The LWF Blog
Facilities Management & Fire Safety – Sprinkler System Heads – Part 11June 8, 2017 10:24 am
In this blog series for those who work in Facilities Management with an interest in or responsibility for fire safety, we have been looking at the nature and components of a fixed fire-fighting system. In Part 10, we discussed how water supplies for sprinkler systems are classified and graded and what this means for the fire protection level. In Part 11 we’re going to talk about sprinkler heads and how they work in practice.
There are two main types of sprinkler heads, both of which are in general use and are acceptable. The first is Fusible link sprinklers which become operational when heat from a fire melts a soldered link holding the valve closed, thus opening it and allowing water to pass through.
The second is a glass bulb sprinkler head. In this case, heat from a fire causes liquid contained within a glass bulb to heat, expanding the liquid which ultimately breaks the fragile glass and releases the valve to let water pass through.
Positioning of sprinkler heads is dependent upon usage and also aesthetics. Most conventional heads can be mounted as pendent or upright, when the water is discharged, it first hits a plate which deflects it upward and downward to ensure the ceiling is wetted as well as discharging onto the area of the fire. In the case of spray heads, the discharge of water is predominantly downwards.
In some instances, it may be that protruding sprinkler heads are undesirable from an aesthetic point of view or for any other reason. In those cases, it is possible to use flush, recessed or concealed sprinklers. In these circumstances, flush heads are mounted so that a part of the sprinkler head is above the plane of the ceiling, but the heat sensing element remains below the ceiling.
Recessed heads differ in that all or part of the sensing element is above the ceiling too. A concealed sprinkler is in actual fact a recessed sprinkler, but with a cover plate which falls away when the head is exposed to the heat of fire.
While the three types of sprinkler mentioned are useful from an aesthetic point of view, none would be suitable to protect against a high-hazard risk.
Another type of sprinkler which would not be suitable for high-hazard risks is sidewall pattern sprinklers. These sprinklers are mounted in the plane of a wall rather than from a ceiling and throw water outwards when they become operational. The most likely place these will be used would be a corridor or small room, in lieu of ceiling placed heads.
In Part 12, we will continue looking at sprinkler heads and will discuss the effect of temperature on their operation. 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.