Ural State Mining University (Russia):

Kozin V. Z., Head of Chair, Doctor of Engineering, Professor, gmf.dek@ursmu.ru
Vodovozov K. A., Lecturer, gmf.opi@ursmu.ru

The factors are considered, that cause deviation of ore and benefication products sampling results from the true values, leading to positive product imbalance. It is noted, that product balance calculation is based on the results, obtained both by sampling and direct measuring of mass on weighers or by indirect material weighing in receptacles. Weighing is usually performed by means of instruments that are tested and checked against standards, and should not produce a considerable effect regarding imbalance, whereas ore and benefication products sampling results may lead to excess or lack of metal in calculation even with correct sampling. It is shown, excess of metal or other valuable component is mostly related to understating of its mass fraction in ore. The factors causing understating are defined, including missing of component mass fraction peaks in sampling, as well as discarding predominantly highgrade weights and samples analysis results in accord with analyzing procedures. It is noted, that additional sampling errors — a probable systematic error and an error of method, occur also in sampling of concentrates and tailings. Total impact from these errors, caused by asymmetric distribution of component mass fraction in spot samples and weights, leads to positive product imbalance shift. This imbalance shift is the greater, the smaller determined component mass fraction is in sampled material mass. In order to decrease positive product imbalance shift, a lengthwise flow sampling method is proposed, and a different approach to analysis results application in product balance calculation is advised.

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