Water spray extinguishing systems


Installation with water spray are provided with:

  • fire fighting of solid combustible materials (wood, paper, textiles, plastics, etc.).
  • protecting the objects (structures and equipments of technological facilities, containers of flammable liquids combustible with a inflammable temperature of the vapors higher than 60oC and flammable gases, internal combustion engines, large household electrical cable with flammable insulated) against thermal radiation emitted by a neighboring fire ,to limit the heat absorption to the limit that prevents or reduces damage;
  • preventing the formation of explosive mixtures in confined spaces (reducing evaporation by cooling surfaces that come in contact with flammable liquids) or outdoors (by diluting explosive mixtures or gas leaks that can form explosive mixtures).

The water spraying is done in order to increase the ratio between the outer surface of the droplets and their mass to get a better contact between the water and the environment in the furnace, increasing the heat transfer and therefore quickly extinguish the fire.


When they are assured the flows and pressures required ,the water supply of the fire extinguishing installations is made from:

  • drinking water network;
  • fire water network;
  • industrial water network.

The network of main water pipes are executed, usually of a ring-shaped and the secondary pipe with sprinklers (nozzles), follow as much as possible, as the shape of the protected object.

Water pipes and related fittings, to the distributors, are protected against frost.

The installation vendor is provided with manometer.

The distribution lines from the distributor to the protected object are dry.

The distance between nozzles is determined according to their hydraulic parameters specified by the manufacturer, but it is recommended to not exceed 1.5 m and minimum intensity of spraying (numerically equal to the intensity of fighting).

Plants with water spray are provided with automatic control and / or manual.

Manual operation of the taps for commissioning of the the installation is allowed provided that their handling is done in a timely manner.

For the power plant fire fighting from the mobile pumps are provided the same equipment or features like the sprinkler installation.

Entrying into operation of the fixed water spray is signaling at the fire service control room and protected targets.

The installation is projected with steel pipes. Fittings are from steel or malleable iron.

Sizing the fire with water spray

The specific flow rates, q (is) (l / s) and nominal pressure spraying call H (i) (m H2O), are given by the manufacturer for each type of sprayer (nozzle).

Compared with sprinkler installations or drenchers, sprayers require high water pressure (5 … 7) bar except for improved types of sprayers the can produce a spray of water acceptable for many uses in pressure (3 .. . 5) bar

Number N (i) is determined as spray in systems with drenchers (Article 8.27.).

Location type and size of sprays (nozzles) are set so as to ensure the most disadvantageous point cooling intensity I (r) (l / s) as well as in the systems with drenchers.The distance between sprinklers is determined according to their splash radius, so make sure an extinguishing or cooling intensity as uniform over the entire surface protected.

It is provided a stock of 4-10% of total spray (nozzle) mounted to replace those that are in maintenance (clogged or damaged).

The hydraulic pipe sizing calculation of the branched or ring network, of water supply of the sprayer (nozzle) is performed by the same methodology as for the sprinkler installation.

Fire extinguishing installations with water mist


Fire extinguishing installations with water mist are provided for:

  • protection of the building structural elements (beams, columns etc.).
  • protection of the technological installations equipmentsof the combustible liquid containers for flammable temperature of vapors above 60oC and flammable gases of internal combustion engines, as well as household electrical cable insulated combustion;
  • protection against thermal radiation emitted by a neighboring fire to limit heat absorption to the limit that prevents or reduces damage;
  • fire fighting of solid combustible materials (wood, paper, textiles 919q163j, plastics etc.).
  • prevent the formation of explosive mixtures in confined spaces, or outdoors by diluting explosive mixtures or gas leaks that can form explosive mixtures.

It is recommended adopting the limiting installations and fire-fighting water mist in situations where water supplies are limited or when the water supply is restricted.

Plants with water mist are recommended to limit and fire classes A, B and C.

Limited facilities installations and fire fighting with water mist are not recommended in cases where water in contact with combustible substances which burn, forming explosive mixtures or toxic.


The main components of the firefighting facilities with water mist are the following:

  • water supply source;
  • tanks (or containers) for storage water reserve required fire-fighting with water mist;
  • pumping station (from the storage tanks through piping to the spray nozzles);
  • pipeline network with water of the spray nozzle;
  • water spray nozzles;
  • reinforcements, equipment and control devices, safety and control;
  • own installation of detection, signaling and control in case of fire;
  • electric power sources.

