The New Fire Flow Updates to InfoWater’s Version 11.5

InfoWater’s fire flow tool has been updated to simplify the use of the tool and the results. Fire flow can be evaluated two ways using a standard fire flow run or a design fire flow run. A standard fire flow run maintains the residual pressure at the hydrant and the design fire flow run maintains the residual pressure at the hydrant and at the selected critical nodes. The first update made to the tool was simplifying between these two runs.

The standard fire flow run uses the residual pressure option and calculates the available flow at the hydrant only maintaining the residual pressure at the hydrant. During a standard fire flow run, the user can select the time of day, the duration of the fire flow, the maximum velocity for selected pipes, and generate hydraulic reports for any elements in the system. The options are shown below in the blue highlighted area.

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An example of the standard fire flow results is shown below.

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ID – Hydrant (Junction node) identifier.

Static Demand – This field displays the Static or the Basic Demand imposed on the Junction.

Static Pressure – This represents the static pressure corresponding to the static demand.   This pressure indicated the pressure at the hydrant when it only supplies the Static Demand. The Fire Flow Demand for the hydrant is not assigned while calculating the Static Pressure.

Fire Flow Demand – This is the Fire Flow demand imposed by the user.

Residual Pressure – This represents the resulting pressure because of a sum total of the Static Demand and the Fire Flow demand.

Available Flow @ Hydrant – The maximum flow that is available while maintaining the user-specified minimum residual pressure at the current node, assuming that only this hydrant (node) is flowing.

Available Flow Pressure – Residual pressure calculated for the available flow at the current hydrant (node). This value should equal the residual pressure specified by the user (20 psi).

The design fire flow run is activated by selecting the “Design FireFlow” option shown below. The design fire flow option calculates the available flow at the hydrant maintaining the residual pressure in addition to maintaining the residual pressure of any nodes within the critical node searching range. The critical node searching range has three options – fire flow nodes, domain nodes, or entire network. During a design fire flow run, the user can also select the time of day, the duration of the fire flow, the maximum velocity for selected pipes, and generate hydraulic reports for any elements in the system. The options are shown below in the blue highlighted area.

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The second update is to the design fire flow results report. The report has been changed removing the second evaluation of the critical node and incorporating the velocity constraint to the design fire flow calculation. An example of the new design fire flow report is shown below:

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ID – Hydrant (Junction node) identifier.

Total Demand – The total nodal demand at the fire flow simulation timestep. This value corresponds to the sum of the baseline demand (Static Demand) and the fireflow demand (Fire-Flow Demand) for the selected timestep.

Available Flow @ Hydrant – The maximum flow that is available while maintaining the user-specified minimum residual pressure at the current node, assuming that only this hydrant (node) is flowing.

Critical Node ID – Junction node within the Critical Node Searching Range with the lowest pressure when the current junction is loaded with the total demand.

Critical Node Pressure – The calculated pressure at the Critical Node.

Critical Node Head – The calculated head at the Critical Node.

Design Flow – The maximum flow available while maintaining the user-specified minimum residual pressure at the hydrant and the critical node searching range. Ultimately, the Design Flow as it is the least flow value of all considered residual pressures.  This is the value that an engineer would provide to a local fire department by saying this is the maximum (theoretical) flow possible at the subject junction in order to maintain 20 psi at all times in the distribution system. The Design Flow will now take into consideration the maximum velocity constraint if selected.

 

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