. Chemical weed-control equipment. Weeds; Spraying; Spraying equipment. Nozzles for airplane spraying are tapped from the top or side of the boom and are generally controlled by quick shut-olf valves for each nozzle or group of noz- zles. The valves may be spring-loaded or positive-action, of either gas cook or pop- pet style. Some operators use automatic, spring-loaded ball valves similar to those on ground rigs. Quick shut-off valves are essential to stop the liquid flow at field boundaries. These valves are controlled (by the pilot) with a small cable running the length of the boom and back
. Chemical weed-control equipment. Weeds; Spraying; Spraying equipment. Nozzles for airplane spraying are tapped from the top or side of the boom and are generally controlled by quick shut-olf valves for each nozzle or group of noz- zles. The valves may be spring-loaded or positive-action, of either gas cook or pop- pet style. Some operators use automatic, spring-loaded ball valves similar to those on ground rigs. Quick shut-off valves are essential to stop the liquid flow at field boundaries. These valves are controlled (by the pilot) with a small cable running the length of the boom and back to the cockpit. Nozzles may discharge either a cone or fan type spray. The method described on page 19 for ground-rig booms, using suction on the boom while boom pressure is off, has been adapted to use by planes. The width or coverage of the spray is not so greatly affected by the length of the spray booms as it is by the wing span, the height the plane flys, the design and power of the plane, and arrangement of the boom and nozzles with relation to airstream. Drop- let size is greatly affected by the angle at which the nozzles discharge into the air- stream. Smaller droplets occur when the nozzles are directed against or across the airstream than when they are directed with it. Droplet size is mainly influenced by pump pressure, but the very small nozzle orifices will also decrease the aver- age droplet size, depending upon the type of nozzle. A compromise must be made between the small droplets which give more thorough coverage but have a tend- ency to drift, and the large droplets which settle fast but are not so efficient with respect to coverage. (The number of droplets per square inch varies in- versely with droplet size.) The average size deposited by correctly operating air- plane equipment is between 50 and 300 microns, at which size most weed spray materials react satisfactorily. Strainers are not generally used be- cause nozzle orifices are large. However, spray ma
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Keywords: ., bookcentury1900, bookpubli, booksubjectspraying, booksubjectweeds
