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Spinning Rifflers
(SRs) Reliably generate representative samples
from bulk particulates
What is representative sampling?
Spinning Rifflers generate samples of particulates which reflect very closely the properties of the larger quantity from which they were derived. They integrate appropriately into analytical, developmental, research, and control procedures to provide the representative samples of powders and granular solids upon which you can depend for accuracy, and reproducibility. In fact, the composition of a sample produced by spin riffling usually approximates very closely to the theoretical limits imposed by the statistical functions by which that material is best described and in fact, more closely than all other methods for the preparation of samples of particulate matter.
Representative sampling is important!
Have you ever wondered why there is always dust at the bottom of a cereal packet? This would be due to settling of the contents, combined with a bit of crushing and abrasion. It doesn't normally bother us since we just throw the dust out, but how would you measure the particle size distribution of ALL of the cereal box's content?
The answer would be to pass the entire box's contents through a Microscal Spinning Riffler so that you could obtain a representative sample of the cereal (dust and all) which is small enough to be run on an appropriate analyser but with a size distribution which represents the whole box closely.
Did you know that sixty–five percent of all goods employ powders at some point in their production cycle? The characteristics of these materials tend to change batch to batch and also with storage and preparation conditions. These variables need to be known and evaluated, but without a truly representative sampling procedure being systematically applied, the errors can accumulate and hide the source(s) of the variances ultimately observed.
*[Family photograph of MSR, SR1A, SR1B, SR5B, and SR10AB]*
Unique incremental sampling technique.
The spin riffling technique relies on the concept of random sampling to build a set of fractions from a bulk of material so that each fraction contains all the characteristics, including particle size distribution, as the bulk from which they all came.
The technique builds each sample by a process of multiple addition so that a statistically representative image of the bulk exists in each of the newly created sample fractions.
A spinning riffler comprises three principal components: the Mass Flow Hopper which holds the bulk of particulate to be sampled; a controlled–rate Feeder which steadily transports the bulk from the Hopper to the Sample Collectors; a Dividing Head placed on a rotating platform above the Collectors or integral with them, which cuts the particulate stream from the Feeder into small incremental portions, repeatedly. The Sample Collectors are glass or metal containers each designed to hold the appropriate fraction of the bulk particulate which is to be sampled.
Since the device is designed to allow many passes of the Dividing Head during the course of one sampling operation, each fraction is built up from multiple samples of the bulk. So long as the Dividing Head rotation and the flow of particulates along the Feeder are both constant, the fractions which accumulate in the Sample Collectors during the riffle will be closely representative of the bulk.
Hopper capacity and overall collection capacity are matched to avoid overflows or bridging between sample fractions. Typically, a spinning riffler with a sample collection capacity that exceeds the volume of the bulk to be sampled is employed.
What some people have said about Spin Riffling
"Spin riffling has been shown to be the most accurate and reliable technique for the representative sampling of particulates." Dr. Arthur Hawkins, 1996.
"The real benefit is repeatable test results that are reliable. You save time, resources, material, and ultimately money." Alan Gibbon, Johnson Matthey, 1992.
"The spinning riffler is the best technique by far – it samples unmixed just as efficiently as mixed powders." T. Allen and A.A. Khan, The Chemical Engineer, 1970.
"Extensive studies have shown spin riffling to be a very efficient sampling method." Brian Kaye, Direct Characterization of Fine Powders, 1981.
"The table shows that spin riffling is a superior division method: the rotating tray removes all chance of operator error" L. A. Kressin, Powder and Bulk Engineering, July 1989.
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