The LWF Blog

Fire Safety for Facilities Management Personnel – Sprinkler Installation Design – Part 239

February 12, 2024 12:19 pm

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 238, LWF talked about water supplies for sprinkler systems. In part 239, we will discuss sprinkler heads.

A sprinkler head, as part of a sprinkler system, operates in one of two ways:

• Fusible link sprinklers, which open when heat from a fire melts the soldered link holding the valve closed
• Glass bulb sprinklers, which open when heat causes the liquid contained within a glass bulb to expand and exerts pressure until the bulb breaks to release the valve

Most sprinklers can be mounted pendent (hanging) or upright. When active, water is discharged onto a plate and deflected in an upward and downward direction to provide ceiling wetting as well as discharge onto a fire in similar amounts. With ‘spray heads’ the discharge is predominantly downwards.

It is possible to use flush, recessed or concealed sprinkler heads where it would be undesirable to have visible sprinkler heads protruding below a ceiling.

Flush heads are mounted so that part of the head is above the plane of the ceiling but the heat sensing element remains below the ceiling.

With recessed heads, all or part of the sensing element is also above the ceiling.

A concealed sprinkler is a type of recessed sprinkler with a cover plate that falls away when the head is exposed to the heat of a fire.

None of the three types of sprinkler discussed are suitable for the protection of high-hazard risks. In addition, it is possible to install special sidewall pattern sprinklers that are also unsuitable for high-hazard risks. They are mounted in the plane of a wall and throw water in an outward direction. They are suitable for use in corridors or relatively small rooms in lieu of normal sprinklers where this is undesirable.

Sprinkler heads are manufactured with a range of standard operating temperatures. In the UK, it is usual for the temperature to be 68 ºC. The liquid in the glass bulbs is red coloured, to indicate the temperature of operation. The yoke arm of standard 74 ºC fusible link heads is uncoloured. Sprinklers activating at other temperatures are coded by colouring of the liquid in glass bulbs or the yoke arms of fusible link heads to indicate the temperature of operation.

In part 240 of this series, LWF will continue to discuss sprinkler heads. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 35 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

 

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.