Influence of Reference Nozzle Choice on Spray Drift Classification

The BCPC spray quality classification system utilises the Lurmark 31-03-F110 (F110/1.2/3.0) flat fan nozzle to discriminate the threshold between the classes of Fine and Medium spray. This reference nozzle has also now been used to classify the spray drift potential for other spray nozzle-pressure combinations. This paper discusses whether such a reference nozzle can be described in general terms (F110/1.2/3.0 or ISO 03) or needs more detail by specifying source of manufacturer, type and construction material. Comparisons of performance were made between twelve equivalent rated commercially available nozzles for spray distribution on a patternator, and spray quality and drop speed measurements with a PDPA laser. Drop size and speed data have then been used to calculate spray drift potential for standard conditions with the IDEFICS drift model. Despite identical commercial ratings, large differences can occur for spray distribution and spray quality. Calculated spray drift potential for some nozzle types could even be double that of the currently used BCPC Fine/Medium reference nozzle. It is concluded that for the classification of nozzles towards spray drift reduction classes, a unique, a detailed specification of reference nozzle is needed. Nozzles from different manufacturers of alternative designs and construction materials do affect performance too much to be freely chosen as a reference, despite their consistent specifications for spray pressure, flow rate and top angle (ISO 03 series)