Water Mist Fire Suppression Systems

Our company carries out all design, installation and maintenance operations for high-, medium- and low-pressure automatic water mist systems. The water mist system must be built in respect of the design and installation parameters emerging from the full-scale tests for scenarios similar to that to be protected.

HOW WATER MIST TECHNOLOGY WORKS

A water mist system utilises water in the form of very dense fog in order to either contain the fire underway or otherwise completely extinguish the breakout, depending on the design scenario under consideration. The use of extremely micro-drops with a minuscule diameter guarantees a much higher efficiency than traditional water systems, since the same volume of water in micro-drops has a greater total specific surface. This translates to a greater cooling capacity over the fire and local inertisation by reducing the amount of oxygen around the fire.

COMPONENTS OF A WATER MIST SYSTEM

The system, being very similar to a classic sprinkler, is generally characterised by the following main components: 

• Water supply (accumulation tank, tank, etcetera) generally with a smaller capacity;
• Pumping unit or battery of cylinders;
• Collector and distribution network for the water;
• Dispensing nozzles.

Water mist nozzles can be of the closed type with thermally-activated bulb (that activates when the temperature reaches a certain limit value, just like the sprinklers) and triggered when the temperature reaches a certain limit value (just like the sprinkler nozzles) or else can be of an open type that drains the water from all heads installed at the same time, following a command to activate the detection and extinguishing system.

The nominal operating pressure varies according to the type of system, which can be of low-pressure (<12.5 bar), medium-pressure (> 12.5 bar and <35 bar) or high-pressure (> 35 bar, with a typical value of 100 bar) and are guaranteed by a specially-created pumping unit or, for smaller systems, by a battery of nitrogen and water cylinders.

ADVANTAGES AND DISADVANTAGES

Advantages

• Minimum impact on the goods and materials kept in the protected spaces, as compared to a sprinkler system;
• There is no danger to people in the environment since the extinguishing medium is simply water, thus pre-alarm systems are not strictly necessary as they would be for inert gases or aerosols;
• Minimal cleaning operations, due to the lower quantity of water discharged into the environment;
• Small-scale water storage tanks and pump rooms;
• The use of stainless-steel pipes with extremely small diameter (12–50 mm).

Disadvantages

• Higher costs than a sprinkler system;
• Complicated system design as it depends on the specific certifications of the manufacturer;
• For systems with cylinders, when the supply of nitrogen and/or water runs out, the system will no longer be able to guarantee continuous extinction in the event of a fire that is out of control.

FIELDS OF APPLICATION

All these features render water mist systems suitable for mechanical rooms with gas or steam turbines, transformers, electrical substations, for shipyards, road and railway tunnels, industrial kitchens, archives and libraries, high-rise buildings, hospitals, car parks, buildings of historical and cultural importance, with diesel engines and alternators.

The water mist extinguishing systems can avail of small-scale thrust units and accumulation tanks for pumping and storing water. Moreover, to guarantee the highest degree of efficiency and safety, they can be combined with smoke-detection systems and be subject to the various maintenance offerings in our Service.