The LWF Blog

Fire Safety for Facilities Management Personnel – Drencher & Water Spray – Part 243

March 11, 2024 12:20 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 242, LWF talked about the recommendations for daily and weekly inspection and test routines for sprinkler systems. In part 243, we look at the types of sprinkler systems known as drencher systems and water spray systems.

Drencher Systems

A drencher system is a type of sprinkler system, but rather than being designed to protect the inside of a building, drenchers are commonly installed to protect the outside. The main purpose of a drencher system is to prevent fire spreading from a closely adjacent building to the protected building. Once activated, it will discharge water over windows and other wall openings that may allow fire to access the building.

The drencher system heads can be of the sealed type and operate in the same way as sprinkler heads – by forming an extension to the existing sprinkler system installation. However, the heads of a drencher system may also be open and actuated either manually or automatically by a separate detection system.

As with sprinkler systems, open heads can only be used where there is no chance of the water freezing in the supply pipes due to low temperatures.

Water Spray Systems

A water spray system is either a high or medium-velocity system designed to discharge where there is a fire risk due to flammable liquids. The systems may be automatically discharged, or they may be designed to allow manual control over discharge.

High-velocity spray systems are designed to extinguish fires in non-water-miscible liquids which have relatively high flashpoints (66 ºC and above). Large water droplets are produced by the high-velocity spray nozzles with a diameter of around 1.5-2.5 mm. The large droplets are able to penetrate the up-draught from the fire and cool the liquid until it is extinguished.

The water spray system is designed to work as a deluge, meaning that a group of nozzles in the affected area open simultaneously.

Some environments in which a water spray system might be employed include rooms containing oil-filled transformers, diesel generators and oil-fired boilers.

In part 244 of this series, LWF will continue talking about water spray systems, turning our attention to medium-velocity spray systems. 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.