You are currently reviewing an older revision of this page.
How does the Automated Fire Flow analysis feature work?
The automated fire flow analysis will perform a series of independent steady state calculations, with the various extra demands applied to your fire flow nodes. It first runs a steady state analysis on the scenario in question, with the Fire Flow (Needed) value you entered in the Fire Flow alternative flow applied only to one of your fire flow nodes. It checks the resulting pressure at that node, at other nodes in the same zone, and (if desired) pressure at all other nodes in the model and velocities in the pipes. If these are within the constraints specified in your Fire Flow alternative, it will add a little bit more demand to that node, check the pressures, and repeat, until the pressure constraints are violated or the demand reaches the Fire Flow (Upper Limit) specified in your Fire Flow alternative. Then it reports this Fire Flow (Available) and moves on to the next fire flow node, performing the same steps.
If the pressure constraints (or the optional velocity constraint) are violated when the Fire Flow (Needed) value is applied, the program will start to use smaller flow values until the pressure or velocity constraints are not violated. If negative pressures occur, the available fire flow reported may be zero or simply the base demand applied to the fire flow node. The Fire Flow (Available) will then be reported as above.
If the Fire Flow (Available) is at or above the Fire Flow (Needed) value, the program will report that the fire flow run was successful by setting the field "Satisfies Fire Flow Constraints" to True. If the Fire Flow (Available) is below Fire Flow (Needed), "Satisfies Fire Flow Constraints" will be set to False. The TechNote Understanding Automated Fire Flow Results can be used to review the results and understand what you may see after computing the run.
If you are looking for step by step direction on how to setup the Automated Fire Flow analysis please refer to the Quick Start lesson titled "Automated fire flow analysis" that is located in the Help documentation that comes with the software (File > Help > Quick Start Lessons for CONNECT Edition, Help > Quick Start Lessons for V8i).
You will also need to consider tank level and element status. Since automated fireflow is a series of steady state simulations, they will use the initial status of elements such as pumps and valves and the initial level of tanks. You'll want to consider what to assume for those things. For example a conservative assumption might be to assume a particular pump is off and/or a tank level is low at the time of the fire (note: for assessing tank capacity for fire fighting, see Running a fire flow analysis in EPS (Extended Period Simulation) However, there is some uncertainty here, as seen in this forum discussion.
Understanding Automated Fire Flow Results
WaterGEMS V8 Automated Fire Flow FAQ