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MODULE- 1SAMPLING OF ORESSampling is the art of securing a representative fraction of small weight ( sample) from a relatively large lot .

The samples must contain adequate number of particles ,be selected in a fair way.

Two categories:Exploratory samplingControl sampling

Exploratory sampling: Used in case of prospecting, proving, and developing a mine. In routine exploration of the ores and control of mill operation , samples are taken to check the efficiency of the work

Control sampling:Used in mineral processing industries.The quality of the mineral is checked with sufficient accuracy.Includes checking lump size, moisture content, assay grade, purity, chemical state etc.To check quantity and quality of ores and tailingsSAMPLING METHODS.

CUTTING DOWN THE SAMPLES - GRAB SAMPLES The control sample cut from the original feed is known as Head Sample. It is taken by hand or by mechanical means.Grab samplea small portion of the material removed from the passing car load of ore by handThe sample taken may not be a representative. HAND SAMPLING PROCEDURE Commonly used procedures: a) Fraction selection by a shovel- The ore is shoveled.Every 5th, 10th or 12th shovel is kept separately for sampling.The samples are reduced in size by crushing.Alternate shovelfuls are kept apart from the sample taken.The procedure is repeated till suitable size is made

b) Coining and quartering The ore is brought in sampling floor and collected in a large ring .It is heaped into a cone from all sides.Now it is raked into a ring.It is re-coned and procedure repeated till the whole lot is mixed properly.The cone is flattened. It is marked off into quarters. Opposite quarters are taken as samples.Skill is needed for accurate sampling.

c) Fractional selection by split Shovel, Riffle and Jones sampler

The split shovel is a fork with scoops Each scoop has same width as the space between the scoopsIt is laid on the floorA showelful of ore is spread over the split shovel back and forth across the scoops.Split shovel is lifted leaving the samples spread between the spacing of scoopsWhich is then emptied in to another heapThe riffle is similar to split shovel It is larger and has small handle on each side instead shovel handleThese are used for laboratory assaysJones sampler is a riffle consist of two set of scoops sloping in opposite direction, instead of alternate scoops and spaces. the scoops discharges the ore as soon as it is poured in to them

Moisture samples:The moisture sample has to be taken either just before or just after the ore is weighed to avoid the error due to evaporation Grab sampling is usedThe sample collected is quickly transferred in to tight container.Grab samples are usually taken from the end of the conveying weigherPercentage moisture content is found out

Mechanical sampling:Features:The sampler should take the whole stream of ore at a time and not part of the stream all the time for cutting the sample, the scoop must move fully across and out of the stream in one direction at each cut the scoop must move at same rate in order to take equal portions from all parts of the stream the scoop should be adjustable to take larger or smaller portion of ore the interval of time between cuts should be constant

f) the scoop should be deep and broad enough so that the ore entering the scoop does not fall outg) the machine used in sampling should be simple and easily accessible for cleaning

Snyder sampler:Consist of circular pan with flaring sides, set edgewise on a revolving shaft.Vezin samplerIt consist of two hollow truncated cones bolted together at their large bases. A cast iron spider is attached to the vertical shaft Shaft is supported by collar at upper endThe shaft is driven at constant speedUpper cone caries one or more coops The ore is fed from spout and a portion enters scoops ,passes in to interior cone which is carried to sample bins.

Electric samplers:Self contained and electrically operated sampling are widely used for automatic samplingThey are compact and readily installedSampling of mill products.Head sampling:It varies according to ore , the method of treatment and capacity of the millIt is expensive and difficult.Automatic samplers are used.Concentrate sampling:Uses automatic samplers with short sampling intervalsHand cutters are widely used.Sampling of concentrate aids the control on the performance of the smelter.Tailing sampling:The method employed for sampling are same as employed for sampling of concentrate.