Miller number (slurry abrasivity)
A measure of how abrasive a slurry is, obtained in ASTM G75 by reciprocating a standard wear block through the slurry and recording mass loss. It characterises the slurry itself rather than any particular material exposed to it.
The Miller number describes the attacker, not the defender. That makes it the right starting point when the same slurry is destroying several different components at different rates: the slurry is constant, so the differences are geometry and material.
The companion SAR number, from the same standard, characterises how a specific material responds to a specific slurry. The two answer different questions and are routinely confused.
Sources and references
- StandardASTM G75-15(2021) — Standard Test Method for Slurry Abrasivity (Miller Number) and Slurry Abrasion Response of MaterialsASTM International · accessed August 29, 2026
Where this is covered in depth
- Slurry wear: reading the mechanism before choosing a materialSliding abrasion, impact and erosion-corrosion call for different answers. Identifying which one dominates is what makes a material choice defensible.
- What a worn part tells you about the processA worn liner records what has run through the plant. Where the loss sits — and where it does not — often identifies the cause faster than an instrument.