Hydraulic Calculation Examples

ESFR fire sprinkler installation installed into major car manufacturer’s parts facilities and is somewhat bespoke in its design. The roof level sprinklers are ESFR 25mm with a K-factor of 360 and a minimum head pressure of 3.5 bars. In addition, the rack storage below is protected with 20mm sprinkler with a K-factor of 115 and a minimum head pressure of 1.0 bar. The final water demand requirements for the system was 9849 L/min @ 9.0 bar and the design aided by FHC achieved 98% design efficiency.

This FHC hydraulic model consisted of 810 pipes, 154 loops and 26 heads. It was calculated on a Pentium VI computer in under 0.1 seconds.

An FHC hydraulic calculation that demonstrates its capabilities and shows a perfect balance of flows through the pipe network consisting of 106 pipes and 15 loops in its calculation. The system has loops within the loop, four in all. The FHC software easily produced the hydraulic calculations for this system showing its versatility.

Fire sprinkler systems often use tree pipe work configuration in the system design and although this configuration is not as hydraulically efficient as a loop or grid system it still has its uses.

For complex buildings such as schools, residential care homes and systems which require a dry fire sprinkler installation to be installed, a tree system can be the way to go. The pipe work in tree work configurations can be sized in a conventional way by using pre sized pipe tables for the number of sprinkler heads or by fully calculating the hydraulics by hand without much difficulty, but even for small systems, they are still very time consuming and prone to human error.

By using FHC you have all the advantages of full hydraulic calculations in helping you reduce your pipe sizes and/or the water demand. Furthermore, the calculations will not have the human error factor and will only take a fraction of a seconded to calculate allowing you the designer more time to optimises the system and reduce costs.

Deluge installation of any type can be modelled with the FHC program. In this example, medium velocity sprayers are protecting a vertical cylinder. Within the FHC hydraulic model, we specified an area for each nozzle and a minimum design density of 10 mm/min.

A calculation for a high-pressure water mist fire protection system designed to NFPA 750. For high-pressure systems, you should use the Darcy-Weisbach pressure loss equation which can take into account both the fluids absolute viscosity (centipoises) and the density of the fluid.

The water supply can be from a pressurised cylinder, constant pressure pump or any other type of water supply. Custom nozzle and pipe data files can be used for the hydraulic modelling of water mist systems.  Canute can provide customised pipe data files and nozzle data files based on any water mist manufacturer data.

This hydraulic model represents a large storage tank with a fixed cone roof and is protected by three foam chambers. The foam chambers are located above the liquid level of the tank and the deflector is located inside the tank to distribute the foam solution over the surface.
The number of foam chambers is determined by the tank diameter for a fixed cone or open top tank and the flow rate can be calculated by multiplying the area by the required density.

The tank in this example has a diameter of 30m and therefore a surface area of 707m². If we base the design density on 4.1 mm/min this will give us a minimum flow rate of 2899 L/min and will require a minimum of two foam chambers but to give a give faster foam distribution we have used three. Also, the volume of foam from each pourer is also reduced which will allow for a smaller riser pipe to each of the foam chambers. For this design, we have used 80mm Viking Model FC foam chambers and each chamber will protect the 236m² area and require a minimum of 699 L/min discharge. By using the manufacturer's design table we can determine that we will require a minimum pressure of 4.14 Bar at the foam chamber inlet.

With the above information we can now proceed to start the hydraulic calculation for the systems but instead of using a sprinkler or head as the output devices we can specify in FHC the required flow rate and pressure which is required for each foam chamber on our system in the optional items section in the Project Data. When we calculate the hydraulic model in FHC we find that we will require a source duty of 2122 L/min @ 5.525 Bar.

You can find out more information about protection to storage tanks in NFPA 11: Standard for low, medium, and high-expansion foam