Imp r anal ove you ysis r resu lts Cyclone Mill TWISTER Ultra Centrifugal Mill ZM 200 Planetary Ball Mill PM 200

Representative analysis results require adequate sample preparation The following situation is typical for many production plants: After a routine quality check, the production process is stopped or an already produced batch is suspended, because the analysis results were not within the relevant critical values. But does the tested product really deviate from the specifications? The quality control managers are convinced of this because modern analysis instruments provide results with very low tolerances. The sample in question was tested several times and the result was confirmed. The question...

Sample handling In general it can be said that the more heterogeneous a sample, the more important the correct sample preparation. Let’s assume that a sample should be taken from a heap of sand. Which sample amount is necessary to represent the properties of the complete heap? Does it matter from which point of the heap the sample is taken? Figure 2 gives answers to both questions: The heap of sand consists of a mixture of bigger stones and smaller sand grains. The stones are found in the upper part, the grains are at the bottom. If, as shown in the picture, a sample is taken only from the upper...

not altered by the preparation process. This can also be explained with our example: if the particle size distribution of the sand sample is to be determined, the sample must not be ground. If the moisture content is analyzed, the sample must not be heated to prevent the contained water from evaporating. In the following the two sample preparation methods are discussed in detail. sample splitter rotating sample divider rotating tube divider Sample division If all properties are distributed evenly in the sample and if there is no segregation, a small part of the sample could be extracted, e.g....

vides better results as the division process is realized by a defined tool. However, the fact that the sample is fed in manually is again a potential source of errors. In rotating sample dividers and rotary tube dividers the sample feeding and the division itself are automated. If the division is carried out with fixed parameters (rotation speed, feeding speed), the sample and thus its properties are evenly distributed into the laboratory bottles. The sub-sample represents the initial sample. If the division is repeated with identical parameters, it provides comparable results so that the analysis...

SIZE REDUCTION PRINCIPLES Pressure Force is applied between two solid surfaces that either represent the grinding tool surfaces directly or may be the surfaces of adjacent particles. Pressure is exerted by the grinding tools. Example: jaw crushers Impact effects Force at a solid surface. This could either be that of a grinding tool, or be represented by other particles. Strain by impact is II. Analytical fineness The term “analytical fineness” describes the maximum particle size a sample may have where no systematic error occurs in the subsequent analysis. There are different types of analysis:...

Grinding tools The selection of suitable grinding tools is an important aspect of neutral-to-analysis sample preparation, as the following examples show: • If a soil sample is to be analyzed for its calcium, silicon oxide or cobalt contents, it must not be processed with grinding tools of stainless steel or hardened steel, as these steels contain the elements to be analyzed. • Cement clinker, in contrast, can be ground with grinding tools of these materials if the calcium and silicon oxide content is to be determined. • PTFE, zirconium oxide and glass are materials which can be sterilized and...

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