Airless spray pumps were designed as the ever-growing need for transfer efficiency increased. Airless spray pumps have proven to be extremely versatile, being able to spray both industrial coatings as well as fine-finish coatings. . As the range of airless spray pumps continues to develop and expand, it is becoming more and more challenging to choose one that will suit your specific application. In this blog we will break down the selection process for you. For more information on how airless spray pumps work and their advantages read our blog ‘What is Airless Spray?’
There are four main, different types of spray pumps to choose from. While all of them have a fluid section that pumps paint to the gun, the motor that drives the fluid section will differ.
- Pneumatic airless spray pump (driven by a pneumatic air motor)
- Electric airless spray pump (driven by a 220V or 380V electric motor)
- Petrol airless spray pump (driven by a petrol motor)
- Hydraulic airless spray pump (driven by either an electric or petrol motor)
Let’s take a closer look at the output of these different pumps.
|Spray Pump||Litres per Minute||Bar|
|Pneumatic||9.4 – 18.6 (refer to *pressure ratio)||180 – 500|
|Electric||2.1 – 4.5||210 – 230|
|Petrol||10||210 – 230|
|Hydraulic||10||210 – 230|
*Pressure ratio of pneumatic airless pumps (30:1, 63:1, 95:1, etc.)
In each ratio, the number 1 represents 1 bar air pressure which is then multiplied by the higher number representing fluid pressure. For example, a pump with a pressure ratio of 63:1 means that for every bar of air pressure supplied, the pump will produce 63 bar fluid pressure.
While electric, petrol and hydraulic pumps vary in outputs of 210 – 230 bar, a pneumatic spray pump varies in output from 180 – 500 bar! Generally speaking, we need between 80 – 180 bar to atomize paint at the gun. So why would you then even consider purchasing a spray pump that can produce a higher output? We will get to this a bit later.
Knowing the difference between the different types of pumps and their outputs is a fantastic starting point; however, without proper knowledge of the paint you are spraying a choice between them cannot yet be made.
The paint you are using for your application determines the size of the airless spray tip you will use. For most industrial applications, your data sheet will recommend which spray tip to use. For more on selecting the correct spray tip read our blog ‘Spray Tips – How to Choose the Right Size’. Although your spray tip is one of the smallest parts of your spray setup, it actually plays one of the biggest roles. The larger the spray tip the more volume must be produced by the airless pump in order to handle the increase in demand. It is ultimately the spray tip that determines the volume output that a spray pump must be able to produce which now becomes the basis for selecting your spray pump.
Unfortunately, this is not where your selection process ends! Paint is a complicated subject matter. Often when recommending the tip size, the data sheet fails to take into consideration a few other factors. The viscosity and volume solids of the paint must be taken into account. If the volume solids are below 65% it is safe to use electric or petrol driven pumps; when the volume solids are higher than 70% it is advisable to use pneumatic driven pumps. If paint is cold (or has a high viscosity) and the airless spray hoses are long you might also want to consider using a higher ratio pneumatic spray pump. Paint with a high viscosity has a resistance to flow inside the paint hose. A higher pressure pump is ideal to push the paint through. Depending on the pigment of the paint, the spray tip can get blocked by the paint itself and would therefore require a spray tip with a larger orifice, which would then result in getting a spray pump that can produce a larger volume output. If you need to achieve a high coating thickness, a pump that can produce a larger volume output is also recommended for more speed on the build-up. Hydraulic and pneumatic pumps can produce higher output volumes than electric and petrol pumps.