Airless sprayers are mainly defined by three main categories: 

1)     Diaphragm Airless Sprayers

Diaphragm airless sprayers use a hydraulic piston to draw hydraulic fluid from the sump and then compress the hydraulic fluid under a plastic diaphragm. The diaphragm pulses up and down causing the suction valve above the diaphragm to open and close which creates enough suction to draw paint product through the suction hose. Once the paint has passed through the suction valve it enters the outlet valve which usually contains a ball and seat or check valve. This allows the paint to exit the outlet valve but does not allow pressure in the hose to push back through the outlet valve.

Diaphragm airless sprayers are controlled by a pressure control valve which regulates the rate of which the hydraulic fluid is released from the piston block back into the oil sump.

Diaphragm airless spray pumps can be driven by AC Electric motors and petrol/gasoline motors with a simple eccentric bearing on the end of the crankshaft, the bearing pushes the hydraulic piston up and down compressing hydraulic fluid under the diaphragm.

Diaphragm airless pumps are more common in countries that use 220/240v power such as Ireland, Germany, Japan, China and Australia to name a few. In countries where the power grid only supplies 110v, diaphragm airless sprayers have only been popular in low capacity machines.

Diaphragm airless sprayers are a simple mechanical type of airless sprayer that has no electronics such as computer boards and sensors. In terms of use they will deliver paint out of the spray tip in exactly the same fashion as a piston airless sprayer.

 2)    Piston Airless Sprayers

Piston airless sprayers use a double acting pump in order to draw the paint from a container, this double action allows the pump to draw and transfer paint at the same time by using an inlet valve (foot valve) at the bottom of the pump and an outlet valve in the piston rod.

Once the airless pump is running the fluid is transferred in a continues flow through a small hose usually to a high pressure filter fixed to either the pump and motor or frame of the airless sprayer, this filter traps any small particles of debris or rubbish in the paint that could potentially block the airless spray tip.

The pressure of the airless sprayer is regulated by an electronic sensor that tells the motor when stop and start according to either the pressure selected by the operator or the maximum pressure setting default of the computer. Piston airless sprayers these days have complex computer boards that not only tell the machine when to stop but they can also adjust the speed of the motor depending on the size spray tip selected by the operator.

Electronic Piston airless sprayers are driven by DC Motors, although these motors are light and produce high torque they require more components than a diaphragm machines such as computer boards, pressure sensors and electronic pressure control. Piston machines are very popular in the USA because the DC Motors used can produce more power on a lower power grid such as 110v.

3)    Pneumatic or Air Driven Airless Sprayers

Pneumatic Piston airless sprayers use a double acting pump in the same manner as electronic piston airless sprayers but the drive unit is an air driven motor. Air driven motors are a simple reciprocating motor that works on basic resistance of the air pressure in the motor versus the pressure in the fluid pump.

Pneumatic airless sprayers are usually classed by the ratio of the air pressure fed into the pump air motor which determines the fluid pressure that flows out of the pump. To give an example of how this ratio is applied to the size of the pump, see below:

30:1 Ratio Pneumatic Airless Sprayer

Fluid Pressure 30psi for every 1psi of air pressure fed into the air motor. If the air motor inlet pressure was regulated to 50psi, the fluid pressure in the pump would be 1500psi (50psi x 30psi = 1500psi)

Pneumatic airless sprayers are used mainly for industrial type coatings were possible electrical hazards exist such as in steel manufacturing or applications were electrical supply is limited or not available. Pneumatic airless sprayers are also useful for thicker industrial coatings that require higher atomization pressure at the spray tip. Electric piston machines do not exceed 3300psi but pneumatic airless sprayers can spray up to 8000psi.

ATOMEX GM-20E Airless Sprayer Package - $1099.00