Design of Optimum Sampling Plans for Dry Powders and Slurries

Abstract

Generally, in order to learn about a certain quality of a population, a small portion (sample) is extracted and analyzed for the desired property. In order to obtain accurate information, the sample has to represent the stream it is taken from (plant feed, intermediate product, and/or final product). In materials processing sampling of materials (powders or slurries) is very important to the quality control and quality assurance purposes. This sample can be too large and has to be further subdivided, or too small and a two-stage sampler has to be introduced. In most cases, the desired property is determined by analyzing a sample as small as a few milligrams. In this regard, obtaining a representative sample is not as straightforward as it sounds. For homogeneous materials, it is easy to use statistical probabilities to estimate numbers and sizes of samples that accurately represent the whole population. However, this is not so easy in the actual practice especially dealing with inhomogeneous materials. Therefore, sampling representativeness, perhaps the most important aspect of sampling practice is emphasized in this paper. Sampling strategies and equipment for dry materials and slurries are discussed with links to related literature and sampling equipment manufacturers.

Keywords

• sampling
• representative samples
• dry powders
• slurries
• sampling errors
• sampling equipment
• sampling rules