The American Henry S. Parmalee is considered the inventor of the first automatic sprinkler, patented in 1874.

Just four years later Frederik Grinnell improved on Parmalee's idea by introducing what became known as the Grinnell sprinkler.

Since then automatic sprinkler systems represent the most popular fire prevention solution worldwide thanks to their simplicity and intrinsic effectiveness.


How a sprinkler system works

Pipes constantly pressured with water (wet) or air (dry) are connected to irrigation heads capped by thermosensitive elements. In the early stages of a fire the heat produced increases and hot fumes accumulate in a layer a few tens of centimetres below the ceiling; the sprinklers closest to the vertical point of the fire are the first to overheat and, once the calibration temperature has been reached, they open and supply water to the flames. The ceiling begins to be cooled by the water that wets it directly and by that which is pulled upwards by the ascending fumes; the growth of the fire is mainly slowed as a result of wetting of the combustible material surrounding the fire itself.

Effectiveness of a sprinkler system

The effectiveness of sprinkler technology immediately needed to follow precise technical standards with regard to design and installation. In the wake of the NFPA13, British FOC and German VdS standards, national and international standardisation bodies and insurance companies have largely standardised the sector. With millions of installations around the world, statistics demonstrate that less than 3 heads are sufficient to control 50% of fires and 9 are enough to control over 80%. Although the purpose of the sprinkler system is not to directly protect the persons involved - given the temperatures at which the system is activated - but to control the fire, preventing it from spreading and allowing safe and effective intervention by the emergency teams, the effectiveness in terms of occupant protection is very high.

The different types of sprinkler systems

Nevertheless, sprinklers with different thermosensitive elements have been designed to activate the system at different temperatures, whether they are based on the fusion of an eutectic alloy or on the expansion of a liquid until the quartz glass bulb is broken, in both cases to allow water flow from the dispenser.

The operation of a sprinkler system is a delicate compromise between the operating temperature and the flow rate of the water supplied depending on the number of dispensers that are activated. Another variable concerns the way the water flow is delivered.

The research has gone on to develop different forms of deflectors both to orient and shape the jet and to determine the size of the drops, thus acting on the penetration capacity of the hot fumes. With the development of storage systems that allow large quantities of material to be stacked, the challenge for installers and manufacturers is to develop systems that allow them to hold the correct quantity of water to tackle fires, the so-called "height challenge".

These sprinklers, the so-called large drops, are sized to attack the fire and to reduce it as well as control it; the "coarse" or "heavy" drop technology was later joined by the CMSA Control Mode Specific Application systems.

The substantial difference between these two types lies in the design of the system that not only considers the discharge density and the area to be protected but which adheres to specific parameters for the application for which it is intended. Designed for an actual suppression action, the ESFR (Early Suppression Fast Response) sprinklers are designed to require only a minimum intervention to complete the emergency team. Compared to large-drop sprinklers, these systems protect complex areas, in terms of fire safety, such as large warehouses with vertical storage of more than 10 meters, exclusively with ceiling systems without regulators at the intermediate levels of the shelves.

However, this is a type of system that must be used according to stringent technical specifications that concern both the plant aspects and the characteristics of the structures to be protected. For intensive storage areas, so-called ELO Extra Large Orifice sprinkles are also available.

The sprinkler: a highly reliable system

In over one hundred years of use of sprinklers the statistics confirm that the probability of accidental opening of a sprinkler head, appropriately chosen by type and calibration and correctly installed, is less than one in a million.

If we add to this the fact that, except in cases where water is actually harmful to the stored materials, the damage caused by operation of the system is the minimum achievable in a fire extinguishing action, it can be stated that the sprinkler system, apart from being highly reliable, minimises the damage of the extinguishing action; in fact, it acts in an extremely precise manner by activating only the heads directly involved in the fire.


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