Thanks to the University of Northern Iowa and the Iowa Waste Reduction Center
High Volume – Low Pressure (HVLP) spray guns are often viewed as the holy grail of spray painting transfer efficiency (TE). Quite often, HVLP is automatically assigned a generous TE rating of 65% without much (if any) consideration of coating characteristics, spray gun setup parameters, finish quality requirements, and the geometry of the work pieces being coated. In general, any type of spray equipment (including HVLP) is capable of being used inefficiently if set up improperly. This is largely how conventional air spray equipment has developed such a bad reputation for transfer efficiency (generally considered to be 50% at best).
Don’t get me wrong, HVLP spray equipment definitely offers some impressive benefits in certain applications and if used properly. It does, however, have its share of limitations. Most notably, it lacks the energy needed to sufficiently atomize high viscosity (i.e., high solids – low VOC) coatings. In an effort to remedy this, particularly in situations where HVLP use is required, a spray operator may reduce the coating’s viscosity by adding solvent. This quickly negates the environmental benefit of high solids – high performance coatings.
The following are two fundamental points I’ve learned from over a decade of experience in working with companies that apply coatings:
- · Spray equipment needs to be compatible with coating characteristics, finish quality requirements, production demands, and product characteristics; and
- · Optimal efficiency (in any type of coating application) is most effectively and readily achieved by the proper selection, set up, and operation of spray equipment. This, of course, is complemented by the ability to recognize and diagnose application problems.
If this article has sparked any interest on how proper spray gun selection and setup might benefit your coating operation, you might be interested in reading a case study made available through the following link. It compares the application efficiency and finish quality of pressure-fed HVLP and conventional air spray equipment, using spray gun operating conditions deliberately set up for performance. The findings may surprise you.