- In particle comminution processes, the size of the original particles (mother particles) will continuously decrease to finer sizes (daughter particles). This size reduction process can be mathematically represented (in simplified form) by two major functions: selection function (breakage probability) and breakage function. In the present study, a new horizontal impact experimental system is developed, constructed and tested. The experiments from the impact system are used for development and validation of the selection and breakage models. Ability of a number of statistical formulations to accurately describe the probability of the particles to break under an impact load and the probability of the particle fragments size are examined and compared. Selected models are analyzed and general expressions including the effect of the material and particle size are developed. The findings will significantly improve the accuracy of comminution processes simulation, and optimization of industrial processes.