A New Way To Spray And Live Another Day
Like many of you, we aren't professional automotive painters, but that doesn't stop us-or most of you, for that matter-from giving something new the "old college try," as it were, like wielding a spray gun. Over the last year we have been bringing you body and paint basics stories, some of which were familiar territory to begin with, but much were new to us as well, which in our opinion is often the most fun. After all, if we aren't continually learning, what's the point?
HVLP painting has been around for more than a few decades now; in fact, HVLP was basically born from old canister vacuums that could be reversed and blow air, and eventually you could order a spray gun of sorts with your vacuum to paint your house...or even your automobile! Obviously, the process and equipment have been far improved from those days, and there's no doubt that the majority of you have heard if not used an HVLP spray gun by now, but what is HVLP, exactly? HVLP (high volume low pressure) guns use much less pressure to push the paint into the air stream, where it is atomized by a higher volume of lower-pressure (10 psi or less) air. HVLP spray guns are accepted as superior to conventional paint guns for many reasons, including anywhere between 40 and 60 percent less (depending on who you ask) material usage. That means significant material/money savings because the paint is going directly to what you are spraying instead of in the air. This increased efficiency is better for the environment as well as your pocketbook. Some HVLP guns work with an air compressor and some with a turbine, so which should you use?
Air Compressors And HVLP
An air compressor uses pistons or a diaphragm to push a relatively small volume of air at high pressure into a holding tank. Until about 15 years ago, most spray guns required an air compressor. The air compressor is capable of pressures of 125 psi and more, but are heavy, and can produce contaminated air when they are worn out or improperly filtered.
But one of the biggest problems many of us non-pros face when it comes to automotive painting is not having the optimum tools or equipment to do the job right, and having an adequate air compressor is on the top of the list, especially for non-HVLP users. To run a non-HVLP gun, you generally need at least a 5hp compressor and a minimum 20-gallon air tank; for an HVLP gun you'll need about 3 hp and a 20-gallon tank.
On top of the proper air compressor you'll need a quality, genuine HVLP gun-not a swap meet or cheapo one, as most often these are converted conventional guns-a regulator, air filters, an inline evaporator, and, of course, an air hose. You'll also need a high-quality respirator or even a fresh air respirator since the paint industry knows so much now about all the bad stuff in paint that is known to cause diseases such as silicosis, isocyanate poisoning, emphysema, and even cancer that can be directly attributed to breathing air contaminated with toxic vapors and mists. Anyone around paints has been subject to and is at risk for all the above-which is a whole 'nuther story...more on this later. Each and every one of these things adds up to quite a bit of money, not to mention space. Even though those giant compressors at the home improvement store look impressive, not all of us have the room for one, so what about turbines?
A turbine is a high-speed centrifugal blower motor that provides the gun with high cfm flow at low pressures. Because of the high rpm (near 20,000 rpm in some cases) a turbine operates at, the air is frictionally heated. This heat serves to eliminate all moisture from the atomizing air. The high rpm also increases the atomizing air temperature, which reduces flash time. Turbines are also lightweight and provide a reliable source of dry, oil-free air, unlike an air compressor on its own.
AXIS Products offers a high-quality turbine HVLP system-with a twist. Until now, a person using either a turbine or air compressor HVLP system was faced with hooking up a separate fresh air respirator along with whichever paint system to receive adequate breathing protection. It seems to be widely known that most non-professional air purifying respirator devices fail to protect a person's health in today's painting environment. To solve the problem, Axis Products developed their Citation HVLP sprayer/respirator system which combines the sprayer and fresh air system into one compact, economical package so you'll never be without fresh, clean, dry air whenever you paint or sand/grind hazardous materials.
I was totally in the dark about turbine HVLP systems, so I called and spoke with Jan from AXIS Products at length to bring me up to speed and educate me. One of the first things I asked her was if you can use an HVLP gun designed to be used with an air compressor, and she informed me that guns for each system are specific, but there are adapters to use a turbine gun with a compressor, but not the other way around. Turbine guns differ from conventional spray guns in two main areas. First is the size of the internal air ports. Compressor-type spray guns' internal air port openings are approximately 1/4-inch in diameter, while turbine guns need more air and use 5/8-inch air ports, more than six times larger than those in compressor guns. Keep in mind that HVLP atomizes with a high volume of air and low pressure. The second major difference is the manner in which the material is moved from the cup out of the nozzle. Turbine HVLP units pressurize the cup, forcing material to the nozzle. A conventional gun creates a vacuum to siphon material to and through the nozzle.