The LWF Blog
Facilities Management & Fire Safety – Sprinkler Systems – Part 6
May 4, 2017 1:06 pmIn this Fire Safety blog series for those who work in facilities management and have a responsibility for, or interest in, fire safety, we have been discussing fixed firefighting systems in general and most recently, sprinkler systems. In Part 5, we began to look at the principles of sprinkler operation and how they differ in buildings or areas where there is cold storage. In Part 6, we’re talking about how sprinkler systems work.
The sprinkler system is controlled by the main valve set which consists of an installation stop valve and an alarm valve. The alarm valve is triggered when the sprinkler head opens. Water flows down into the installation and the alarm valve allows water to travel into small-bore pipes which lead to a water-driven gong which is often located outside the building. This provides a warning.
In cases where the sprinkler system is connected to a fire alarm system, a pressure switch may be fitted which connects the two. This allows the fire alarm system to become operational when the sprinkler is activated. Additionally, flow switches may be included and fitted to installation pipes in order to activate the fire alarm system or to provide a control panel with detailed information about the location of a fire.
A good example would be a sprinkler installation which serves several areas, shops or rooms. While a pressure switch would indicate that the system was discharging water, and thus there was a fire, a flow switch in the pipework to each area would indicate where the sprinkler head was operational and therefore, which compartment the fire had originated.
Some installations can be classified as ‘pre-action’ and this means that upon operation of an automatic fire detector, the dry pipework is charged with water so it is ready to operate as needed, even if the detection system fails to operate. Such systems can also operate as dry installations, as discussed in Part 5 of this series.
More commonly, however, the system is configured so that the pipework only becomes charged with water ready for operation, if a fire detector is triggered. A pre-action valve set can however prove an expensive option.
A pre-action system is usually only seen in cases where it is deemed necessary, such as an area where water damage might be a major concern in case of accidental damage to sprinkler heads or there is a requirement to speed up the operation of a dry system. Where a pre-action system is necessary, requirements on the interface between the system and the fire detection and alarm system can be found in BS 7273-3.
In Part 7, we will look at the design principles of sprinkler installations. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact Peter Gyere in the first instance on 0208 668 8663.
Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.