What should you check when a sieve result changes?
Check the test portion, mesh condition, stack loading and recovered mass before adjusting the shaker. Then compare motion and time with the previous run. These checks distinguish a change in sample composition from a change introduced during separation or weighing.
Start with sample division
When two distributions disagree, establish how each test portion was taken. A divider or riffler subdivides the bulk material before sieving. A convenient scoop can favor particles from one part of the container, and changing shaker settings cannot repair that difference.
Inspect the sieve and compare the load
Record the aperture, sieve identifier and material charged to the stack. Inspect the mesh, frame and joints for damage, blocked openings and residual material before the run. Keep a reference sieve in good condition for comparison when a routinely used sieve produces an unexpected fraction.
Why can the same sieve give different results on two shakers?
Compare the actual motion and run time before attributing a shift to the sample. In the electromagnetic shaker example, amplitudes of 1 to 2 mm were common even though the design could reach 3 mm. Record the amplitude actually used when comparing retained fractions. For a RETSCH AS 200 control, retain the instrument identification and recalibration record with the method so that a change of shaker can be investigated. An elongated grain or fiber can pass through an opening when its narrow dimension aligns with the mesh. The orientation presented by horizontal motion can differ from that produced by throwing motion.
How should retained sieve fractions be reconciled?
Weigh the retained fractions using a balance suitable for the loaded sieve and the expected mass differences. The example specifies a balance range up to 5,000 g and accuracy between 0.01 and 0.1 g. Check the requirements for the sieves and test portion used in your own procedure. Compare the sum of the recovered fractions, including the pan, with the starting test mass. Investigate material lost during transfer or left on the stack before interpreting a change in the size distribution.
Clean without changing the mesh
Use a cleaning method compatible with the mesh and the residue. A stiff brush can distort fine openings. Inspect the dry sieve before the next measurement and replace a visibly damaged screen. Record any change of sieve when comparing results across runs.
What should be checked before changing sieve shaker settings?
Inspect the sieves and define sample loading before adjusting shaker settings. Cleaning, wear and retained material influence separation and mass balance. A documented endpoint helps distinguish a completed separation from a convenient but inconsistent run time.
| Consideration | Information to provide |
|---|---|
| Sieve condition | Inspection and cleaning history |
| Loading | Test mass and sieve stack |
| Endpoint | Repeatability and retained-fraction evaluation |
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