The LWF Blog

Fire Engineering Design and Risk Assessment – Sprinkler Heads – Part 21

November 16, 2017 10:53 am

In this Fire Engineering Design and Risk Assessment blog series for Architects or those who work in building design, we have been looking at sprinklers in terms of the variety, composites and uses. In Part 20, we discussed how sprinkler systems could be used as part of a fire engineered solution in order to accommodate longer travel distances, based on available and required safe egress times. In Part 21, we will give an overview of some of the other devices which may be employed to vary a sprinkler system for purpose.


Multiple controls are valves held in the closed (off) position, controlled by a heat-sensitive device. When the heat-sensitive device is triggered, water is fed to already open sprinkler heads or spray heads.


A medium-velocity sprayer is designed to produce a directional spray of fine water droplets. The purpose is to control a fire which involves combustible liquids and gases, both of which have low flashpoints. The water spray is able to cool the surface of the vessels.


A high-velocity sprayer has open nozzles which can produce a directional spray consisting of larger droplets. This works to extinguish fires involving combustible liquids with higher flashpoints.


In order to avoid water accumulating in the pipe leading to the sprinkler head and potentially freezing in place (which would make the system of no use and might damage the pipes), dry pendent sprinkler systems are constructed of pipes with a valve at one end and a sprinkler head at the other. When the sprinkler head becomes operational, the bottom end of the drop pipe opens the valve at the top and this allows water to pass down the pipe to the outlet. Dry pendent sprinklers are usually found in either dry or alternately wet and dry systems, or pre-action systems.


Dry upright sprinklers can also be found, but less commonly than dry pendent systems. Such sprinklers are similar in design to standard dry pendent sprinklers and would be used to avoid either pipe scale and sediment settling in the bottom of the sprinkler pipe, which could cause an obstruction over time, or water condensation/water remnants left over after draining the system could fill the pendent or sidewall sprinkler, causing it to freeze when the temperature drops.


Window drenchers can be employed to prolong the resilience of fire-resistant glazing. Such sprinkler systems are designed to maintain the structural integrity of the window for longer in a fire situation and therefore avoid the spread of fire to another compartment or adjacent building.


In part 22 of this series, LWF will look at the thermal sensitivity of sprinkler heads. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.


Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.


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