HIGH VOLUME/LOW PRESSURE PAINT SPRAY SYSTEM
|Overview:||A High Volume/Low Pressure (HVLP)
paint spray system is an efficient technology for the application of paint
to specific workpieces. These systems operate at low pressures, which
result in the application of paint at low velocities.
HVLP paint systems atomize paint by delivery a high volume of air at a low pressure [less than 10 pounds per square inch (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 cubic feet per minute (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.
|Compliance Benefit:||The higher transfer efficiency
achieved by the HVLP paint spray system reduces the
total volume of paint that is used, which in turn results in the following
Specific compliance benefits include: 1) reduced recordkeeping and reporting requirements under the Title V permitting program, the NESHAP Program, and under SARA programs; and 2) reduced permit fees.
The compliance benefits listed here are only meant to be used as general guidelines and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g., the amount of workload involved.
|Materials Compatibility:||HVLP paint spray systems can
be used in a wide variety of painting applications. The finer atomization
of HVLP systems produce smoother surface finishes. There are many paint
gun models, with a variety of tip sizes to accommodate most coatings,
including solvent-based paints, water based coatings, fine finish metallic
coatings, high-solids polyurethane, contact adhesives, varnish, top coats,
lacquer, enamel primer, latex primer, epoxy, and vinyl fluids. The
manufacturers guidance should be followed in all maintenance and operating
aspects, particularly when spraying high solids paints. Clogging problems
can hamper painting operations if the technician is not familiar with the
equipment or the application techniques required. The efficiency of this
system is reduced if painting is in exposed areas.
|Safety and Health:||Proper design, operation, and
maintenance of the equipment is required for its safe use. The spray booth
must be well ventilated. The coating characteristics and application
procedures (such as surface preparation, spraying and clean up) present
additional health concerns. The inhalation of lead or zinc can irritate
the respiratory tract and may even result in instances of poisoning. Some
lead compounds are even known to be carcinogenic. Solvent-based paints can
irritate the lungs and mucous membranes. Prolonged exposure can affect
respiration and the central nervous system. Proper personal protective
equipment (PPE) should be worn.
Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing any of these technologies.
|Economic Analysis:||Costs will vary depending upon
specific applications, painting/coating type, paint volume, workpiece
specifications, and technique. Generally, HVLP paint spray system
equipment costs approximately $1,000 for a gun, hose, and paint pot.
Airless or air-assisted airless paint spray systems range from $2,000 to
$3,500. Installation costs will also vary, depending upon location.
Annual Operating Cost Comparison for HVLP Spray Systems and High Velocity Spray Systems
Economic Analysis Summary:
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*There are multiple MSDSs for most NSNs. The MSDS is only meant to serve as an example. To return from the MSDS, click the Back arrow on the Tool Bar.
|Approving Authority:||Appropriate authority for making process changes should always be sought and obtained prior to procuring or implementing any of the technologies identified herein.
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.
|Points of Contact:||For more information|
This is not meant to be a complete list,
as there may be other suppliers of this type of equipment.
US Air Force Table of Allowance (TA) 480 should be used by Air Force personnel for National Stock Number (NSN), sources of supply and costs.
Fluid Air Products (Government Distributor) ITW Industrial Finishing
Fluid Air Products (Government Distributor)
ITW Industrial Finishing