Water curtains and wetting of fire separating structures
One of the principles of fire safety in buildings is the division of the building into fire compartments. The fire resistance period of the structures separating the individual fire compartments can be extended by sprinkling with water. In some cases, a screen made of sprayed water droplets can also replace the dividing structure.
Sprinkling water to separating structures
To cool the fire shutter or glazing, water is sprayed over the surface of the structure in the event of a fire. Examples of structures that are sprayed are fire glass, wire glass, tempered glass windows, fire shutters, etc. A structure that is sprinklered must have a fire resistance of at least 15 minutes and resist thermal shock after sudden cooling by water. Therefore, it is not possible to apply water to, for example, an plasterboard partition or plain glass. The glass should at least be tempered glass.
The water curtain works on a completely different principle. The fire separation structure is formed by a cloud of finely atomized water droplets. The radiant heat, which is electromagnetic heat radiation, is blocked by the optical effect of the droplets. The efficiency is better if the droplet size is close to the wavelength of the thermal radiation, that is, the droplets should preferably be very small. The larger is the width of curtain, the more effective it is. Fine water droplets also cool the flowing hot flue gases, but they can be easily blown away. Curtain will not limit the penetration of smoke and reduce its toxicity. Water curtains are used, for example, on outdoor process equipment, in industrial buildings and as protection for conveyor belt penetrations. The conveyor is covered by a protective tunnel into which water droplets are sprayed. For larger penetrations and roller conveyor penetrations, a fire shutter is preferable.