Spinning riffler sampler

FIGURE 7 Subsampling (a) coning and quartering (b) table sampler [6] (c) oscillating hopper (paddle) sample divider [6] (d) spinning riffler (BSI) (e) riffle/chute splitter (BSI) if) revolving sample splitter [14]. 

In another set of experiments, the relative efficiencies of different samplers were compared, and it was concluded that very little confidence could be placed in cone and quartering, scoop sampling, or table sampling. The spinning riffler emerged as so superior to the others that it should be used as often as possible. With the riffler, a minimum of 35 presentations are needed for optimum results to be obtained, and if the speed of rotation is too great, the efficiency falls as a result of air currents setup. ... 

Figure 1.4. Several devices are available for taking a small representative sample from a large supply of powder [31, 32, 34]. a) A thief sampler consists of two concentric cylinders, b) The spinning riffler can efficiently produce small, representative samples.

Sample Size Reduction. The sample obtained from the sampler is generally larger than the sample required for analysis. If a small portion of this sample is arbitrarily scooped for analysis, it will introduce a bias. The sample size can be reduced to the analytical size using various sample reduction techniques (1) spinning riffler, (2) chute riffler, (3) ICI method, and so on. All these methods follow the golden rules for sampling. For details on these sample reduction techniques, see AUen (1981). 

Sample Size. An ideal sample size is equal to the scale of scrutiny or the scale at which the product specification has been developed. If the scale of scrutiny is much smaller than the minimum amount of sample that can reliably be obtained from a sampler, suitable sample reduction techniques must be utilized. The spinning riffler has been found to be the most reliable method of reducing the sample size (Allen, 1981). The sample size must be greater than the minimum amount required for the analytical technique. 

Typical sampling devices are rotary samplers or spinning rifflers (Allen 1997) which apply these two golden rules. Allen quotes an example of how... 

---