… is not really a secret, because it’s just physics. Droplet size has a significant impact on extinguishing performance, even if, of course, it’s not the only decisive factor. But what droplet sizes are produced by today’s extinguishing technology?
In modern normal pressure O-stream nozzles, the average droplet size is about 500 µm (0.5 mm). The Rosenbauer NEPIRO high-pressure O-stream nozzle combined with a Rosenbauer high-pressure pump produces an average droplet size of approx. 150 μm (0.15 mm) and about 100 microns (0.1 mm) with a UHPS ultra-high pressure extinguishing system at 100 bar.
Influence of droplet size on extinguishing success
It is undisputed that smaller water droplets and thus an increase in the surface area lead to faster evaporation and thus faster extinguishing success with a lower risk of water damage at the same time. Because the faster it is extinguished, the less fire damage to occur. Although not always completely avoidable, water damage is becoming less and less acceptable.
But despite all the discussion about droplet sizes, the most important aspect must not be forgotten: the droplet size is only a supporting factor of the cooling and choke effects; the amount of water applied per time unit is what is crucial. More water removes more energy from the fire in a given period of time, and thus extinguishes it better, as long as the water is vaporized. Therefore, it can be summarized that the amount of water is the most crucial factor in extinguishing success since the droplet size “only” helps to make the water evaporate as best as possible. And the pressure of the extinguishing system also “only” helps to generate certain droplet sizes. But higher pressure does not contribute directly to extinguishing success – which is a common misconception!
Choosing the right extinguishing system
There is no single perfect extinguishing system for all types of fire and fire sizes. When it comes to procurement, a fire department is always faced with the decision of choosing the right extinguishing system based on the potential dangers it faces.
Rosenbauer offers a broad portfolio of extinguishing systems for all applications based on the required flow rates, extinguishing efficiency and vehicle concepts
The Rosenbauer high-pressure extinguishing system impresses with many advantages
The Rosenbauer high-pressure extinguishing system, which has been continuously improved since the 1950s, is still able to assert itself when compared to ultra-high pressure or compressed air foam extinguishing systems. Of course, a high pressure extinguishing system cannot be considered the “only true” extinguishing system, just as is the case with a normal pressure, high pressure or compressed air foam system. Every system has its advantages and disadvantages. It is all the more important to compare them in an unbiased manner and then to opt for the best choice.
To this day, the combined Rosenbauer NH centrifugal pump is unique. It combines a normal pressure and a high pressure pump on one common pump shaft. The high pressure pump is designed as a 4-stage centrifugal pump, which is characterized by a high performance (up to 400 l/min at 40 bar) and a flat pump curve, which brings advantages in parallel use of two high-pressure nozzles.
The NH pump can also be equipped with an around-the-pump foam proportioning system for the high pressure part (HP-FIXMIX). Thus, water can be discharged through the normal pressure pump and foam can be discharged simultaneously through the high-pressure pump.
The foam quality of high pressure foam is still underestimated. Due to the higher discharge speed at the nozzle, the foam pipe of the NEPIRO nozzle produces a much more homogeneous and stable foam than normal-pressure extinguishing systems. Also, the throw distance is higher compared to normal pressure extinguishing systems with the same performance. In terms of quality, one can almost compare high pressure foam with compressed air foam (CAFS).
Rapid operational readiness
With just one push of a button, the pump is put into operation. After opening the outlet and pulling down the high-pressure hose from the reel, the extinguishing operation can be started immediately. Furthermore, the start of the high-pressure around-the-pump foam proportioning FIXMIX works with just one push of a button!
After the extinguishing operation, the high-pressure hose just needs to rewind, thereby quickly and immediately restoring operational readiness!
Extinguishing without having to enter the location of the fire
A multi-functional penetration device is also available for the Rosenbauer NEPIRO high pressure nozzle. This will knock a hole in a door, car hood, etc. The lance is simply attached to the NEPIRO nozzle and inserted through the hole. Thus, a fire source can be safely extinguished without entering and without the risk of supplying additional oxygen to the space.
Additional functions of high pressure
Due to the pressure of 40 bar, the high pressure is also ideal for cleaning after floods and along dirt-contaminated roadways. This can be done either by a vehicle-mounted high-pressure road cleaning system or by the high-pressure washing lance, which can be coupled to the NEPIRO nozzle.
Rosenbauer high-pressure pumps can be used in a wide variety of vehicle concepts, for municipal, industrial as well as airport fire departments. They are in operation in Rosenbauer trucks all over the world!