The LWF Blog
Fire Safety for Facilities Management Personnel – Sprinkler Installation Design – Part 237
January 29, 2024 12:04 pmLawrence 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 236, LWF talked about high-hazard occupancies, where the risk of fast-spreading fire is greater than in ordinary-hazard occupancies. In part 237, we continue to discuss high-hazard occupancies, classifications and the resulting design of the sprinkler protection installation.
The first step in designing and deciding the specification of a sprinkler installation is to classify the occupancy, as well as the definition of the required design density and AMAO. The process determines the nature of the water supply and the size of pipework required. As the design density and AMAO increase, a greater flow rate will be required from the water supply.
Where the supply is the water authority main, it must be capable of providing the required water pressure and rate of flow. If it cannot, as is normally the case with high-hazard risks or high buildings, then a tank and pump (or multiples as required) must be provided. The minimum required flow rate will determine the rating of the pumps needed.
The system must be capable of supplying water for the minimum specified time and so the hazard classification and rating of the pumps will inform as to the required capacity of the tank(s).
The water must be able to flow at a sufficient rate to the most remote area of the building, for this to be the case, the pipework diameter must be adequate. The hazard category has a major effect on the pipe sizes needed and the cost of the installation.
There are two main methods of establishing and designing the pipework. BS EN 12845 provides schedules of pipe sizes. The second option is for the entire installation to be hydraulically calculated by means of a purpose-designed computer program. The computer-designed installation is likely to result in a more cost-effective installation. It can, however, restrict future changes to the system, but in the case of high-piled storage with in-rack sprinklers, it is essential.
In part 238 of this series, LWF will talk more about water supplies for sprinkler 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