EPANET - Pump Curve

A pump curve represents the relationship between head and flow rate that a pump can deliver at its rated speed setting.

• Head is the height gain imparted to the water by the pump and is plotted on the vertical (Y) axis of the curve. The flow rate is plotted on the horizontal (X) axis
• A valid pump curve should have decreasing head with increasing flow
• EPANET will use a different shape of pump curve depending on the number of points provided (property Pump Type - Defines pump curve data types):
  1. Parabolic Curve - A single point pump curve defined by a combination of main flow representing the desired operating point of a pump.
     EPANET fills in the rest of the curve by assuming:
     • A closing load at zero flow equal to 133% of the design load
     • A maximum flow at zero load equal to twice the design flow
     For a flow rate of 5 liters per second and a load of 1 meter, Nodes would have the following curve:
     
  2. Continuous Curve - A pump curve defined by three operating points:
     • Low flow (flow and pressure in low or zero flow condition)
     • Design flow (flow and load at desired operating point)
     • Maximum Flow (flow and load at maximum flow)
     EPANET fits a continuous function through the three points to define the entire pump curve:
     
  3. User Defined - A multipoint pump curve is defined by providing a pair of head flow points or four or more such points.
     EPANET creates a complete curve by connecting the points with straight line segments:
     
  4. Constant power curve - A Constant power pump is a pump that operates at a Constant power or kilowatt rating at all combinations of flow and head.
     The user only needs to provide the power rating of the pump
• For variable speed pumps, the pump curve changes as the speed changes. The relationships between flow (Q) and head (H) at speeds N1 and N2 are:
  
  Q1 / Q2 = N1 / N2
  H1 / H2 = (N1 / N2)^2
• EPANET will turn off a pump if the system requires a pressure higher than the first point on the curve (i.e. cut-off level)
• A pump curve must be provided for each pump in the system unless the pump is a Constant power pump

Note: To create/edit a curve, use the command EPANETCURVES