Strona 2_redak - Instytut Agrofizyki im. Bohdana Dobrzańskiego ...

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also be performed as a function of: consolidation time, normal pressure, ambient
temperature and humidity. The apparatus applied is a direct shear box (Jenike
method) equipped with consolidation bench. Ring shear apparatus is also available
that apart of typical application of Jenike tester enables the estimation of wear of
material due to attrition. For cases where determination of parameters does not give
satisfying description of the process, consultants propose model investigations.
13.1. Quality determination
Quality control is an important task in the production and processing of granular
materials because it allows for undisturbed flow of material and keeping constant
composition of processed powder. Therefore, several new solutions of material testers
have been proposed in recent decades that are currently verified [53]. Quality control
has to be carried out in such points along the production line where product properties
may change and result in damage of equipment or deterioration of product quality.
Determination of quality of raw material is performed for protection against
introducing portions of material of low value or undesired flowability. Variations in
flowability may be the result of action of numerous factors. For complex processes
many ingredients are used that are delivered from different producers. Constancy of
properties of raw material depends on the method of production. Confirmation of the
consistence of nominal properties of the material and its actual properties requires
regular examination.
In numerous processes equipment is tuned during start up procedure when
sometimes a large amount of by-product is produced. Examination of this start up
product allows to decide if it may be reintroduced in the line. In typical process
conditions maximum cohesion is determined to avoid flow problems in the system.
In some cases, however, the value of end product is determined by minimum
cohesive strength. For certain group of materials the best product is the most
difficult to produce, and increase in quality above an acceptable level is very costly.
In such cases quality control is particularly important.
Ploof and Carson [134] summarized the quality requirements posted by the market
for a powder quality tester. First of all the tester has to be easy to use, with minimum
requirement for skills and training. Time needed for performing measurement and
analysis of results should be possibly short. Moreover, results of measurements should
be precise, repeatable and should deliver significant information about the material. And
finally, the construction of the tester should be simple and compact, allowing for
mobility. Such a kind of equipment may be easily placed in proper location on the
production line instead of delivering material samples to the laboratory.