RED DUNE
Red Dune · Process Engineer Toolkit

Washability Calculator

Enter float–sink results as fractional or cumulative data, for one source or several combined. Get both tables, the washability curves, near-gravity material, and product and discard quality at any separation density.

A RED DUNE TOOL · v0.1
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Float–sink data

Example data loaded

Washability curves

Cumulative floats Cumulative sinks Elementary (fractional) Relative density (right axis)

Separation at a density

Near-gravity material ±0.1 RD

Washability tables

Method

Cumulative floats are running totals from the lightest fraction; each quality is the yield-weighted average. Cumulative sinks are the remainder from the heaviest end. Entered as cumulative data, fractional yield = Yi − Yi−1 and fractional quality = (YiQi − Yi−1Qi−1) / fractional yield.

Curves between data points use a monotone cubic (PCHIP) spline, so they never overshoot. The elementary curve plots each fraction's quality at the middle of its yield band.

Reading the results

  • Product at a density is all floats lighter than it; discard is everything heavier.
  • Multiple sources (seams, pits or size fractions) combine as fractional yield = Σw·y / Σw, with each quality weighted by w·y.
  • Near-gravity material is the share of feed within ±0.10 RD of the separation density, rated on Bird's scale from simple to formidable.
  • Results are theoretical (perfect separation). A real plant misplaces some material; see the DMS Efficiency Test tool.

Limitations

Converting cumulative data back to fractional data magnifies rounding: if cumulative values are rounded to one decimal, fractional values can come out unrealistically high, low or negative. The tool flags these; smooth the cumulative data or use more decimals.

References

  • ISO 7936:2022, float and sink characteristics.
  • Bird, B.M. (1931). Interpretation of float-and-sink data. Proc. 3rd Int. Conf. on Bituminous Coal, Pittsburgh.
  • Osborne, D.G. (1988). Coal Preparation Technology.