known and used popularly around the world on various​ ​sized​ ​mining​ ​operations.

Source: Savona Equipment

Miners in the worldwide mining business commonly use gold trommels. In this, gold bearing gravel is added to the hopper and it enters the rotating drum that further helps to break apart the material. It is used to help separate and classify out the material for further processing, so as to separate the smaller gold bearing material from the larger substrate like rocks, pebbles and boulders. These can​ ​be​ ​manufactured​ ​in​ ​any​ ​size​ ​to​ ​suit​ ​the​ ​needs​ ​of​ ​the​ ​miner.

On larger operations, it is generally incorporated into an entire wash plant setup. Generally speaking, to efficiently operate a trommel, two people are required. One person would feed material, and the other one would clear any discharged waste material​ ​so​ ​that​ ​more​ ​material​ ​can​ ​be​ ​fed​ ​into​ ​the​ ​machine.

Application

As mentioned above, ​trommels are widely used in gold mines, since they are extremely efficient and very effective at recovering fine gold. The larger-sized models can handle impressive volumes of gold-bearing gravel when operating at peak efficiency. They are often powered​ ​by​ ​large​ ​diesel​ ​or​ ​electric ​engine.

How it Works

Let us understand in detail how a gold trommel works and how efficiently it can be operated. To begin with, once it is set up, the motor starts rotating the cylindrical drum, the water sprayer also gets activated. Gold bearing material is added to the hopper and the force of water washes it down or cleans it to break up the material and help separate the gold.

The drum keeps on moving round and round. Any pieces of material (rocks and gravel) larger than the drum screen hole size are forced down the drum into the tailings bucket and out, forming a coarse tailings pile at the bottom of the unit. The rest of the gold-bearing gravel falls into the sluice box below, where hydraulic action helps to trap the black sands and gold while allowing the waste to flow out the lower end of the box into additional tailings (fine tailings). Here is when the other person cleans the sluice box. Finally, the concentrates are then run through a concentrator​ ​where​ ​the​ ​gold​ ​is​ ​recovered.

Since​ ​the​ ​goal​ ​is​ ​to​ ​completely​ ​break​ ​apart​ ​any​ ​clays​ ​and​ ​mud​ ​that​ ​could​ ​retain​ ​placer​ ​gold and​ ​prevent​ ​it​ ​from​ ​being​ ​caught​ ​in​ ​the​ ​sluice,​ ​different​ ​designs​ ​and​ ​amounts​ ​of​ ​water​ ​jets are​ ​used.​ ​It​ ​is​ ​basically,​ ​high​ ​pressure​ ​water​ ​together​ ​with​ ​the​ ​rotating​ ​drum​ ​which​ ​breaks apart​ ​any​ ​clays​ ​and​ ​dirt​ ​as​ ​the​ ​slurry​ ​moves​ ​through​ ​the​ ​drum.

Some processes might require a grizzly prior to feeding the trommel in order to separate out the largest boulders. This depends on the quality of your equipment and the type of material that you are feeding into it. Some larger wash plants in large scale operations have grizzly set up directly over​ ​the​ ​hopper​ ​when​ ​the​ ​material​ ​is​ ​added​ ​so​ ​as​ ​to​ ​increase​ ​the​ ​efficiency​ ​of​ ​the​ ​process.

Key​ ​Components.

A​ ​gold​ ​trommel​ ​has​ ​the​ ​following​ ​major​ ​components:

Rotating Drum or Cylinder​: Mounted at a downward inclined angle, the drum or cylinder is usually constructed of high-grade aluminum, stainless steel, or expanded metal with screens in it typically running 1/4 inch to 1/2 inch. This kind of structure is considered most efficient for gold recovery. Small gasoline engines, batteries, electric motors, or large diesel engines are used to power the drum’s rotation. Diesel engines among these options are the most commonly used.

Metal​ ​Frame​ ​(including​ ​wheels​ ​and​ ​tow​ ​bar​ ​or​ ​hitch):​​ ​The​ ​frame​ ​is​ ​the​ ​trommel’s​ ​metal​ ​and supports​ ​all​ ​the​ ​other​ ​components.​ ​In​ ​larger​ ​models,​ ​a​ ​set​ ​of​ ​wheels​ ​is​ ​mounted​ ​on an​ ​axle​ ​at​ ​the​ ​bottom​ ​of​ ​the​ ​upper​ ​end, ​and​ ​a​ ​tow​ ​bar​ ​or​ ​hitch​ ​at​ ​the​ ​opposite​ ​end

Sluice​ ​Box:​​ ​The​ ​sluice​ ​box​ ​is​ ​fitted​ ​below​ ​the​ ​rotating​ ​drum.​ ​The​ ​utility​ ​of​ ​a​ ​sluice box​ ​has​ ​been​ ​explained​ ​earlier.

Hopper​ ​or​ ​”Feeder”​ ​Chute:​​ ​​ ​This​ ​is​ ​a​ ​square​ ​or​ ​rectangular​ ​box​ ​attached​ ​to​ ​the​ ​upper​ ​end​ ​of the​ ​trammel​ ​is​ ​fed​ ​with​ ​auriferous​ ​material.

Drum​ ​Side​ ​Panels​ ​and​ ​Tray:​​ ​Panels​ ​play​ ​a​ ​very​ ​important​ ​role​ ​in​ ​the​ ​movement​ ​of​ ​the material.​ ​The​ ​panels​ ​ensure​ ​that​ ​the​ ​material​ ​does​ ​not​ ​fall​ ​from​ ​the​ ​sides​ ​of​ ​the​ ​turning drum and the tray pushes the gold-bearing material through the screen holes in and downward​ ​toward​ ​the​ ​sluice​ ​box.

