Nozzle height

Booms and nozzles need to be set sufficiently high above the target so as to ensure that the spray output across the swath is even. To ensure that this occurs, the following table provides approximate heights for each fan angle at 50 cm spacing, which should provide single coverage

The effect of variations in boom height can be further minimized if these heights are doubled or the distance between the nozzles halved.  This is often referred to as double overlap or double coverage.

If at all in doubt it is best to set the boom too high rather than too low.

Single coverage spray pattern showing the approximate 30% overlap between adjacent nozzles.

Double coverage spray pattern to minimize effects of boom height variation.

Ground speed  - Boom spraying

Depending on the smoothness of the field, operating speeds may be increased if boom stability is improved.

Better boom suspension has meant more stable units which are capable of higher speeds.  Most broad acre contractors can travel up to 20 km/hr and could use higher speeds but are generally restricted by either marker performance, operator stress or equipment fatigue.  Boom design and strength needs to be emphasized more.  Some manufacturers are now using vertical welded high tensile steels to improve reliability along with boom trailers, which have a full suspension.

To overcome stripping through boom bounce, outrigger wheels need to be fitted to booms.  These wheels do not support the boom weight but stop it dropping below the desired height.  BMX type wheels have been successfully used on lighter booms whilst small trailer wheels are recommended for booms of heavier construction.