The LWF Blog
Facilities Management & Fire Safety – Sprinkler System Heads & Heat – Part 12June 15, 2017 3:29 pm
In this blog series for those who work in Facilities Management and who have a responsibility for or interest in fire safety, we have been looking at how sprinklers operate in buildings and in Part 11, we began to look at sprinkler heads. In Part 12, we’re going to discuss the effect of temperature on the operation and design of sprinkler heads and how the choice of the most appropriate type of sprinkler head can have a positive effect on the sprinkler system.
Throughout the world, sprinkler heads are manufactured with a range of standard operating temperatures. In the United Kingdom, the heads operate when they reach 68°C most commonly. The heads incorporate a glass bulb which contains a coloured liquid, this indicates the temperature of operation for the sprinkler head. UK heads have bulbs which contain red liquid. On occasion, it is possible that the yoke arms of fusible link heads will be coloured to indicate temperature of operation, rather than the liquid inside the bulb.
When a fire starts in a place with a sprinkler system, the temperature of the sprinkler head and the temperature of the surrounding air can be significantly different. The sprinkler head may take a little time to become heated by the hot gases which rise from the fire. As different designs of sprinkler head may heat at different rates, this can mean that two heads which are rated the same temperature for operation might begin working at different times. The delay may only be slight and acceptable in lower risk circumstances, but should be taken into account.
To reduce the chances of this occurring in situations which require fast reaction times, such as high hazard storage or residential units, the use of ‘quick response’ heads with a low thermal inertia can be used. This time saved can be valuable and this is demonstrated by the suggestion that design fire size for smoke control systems might be reduced on the basis of using ‘quick response’ heads.
The Factory Mutual Insurers in the United States created a particularly fast response sprinkler system for use with ceiling sprinklers to reduce the high risk in storage facilities. The Early Suppression Fast Response System (ESFR) is now recognised by insurers within the United Kingdom too, however, the design of such systems means that they are less forgiving of building features which can affect sprinkler efficiency than the traditional ceiling and in-rack sprinkler installations.
In Part 13 of this series, we will give an overview of the importance of the location and placement of sprinkler heads as part of the sprinkler system within your buildings. 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.