Centrifugal Fertiliser Spreaders: A New Method for their Evaluation and Testing

Keywords: spreading, spatial distribution, radial test bench, mineral fertilisers.

Mineral fertiliser spreading is mainly carried out by centrifugal spreaders, which are simple and efficient. Making prototypes, developing and working out setting tables, etc. are operations that rely on transverse bench tests. The distribution curve obtained in this way shows the quantities spread in relation to the distance to the spreader’s axis of work. This is a curve simplifying real spreading conditions, which only represents the final result of spreading when it is carried out in ideal conditions, in a straight line and with optimum overlapping between runs.

The size of the test bench to be used is also extremely important and therefore requires a hall in which climate conditions are controlled. The area of this facility increases exponentially with the working width of appliances to be tested.

So, a new test device has been devised with the prime objective of providing characteristic spatial values of spreading. The configuration and operating method of this bench help cut down the size of the hall needed. Investment, maintenance and air conditioning costs are therefore greatly reduced.

The patented method consists of measuring spatial distribution on the ground of fertiliser broadcast by a spreader, by weighing the amounts of fertiliser broadcast radially to the spinning disc in real time. To limit the area to be covered and the required number of testing units, just one row of collection trays fitted with load cells (80 in all) is placed radially to the spreader. It is the spreader that rotates around itself during spreading. The fertiliser pattern on the ground is measured in a period of between 50 sec. to 2 min. Characteristic values (range and angle) can then be extracted as well as standard transverse curves.

The assembly requires a covered area of about 500 m ² and short bay widths (10 m) compared with 4800 m ² and bays in the region of 60 m with the traditional method.

On the one hand, the system provides the means to carry out research work on the properties of the actual fertilisers (spreadability, aerodynamic properties, etc.), but also on spreading systems envisaged. It is also possible to validate the spreading models by adding sensors.

Comparison with results obtained by the traditional method is possible (quick, automated measurements) up to working widths in the region of 30 m.

E Piron and D Miclet, Cemagref, Groupement de Clermont-Ferrand Domaine des Palaquins – Montoldre, 03150 Montoldre (Allier), France.

22 pages, 12 figures, 8 references.