Types,​ ​Working​ ​Principle​ ​and ​Applications of Screening Plants

Screening is the process by which granulated ore material gets separated into different grades of particle size. In other words, it’s a mechanical process that stratifies (divides) particles according to required size. Once particles have been divided, the surface opening then​ ​accepts​ ​or​ ​rejects​ ​the​ ​particles.

Source: Savona Equipment

A “Screen Plant” can be simply defined as a machine with surfaces that are used to classify materials by size. For example – In a mining process, it is a type of machine used to extract​ ​ores​ ​from​ ​the​ ​ground​ ​using​ ​water​ ​and​ ​sedimentation​ ​processing.

They are designed to provide high-capacities, in various industries ensuring optimum productivity​ ​of​ ​your​ ​production​ ​process​ ​at​ ​a​ ​low​ ​maintenance​ ​cost.

The following​ ​are​ ​the​ ​key​ ​factors​ ​you​ ​must​ ​consider​ ​for​ ​your​​ ​plant:

• Size​ ​and​ ​type​ ​of​ ​material​
• Application​ ​and​ ​use​ ​of​ ​the​ ​crushed​ ​material

Applications

As explained above, the most common application is to separate a conglomerate of materials into different size fractions. Other popular uses are dewatering, scalping, dedusting,​ ​and​ ​washing.

They form an essential stage of any mechanical process and are used in a range of industries including mining and mineral processing, agriculture, pharmaceutical, food, plastics, and​ ​recycling.

Working​ ​Principle

Let us now understand how this machine works. It has an inbuilt drive that induces vibration and a media that helps in particle separation. There is a deck which holds the media and the drive and is basically the mode of transport for the vibration.

A simple example is of a single deck with an inclined frame. This inclined frame is mounted on springs. When the vibration is generated from an unbalanced flywheel it results in a very erratic motion which is developed due to the rotation of the wheel. This type of will typically be used in smaller operations and rock quarries where sizing is not the key consideration. Free fall is based on the theory of free fall of the material through and over​ ​the​ ​Deck​ ​i.e.​ ​in​ ​this​ ​way​ ​no​ ​particle​ ​layer​ ​will​ ​build​ ​up​ ​on​ ​its ​deck.

There are various physical factors that affect the process. For example, vibration, g force, bed density, and material shape. Sticking and Plugging can be caused due to water attraction. Further, Electrostatic forces can also affect efficiency. Very dry material can​ ​also​ ​generate​ ​a​ ​charge​ ​that​ ​causes​ ​it​ ​to​ ​attract​ ​to​ ​the​ ​screen​ ​itself.

Common​ ​Vibrating​ ​Applications

Various​ ​kind​s​ ​and​ ​their​ ​applications​ ​are​ ​mentioned​ ​below:

Scalping: ​When a feed is mostly finer, this type is used to remove a small amount​ ​of​ ​oversize​ ​without​ ​taking​ ​into​ ​account​ ​crushed​ ​product​ ​sizes.

Sizing (​Dry and wet): When there is a need to produce material sizes that meet requirements in particular range of sizes, they are used. They mostly operate at high​ ​and​ ​constant​ ​rate​ ​of​ ​efficiency.

Washing:​ These are built to facilitate water usage wherein water can be sprayed on​ ​the​ ​material.​ ​Usually​ ​water​ ​is​ ​used​ ​to​ ​clean​ ​material​ ​and​ ​/or​ ​assist​ ​in​ ​the​ ​sizing​ ​as​ ​well.

Dewatering​:​ ​These​ ​are​ ​simply​ ​used​ ​to​ ​remove​ ​liquid​ ​from​ ​material Rescreen (Dry and wet): Often, material still have contaminants. They ​are​ ​used​ ​to​ ​remove​ ​contaminants​ ​from​ ​already​ ​screened​ ​material.

Types

Screens are classified on the basis on pattern into Horizontal, Circular, Inclined and Rotary. They​ ​are​ ​further​ ​explained​ ​as​ ​below:

Horizontal: These vibrate back and forth facilitating removal of larger ores by this vibratory movement. These have a huck bolted construction and power is generated through timed shafts with eccentric counterweights. Ideal for wet washing or low head​ ​operations.

Circular: These types are also called​ circular-motion vibrating screens. They are commonly used to classify medium to coarse-grained bulk materials (5.0 mm to 100 mm). They operate using indirect excitation of the mesh. Because of unbalanced massed, there is a circular vibrating motion. For a specific transport speed, the circular vibrating system may be tilted at different angles. However,​ ​the​ ​optimum​ ​angle​ ​has​ ​been​ ​15°​ ​to​ ​30°​ ​usually​ ​used​ ​in​ ​practice.

Inclined: It’s a single deck which is put on an inclined frame and uses gravity to help move material downwards and a circular stroke helps to classify the material for further sizing. The frame is mounted on springs. The vibrations is generated from an unbalanced flywheel. They are commonly used for crushing rocks, sand and gravel; recycling; ore​ ​processing;​ ​wet​ ​screening​ ​and​ ​for​ ​the​ ​chemical​ ​industry.

Rotary: ​A common usage is the separation of solid pollution in wastewater. They are equipped with a slot tube, which are rods in axial direction of the tube. Owing to the gravitational force, water falls on the slot tube and passes through slots. The solid material that does not fit the slot is a residual which is on the exterior of the rotating slot tube and it is scrapped and falls down in a container. Finally, treated water, flows out from the​ ​lower​ ​part​ ​of​ ​the​ ​rotary​ ​screen. It is commonly used in food-processing industry such as meat-processing factories, slaughterhouses,​ ​dairy​ ​works,​ ​canning​ ​factories​ ​etc.

Wash​ ​Plants

In simple words, a Wash plant is defined as a plant where slimes are removed from relatively coarse​ ​ore​ ​by​ ​washing,​ ​tumbling,​ ​or​ ​scrubbing.
Nowadays, ​Portable crushing & screening plants ​are commonly used for rock crushing in quarries and mines. They are more efficient in terms of time and resources, since they can quickly move with ease around the jobsite by remote control features and can be moved from one​ ​location​ ​to​ ​another​ ​as​ ​well.

Conclusion

With screeners, there are several other terms which are frequently used such as blinding, contamination, frequency, amplitude, and others which describe the basic characteristics. They ​feature​ ​further​ ​define​ ​the​ ​overall​ ​process​ ​of​ ​dry​ ​or​ ​wet​ ​screening.

As also mentioned earlier, the way a deck is vibrated differentiates screens. Different types of motion have their advantages and disadvantages. In addition, media types also have their different​ ​properties​ ​that​ ​lead​ ​to​ ​advantages​ ​and​ ​disadvantages.

Finally, there are problems and challenges associated. Efficiency is often​ ​affected​ ​by​ ​tearing,​ ​contamination,​ ​blinding,​ ​and​ ​dampening.

Leading manufacturers of screeners include​ MCcloskey​, Masaba, Kleemann, Nordberg,​ Sweco​, Terex​,​ ​​Metso​​ ​(Allis​ ​Chalmers),​ ​​Sandvik​,​ ​​Telsmith​,​ ​Deister,​ ​JOST​ ​and​ ​​Derrick​. However, a thorough research of the plant which suits your process is essential before​ ​buying​ ​one.

We​ ​will​ ​help​ ​you​ ​buy​ ​the​ ​most​ ​suitable​ ​trommel​ ​for​ ​your​ ​operation,​ ​​contact​ ​us​​ ​today.

https://www.savonaequipment.com/en/equipment/screens-e41600?s=p