Sampling from heaps

In industry it is common to sample small heaps by coning and quartering. The heap is first flattened at the top and then separated into four equal segments with a sharp-edged board or shovel. The segments are drawn apart and, frequently, two opposite quadrants are recombined and the 

The solution to the problem of sampling from a heap lies in the fact that the powder must have been poured to form the heap, and this is the time the sample should be collected. 

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If the powder has been charged on the conveyor, fines concentrate at the center of the belt while coarse particles roll to the outer edges such as the segregation seen when sampling from a heap. 

This sampling method is similar to the sampling from a truck. The same sampling quantities are required and it has the same advantages and disadvantages as the sampling from a truck. One additional disadvantage is that there is the possibility of heap contamination by other materials and hence contamination of the sample received. 

Before a size analysis can be carried out, it is necessary to collect a representative sample of the solids, and then to reduce this to the quantity which is required for the chosen method of analysis. Again, the work of Allen gives information on how this is best carried out. Samples will generally need to be taken from the bulk of the powder, whether this is in a static heap, in the form of an airborne dust, in a flowing or falling stream, or on a conveyor belt, and in each case the precautions which need to be taken to obtain a representative sample are different. 

Sampling.—When the sample is in sacks, portions are taken from the inner and outer parts and thoroughly mixed, and a similar procedure is followed with flour in cases or heaps. Of the mixture, the amount necessary for the analysis (about 500 grams) is stored, preferably in a glass bottle. 

If, however, the different portions from the sacks or heaps do not appear uniform, separate samples of the different varieties of sugar are taken in the proper amounts and treated as above. 

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