Sprinklers for fire protection

  Posted on 15th March 2017 by Loralee Hyde in UFBA News

A Technical Artlcle from the NZFBI

A 'firefighter' in every room

SprinklersSprinkler systems are the most widely used and most reliable automatic fire protection system in New Zealand.

Historical data indicates sprinkler systems have a 99.5% record of reliability.

Benefits of sprinklers

Sprinkler systems:

Automatic sprinklers provide:

Myths

A great number of myths have been created in respect of sprinklers.

Firefighters are often asked questions related to the operation and effectiveness of systems. Here are some explanations about the protection and detection sprinklers provide.

Sprinklers will cause severe water damage during a fire or if they leak

Less water damage will be sustained in a sprinkler protected building as the sprinkler detects the fire in its early stage and discharges an average of 75 litres a minute.

Systems also incorporate a water flow alarm and direct connection to a monitoring agency gives notification of any accidental water flow.

When a fire occurs in a building, all the sprinkler heads operate

Each sprinkler head is a thermally operated detector and only reacts when the heat from a fire causes individual heads to open.

They only operate when there is sufficient heat in the immediate vicinity. 65% of all sprinkler-controlled fires required the operation of only one head.

There is an electrical shock hazard associated with electrical equipment and sprinklers

There is a widely held belief that water discharging from sprinklers onto electrical equipment is undesirable. This is not correct - where switchgear and other electrical equipment is installed statistics indicate that it is not necessary to take special precautions as it is more important to control the fire promptly

Tests with sprinklers discharging onto electrical equipment have concluded that the induced currents even in 480 volt 3 phase power were relatively small and posed no appreciable shock hazard.

Smoke generation is increased by sprinklers

Sprinkler operation is automatic and occurs in the early stages of fire development. A fire that is controlled by sprinklers will generate less smoke than fires in non-sprinklered buildings were an extended development period can occur due to the lack of early detection and control factors.

It is correct that between a fire starting and the time a sprinkler head operates there can be a build up of products of combustion including heat and smoke at ceiling level. When a sprinkler operates some products of combustion are driven toward the floor and some of the water is converted into steam

It is also true that fires controlled by conventional hose lines also create a situation of incomplete combustion generating smoke and steam.

Steam generated by a sprinkler-controlled fire can cause burns

The amount of steam generated in extinguishing a fire is the same whether it comes from a sprinkler head or a conventional hose line. It can be assumed that considerably less water will be used for a sprinkler controlled fire. Therefore, although the heat absorbed is the same, less water will be used to achieve the same result.

The more efficient use of water can create an impression of excess steam generation but this will not necessarily increase the likelihood of steam burns.

Sprinkler heads can operate spontaneously in non-fire conditions

Sprinkler technology has advanced since the 1980s and the common sturdy 8mm sprinkler bulb used predominately at that time posed very few handing problems because of the strength and construction of the bulb.

In the late 1980s and early 1990s development of the more closely engineered 3mm fast response bulb and move toward residential sprinkler systems introduced a need to improve past handing and installation procedures.

There have been a few occasions when rapid response sprinkler heads damaged due the method of handling and installation have activated. However, strict handling procedures and installation instruction, pre-assembled droppers and using the correct tools for 3mm fast response sprinkler heads have all but eliminated this problem.

Conclusion

Firefighters are often asked to give an opinion on the best form of fire protection and detection. There is no doubt that a combination of smoke detection and automatic sprinklers is by far the best option.

Note: The New Zealand Standard Drafts DZ 4517 Fire Sprinkler Systems for Domestic Occupancies and DZ 4514 Smoke Alarms are both out for public comment at the present time. Check out www.standards.co.nz

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