Types of Technologies Used in Stone Crushing Units

Various types of technologies are used for mining, transporting, crushing and screening operations, which are briefly described below. As mining and transporting operation are an integral part of the stone crushing industry, it is briefly discussed below:

Technologies used for Mining

The technologies used for mining of stones vary from manual excavations up to highly automized lare scale blasting with mechanical excavations. The smaller stone crushers source the raw material generally from river beds, or small hillocks in the local region or at times they procure/purchase raw stones from mine owners in the vicinity. Such small crushers crush only a few truck loads (typically less than 2 to 10 truck loads per day).

The medium size stone crusher mostly have their own open-cast mines adjacent or in close vicinity to the crusher site. The mining is done by drilling holes in the rock strata and blasting it generally once in a day. The drilling is done mostly manually or by mechanical means. The blasted rock boulders are at times manually broken to about 10 to 20 inch size so as to suit and are manually the primary jaw crusher, loaded in to trailors or trucks. Mechanical Loaders are also used for retrieving mined stones and loading in the vehicles.

In large stone crushers, the mines are generally owned or leased for long term. Scheduled and frequent blasting are carried out. A combination of primary and secondary blasting techniques are followed. In the primary blasting, substantially large area is blasted to loosen big boulders from the earth strata. The bigger boulders are further blasted during secondary blasting. The drilling is generally carried out either pneumatically or hydraulically. After blasting, the stones are excavated with the help of excavators and loaders and are loaded in to dumpers.

Transportation Technologies

The mined stones are transported to the crusher sites using vehicles of various capacities starting from bullock carts, trailors up to automatic dumpers. Most of the transportation vehicles have hydraulically operated tilting arrangement for easy and faster unloading of stones at the crusher sites.

The capacity range of smaller vehicle like trailors is about 4 tonnes whereas bigger dumpers can carry in the range of 15 – 20 tonnes materials per trip. The loading operations are manual in smaller vehicles and are mostly mechanical using material handling equipment for large dumpers and trucks. There are no continuous material handling system like long belt conveyors or trolley type conveyors to carry stones from mines to crusher sites, even in the largest stone crushers in the country and therefore transportation by vehicle is most common.

Crushing Technologies

Various types of crushers are used in the stone crushing industry such as Jaw Crushers, Roller Crushers, Cone Crushers, Impactor, Rotopoctor etc. Generally, only Jaw crushers are used as Primary crushers. For secondary and tertiary crushing application either of Jaw, cone, roller, Impactor or Rotopoctor type crushers are used.

Screening Technologies

Screening is a process of separating into groups of different products of various sizes. Each group consists of products of approximately same size. The mass, which remains, on a screen is called the oversize of the screen and the material, which passes through the screen is, called the undersize. The screens in between the primary and the secondary crusher help in separating the oversize. The oversize goes to the secondary crusher while the undersize is discharged through a chute on to the same conveyor belt, which receives the discharge from the secondary crusher. This saves considerable power in the second crushing stage and also increases the capacity of the secondary crusher, as it eliminates possible choking of material in the crusher, particularly during wet weather or wet material.

Screening is generally classified into two types. (i) Coarse screening, which is achieved through Grizzlies, Vibratory Screens, Revolving Screens or Shaking Screens and (ii) fine screening which is achieved through Vibrating screens, Shaking Screens.

Washing Technologies

Sand and gravel often can be washed during the screening process but if the material carries undesirable matter a scrubber washer should preceed the screening process. When the stone from the crushing plant is coated with clay or other sticky substances they are put through rotary scrubber to scour the gravel before it goes to the screen. Material that contain smaller amount of clay and silt may be cleaned satisfactorily by a log washer. Washing is very rarely employed in Indian crushers, but it is common in developed countries.

Material Handling Technologies used in Stone Crushing Units

Various types of material handling technologies are used in the stone crushing industry for the purpose of moving the stones from one equipment to other, right from the point of raw material unloading upto stockpiles of products. Primarily, feeders and conveyors are used in almost all crushers.