Metal Finishing Guide Book

2013

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shorting condition. This can potentially short some or all of the high voltage to ground. This can greatly reduce the electrostatic affect which can lead to poor transfer efficiency. Example: A fluid supply hose, of a fluid supply container too close to ground, can short the system out completely or create a high load (high microamp reading) on the power supply which in turn lowers the actual voltage at your applicator. This can significantly reduce transfer efficiency. In addition to keeping all the equipment isolated, the cages (fluid supply) must be kept relatively close to the application equipment.This can result in a significant amount of lost floor space. In many occasions, the amount of floor space it takes to enclose the fluid supply may not be available. In many installations, floor space is extremely valuable and cannot be afforded when lost. External Charging (Indirect Charging of Material) External charging of waterborne coatings allows the fluid supply to remain grounded. The fluid supply area can remain the same as it was configured for a solvent based coating. Since the paint particles are charged externally, or as some say "indirect," the high voltage does not follow the conductive path through the fluid lines back to ground. The indirect charge of the material is accomplished by placing a probe, which is at high voltage, a few inches away from the gun electrode.This probe creates the electrostatic field to charge the paint particles without coming in direct contact with the waterborne material. Thus, the high voltage does not follow the conductive path back through the fluid lines. 191

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