Common causes of failure of pneumatic distributors in high precision pneumatic seeders: Proposals towards predictive maintenance

Modern precision pneumatic drills (1-500 kg/ha) used in the cultivation of high density crops such as winter cereals (up to 400 plants/m2) are very high performance equipment that triple the working width (up to 9m) and rates (up to 14 km/h) compared to those used fifteen years ago. Most of enterprises commercialize such devices using as cornerstone a central pneumatic distributor in combination with a large number of radial outlets (24-48). In spite of the unquestionable advantages of these devices with regard to more conventional gravitational distributors, the main drawback remains the lack of transversal uniformity which has proven to be fairly sensitive to seed size and shape, to slight air flow changes related to partial obstructions of outlets, elbows and grips in discharge outlets, or vibrations and inclinations of the central distributor, as well associated to inadequate maintenance of the machine by untrained operators. Moreover, the lack of behavior predictability derives in a certain discredit of the pneumatic procedure. This work proposes a theoretical-empirical methodology to analyze the pneumatic circuit and its interaction with a variety of seeds types to be delivered, and selected operational machinery settings, within the aim of elaborating a test protocol which combined with low cost instrumentation will serve a base for predictive maintenance. Experimental data gathered in static and dynamic tests performed by the authors on at least two different seeders together with published information available on technical papers will be reviewed and used for further discussion on reliable diagnosis procedure