When using an Hvlp spray gun the painter should be aware of a few things. These are pressure adjustment, fan adjustment, fluid control, changing the pressure to match the spec sheets, painting, and proper pressure.
To adjust the pressure, open the compressor regulator to about 90 pounds per square inch (psi), so there is enough air pressure in the line to the gun. Now, pull the trigger on the gun and set the regulator on the gun’s handle to 50 psi or what is advised in the instructions for the gun. Close the valve at the bottom of the gun handle and while continuing to pull the trigger open the valve on the bottom of the handle until the air volume remains steady.
Adjusting the fan is accomplished by opening the fluid volume control, located at the back of the gun, about 3 turns. Close the fan control located on the left side of the gun behind the nozzle. Position the gun 6 to 8 from a test surface, move the gun across the surface and pull the trigger. While moving the gun, adjust the fan control until the desired fan shape, usually a 5 to 6 inches wide top to bottom oval shape, is accomplished. If spraying up and down on a surface, change the nozzle at the front of the gun 90 degrees to create a horizontal fan.
After adjusting the fan, continue spraying and adjust the fluid volume located at the back of the gun for the final adjustment. This adjustment is necessary for correct fluid for the gun speed. This needs to be a heavy volume, but not to the point where the paint runs at normal gun sweep speed.
After completing all these adjustments, the gun is ready to paint. With 50 psi at the handle, the gun is spraying about 10 psi at the cap. If 5 psi is required at the cap, set the handle regulator at 25 psi. Most guns internally regulate the pressure down based on the inlet pressure while some more expensive guns have a gauge located off the back of the handle that reads the cap pressure.
Observe the item painted and the way the paint is going on the surface right behind the gun and adjust from that position. For instance, to spray a small area, turn the fan down to a small round size. The fluid volume will also have to be greatly reduced at the back of the gun at the same time to avoid runs. The air pressure at the regulator on the handle can be reduced to 25 to 35 psi to accomplish this task.
Remember that a high air pressure will be needed, as per spec sheet, so that the proper atomization is reached and the volume is raised. The higher pressure will lower the amount of runs because the atomization is better. This is important with sealers, bases and clear coats so that a good coverage without runs can be accomplished.Remember