HVLP paint systems atomize paint by delivery a high volume of air at a low pressure (less than 10 psi). Because the atomized paint particles are delivered at low velocities to the object being painted, less paint is lost as overspray, bounce, and blow back. Typically the transfer efficiency with HVLP paint system is 50 to 65%.

The effect of this technology on pollution prevention concerns the fact that delivering at low velocities results in a higher transfer efficiency, compared to conventional paint spray systems. In conventional spray systems, a stream of liquid paint is met by jets of pressurized air which form the paint into a fine mist. A typical system employs 100 psi of constant air pressure in a volume of approximately 25 cfm. The atomized paint particles travel at high velocities and tend to bounce off the object being painted rather than adhering to the surface. In addition, the expanding high pressure air (above 100 psi) passing through the small face cap openings causes turbulent flow of the paint stream following air currents within the paint booth. The amount of paint that bypasses the workpiece (overspray) is relatively high for air pressure atomized spray painting. Transfer efficiencies of 25 to 30% are associated with conventional spray systems.

There are three other types of high transfer efficiency paint guns: airless (also called pressure atomized), pressure atomized air-assisted, and electrostatic. Electrostatic paint spray systems are discussed in a separate Pollution Prevention Opportunity Data Sheet, Electrostatic Paint Spray System. The other two systems are described below.

Airless spray painting systems atomize paint by forcing it through a small tip orifice at high fluid pressures (1,500 to 3,000 psi). Transfer efficiencies with airless spray painting are lower than HVLP systems, typically 20 to 40%. Large areas can be painted quickly by pressure atomized paint systems. This technology is, however, inappropriate for fine finishing work, because a large quantity of paint is delivered with particles that are less finely divided.

Pressure-atomized, air-assisted systems combine the features of the air atomized (conventional) and airless systems. An airless fluid spray nozzle is used to atomize the coating into a fan pattern at high pressures (400 to 800 psi). A second, low-pressure air stream (10 to 30 psi) is injected after the nozzle to improve atomization and the spray pattern. This system is reported to provide the fine control of air-atomized spray guns and the improved transfer efficiencies of airless systems. Transfer efficiencies for pressure-atomized, air-assisted systems are comparable to HVLP systems. The airless systems generate significant waste during clean-up and material changes, as compared to the HVLP system.

• reduced emissions of volatile organic compounds (VOCs) used as solvents in paints which are associated with formation of smog and are typically regulated by state and local air pollution control districts;
• reduced emissions of hazardous air pollutants (HAPs) used as solvents in paints which are most typically associated with increased cancer risk and which are regulated under federal, state and local regulations including National Emission Standards Hazardous Air Pollutants (40 CFR 63);
• reduced emissions of substances which may result in reduced reporting requirements under the toxic release inventory (TRI), Tier I/Tier II, and other SARA Title III reporting requirements (40 CFR 300, 355, 370, and 372; and EO 12856); and
• potentially reduced occupational exposures which are regulated under 29 CFR 1910.120.

Specific compliance benefits include: 1) reduced recordkeeping and reporting requirements under the Title V, the NESHAP Program, and under SARA programs and 2) reduced permit fees.

Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing any of these technologies.

• Higher transfer efficiencies result in significant reductions in both paint usage and waste generation.
• Less maintenance is required for pollution control equipment serving the painting area.
• Paint solvent waste and emissions can be further minimized by utilizing a paint gun cleaning station and solvent recovery system. The USAF has authorized paint gun cleaning stations for use under Table of Allowance (TA) 480.

• HVLP systems are sensitive to changes in temperature, pressure and air flow rate. The operator must monitor these conditions to ensure that proper transfer efficiencies are maintained.
• Solvent-based paints (epoxy, lacquer, polyurethane, and oil-based enamels) will require a solvent to adequately clean the spray guns.

Assumptions:

• Gallons of paint applied to surface per year: 5,000 gallons
• Gallons of paint purchased per year with HVLP system: 10,000 gallons
• Gallons of paint purchased per year with high velocity spray system: 20,000 gallons
• Paint procurement cost: $50/gallon – Most paints used by the Air Force are two component epoxies or polyurethanes coatings that cost around $100 for a two gallon kit.
• Transfer efficiency of HVLP gun: 50%
• Transfer efficiency of high velocity spray system: 25%
• Labor requirements: The only significant difference in labor between these systems is the maintenance requirements, as there is no difference in painting times.
• Labor for High Velocity Spray Systems: 400 hours
• Labor savings for HVLP: 10%
• Labor rate: $45/hr.
• Waste paint collected using dry filter system.
• Dry filter replacement rate: 1.25 dry filters/hour
• Dry filter disposal cost: $1/filter

Annual Operating Cost Comparison for HVLP Spray Systems and High Velocity Spray Systems

Economic Analysis Summary

Annual Savings for HVLP Spray Systems: $501,850
Capital Cost for Diversion Equipment/Process: $1,000
Payback Period for Investment in Equipment/Process: Immediate

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The HVLP system is the preferred paint system by the Air Force in T.O.1-1-8 for general paint applications. It is authorized in Table of Allowance 480, but authority resides at the local level.

*There are multiple MSDSs for most NSNs.
The MSDS (if shown above) is only meant to serve as an example.

Accuspray, Inc.
23350 Merchantile Rd.
Cleveland,  OH   44122
Phone: (800) 618-6860 
or (216) 595-6860
FAX: (216) 595-6868