The golden rule states that for correct sampling all parts of the material being sampled must have an equal probability of being collected and becoming part of the final Therefore for a representative sample The total stream should be sampled The sample cutter should intersect the sample at right angles to the flow. The sample cutter should travel through the stream at a linear and constant speed speed deviations max 5.<br /> If these rules are not adhered to a sample bias is easily introduced sample for analysis Gy. A statistically significant difference between a single measurement or the mean of a series of measurements and its value in a Certified Reference Material its value measured in accordance with a recognized reference procedure or its value measured against a Certified Weight<br /> Systematic Error<br /> Sampler supplier role is to minimize sampling errors that cause bias Increment delimitation and extraction errors that cause significant bias may be caused by for example Incorrect cutter geometry Cutter speed too high Cutter speed not constant Insufficient cutter capacity Incorrect sampler installation Others. Incorrect. Increment Delimitation. Taking part of the stream all of the time fixed cutter or probe in a slurry stream<br /> sample bias due to segregation. Correct increment delimitation only possible with completely homogenous conditions<br /> liquids with no suspended solids.<br /> Incorrect<br /> Increment Delimitation<br /> Taking part of the stream all of the time fixed cutter or probe in a slurry stream usually suitable for analyzer feed only.</p> <p>How Not to Sample<br /> Incorrect<br /> Increment Delimitation<br /> Taking part of the stream part of the time grab sampling ie shovel on a conveyor cup in a slurry discharge. Correct increment delimitation only possible with completely homogenous conditions liquids with no suspended solids.<br /> How Not to Sample a Belt<br /> Incorrect<br /> Increment Delimitation<br /> Cross Stream Cutter<br /> poor design and or manufacturing<br /> cutter edges worn damaged or solids accretion near</p> <p>outer edges<br /> CUTTER TRAJECTORY<br /> INCORRECT CUTTER GEOMETRY</p> <p>DIRECTION<br /> should not be included<br /> Incorrect<br /> Increment Delimitation<br /> Cross Stream Cutter<br /> poor design and or manufacturing<br /> cutter edges damaged or solids build up near center of<br /> cutter. CUTTER TRAJECTORY<br /> INCORRECT CUTTER GEOMETRY<br /> CUTTER DIRECTION<br /> Material not collected in shaded section should be included. Incorrect Increment Delimitation Cross Stream Cutter<br /> poor cutter alignment during installation cutter too short trajectory may have changed ie Process fluctuation<br /> MISSING PORTION OF THE INCREMENT<br /> STRAIGHT PATH CROSS STREAM CUTTER<br /> Incorrect Increment Delimitation Circular Path Cross Stream Cutter Vezin use of non radial or parallel cutter edges maintenance department often replaces blades assuming they should be same as the other sampler which happens to be a linear cross stream sampler.<br /> Cross Stream Cutter solids buildup on cutter blades Bridging Water Flush Incorrect Increment Delimitation & Extraction Cross Stream Cutter solids build up on cutter blades cutter blade on one side is missing Insufficient capacity resulting in backflow Incorrect Increment Delimitation Circular Path Cross Stream Cutter Cutter blades parallel Cutter blades have different angles and height Segregation occurs not desirable for sampling Problems w Multi-Cutter Technology very high maintenance 5x more sample volume vs single cutter designs multi stage system may have many cutter each cutter must be identical to prove theory but the theory is not practical or realistic as the video shows Extraction Error Backflow Sample flow entering the cutter higher than flow of the sample leaving the cutter Insufficient capacity of cutter Discharge diameter too small Obstructions or damage to discharge pipe

How to collect a slurry sampling in a plant mineral processing</p> <p>Detrimental effects to<br /> operations<br /> The assays from samples are used for control and accounting purposes<br /> Planning<br /> Production targets<br /> Plant need to make a certain amount of money to pay its bills and make a profit. This effects how much tonnage to push through a mill.<br /> Plant control<br /> Grade / Recoveries<br /> Target values for these are set and accurate, nonbiased, assays are required to achieve this.<br /> Metallurgical Accounting<br /> Unbalanced results (poor sampling, assaying or weighing of stream)<br /> Unaccounted loss (lack of measurement accuracy)</p> <p>How is sampling inaccurate<br /> Problem with samplers which do not adhere to sampling theory<br /> Launder and pressure samplers contain a bias, or errors, which can be constant (biased) or fluctuating (random). The ratio of finescoarse, or lightheavy, particles entering the fixed cutter or nozzle will vary even without fluctuations in the process.<br /> Segregation by particle size, density, etc. is always present as there can be no guarantee that the slurry to be sampled is homogenous<br /> Segregation caused by pipe bends or intersections, etc.<br /> Unfortunately these errors change over time due to fluctuations in feed tonnages, particle size, densities, flow rates, pressure, etc. which can cause precision errors<br /> OSA and Sampler Errors<br /> (Online Assays)<br /> OnStream Analyzers (OSA) only analyze the samples it is presented<br /> If the sample feed to the OSA is biased, the results are biased</p> <p>Grade Recovery<br /> This statement can be found in the Will’s Mineral Processing Technology book<br /> The aim (of a flotation control system) should be to improve the metallurgical efficiency, i.e. to produce the best possible graderecovery curve, and to stabilize the process at the concentrate grade which will produce the most economic return from the throughput.<br /> This statement has a few key points<br /> A concentrate grade is decided upon ( could be by planer, metallurgist, control system or other and depends on feed grade)<br /> Keep the process stable ( upsets are not good)<br /> Increase the recovery as close as possible, to the best grade recovery curve, without destabilizing (upsetting) the circuit<br /> Maximize recovery at a target grade</p> <p>

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