Effect of Position and Motion on Personal Exposure in a HVLP Spray Painting Operation

Worker exposure to particles is a problem in most spray painting processes. Previous studies, using a stationary mannequin and simple spray nozzle, showed that dimensional analysis could be used to correlate a dimensionless breathing zone concentration (which requires knowing the gun transfer efficiency) with a dimensionless nozzle pressure term (the Carlton number). This work expands on that study by using a real high volume-low pressure (HVLP) gun, and adding a representative spraying motion. A robot-mannequin, capable of holding and actuating the spray gun, and also performing a repeated side-to-side spraying motion was used. Vacuum pump oil was sprayed onto a flat plate in a wind tunnel to determine the relationship between nozzle pressure and breathing zone concentration. "Breathing zone" samples were collected using a cassette modified to mimic the IOM inlet. Data collected in the absence of motion show that the dimensionless concentration in the 90° position is lower than the 180° position until a crossover point is reached at low values of the Carlton number (8 x 10[5]). After this point, the dimensionless breathing zone concentration in the 80° position is lower than in the 90° orientation. For the case with motion, the importance of position to dimensionless breathing zone concentration was mitigated. Using task representative Carlton number values (alpha values) allows for simplification of the results. Alpha values for the 90° and 180° orientations without motion were 0.232 and 0.028. It was observed that the motion mitigated the positional effect in such a way as to make the alpha value for motion close to the average of the two no motion alpha values, 0.102. These results allow for the supposition of a formula to predict breathing zone concentrations or transfer efficiencies for conventional and HVLP spraying guns. The results also stress the association between contaminant generation, transport, and exposure. Models, such as the one used, are beneficial because they relate exposure to processes parameters that can be controlled to reduce it.Master of Science in Public Healt