Types of Spray Painting Equipment

Introduction

The main categories of spray painting systems are briefly explained on this page, covering conventional, HVLP, airless, air-assisted airless, and electrostatic. More information on individual machines can be found in other sections of this site.

Please contact The Surface Finishing Equipment Group - Hogg Blasting and Finishing Equipment in the Northeast UK and Abraclean in the Northwest UK for impartial advice on the best type of equipment for your application.

Airless

The name “airless” derives from the fact that the material being sprayed is atomised by only hydraulic pressure at the spray tip.
Working at high pressures, airless spray units are designed to cover large surfaces quickly.
By varying the tip size a variety of coatings can be applied.
Typical applications are the applying of protective coatings on ships, bridges, construction vehicles, railcars, or containers, as well as interior and exterior painting and decorating, and the application of fire protective coatings.
Airless spray machines can be electric, petrol or pneumatically driven.

Air-assisted airless

Air-assisted airless uses a combination of airless and air-spray to atomise the material.
The Spray guns first partially atomize the fluid with a fluid nozzle tip similar to a standard airless tip. They then complete the atomization with small amounts of compressed air from the face and/or the horns of the air nozzle fitted to the spray gun.
The result is a finer atomized spray pattern than that of a standard airless system, giving a better finish but reduced coverage.
Typical uses are furniture manufactures, and joineries - spraying light to medium viscosity, water and solvent based lacquers and paints.

Conventional

A conventional air atomising spray gun uses compressed air to atomise the material. Air and the material enter the gun through separate passages and are mixed at the air cap in a controlled pattern.
High velocity air jets break up the paint. The high air speed also results in overspray / bounce-back and a relatively low transfer efficiency.
A high quality atomisation and fine finish are possible.
Unlike most other methods of spray painting, the pattern width can be adjusted whilst spraying for a high degree of flexibility.
Typically applications are automotive or plastics spraying.

HVLP

HVLP, or High-Volume Low Pressure is a development of conventional but uses a high volume of air delivered at low pressure to atomise paint into a low-velocity pattern of paint particles.
By definition, HVLP equipment has an atomisation pressure of 10 psi (0.7 bar) or less.
This type of gun was required to be used in many market sectors by the 1990 UK Environmental Protection Act. As a result of the low velocity, less material is lost in bounce-back than with conventional equipment and there is a higher Transfer Efficiency from gun to object.
The disadvantage is the atomisation and finish quality is not always as high as Conventional.

Hvlp development - trans-tech

Most manufacturers have developed HVLP to improve finish quality and have there own names for there technology. If the technology can be proved to work in excess of 65% paint transfer efficiency then the 10 psi atomisation pressure restriction need not be applied for the gun to comply with Environmental Protection Act legislation.
These guns often achieve the finish quality of conventional combined with the low overspray of HVLP.
Examples are the ITW Devilbiss “Trans-Tech” which means “Transfer-efficient Technology”.

Electrostatic spray guns

Any of the above types of spraying can be sprayed Electrostatically.
Electrostatic Spray Guns add a controlled negative charge to the atomised paint as it leaves head of the spray gun.
The work-piece being coated is grounded and the particles of the paint are attracted to the surface of the object creating a “wrap” effect. As a result of electrostatic attraction, paint that would normally be lost ends up on the back and sides of the work piece.
Very high levels of transfer efficiency can be achieved giving advantages in terms of painting savings, application speed, and uniform material coverage. The low amounts of overspray give a clean working environment, with booth filter savings, and reduced VOC emissions.
Typical applications are the coating of intricate metal components such as furniture, poles, and fences. Commercial and off road Vehicles, Automobile Parts, and Aerospace Industry.