For the ensuring of uniform grain supply the silo has to be equipped with various portioning devices. The feature of the most widespread locks is the fact that at each lock opening – closing, the grain is damaged. In the article the authors describe the experimental valve device consisting of two regulating shutters: vertical and rotary. The developed experimental valve device minimizes grain damage at each cycle of an opening – closing. The statistical mathematical model is developed considering the influence on grain consumption of unloading crack height and a rotation angle of a rotary shutter. The obtained results will be used in the development of the automatic control system of grain consumption.