SAMPLING GLASS RAW MATERIALS

The physical properties of commercial glasses are controlled, in large part, by controlling the chemistry of the raw material make-up of the batch. Thus, a precise chemical analysis of samples of the batch raw materials is critical to controlling glass production. It is self-evident that the raw material samples so analyzed must be representative of the raw materials used, or errors may be introduced when calculating the batch. For these reasons, representative (probabilistic) sampling of glass raw materials is an essential part of controlling glass production. To accomplish representative sampling all parts of the lot of raw material to be sampled must be allowed equal probability of being collected in the sample increment. For this requirement to be met it is necessary to sample from a falling stream of the material, taking all of the stream part of the time. A generalized procedure for sampling raw materials in various situations is outlined, including material in stockpiles, motor trucks, railcars, silos, semi-bulk containers, bags, etc. Some "hopeless cases", where representative sampling is not possible, are described. The emphasis is on practicality, and actual sampling cases are illustrated.

Presented at the 63rd Conference on Glass Problems, Columbus, Ohio, October 2002