Fire sprinkler systems use water to suppress, and in best case scenario to extinguish, fires in buildings. Piped systems are used to distribute the media throughout the building to wherever the fire is present. Sprinklers can be made in various designs to perform different spray patterns, time of response, pressure, droplet size and so on.
Fire sprinkler installations must comply with fire protection standards, which there are legislative and mandatory provisions to indicate requirements for planning, installation and maintenance of fire protection systems. Fire protection standards can be written by independent organisations, insurance associations or government authorities to minimise the possibility and effects of fires.
European countries intend to harmonise the EN standards across Europe, instead of having individual a fire standard in each country.
Fire protection standards describe:
- Planning (buildings, hazard types, design criteria’s, water supplies, components)
- Installation (type, design characteristics, pipework, commissioning)
- Maintenance (user inspection and test, service and maintenance schedule)
The building owner will decide the standard to be used in collaboration with the insurance company and local authority having jurisdiction (AHJ).
Fire sprinklers can be automatic or open-orifice. Automatic sprinklers are activated by heat that breaks the sensing device keeping the sprinkler closed. The water from the pipe comes through the sprinkler and hits the deflector and gives a water spray.
Automatic fire sprinklers operate at a predetermined temperature, utilising a fusible element, that either melts or breaks the glass bulb containing liquid, allowing the plug in the orifice to be pushed out by the water pressure. This results in a water flow from the orifice.
The water hits a deflector, which produces a specific spray pattern designed according to the sprinkler type. Most automatic fire sprinklers are activated individually by heat from a fire. Automatic fire sprinklers have glass bulbs, which comply to a standardised colour coding indicating their activation temperature. Fire sprinklers are selected in accordance of the building hazard.
Design of the sprinklers are described by the fire standard authorities such as NFPA and VdS.
Deluge fire sprinkler systems have open orifice sprinklers where all sprinklers operate at the same time. The open orifice sprinklers are similar to the automatic sprinklers but without the heat sensitive element.
A special sprinkler type for mainly residential occupancies, where a fast response is lifesaving, is the ESFR (Early Suppression Fast Response) sprinkler. This sprinkler has a very fast response time and opens quickly compared to normal sprinklers.
Sprinkler water supply
The water supply to the fire pump in fire sprinkler installations must fulfil the requirements for flow, pressure and duration. Sources can be public water mains, water storage tanks and inexhaustible sources such as lakes, rivers and canals.
Sufficient water supply to fire pumps is essential. Depending on the hazards, single or duplicate water supplies have to be installed to ensure adequate and reliable water source for the fire pumps. A duplicate water supply could be from two different public water mains or one public water + one storage tank. There is typically one suction line installed to each fire-pump from the water supply to avoid interference between the pumps. These design criteria are described in the various fire sprinkler installation standards.
The water must be free of objects and sufficiently clean to be handled by the fire sprinkler installation. In order to avoid undesired objects getting in to the system a strainer located at the inlet to the suction pipe for the fire pumps should to be installed. Or ideally a strainer is fitted on any suction pipework that feeds into a break tank to prevent any sediment from building up in the stored water.
Most installations prescribe a max 40 °C for water supply temperature and 25 °C for submersible fire pumps.
Grundfos supplies fire pumps for water supply as part of approved fire sprinkler systems for industrial and commercial fire protection.