Rosin-Rammler Fit

Give it your sieve analysis and it fits the standard Rosin-Rammler distribution, so two numbers describe the whole product: how coarse it is and how wide the spread is. Then it can predict any sieve you did not measure. If the points do not lie on the line, your product is not a single distribution — and that itself tells you something. Press SIEVE ANALYSIS to type yours in.

Why this matters now

Clinker reduction, high electricity prices and tighter cement specifications put the grinding circuit under pressure. The fastest gains usually come from finding the real constraint before changing equipment or operation.

What this tool helps decide

Convert sieve results into a particle-size curve, characteristic size and spread that support fineness, quality and mill-setting decisions.

What subscription adds

Build a connected grinding audit: save every mill separately, reload previous measurements, compare changes over time and issue an editable report for the plant team.

Connected to the industry conversation around clinker-factor reduction, grinding energy, blended cement and quality control reported in World Cement, CemNet and Global Cement.See process-tool plans

Your sample, fitted

The sample

Just a label for the chart. Cement product, mill discharge, separator return — whatever this sample is.

Sieve results

Sieve size in micrometres, and % retained on that sieve. Leave a row at 0 to skip it. Three rows is the minimum for a fit; more rows make it better. The right-hand column shows what the fitted curve says, so you can see which points disagree.

Sieve µm% retainedfitted
THE TWO NUMBERS THAT DESCRIBE IT
SIZES YOU CAN QUOTE
Spread (slope n)
Position d′
How well it fits
Sieves used
10% is finer than
Half is finer than
90% is finer than
Predicted at 45 µm

What this tells you

How the numbers are worked out

The distribution. R = 100 × exp(−(d/d′)n), the standard Rosin-Rammler form, DIN 66145. Take logs twice and it straightens out into ln(ln(100/R)) = n·ln(d) − n·ln(d′), so a least-squares straight line through your points gives n as the slope and d′ from the intercept. The chart plots those exact axes — that is why a good fit looks straight.

d′ is the size at which 36.79 % is retained (100/e). It is not the average; it is the natural anchor of this distribution.

n is the spread. Higher means narrower. A closed-circuit ball mill with a good high-efficiency separator usually lands around 0.9 to 1.1. Below about 0.8 the product has a long tail in both directions.

Deliberately not shown: a Blaine figure. The surface integral of this distribution contains Γ(1 − 1/n), which blows up as n approaches 1 — and cement sits right there. Any Blaine printed from an RRSB fit would be a meaningless number. Blaine comes from workbook formula #4b instead.