Technical Article

Sprinklers Fire Protection

Sprinkler systems are by far the most widely used and most reliable automatic fire protection system in New Zealand and historical data indicates that sprinkler systems have a 99.5% record of reliability.

Sprinklers automatically detect an outbreak of fire in the early stages of development, give an alarm of fire to the occupants of the building, transmit a call of alarm, control the outbreak of fire until it can be fully extinguished and in many cases sprinklers extinguish the fire before the arrival of the fire service.

 

Automatic sprinklers provide a significant level of protection for the occupants of a building and protection of the environment by minimising the effects that a major structural fire could have. They also safeguard against the loss of plant, machinery, equipment and building contents as well as protecting business by mitigating loss of continuity of operations and production.

 

A great number of myths have been created in respect of sprinklers and firefighters are often asked questions related to the operation and effectiveness of systems.

 

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 swithgear 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 1980’s 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 1980’s and early 1990’s 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.

 

Firefighters are often asked to give an opinion on the best form of fire protection and detection and 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 the web site on www.standards.co.nz
 

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