After the way of formation of the water mist fire fighting required consists of:

  • systems with direct cold water spray,at the water pressure in the pipe;
  • plants with cold water using a spray atomization gas, usually compressed air or nitrogen under pressure.

In case of extinguishing installations operating on water and air (or nitrogen) compressed for the water mist, besides the art components. 10.5 may occur:

  • battery cylinder air (or nitrogen) compressed;
  • battery operated devices with bottles of air (or nitrogen) compressed;
  • distribution lines for air (or nitrogen) compressed;
  • closing valves, safety and control air (or nitrogen) compressed.

The direct spraying installations with cold water, at the water pressure pipe, can use regular construction nozzles (standard), with a discharge in outlet always open, or specially designed nozzles (automatic), equipped with thermal activation (depending temperature caused by fire).

In the first case (art. 10.8) the installation is filled with cold water up to a pressure control valve and control system operated by the fire detection system. in case of fire ,the detectors transmit the signal at the detection and signal power plant that verifies the signal authenticity and if so, commands the valve opening so that cold water pressure in the pipes to direct download through all spray nozzles mounted on respective lines, forming mist the water.

In the second case (art. 10.8)the installation is filled with pressurized cold water to the nozzles fitted with thermal activation. in case of fire, the thermal activation devices, automatically open the discharge outlet nozzle at a predetermined temperature (producer nozzles) and cold water pressure in the pipes is sprayed through nozzles to form water fog.

Installations with cold water using a spray atomization gas (pressurized air or compressed nitrogen) are equipped with automatic nozzles, equipped with thermal activation and can make the following systems:

  • with a network of pipes filled with cold water under pressure to the valve command and control and air (or nitrogen) tablet, the command and control valve to the nozzles;
  • with distinct networks of pipes, cold water pressure or air (or nitrogen) tablets, which are powered by connecting ducts, each nozzle.

At the first system (art. 10.11) in case of fire, the thermal activation devices open the nozzle outlet openings at predetermined temperature and compressed air (or nitrogen) is discharged through the nozzles. Due to the pressure difference between the water pressure, respectively, compressed air (or nitrogen) command and control valve opening pressure of the cold water inlet pipe to be sprayed through nozzles activated water mist forming.

At the second system (art. 10.11) in case of fire, the thermal activation devices open the nozzle outlet openings at predetermined temperature and compressed air (or nitrogen) trains a stream of cold water pressure at each nozzle activated by ejection phenomenon, spraying water as fog.

This system has applications, especially in local installations fire-fighting water mist, when the number of nozzles is relatively small. in local facilities, water and air (or nitrogen) can be stored in compressed cylinders located near object protected against fire.

After the spraying water pressure values ??(working) fire extinguishing installations of water mist are:

  • High pressure installations: over 34 bar;
  • medium pressure installations: between 12 bar and 34 bar;
  • low pressure installations: between 6 bar and 12 bar.

Depending on how it is ensured the fire in the protected space, installations of water mist extinguishing are:

  • with total flooding;
  • with zonal flooding;
  • with local flooding.

The total flooding water mist can be enclosed only on the doors, windows, pipes, etc.. can be closed before or simultaneously with the start of spill water fog.

For fire extinguishing inside enclosures total flooding, the entire enclosure space must be filled with water fog, so the percentage of oxygen to fall in the shortest time possible, keeping below the combustion.

At the total flooding systems for instantaneous and surface fires (flammable liquids triggered), the amount of fog water input, must cover leakage due to leak. Total area – in m2� – of goals that can not be closed shall not exceed 3% of the total – in m3� – protected enclosure or 10% of the total – in m2� – lateral surfaces and the upper and lower chamber. In case of technical or technological reasons these conditions can not be achieved it will be adopted the system of local flooding.

The zonal flooding with fog water is done in case of fire, by activating a group of nozzles located, usually in a fire compartment of the building.

The flooding zonal system can be used automatic nozzles, heat activated, or through a self-detection, signaling and control, in case of fire.

To the systems with local flooding, it is ensured water flooding fog on the limited surfaces or around protected object. The method is used for the surface fire, especially combustible liquid or solid surfaces and generally in areas where there are conditions for total flooding.

Local flooding systems are activated in case of fire, the automatic nozzle, or a proper detection system, signaling and control.

All the protected enclosures the fire-fighting installations of water mist will be provided with mechanical ventilation systems – exhaust able to provide evacuation after the fire, the release resulted from fire (smoke, combustion gases and steam). Facilities will be operated with manual buttons, buttons centrally located near such enclosures door.

