Different applications and ambient environmental or operating conditions require different flat fan nozzles. With its broad portfolio of flat spray nozzles, Lechler offers the optimum nozzle solution for every task. The following criteria are helpful in selecting the optimum flat fan nozzles.
The impact force of a liquid jet on a surface, for example, plays an important role for reliable cleaning or in surface technology in general. The impact is calculated as the quotient of the impact force and the impact surface.
Calculation of the impact force:
The impact surface is the area where the droplets strike. This is the area affected by the liquid jet.
The smaller the surface area, the greater the impact values. Nozzles with high impact are, for example, flat fan nozzles with a narrow spray angle as well as solid stream nozzles.
Increasing the connected pressure results in an increase in the spray impact. Doubling the pressure while maintaining the same flow rate results in a doubling of the impact.
Increasing the flow rate by using a larger nozzle increases the impact, assuming that the other parameters (spray angle, pressure and medium) remain the same.
For a high impact, the droplet size is also very important – in addition to the impact force and the impact surface. Large droplets at high speed are advantageous for high impact. As the pressure increases, the droplet velocity also increases, but the droplet size decreases. This means that an increase in pressure above the recommended operating pressure will only have an impact close to the nozzle. As the distance increases, the small droplets quickly lose speed and there is less impact.
Basically, Lechler flat fan nozzles are designed for parabolic liquid distribution. Unaffected by transient pressures, they are suited for universal application. Their performance data are exactly defined. Operational values, such as flow rates, spray width, jet thickness and liquid distribution are readily available for a great variety of feed pressures. There are also special-design nozzles with rectangular or trapezoidal distribution of liquid.
Lechler flat fan nozzles provide a consistent, uniform coverage over the impact area. For this purpose, the spray widths B ought to overlap each other by 1/3 to 1/4. To avoid interferences of the sprays, the nozzle orifices must be offset 5 – 15° to the pipe axis.
In order to achieve an even surface coverage the nozzles need to be aligned in such a way that spray widths B overlap by 1/3 to 1/4. Therefore the nozzles should be inclined in an angle of 15° to the vertical of the horizontal axis of the tube (either with a weld base at an angle or a Lechler ball joint nozzle mount) in order to prevent a disturbance of the spray.
The spraying behavior of flat fan nozzles is determined by several factors:
Viscosity is a measure of the flowability of a fluid. The higher the viscosity, the thicker (less flowable) the fluid is. The lower the viscosity, the thinner (more fluid) the fluid is, i.e. it can flow better under the same conditions.
Examples for fluids with different viscosities:
The viscosity is specified dynamically (mPa-s or centipoise) or kinematically (m²/s or 106 centistokes).
The temperature has an enormous influence on the viscosity. It is therefore by no means negligible. This influence can be observed when olive oil is placed in a pan at room temperature (80 mPa·s at 20° C) and heated. As the temperature increases, the olive oil becomes more liquid (20 mPa·s at 60° C; 10 mPa·s at 80° C).
The following example shows the changing spray behaviour of a 652 series flat fan nozzle at constant pressure and increasing viscosity.
The pictures clearly show how the spray angle becomes smaller and smaller with increasing viscosity. If a nozzle with a different performance size were used, it would also be apparent that the influence of viscosity also depends on the performance size of the nozzle. The spray angle at smaller performance sizes decreases more strongly.
The use of flat fan nozzles for viscous media is generally only recommended to a limited extent. The following statements apply primarily to flat fan nozzles, but can also be partially transferred to other nozzle types: