How an Airless Spray Gun Works
An airless spray gun pumps paint under high pressure through a hose to a tip that converts the stream into a spray. Pressure is controlled on the pump and the spray pattern is determined by your choice of gun tip.
The spray tip slots into the gun guard and is a snap to change for viscous or thinner coatings. It also helps eliminate ‘tails’ at the ends of the spray pattern which can be corrected by adding thinner, increasing pressure or replacing a worn tip.
Pump
The pump that comes with an airless spray gun is used to pressurize paint and then push it through the nozzle at a high rate. Airless guns don’t use an air compressor but rather an electric or pneumatic (airless) pump or in some cases a gas engine to accomplish this task.
The working pressure on an airless system is measured in pounds per square inch or bar and varies between 300 to 7,500 psi. This is a lot of pressure that forces the material through the nozzle to atomise it.
Unlike HVLP sprayers that operate at lower pressures, airless systems are designed to cover large areas quickly with thicker coats of material and fine detail work. These systems also have the advantage of low overspray.
Airless sprayers require more time to set up because the hose and the pumps must be connected and it takes longer to clean an airless system after you finish using it. You will also have to take extra precautions with health and safety protocol when operating the sprayer. You will need to mask and protect adjacent surfaces from the spraying and you will have to spend time flushing out the pump, hose and gun with water (if you are spraying latex) or solvents (if you’re spraying oil-based products). The cost of an airless system can add up over time since you will have to purchase the system, spray hose and filters and then clean them all.
Hose
An airless spray gun doesn’t use an air mechanism like a turbine or compressed air, it instead uses an electric or pneumatic pump and in some cases gas (hydrocarbon) powered engine to pressurize the airless spray gun paint and push it through the nozzle. This allows it to work with a variety of liquids including water based and chemical paints as well as industrial coatings, linings, mortar, grout, and block filler.
Once the pressure reaches the nozzle it decreases and the material is partially atomized. This is a result of the shape and size of the nozzle itself. The nozzle needs to be properly set for the type of material you are spraying in order to achieve a good pattern with no tails or excessive overspray. Airless spray guns can be fitted with different nozzle sizes which allow you to adjust the size and shape of the spray pattern.
Using the sprayer correctly takes practice however it is quite quick to master and can make the process of painting much quicker than traditional methods. As with all power tools always wear safety glasses and ensure the area is kept clear of flammable objects or materials.
The hose that comes with the gun can be extended to a longer length which helps reduce hand fatigue and provide more maneuverability. It can also be connected to an external bleed valve so you can easily stop the flow of paint if the nozzle gets clogged with paint. It can also be connected to a reversible tip for greater flexibility in spraying.
Nozzle
The nozzle is the part of the gun that sprays the coating. It is connected to the pump, and the paint is pushed through the nozzle at high pressure. This forces the liquid into tiny droplets that form a fan-shaped spray pattern. The size of the nozzle determines the spray pattern and how much paint is sprayed. There are many different sizes of nozzles to choose from, and the right one can make the difference between a smooth professional finish and a mess with lots of overspray.
The airless nozzle also has an orifice that determines how much fluid exits the gun. This can be adjusted, as too little can cause an uneven spray and too much will wear out the tip faster. It is important to relieve the pressure before connecting a new tip, after spraying and before cleaning. The nozzle must be removed and cleaned thoroughly to ensure no residue or clogs are left behind.
A quality gun will have a high transfer efficiency and fine atomisation, which helps to minimise the amount of paint being wasted. A quality airless spray gun will also be durable and easy to use. This is especially important when working with large areas and thicker coatings like enamels. It is worth investing in a high-quality gun to save time and money.
Tips
An airless spray gun is designed to pump liquid through a small tip at high pressure down a long flexible hose. It doesn’t use compressed air to atomize the paint so it’s important to select the correct tip size for the material you’re spraying. Too large a tip can create runs and too thin a material may not be covered properly.
Tips slide into a hole in the front of the spray gun and are usually identified by a three digit number. The first digit indicates the spray fan width with the gun held 12 in. from the surface. Doubling the first digit gives you the maximum fluid flow rate in GPM (Gallons Per Minute).
If you are spraying a thin material like a stain or enamel it’s recommended to select a smaller tip size of between 207 and 311 if you are using a full bodied coating chips packing machine then go larger if necessary. You should also ensure that the tip is properly cleaned and kept free from dried paint. It’s also a good idea to have a few extra tips to avoid the inconvenience of having to clean one when it gets worn.
Lastly, it is recommended to always work in a well-ventilated area. Wear safety glasses and an approved respirator. It’s also a good idea for all workers to be aware of proper grounding procedures to prevent sparks when working with the spray gun and metal pail.