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Automatic sampling: efficient, easier, essential

Published by , Editorial Assistant
Global Mining Review,

Nate Leonard, Sentry Equipment, USA, considers the benefits of automatic sampling in the mining industry.

Automatic sampling: efficient, easier, essential

Without being able to determine the makeup of materials at a smaller scale, the mining process would be inexplicably inefficient. Attempting to measure the quality and characteristics of a large collection would be near-impossible, which in many cases would render it almost useless. The solution for this issue is representative sampling.

Representative sampling refers to a process in which a large amount of small samples are taken throughout processing in order to accurately depict the makeup of everything that is being mined. Companies who use representative sampling methods can observe the qualities and makeup of each small sample, which, when averaged with all other samples taken, will become fully representative of the whole solution. Moreover, representative sampling helps mining companies complete tasks essential to their success, such as measuring whether their excavation process is effective or determining valuations. If everything is done correctly, representative sampling can also help mining companies improve the consistency, repeatability, and safety of their processes.

While the process of gathering representative samples may not initially seem difficult, it can be quite challenging, as different materials and states of matter have different characteristics that make them vary in sample size, sample frequency, and gathering technique. It can also be difficult to manually obtain a sample free of unintentional operator contamination. Mining companies that are attempting to collect representative samples must always pay heed to Gy’s sampling theory, which states that every particle in the process stream must have an equal probability of being selected in each sample. These factors can make representative sampling difficult as it can require precision and expertise to avoid gathering inaccurate samples.

An efficient solution for a challenging process

Luckily, there is an efficient answer to avoid these concerns: automatic sampling systems. While these systems still require the knowledge to make the proper adjustments to variables such as cycle rate, dwell time, and total volume, far less expertise is required than previous sampling solutions. This is because these systems no longer require the manual division of materials into satisfactory samples that are truly representative. It is still important to understand how the process of automatic sampling works to set the variables so that the samples collected are valuable, but it is far less challenging and time-consuming to collect large sums of accurate samples than it was when samples had to be manually extracted.

For example, in cases where samples are being collected from a pipeline, a pneumatically actuated automatic point plunger-style sampler is the natural solution. When fixed to the pipe in an area where the flow of materials and slurry are frequent and voluminous, the plunger sits just outside the flow. Then, when actuated, it descends into the pipe as the slurry continues to run through. The plunger captures the ideal amount of the desired solution and, once it has accomplished this, retracts to its initial position. It is essential during this process that the plunger fully intercepts the flow of the slurry; if it does not, the sample will likely not be fully representative as content segregation occurs frequently in slurries. It then dispenses the entirety of the captured solution into a sampling container for further inspection, thus providing a full and accurate sample and avoiding the disruption or contamination of future samples.

Previous sampling methods, such as taps in the side of slurry pipes or pressure pipe samplers, often did not capture accurate representative samples despite being commonly used across the industry. As R.J. Holmes discusses in the Journal of The Southern African Institute of Mining and Metallurgy, these methods did not fully intercept the flow of the slurry and thus could not account for the separation and segregation that formed in the slurry as it travelled through the pipes. They also typically failed to account for the fact that any small portion of the slurry that may have escaped the pipe at the point of interception needs to be accounted for when accurately collecting a truly representative sample.

Armed with the ability to adapt the automatic sampling process quickly and easily to the needs of any given solution without fear that the sample will be inaccurate or the threat of sample contamination, this method is revolutionary and essential for precisely sampling the contents of mined materials.

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