Firewater Systems

Increasing safety efficiently 

Firewater Systems are essential for any large building or industrial installation. A typical system contains wet and dry piping. And may include a combination of sprinklers, hydrants, and monitors to provide water and foam to areas affected by a fire. 
The following activities may be part of the design and analysis or your firewater system:

Insufficient sprinkler coverage

In this example, the red area needs to be fully covered by the water from the sprinklers. Obstacles and spacing can be an issue in relation to spray coverage. In this case, the sprinkler lay-out will need to be redesigned in order to fully cover the red area. 

Sufficient sprinkler coverage

When the sprinklers are moved closer together and the obstacle is removed, the red area can be fully covered by the sprinklers. Alternatively, it might be required to add sprinklers underneath the obstacle. In this case the spinkler coverage is sufficient. 

1. Sprinkler lay-out design

The result of the firewater demand calculation provides an estimate for the minimum required flow rate on the specified areas. It is important that sprinklers, hydrants and monitors are positioned so that the entire surface area is covered by their spray patterns.

Depending on the geometries, this may require more sprinklers than strictly necessary to achieve the minimum flow rate. An improved sprinkler layout design provides recommendations for the optimal nozzle types, spray angles and positioning to ensure the safest and most efficient design.

2. A code compliant design

DRG is experienced with a range of international design codes and standards, and has designed large scale firewater and foam deluge systems with designs class certified by DNV.

We base each design on the clients’ Active Fire Protection Philosophy, and make sure the design complies with the applicable international codes and regulations. If necessary, additional guidance may be taken from various applicable class requirements, codes and standards such as DNVGL-OS-D301, NFPA and ISO 13702.

The code requirements will form the basis for the firewater demand calculation and the firewater system layout design.

3. Firewater demand calculation

A firewater demand calculation is performed to determine the amount of water required to provide sufficient coverage on specific areas and equipment. 

The firewater demand calculation is a starting point for the design of a any firewater system. It gives a good indication of the flow requirements and the number of spray nozzles, hydrants, and monitors required at different areas. 
The results of the demand calculation will form the basis for the detailed system design.

4. Dynamic load analysis

A firewater deluge system consists of an empty pipe network connected to sprinklers and/or monitors. A control valve separates the empty pipe system from a dedicated water supply. When firewater/foam is required, the control valve opens and water fills the empty pipes, activating sprinklers and monitors.

Filling of the initially dry system can result in high dynamic loads on the piping, as the waterfront moves through the system and changes momentum through each bend. When the waterfront finally reaches a sprinkler or monitor at the end of the line, the sudden flow restriction can cause pressure surges resulting in high unbalanced loads.
DRG has more than 40 years of experience in solving surge problems, that often occur in deluge systems. Our inhouse developed professional software solution BOSfluids is used to analyze the interaction between the fluid, the pipe and the structure.

Read more about a pressure surge analysis here.

5. Hydraulic calculation

The hydraulic calculation is performed to ensure that the piping can accommodate the water required at peak demand, and that sufficient flow reaches all areas of the system. The analysis is carried out using our inhouse software solution BOSfluids. A detailed 3D model of the piping, nozzles, hydrants, and monitors is created, for which a steady state flow analysis is performed.

The hydraulic calculation will give a clear picture of the pressure distribution and flow rate throughout the system. Based on the results, we will provide recommendations regarding line sizing, nozzle selection, and any required changes to the system lay-out.