Electric versus air atomising nozzles

Air atomising nozzles are an effective way of delivering fine sprays on target. They're commonly used in a variety of coating applications and precision spray applications.

With these types of the nozzle, the air is used to atomise the spray and to drive it onto the target area. This can be combined with air actuation which is using air to shut nozzles on and off. Air actuation can generate impressive responsive times of up to three on/off cycles per second.

Electronic nozzles such as the EHP system controlled by the FlexFlow™️control system are a good alternative to air atomising nozzles on, say, a coating application. These nozzles have an integrated solenoid valve within the nozzle body itself and they can very rapidly shut that orifice on and off at either 50 or 150 times per second, depending on the model. They don't use any air at all; atomisation of the fluid is achieved purely by the fluid pressure itself, through the nozzle.

 So how do they compare?

Advantages of electric nozzles

- Reduce mist
Spraying fluids such as oil with air atomisers can get very messy. The air helps to carry the finely atomised spray to the target, but you can get an oil mist coming off of that and some of it may go off target. It could also mist up in the factory, creating more mess and waste. Because electronic nozzles don’t use any air, any misting and spray carry is reduced dramatically.

- Reduce noise
The air is noisy, and this can be a big issue in some factories. The electronic nozzles are a lot quieter.

- Lower running cost
Despite the bigger CapEx on this type of system, they don’t use any air. This lowers the running cost as they only use an electrical signal to shut the nozzle on and off. Although this is an advantage, it's not hugely significant, because the air atomising nozzles don’t use a great amount of air.

Easier to set up and adjust
Air atomisers have two inputs – the air input and the fluid input. The variation between air and fluid pressure can have quite a dramatic effect on the spray pattern type, atomisation level and the flow rates. That interplay can be quite delicate depending on the type of nozzle and setting them up can be quite a lot harder. Electric nozzles have an electronic control system that controls the on/off cycles very easily. The overall spray type that comes out of the nozzle is dictated primarily by the fluid pressure. There’s only one variable to control.

Advantages of air atomising nozzles

- Delivering low flow rates
The air can help drive very fine sprays at very low flow rates to ensure the target is met. Whereas electronic highly actuated nozzles just rely on fluid pressure to atomise spray and to form the spray. There’s some lower limitations on the flow rates that can be achieved, so if a fine coating application is involved, air may be needed to produce a proper spray pattern.

Wiring problems
- If there are practical problems in wiring electrical components close to the spray head, this can be a reason to use air atomisers. Electronic nozzles have a solenoid valve built into the nozzle body itself, and this needs wiring in extremely close to the actual spray head to receive the signal. There may be a variety of reasons why that’s just not practical in a factory.

Air atomisers are controlled by air, therefore an air supply into the nozzle body is required. This air supply can be controlled by a solenoid valve some distance away from the actual spray head. Any electrical components can be a lot further away from the spray head and spray zone, which can be useful in many situations.

- Smaller drop sizes
If finely atomised fluids are required, air atomisers can help achieve smaller drop sizes, particularly if the fluid pressure is restricted. Despite the fancy control system in electronic nozzles, they are just basic hydraulic nozzles. There are some things that can be done to reduce flow rates such as pulse-width modulation. But in terms of the actual atomisation of the fluid, it's still just a basic hydraulic nozzle which relies on the fluid pressure to atomise it, and there are some limitations.

- Spraying viscous fluids
Electric nozzles (PHP) can correctly set up and handle fluids up to 25 centipoise, which is 20 times the viscosity of water. It's not quite as simple as just giving a specific number that they can handle, but it’s around there that these nozzles can start to struggle.

The right kind of air atomiser can handle fluids of up to 3,000 centipoise. Again, it's a complicated topic. There’s no guarantee that all fluids up to 3,000 centipoise can be handled by air atomisers as it depends on a variety of factors. But the range of viscosity that air atomisers can handle is a lot higher than electronic nozzles.

Cheaper CapEx
- As noted before, air atomisers have a slightly higher running cost due to the air supply. However, the overall CapEx that’ll be spent on an air atomising nozzle system is likely to be significantly lower.


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