Understanding Fireflow Analyses

Step-by-step:

InfoWater Pro provides comprehensive fireflow modeling capabilities to identify hydraulic vulnerabilities due to proposed operational changes. Fire demand requirements for hydrants can be specified based on:

• various types of building structures
• land use
• fire marshal or city requirements

The fireflow modeling process in InfoWater Pro is a batch analysis of:

• all nodes with a fireflow demand assigned
  OR
• all nodes within a domain with a fireflow demand assigned

The basic fireflow analysis is a two-step process that automatically assigns the fireflow demand to each junction (or hydrant) and solves for the residual pressure. It then sets the residual pressure to the specified value and solves for the resulting flow. Users can then determine the available pressure at the desired fireflow demand and the available flow at the minimum residual pressure.

Fireflow demands are assigned to a selected junction node using the Model Explorer Tools drop-down, or a common fireflow demand can be assigned to all junction nodes in the current network domain by using Group Editing.

Fireflow demands are set based on the units you set in the Simulation Options and will match whatever your junction demands and flow units are. So, for example, if you set your flow units to gallons per minute, then you could assign demands such as 1500 gpm for new homes. You could assign 1000 gpm for some legacy areas, or 500 gpm for older areas with smaller pipes.

Fireflow simulations are set up and run in the Run Manager, on the Fireflow tab:

• Standard Fireflow Run
• Design Fireflow Run

Standard Fireflow Run example:

• Residual Pressure (20 psi, for example), for each hydrant (junction node) in the modeled fireflow set
• Time
• Duration
• Maximum Velocity constraint for the assigned pipes (connecting pipes or domain pipes)

TIP: Click Edit Fireflow Table to open the DB Editor, where you can edit fireflow settings for all junctions selected for the simulation.

In the Report Manager, Fireflow Standard Report, there are 2 key fields:

1. Residual Pressure: if below the Residual Pressure set in the Run Manager, this is an indication that the location cannot support the required fireflow assigned.
2. Hydrant Available Flow: represents the flow rate which creates the specified residual pressure at the junction.
   

A Design Fireflow Run example:

• set a Minimum Pressure so that pressures are not substantially reduced elsewhere in the system
• with or without velocity constraints

In the Report Manager, the Fireflow Design Report displays:

• the minimum pressures in the critical node searching range
• returns a design flow to be used as a maximum available fireflow
• maintains minimum pressures in the distribution system
  

Multi-Fireflow: Fireflow analyses where more than one hydrant is opened are simulated in the Run Manager.

• useful for examining fireflow either in a steady state or an extended period analysis
• can be used with an EPS simulation in which one or more fire demands are evaluated over a period of time
  

Hydrant Curve analysis: A fire hydrant rating curve that shows the relationship between residual pressure and the available flow for any hydrant:

• often required by fire departments responsible for ensuring that a specific hydrant can adequately control a potential fire demand and maintain minimum pressure
• resulting graph details how the hydrant will operate at any given flow rate
• any breaks in the curve are caused by a change in operation at the specified flow rate