| RE:Paint/autobody: Anybody here do their own work? |
Subject: RE:Paint/autobody: Anybody here do their own work? by Qack on 2008/1/11 20:16:45 Quote: What is an HVLP gun? HVLP stands for High Velocity Low Pressure, and it was a new technology about twenty years ago, forced by EPA emissions requirements. The essential benefit of HVLP over High Pressure is overspray. High Pressure guns typically result in about 20% of the paint going on the object being painted and about 80% becoming overspray. With HVLP, the numbers are just about reversed -- there is typically less than 20% overspray -- I forget the requirement but it's quite low -- which means over 80% goes on the object to be sprayed. Thus, lower pollution by a lot. Air source. If you use a compressor, you are pressurizing air to around 100 psi, then reducing it down to about 30-40 psi for a High Pressure gun and to below 10 psi for an HVLP gun. As the air is initially compressed, it heats up. It then gives up some of its heat as it sits in the tank and hoses. When you use the air for your spray gun, you reduce the pressure; thus, the air gets colder -- quite a bit colder than when it started in the first place. Thus, the moisture in the air comes out as water droplets. You need to have a really good moisture trap to get rid of the water. Otherwise it will ruin a perfectly good paint job. Just ask anyone -- like me -- who was bit by that problem. It's really frustrating. With a turbine compressor as a source, you only compress the air -- typically to about 5 - 7 psi. Thus the "Low Pressure" part of HVLP. It makes up for the low pressure by using high volumes of air. A turbine compressor is ideal for that type of air source. You never store the air, so it doesn't have much opportunity to cool down before you use it so there isn't much of a moisture problem. There really isn't a turbine gun, just a turbine compressor. |
