The LWF Blog

Facilities Management & Fire Safety – Sprinkler System Overview – Part 5

April 27, 2017 2:19 pm

In this fire safety blog series for those who work in Facilities Management, we have been looking at fixed firefighting systems and the relevant design codes affecting their installation and use. In Part 5, we discuss the components of a designed sprinkler system and the principles of its operation within buildings.


A typical wet pipe sprinkler installation comprises a water supply, a main valve set, a network of pipes to feed the water as required and sprinkler heads placed appropriately.


Each of the sprinkler heads contains is sensitive to heat and so will become operational when the area covered reaches a defined temperature. The triggering of the head causes the valve to open and water is discharged into the area via the sprinkler head. Each head works independently of its fellows and so only those heads in the affected area will discharge. In the case of a small fire, it is common for only a few sprinkler heads to activate and this is sufficient to control or extinguish the fire.


There are systems which do not work with the heads independent of each other and these are known as deluge systems. A deluge system is one where all the heads operate simultaneously when one is triggered and such systems are designed to protect special risks and are not seen in general building occupation often.


In the majority of buildings with sprinkler systems installed, the pipework is known as ‘wet’. This simply means that water is contained permanently within the pipes leading to the heads so that when the head becomes operational, water is released immediately.


Some situations, however, would be unsuitable for a permanently ‘wet’ system and these are most likely to be found in unheated warehouses, for example. The reason is that if the weather is sufficiently cold, the water in the pipes could freeze and the system would be unable to perform if the detector was triggered by a fire.


In these cases, it is often the case that during the Summer months, it operates as a standard ‘wet’ system and in the Winter, the water is drained from the pipes and charged with air. In such circumstances, a special alternate valve set is needed which permits water to enter the pipework when the air pressure is lowered by operation of the sprinkler heads.  Of course, in an area such as a cold store where temperatures will be consistently too low for a standard ‘wet’ system, a fully ‘dry’ one as described might be used all year round.


In part 6 of this series, we will continue to look at the operation of sprinkler systems. 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.


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