Those crushers typically having two or more numbers each of primary, secondary & tertiary type crushers with at least 2 or more vibratory screens with mechanized loading, unloading conveying operation s and producing more than 100 TPH crushed stones are categorized as large crushers.
Typically large stone crusher are owned by bigger construction companies like L&T, Dodsal Construction, etc who have their own large construction projects demand. Such crushers have a capacity range of 100 –200 TPH. These type of crusher generally have their own/leased open-cast stone mines and a fleet of mechanical mining equipment , trucks and dumpers, loaders etc. These crushers involve high capital investment and mostly operate round the clock. All conveying operations are done through proper belt conveyors.
Types of Technologies used
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.
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.