Perfformances evaluation of different vertical patternators

Abstract

Assessment of vertical spray profile is one of the main steps to adjust sprayers for bush and tree crops, as it allows to verify that the spray plume matches the target canopy profile. The equipment used for assessing the vertical spray profile is typically a vertical test bench or patternator. Even if the sprayer adjustment is recommended in EU Directive 128/2009/EC, the use of vertical test benches is only optional in the procedures for the inspection of air-assisted sprayers in use currently adopted in the EU Member States, that mainly refer to EN 13790- 2 and to new ENISO FDIS 16122-3. At present, in the International Standards, there is not any indication of the minimum requirements that the vertical test benches have to fulfill, neither in terms of constructive characteristics or of functional parameters. For this reason, the types of vertical test benches used in the test stations, even if are based on the same principle of functioning (presence of a vertical surface to collect the whole liquid sprayed and of graduated tubes for measuring it), present some differences in terms of structure, mainly related to collectors types and their disposal along the test bench. Two main categories of vertical test benches can be identified: 1) equipped with a continuous collecting wall; 2) equipped with a discrete number of separated collectors. In each category it is then possible to have different models, depending on the size, materials, number and position of the collectors. With the main purpose to define methodology and criteria for the vertical patternator evaluation, specific performance tests were carried out in laboratory using four different types of vertical test benches and a horizontal test bench complying with ISO 5682-1 requirements. Spray recovery capacity and reproducibility of results, both in terms of recovery and of spray profile were assessed using different droplet sizes, air speeds and air directions. Results of these first experimental trials pointed out that the criteria applied to assess the performance of the vertical test benches seemed able to discriminate the differences between the models tested. Amount of spray recovery was mostly affected by droplets size rather than by air velocity. Spray profile detected on the different vertical patternator types examined resulted generally similar. These first experimental results could constitute a basis for the development of a SPISE advice about test methodology and requirements for vertical test benches.