ID 115

Improved Industrial Coating Transfer Efficiency Through Precision Spray Control

 

Abstract:

Industrial coating applications have a particularly high emphasis on transfer efficiency, where inefficiencies can result in significant costs due to lost spray material, poor-quality products, and health hazards due to airborne particles. In this study, detailed spray investigations are carried out to examine the transfer efficiency from hydraulic as well as air-assisted spray nozzles in order to identify the major factors leading to an effective coating process. Spray characterizations of volume and drop size distributions provide insight into the spray properties that result in high vs low transfer efficiency. Pulse width modulation spray control offers high-frequency pulsed sprays by providing a square-wave type input to control specialized nozzle actuation. Pulsed hydraulic sprays are examined and found to be capable of producing fewer fine droplets (most susceptible to missing target) as well as the ability to turn up/down the delivered flow rate. Focus is given to applications where oil-based sprays are typically used, and the results of this study demonstrate that hydraulic pulse-width-modulation spray control offers gains in transfer efficiency, while maintaining many of the desirable spray characteristics of air-assisted nozzles.

This investigation provides an estimation of the drop size distribution that adheres to the spray target, based on mass and velocity, by examining the loss ratio of different classifications of droplets. Examining the drop size distribution with these metrics demonstrates that the different nozzle types create a similar coating, but the pulsed hydraulic spray offers notable transfer efficiency improvements and versatility.