Sprayer: Available in various forms, the most common type of sprayer is a length of perforated PVC or metal piping that is fixed in place near the top of the drum which is independent of the drum’s​ ​rotation.​ ​Its​ ​working​ ​is​ ​simple,​ ​water​ ​is​ ​fed​ ​into​ ​the​ ​piping​ ​via​ ​a pump​ ​and​ ​length​ ​of​ ​hose,​ ​or​ ​less​ ​frequently,​ ​by​ ​gravity.

Tailings Tray or Chute: The tailings tray also known as chute is attached to the lower end.​ ​They​ ​are​ ​positioned​ ​above​ ​the​ ​sluice​ ​box​ ​mount​ ​and​ ​flows​ ​away​ ​waste​ ​material from​ ​the​ ​drum​ ​and​ ​sluice​ ​box.

Assorted Motors, Belts, Hoses, Pumps, Pulleys, etc​.: These components are also essential and​ ​come​ ​in​ ​variety​ ​of​ ​models.

Advantages

Trommels​ ​have​ ​the​ ​following​ ​main​ ​advantages:

1. They​ ​are​ ​generally​ ​low​ ​cost​ ​and​ ​easy​ ​to​ ​maintain. ​ ​​ ​​ ​​ ​​ ​​ ​​ ​
2. In​ ​terms​ ​of​ ​Efficiency​ ​: A​ ​properly​ ​constructed​ ​trommel​ ​that​ ​is​ ​set​ ​up​ ​for​ ​peak​ ​operation are​ ​very​ ​efficient​ ​gold​ ​grabbers​ ​and​ ​helps​ ​in​ ​recovering​ ​extremely​ ​fine​ ​or​ ​flour​ ​gold​ ​in the​ ​micron​ ​range​ ​in​ ​a​ ​consistent​ ​manner.
3. Ease​ ​of​ ​setting​ ​up:​ ​They​ ​can​ ​be​ ​set​ ​up​ ​anywhere​ ​near​ ​the​ ​source​ ​of​ ​auriferous material,​ ​where​ ​water​ ​can​ ​be​ ​fed​ ​into​ ​the​ ​drum​ ​unit​ ​and​ ​there​ ​is​ ​a​ ​power​ ​source​ ​to operate​ ​the​ ​unit.
4. They​ ​can​ ​handle​ ​a​ ​wide​ ​range​ ​of​ ​materials​ ​including​ ​heavy​ ​clay​ ​content​ ​ores.
5. They can easily break up cemented or compacted material in the scrubber section; and
6. Handles​ ​high​ ​volumes:​ ​It​ ​can​ ​be​ ​used​ ​for​ ​feed​ ​sizes​ ​including​ ​large​ ​rocks.​ ​And​ ​can​ ​be

built​ ​to​ ​handle​ ​a​ ​huge​ ​range​ ​of​ ​capacities,​ ​which​ ​can​ ​be​ ​fed​ ​by​ ​a​ ​single​ ​individual​ ​with​ ​a hand​ ​shovel​ ​up​ ​to​ ​500​ ​cubic​ ​yards​ ​per​ ​hour.

Disadvantages

Following​ ​are​ ​the​ ​main​ ​disadvantages​:

1. Portability issue: Often, the larger production units are not very portable and when set up often remain stationary while gravels are hauled to them and waste gravel and rocks moved away​ ​It​ ​is​ ​difficult​ ​to​ ​carry​ ​them​ ​to​ ​remote​ ​areas​ ​unless​ ​they​ ​are​ ​towed​ ​to​ ​the​ ​site.
2. The​ ​larger​ ​production​ ​units​ ​are​ ​also​ ​not​ ​cheap​ ​and​ ​may​ ​have​ ​significant​ ​set​ ​up​ ​costs.
3. Additionally, they require tools, spare parts, gasoline or diesel fuel (in fuel models), batteries, and​ ​the​ ​like.

Conclusion

Since both are used for particle size classification, one might get confused in selecting between trommels and vibrating shaker screens. Vibrating screens may be strongly preferred by the aggregate industry whereas trommels are preferred for placer mining because of their ability to break​ ​up​ ​and​ ​wash​ ​gold-bearing​ ​gravel,​ ​thereby​ ​increasing​ ​recovery.

There are a number of manufacturers that provide a large range of stationary trommel systems; including several of the manufacturers of portable units. Current screen manufacturers include: McCloskey, Doppstadt, Powerscreen, Telsmith, Wildcat (Vermeer), Komptech, Northern Placer, Aureco, Extrac-Tec, Savona and Screen Machine Industries. Some of the leading manufacturers among these are ​Savona​, ​Telsmith​, ​McCloskey, ​Northern Placer​, Aureco​, Extrac-Tec​.

There are a number of differences between each brand, but some of the primary differences one should take into consideration are the equipment’s sorting ability, drums size, spiral, whole drum screens, inclined screen cloth segments, durability, conveyor system and​ ​infeed​ ​hopper​ ​size.

If you have any questions, or need assistance in choosing a new trommel according to your requirements, please feel free to ​contact us​. If you are looking for a used ​trommel screen​, please​ ​see​ ​our​ ​selection​ ​of​ ​the​ ​same.

https://www.savonaequipment.com/en/equipment/trommels-e41572?s=p