These facilities will be sized appropriately to safe and complete evacuation clearance. Ventilation will provide a flow equivalent to more than 10 exchanges zones. Exhaust pipe will be as short routes and, if possible, without crossing other unprotected areas.

Spray nozzles shall bear the manufacturer, their main technical characteristics such as: type nozzle orifice diameter discharge and corrosion protection.

The nominal temperature of the trigger nozzle fitted with thermal activation system, should be higher than the maximum temperature of the environment in which they are mounted (to avoid false triggering), as specified by the manufacturer.

After the thermal response time of the automatic nozzle through thermal activation, the nozzles can be: with rapid thermal response, special or standard.

The thermal response time for each type of automatic nozzles specified by the manufacturer and intervenes in determining operating time of fog formation water curtain and the total time of flooding enclosure protected against fire.

The nozzles are placed according to fire hazards, flammability and fire resistance of the elements of construction, the position and size of beams, columns and so on, various equipment, machinery or stacks of materials and hydraulic parameters (flow, pressure, shape and flow characteristics) given by the manufacturer, so as to ensure:

  • entering into operation of the nozzle in the shortest time from when ignition;
  • minimum normalized intensity of fighting;
  • protecting load-bearing elements of the building with fire resistance limit reduced;
  • achieving water mist curtains as uniform on the protected area.

The spray nozzles are placed in rooms and spaces that are protected, so as to achieve a rapid and uniform flooding.

The nozzles are placed, usually perpendicular to the surface protected from water spray direction being from top to bottom.

The nozzles are mounted on ramifications of (branches) pipeline network, closer to the object protected by the fire-extinguishing installation type: with flooding focal, zonal or total.

in case of fire extinguishing installations of water mist with total flooding nozzles are placed, usually the room ceiling

If through the instructions given by the manufacturer do not state otherwise, the location of the nozzle is recommended in the following distances:

  • between the nozzles and continuous ceiling, at least 8 cm and maximum 40 cm;
  • between the nozzles and the surface (object) protected least 60 cm;
  • between the nozzles and the chamber walls, distance should not be higher than half the distance between nozzles;
  • the distance between the nozzles is determined based on hydraulic parameters specified by the manufacturer of nozzles and sprinkler minimum intensity, but it is recommended that no more than 1.5 m;
  • if the objects that exist in the room are stacked, placed in boxes and stored on shelves (except for deposits with high stacks) free space around the nozzle must be 0.90 m (0.90 m radius hemisphere as nozzles) .

It is recommended that the spray nozzles for obtaining water fog to be made ??of corrosion resistant metals and alloys.

The water spray nozzles shall have adequate mechanical strength for use in normal operating conditions of the installation of fire with water fog (pressure, temperature, mechanical damage).

If the placement and operating conditions can lead to clogging of nozzlesthey must therefore be be provided with rupture discs or caps. These devices should provide an opening shutter reliable, complete and fast when the extinguishing system comes into operation without risk of injury for the staff intervention and exploitation.

The extinguishing systems with water fog, especially those with local or regional flooding, fixing nozzles must be safe, to prevent their separation.

Both through the placement and installation of the plant, and through the protective measures to protect against mechanical damage nozzles, thermal effects and mutual influences during their triggering.

To avoid clogging of the nozzles for spraying water holes, on the ramifications of pipeline network on which they are installed, they are provided with water filters.

For replacing the fine water spray nozzles, damaged or triggered in case of fire, a reserve of nozzles of the same type and with the same characteristics are provided as follows:

  • for systems with up to 50 nozzles, the nozzles reserve is at least 3;
  • for systems with 51 to 300 nozzles, the reserve is at least 6 the nozzles;
  • for systems with 301 up to 1,000 the nozzles, the reserve is less than 12 the nozzles;
  • for systems with more than 1,000 the nozzles, the reserve is at least 24 the nozzles;

The type of nozzles are hosen from the manufacturer’s catalog depending on the type of installation (high, medium or low pressure) and the release mode so that intensity values spray with water mist to be higher or at least equal to the intensities of the fire extinguisher.

Depending on the nature of the combustible materials, namely their extinguishing intensity values ??(ranging between 0.07 and 0.17 l/sm2 l/sm2), it is recommended that simultaneous trigger nozzle area, A (s), not to exceed 200 m2.

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