Inventorisation of Stone crushers in Various States
Stone Crushers are primarily small scale industries mostly owned and operated by less educated individuals and are scattered all over the country. This sector primarily being an un-organized sector & has only local level (district/region level) associations. In the absence of any centralized National or State Level association, the source to get a list of stone crushers in the state was identified as the State Pollution Control Board.
It was therefore, for the purpose of collecting information on number of stone crushers in various states, their capacities, technologies used etc, request letters were sent to all State Pollution Control Board offices through CPCB. Many SPCB have responded with the list of stone crushers in their respective states, some states have sent only partial list for some districts/region and some states have not responded. The compilation of the information received from various states has been made and is given at table below for information.
Typical Set-up & Sizes of Stone Crushers
There are large variations in the types of stone crusher setup across the country depending on geographical locations, type of demand for crushed products, closeness to urban areas, type of raw material, availability of plant and machinery locally etc. Primarily the stone crusher industry sector could be divided in three categories small, medium & large. The typical characteristics of each category of stone crushers are briefly discussed below.
Small Size Stone Crushers
There are different types of small crushers in various states with a production capacity ranging from 3 to 25 TPH. Typically, the units having only one Jaw type crusher used as primary or secondary crusher along with one or maximum 2 screens are grouped as small stone crushers. A few most representative types of small crushers are described below.
Crushers with completely manual breaking/feeding/ retrieving/stocking operation with single jaw and single rotary screen .
Small stone crushers
In these types of small stone crushers, the mined raw stones are transported to the crusher site by trailors or truck and unloaded & stocked at ground level near the crusher. Big boulders are manually broken one by one to about 8-10 inch size.
Typically a team of about 15-20 workers does breaking throughout the day. The coloured stones are manually sorted and separately stocked, this is done to avoid mixing of different coloured stones in the crushed products, else it may fetch less price. The broken stones are manually carried on head load to feed in the jaw crusher .About 10-15 workmen are engaged for the purpose.
The crushed stones are discharged through a chute in to a rotary screen. The screened products of various sizes are discharged on the ground below the rotary screen and the products are manually retrieved and taken to stock piles. These type of crushers typically operate with crushing capacity in the range of about 2-5 TPH. Such crushers are highly labour intensive and about 50 to 60 persons are involved in the operations such as breaking, feeding, retrieving and stocking. These crushers claim to produce stones of good quality due to manual sorting, uniform breaking etc and lesser quantity of fines.
In some crushers the rotary screens are installed at elevated position and the screened products are separately collected and transported via belt conveyors to stock piles. The dust product smaller than 6 mm size is stored mostly in closed silos.
Such crushers typically operate with crushing capacity range of about 5 – 15 TPH. The above two types of small crushers are mostly found in the state of Orissa, Bihar, West Bengal, North Eastern States, Himachal Pradesh & Tamil Nadu, Andhra Pradesh.
Mechanical/Gravity feeding, single jaw with vibratory type screens with belt conveyors
In these type of crushers the mined raw stones are transported to site by trailors/trucks and are unloaded in an elevated stone well. The stones are retrieved from the stone well through a chute at the bottom side end and the stones are fed by gravity in to the primary jaw crusher.
The crushed stones are conveyed to rotary/vibratory type screens by belt conveyor . The oversize from the screen is returned either to the stone well or directly in to the crusher for further size reduction. These type of crusher generally have production capacity in the range of 15-25 TPH. These types of crushers are widely found in almost all the states & the most common type of crusher set up.
Single Jaw Bucket Elevator, Elevated vibratory screen with storage bunkers type compact units
In some crushers the crushed stones from the jaw crusher are raised to a high elevation with the help of bucket elevators which discharges the material in vibratory screens and screened products are directly discharged in various storage hoppers. The Products are directly loaded in to trucks standing below the storage hopper. There are no belt conveyors in the units. These type of crusher are generally found in the States of Maharastra & MP etc.
Medium Size Crushers
Typically those crushers having than one crusher i.e., one primary and one secondary or one/two primary & two secondary crushers along with one or more vibratory screens are categorized as medium size crushers. The mined stones are transported mostly by trucks/dumpers and unloaded in to elevated stone wells. The stones are fed by gravity to primary crushers.
The Crushed stones are conveyed to vibratory screens. The screened products of various sizes are conveyed to stock piles by belt conveyors. The oversize is returned to secondary crushers for further crushing and back to the vibratory screen. Such type of medium type crushers have a production capacity in the range of 25 – 100 TPH.
These type of crushers are mostly located near to the bigger cities and in the vicinity of major construction projects such as Highways, Canals, Dams etc. These type of crushers are found in the States like Maharastra, Andhra Pradesh, Tamil Nadu, Punjab, Haryana, Gujarat, Madhya Pradesh, Rajasthan, etc.