Modelling hydrant flows

You can switch on Hydrant Mode at a Basic Node or Hydrant Node to model hydrant discharge flows as part of a fire flow or mains flushing analysis.

A time-varying Hydrant Opening profile for the node is set using a series of date-time / flow value pairs. The feature uses pressure dependant theory to calculate the relevant flow discharge.

To model hydrant flow:

1. Open the property sheet for the appropriate node and choose the Hydrant Flow Profile Page. If the Hydrant Flow Profile Page is not visible, click the Add Control button to add control parameters for the node.
2. Enter the time varying profile for the hydrant using the Hydrant Flow grid. Enter a series of dates and times in the Date Time column, and for each time set the percentage opening in the Opening column.
3. Check the Linear Profile box for linear interpolation to be used between data points. If this box is unchecked each percentage opening value entered is maintained until the next date / time entry, or until the end of the simulation.
4. Select an option for extending the profile before the first time defined in the grid:
   • Extend Back - The first value in the grid is extended back to the start of the simulation
   • Extrapolate Back - Applies to Linear Profiles only: the first two values in the grid are used to extrapolate back to the start of the simulation.
     Note: If Extrapolate Back is selected for a non linear profile, the profile will be extended back.
   • Zero/Unchanged - A value of zero or "off" is applied from the start of the simulation until the date / time of the first value in the grid
5. Select an option for extending the profile after the last time defined in the grid:
   • Extend Forward - The last value in the grid is extended to the end of the simulation
   • Extrapolate Forward - Applies to Linear Profiles only: the last two values in the grid are used to extrapolate forward to the end of the simulation.
     Note: If Extrapolate Forward is selected for a non linear profile, the profile will be extended forward.
6. Check the Repeat Profiles box to repeat the first 24 hours of the defined profile for the duration of the simulation
7. Decide whether local demand is to be applied to the node during simulation by setting the Keep Local Demand checkbox on the Node Control Page of the property sheet. The two options are:
   • Checked - any demand assigned to the node on the Node Demand Page (eg customer point demand), will be applied in addition to the Hydrant Operation. Therefore when the hydrant is disabled local demand will be supplied.
   • Unchecked - demand that will be applied to the node will be due to Hydrant Operation defined on the Hydrant Flow Profile Page and any exceptional demand defined on the Exceptional Flow Profile Page . (If the hydrant is shut and exceptional demand is zero, local demand will be applied).