On making measurements in silo-stored grain

A sectional tubular steel sampler has been designed, with which samples of grain have regularly been obtained at 1 m. intervals to depths of 15 m. in normal grain. A new form of this sampler permits re-closing of the sampling ports after filling, so that contamination of the samples can be avoided. Associated records of the grain temperatures and samples of the intergranular gases have been obtained at similar depths. Certain precautions to be observed in sampling from silo bins are emphasized. Observations are reviewed which show the extensive effects of granular segregation during movement. Material, such as extraneous seeds, holed grains, etc., segregates so that ( a ) it is delayed in the outfall whilst emptying bins, ( b ) it is more concentrated in the central column of the bin after filling, ( c ) in direct sampling it is scarcer in the first part of the sample to fall into the container, with the implication that the sample as whole is deficient in such material. Larger objects settle at the surface of the grain on a moving belt, whilst smaller ones sink between the grains. The consistency of the results suggests strong reasons for a reconsideration of the principles of sampling, either direct or indirect. Meanwhile, samples obtained by any one method are likely to prove fairly consistent inter se.