Example Problems


Problem Statement:
A small fire protection system is to be modeled. The sprinkler system is supplied from city water. The sprinkler headers are maintained pressurized using an air-loaded tank (minimum pressure of 50 PSIA). This tank provides the initial pressure source and water volume until the two parallel pumps are up to speed.

The sprinkler system protects three floors of the building. Each floor consists of a single header (including both a 4 inch section and a 2 inch section) which supplies 8 sprinkler nozzles (at approximately 15 foot intervals). The system is to be designed so that the sprinklers on all three floors can be supplied at the same time. The sprinkler nozzles are designed to provide a minimum of 15 GPM with an inlet pressure of 25 PSIA. Further, inlet pressure to the nozzles must be maintained less than 40 PSIA to maintain a safe flow rate out of the nozzles.
The question to be answered is whether the initial tank pressure (50 PSIA) is sufficient to meet the design constraints at the nozzles.

The network layout is built first. Since all three floors are similar, a single floor layout is first constructed and then copied to create the other two floors. The remainder of the hardware is then added.

The fluid is then specified. For flow information, the tank pressure (50 PSIA) and the nozzle discharge pressures (14.7 PSIA) are specified. DesigNet will then automatically calculate flows to each nozzle. By displaying the flow rates, it can be quickly determined whether the tank pressure is sufficient to meet the design constraints listed above.

Printouts can include graphical reports showing the network layout and flow values (pressures and flow rates, amongst others).