Gas supported node elements include junctions, reservoirs, compressors, regulating valves, variable pressure supplies, check valves, valves, metered connections, intermediate nodes, inline meters, and user-defined devices.
Device Inputs and Graphical Description
Device Text Description
Active Valve – A valve for which the open ratio (stem position) may be specified and varied. The program incorporates the Cv (valve coefficient) ratio as a function of stem position for a number of standard valves (ball, butterfly, globe, gate, etc.). Users can provide data for other valve types.
*Check Valve – Inserted into a pipe, this device allows flow only in the specified direction. If conditions exist for flow reversal, the valve closes and the line carries no flow. Active Valves and Compressors may also incorporate Check Valves. Note: the directional arrow should be in the normal direction of flow.
Compressor (Pump) – A connection of one or more pipe links to a Compressor. The Compressor’s characteristics may be defined by constant power or head-flow data.
*Device 1 and 2 – See User-Defined Nodes.
*In-Line Meters – In-Line Meters report flow volume over time. These devices are used during an Extended Period Simulation (EPS).
*Intermediate Node – Inserted into an existing pipe, intermediate nodes allow for changes in pipe direction and/or elevation.
Internal Nodes – Because these are internal to a pipe, they do not stop a pipe and start a new pipe. However, because no new pipe is created by the addition of the internal node and results are not computed for them, they do not add to model overhead. Check valves, hydrants, intermediate nodes, metered connections, on/off valves and user-defined devices are internal nodes.
Junction – A connection of one (dead-end junction) or more pipe links. A junction may be placed at a high or low point in a pipeline to calculate results for these locations. Junctions may incorporate static demands or demand patterns.
Loss Element – An element identical to a Compressor except instead of a head gain, a head loss occurs across this device.
*Metered Connection – A Metered Connection node can be defined at any junction or inserted into a pipe. Each Metered Connection in a model can have several associated meters, each with its own demand, demand type, name, and user data (e.g., address).
*On/Off Valve – A cut-off or isolation valve which can be closed to prevent flow in the pipeline.
Regulator – A connection of one or more pipes is required on each side of this device, which maintains downstream pressure.
Reservoir – A connection of one or more pipe links to a constant-pressure Reservoir. During a simulation, the Reservoir pressure remains constant unless data is provided to change its value for a particular simulation or at a specified time.
*User-Defined Nodes – Referred to as Device 1 and Device 2, these are passive, internal nodes which may be used to represent other devices. They may also serve as location markers, or may be used to reference data such as addresses, notes, dates, etc.
Variable Pressure Supply – A connection of one or more pipe links to a supply where the supply pressure depends on the supply flow and is determined using multiple pressure-flow data points. This device is ideal for modeling a connection to a distribution system such as a supply to a subdivision.
* These are internal nodes which do not add to model overhead.