|source image: hardi-international.com|
Sprayers of this have about the same range of use as the low-pressure, low-volume sprayers previously described. The spray liquid is carried in a pressure tank and the spraying pressure is developed by means of an engine-powered air compressor. The spray material therefore does not pass through a pump or contact any other moving parts.
These sprayers are available mounted on skids or wheels. Because of the cost and weight of pressure tanks, the tank size is usually limited to less than 300 gallons [1135.5 liters] and maximum working pressure to 75 to 100 pounds (33.9 to 45.3 kg). the compressors are usually rated in cubic feet per minute volume at atmospheric pressure. One cubic foot per minute at the desired pressure, therefore, will equal about 7 ½ gallons (28.3 liters) per minute. Agitation is provided either by means of a mechanical agitator or by an air tube discharging air below the surface of the liquid in the tank. These units are almost always powered by a self-contained engine.