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10 Common HVLP Questions 

1. How does HVLP differ from conventional air spray? Conventional air spray air cap pressure is nearly the same as the input pressure entering the spray gun. HVLP technology reduces the incoming pressure to a compliant 10 psi or less at the air cap.

2. If HVLP means High Volume Low Pressure, why am I using High Pressure (20 to 80 psig) at the gun inlet? If we simply supplied 10 psi inlet air pressure to a spray gun, the volume of air would be too limited for most industrial applications.

3. Is HVLP required in all industries? Simply put, no. At the federal level, the requirements are generally based on Standard Industry Codes (SIC’s). For example, the wood industry does not allow the use of conventional air spray guns while the plastic industry does. The size of the operation will determine whether or not the operation will fall under the federal guidelines. Restrictions could also be in place at the state or local levels.

4. Is it possible to exceed 10 psi at the air cap? The maximum inlet pressure on most HVLP spray guns is determined by the air cap. If a cap is rated for a maximum gun inlet pressure of 30 psi and a pressure greater than 30 is supplied, the “maximum 10” is exceeded. Note that the pressure is measured at the gun inlet, not at the “wall”.

5. How can I be sure I do not exceed 10 psi at the air cap? Do not exceed the maximum inlet pressure designed for the air cap Use an air cap test kit Train the operator/set-up person the proper test methods

6. Do I need to use 10 psi at the air cap in order to atomize? Simply put, not necessarily. When setting up a spray gun, use the minimum air pressure that will achieve the required finish quality. The pressures will increase as the production requirements (fluid delivery) increases. Any pressures beyond the necessary pressure will lower the efficiency of the spray gun resulting in increased coating and booth filter costs.

7. Are all HVLP guns the same? HVLP guns, like all spray guns need to be matched to the application. Spray guns and air caps are available to handle the needs of the touch-up artist to the requirements of heavy industrial applications.

8. What are some reasons HVLP might not work? The two primary reasons: Choking off the air supply. Since HVLP uses a higher volume of air than conventional air spray guns, the pressure drop is higher. This applies to air hoses as well as quick disconnects. Too much fluid pressure. Use no more than required for production. Remember, the efficiency of HVLP is considerably higher than conventional air spray guns.

9. Can I convert my air spray gun to HVLP? In most cases no. For those guns capable of conversion, the range of air caps will probably be limited to light production air caps. In most cases, HVLP is achieved through internal porting in the gun, so conversion is difficult.

10. Is operator technique different for HVLP? The primary difference is gun distance. Use 8-10” for conventional air spray and 6-8” for HVLP.