The Fire Flow Alternative contains the input data required to perform a fire flow analysis. This data includes the set of junction nodes for which fire flow results are needed, the set of default values for all junctions included in the fire flow set, a description of constraints that must be met and a record for each junction node in the fire flow set.

The Fire Flow Alternative window is divided into sections which contain different fields to create the fire flow. These fields include:

The Fire Flow Alternative window is divided into sections which contain different fields to create the fire flow. These fields include:

Velocity (Upper Limit): The maximum acceptable velocity that must not be exceeded for any pipe. This is used if the “Use Velocity Constraint” box is checked and is applied to any pipe in the Pipe Set which by default is All Pipes.

Velocity (Upper Limit): Specifies the maximum velocity allowed in the associated set of pipes when drawing out fire flow from the selected node.

Pipe Set: The set of pipes associated with the current node where velocities are tested during a fire flow analysis.

Fire Flow (Needed): Flow rate required at the junction to meet fire flow demands. This value will be added to the junction's baseline demand or it will replace the junction's baseline demand, depending on the default setting for applying fire flows.

Fire Flow (Upper Limit): Maximum allowable fire flow that can occur at a withdrawal location. This value will prevent the software from computing unrealistically high fire flows at locations such as primary system mains, which have large diameters and high service pressures. This value will be added to the junction's baseline demand or it will replace the junction's baseline demand, depending on the default setting for applying fire flows.

Apply Fire Flows By: There are two methods for applying fire flow demands. The fire flow demand can be added to the junction's baseline demand, or it can completely replace the junction's baseline demand. The junction's baseline demand is defined by the Demand Alternative selected for use in the Scenario along with the fire flow alternative.

Fire Flow Nodes: A selection set that defines the fire flow nodes to be subject to a fire flow analysis. The selection set must be a concrete selection set (not query based) and must include the junctions and hydrants that need to be analyzed. Any non-junction and hydrant elements in the selection set are ignored.

Pressure (Residual Lower Limit): Minimum residual pressure to occur at the junction node. The program determines the amount of fire flow available such that the residual pressure at the junction node does not fall below this target pressure.

Pressure (Zone Lower Limit): Minimum pressure to occur at all junction nodes within a zone. The model determines the available fire flow such that the minimum zone pressures do not fall below this target pressure. Each junction has a zone associated with it, which can be located in the junction's input data. If you do not want a junction node to be analyzed as part of another junction node's fire flow analysis, move it to another zone.

Use Minimum Pressure Zone Constraint?: Check whether a minimum pressure is to be maintained throughout the entire pipe system.

Pressure System Lower Limit: Minimum pressure allowed at any junction in the entire system except of the nodes in the optional applied ‘Nodes To Exclude’ set as a result of the fire flow withdrawal. If the pressure at a node anywhere in the system falls below this constraint while withdrawing fire flow, fire flow will not be satisfied.

Nodes to Exclude: An optional set of nodes that should be excluded from checking the selected pressure constraints. In case that the base calculation of the active fire flow scenario without applying any fire flow demands already violates at least one of the pressure constraints for some nodes, these nodes needs to be added to a new selection set and taken as the set of nodes excluded from the pressure constraints checking. Note that this is only sufficient, if these nodes are not included in the list of fire flow nodes or the individual residual pressure values of these nodes are set to a pressure value below the pressure result of the base compute, else these nodes additionally need to be removed from this node list.

Fire Flow Auxiliary Results Type: This setting controls whether the fire flow analysis will save "auxiliary results" (a snap shot result set of the fire flow analysis hydraulic conditions) for no fire flow nodes, just the failing fire flow nodes, if any, or all fire flow nodes. For every fire flow node that attracts auxiliary results a separate result set (file) is created. When enabling this setting, be conscious of the number of fire flow nodes in your system and the potential disk space requirement. Enabling this option also will slow down the fire flow analysis due to the need to create the additional results sets.