Assay Sampling Protocols for Industrial Metal Scrap Valuation
Assay sampling protocols establish true dry weight and payable metal content, directly governing settlement values, working capital allocations, and lender borrowing base limits.
Particle Size Reduction
Meaning
Mechanical sample preparation represents the sequence of crushing and pulverising used to decrease the grain size of a laboratory sample. Carrying out particle size reduction is necessary to ensure that the small portion used for chemical analysis represents the entire bulk material. This process is conducted in stages to prevent overloading the equipment and to control dust generation.
Mechanical Processing
Large fragments of rock are fed into a jaw crusher to produce a coarse gravel. This gravel is then passed through a secondary crusher or directly into a pulverising mill. The milling action uses high force to grind the material into a fine powder.
This powder can then be split and sampled.
Homogeneity Control
Ensuring the sample is sufficiently fine is the main defense against sampling error. When the particles are small, the minerals are distributed more evenly. This allows the laboratory to weigh out a representative sub-sample.
If the powder is too coarse, the analytical results will vary.
Quality Audit
Technicians use test sieves to check the efficiency of the grinding equipment. A set percentage of the ground sample, often ninety-five percent, must pass through a seventy-five micron mesh. This test is run at set intervals to monitor the wear of the grinding plates and mills.
If the sample fails the sieve test, the equipment must be adjusted. This ongoing check prevents poor precision in the downstream assays.