Powder Booths for Powder coating System

Powder containment is the first requirement of any powder coating system, as breathing in powder spray dust is hazardous to one's health. In addition, ADI, which is the mixture of Air, Dust, and an ignition spark, can cause the dust to catch fire or even explode. To properly contain oversprayed powder, the booth must be designed to provide an average face velocity between 80 fpm and 100 fpm airflow over all openings with the exceptions of: parts taller than 6?0?, parts that are heated above 120oF, short hook up to but not exceeding 18?, and cross drafts of excess of 60FPM in the booth area.

If there is too much airflow, the powder will be drawn away from the parts being coated. Many shops that have an in creased airflow tend to overcompensate with a higher powder-flow rate and decrease first-pass transfer efficiency. This can and has lead to poor application finishes.

Another important factor to consider in the powder booth design is the canopy or enclosure, which contains the over-sprayed powder. The booth canopy resembles a small room with four walls, a floor, and a ceiling. The ceiling has a slot, which runs lengthwise that hangers from a conveyor protrude from to support the parts, or objects that are being coated. The main goal is for the parts or object being coated to receive high first-pass transfer efficiency therefore the powder must be attracted to the part or object and not the walls, floor and ceiling of the booth. To accomplish this, the area around the spray guns must be constructed out of low, non-conductive material, allowing the electrostatic field emitted by the powder guns to attract the powder the part and not the walls, floor or ceiling of the booth.

Distance:

Gun to booth wall distance and gun to part distance are booth very critical issues in receiving high first-pass transfer efficiency. Therefore, the tip of the powder gun must be a minimal of 12? inside the boot to ensure that the electrostatic field is attracted to the object being coated and not the booth canopy. If the powder booth is not wide enough to place the gun inside the booth, then booth wall extender can be added at the gun opening to allow for added space between the tip of the gun and the booth wall. This will also shorten the time needed for booth cleaning during color changes as well as result in more powder being attracted to the part.

There are many variables in the placement of the gun, which depend on the line speed as well as the part specification. However, the place of the gun is usually 8 to 12 inches from the part being coated.

Another vital factor with the powder booth is the issue of humidity and temperature as both can greatly affect the performance of the powder coating system. The powder coating system should always be installed in an environmentally controlled room where the temperature remains between 70 to 80 degrees Fahrenheit and the humidity does not go below 47% nor exceed 55%. Any change in either the temperature or the humidity will affect fluidization, filter efficiency, filter life, as well as have an effect on the powder.