A COMPARISON OF CONVENTIONAL AND HIGH-VOLUME LOW-PRESSURE SPRAY-PAINTING GUNS

The effect of spray-painting gun choice, high volume-low pressure (HVL P) or conventional, on solvent and particulate overspray concentration s was experimentally studied in a downdraft spray-painting booth. This experiment was conducted by repeatedly applying two coats of paint to a car body sheil. The two spray-painting guns were a gravity-fed conv entional and a gravity-fed HVLP gun. During each experimental run, par ticulate overspray concentrations, solvent vapor concentrations, film thickness on the autobody, and mass of paint were measured. The film t hickness per mass of paint for the HVLP gun was 33% higher than that f or the conventional spray-painting gun. This difference was statistica lly significant (p = 0.0015). Apparently, the HVLP spray-painting gun had a much higher transfer efficiency than the conventional spray-pain ting gun. Also, the particulate overspray concentration per unit of fi lm thickness for the conventional spray-painting gun was twice that of the HVLP gun. Again, this difference was statistically significant (p = 0.0009). Finally, the HVLP spray-painting gun reduced the overall s olvent vapor concentrations measured in the booth by 21%, which was no t statistically significant. However, solvent vapor exposures measured on the worker were reduced by a factor of 2 when using the HVLP gun. This difference was statistically significant (p = 0.02).