Introduction to System Head Curves Analysis in InfoWorks WS Pro

Step-by-step guide

System head curves are designed to help InfoWorks WS Pro users in evaluating both existing and proposed pump stations, based on the hydraulics and nature of the water distribution system the pump is operating in. The system head curve simulation can assist in the configuration of a new pump that will be part of a system expansion, or it can replace an existing pump.

IMPORTANT: These simulations do not determine where pumps should be placed within the distribution network; rather, they assist in the generation of system head curves.

A dialog box containing an example of a graphed system head curve, showing Flow on the x-axis and Head on the y-axis, and a number of pump options on the left that control the graph.

The System Head Curve Analysis within WS Pro describes the relationship between the system head and the flow capacity for a pump at different time ranges. Results from this analysis can help you with the selection of suitable pump types in your final network design, and they can assist with the planning of the capacity of pumps.

A system head curve is a pump station analysis, which is an analysis of the entire pump station and not of an individual pump.

A simplified image of a system head curve, in green, with the Head (H) on the y-axis and the Capacity/volumetric flow rate (Q) on the x-axis. The Static head is shown in the space along the x-axis between 0 and the start of the curve, and the Head loss, S is shown to the right of the curve above the Static head.

Most systems will have a family of system curves. The curve will depend on boundary conditions, such as tank levels, demands, and what other facilities are operating. Pumps run where the pump curve and the system curves intersect.

IMPORTANT: As the system changes, the pump will still only operate in between the intersection points of the minimum and maximum system curves.

An example of a simple system head curve that graphs the Flow rate on the x-axis and the Development head on the y-axis. The system head curve is in blue, curving upward, and the pump curve is in red, curving downward. The point at which the pump and system intersect is noted as the Operating point.

In determining a system head curve, a series of steady state runs are carried out in WS Pro, with the flow through a pump station varying between zero and the maximum flow. The difference in head across the pump station at the different flow rates determines the pump curve. WS Pro determines the upper and lower bounds of the system head curve by determining the maximum static lift with the highest headloss, and the minimum static lift with the lowest headloss, respectively.

A detailed view of a system head curve made from SCADA data, with callouts for the calculated pump operating points, the SCADA calculated pump operating points, and the variable speed operating points.

To begin a simple system head curve analysis, create a System Head Curve simulation:

  1. From the SHC Model Group, right-click Run Group and select New > Run from the flyout.
  2. In the Schedule Hydraulic Run dialog box, type a name for the run in the Title field. For this exercise, call this run “SHC”.
  3. Enable Experimental.
  4. From the Model Group, drag and drop the SHC network into the Network panel in the Schedule Hydraulic Run dialog box; the Control and Demand Diagram group boxes populate.
  5. In the Run Type group box, expand the drop-down and select System Head Curve.

The Schedule Hydraulic Run dialog box, with the options set for this exercise, and the System Head Curve run type being selected from the drop-down.

  1. From the Model Group, drag the Pumps selection list into the System Head Curve Options dialog box and drop it into the Selection List panel.
  2. Enable Calculate at maximum demand.
  3. Set the Number of curve points to 10.
  4. In the Calculation Times group box, set the calculation time to May 2nd 2022 at 10:00.
  5. Click OK.

The System Head Curve Options dialog box, with the selected pump active, the Calculate at maximum demand option enabled, the Number of curve points set to 10, and the desired date entered.

  1. Click Save.
  2. Click Run.

To access the System Head Curve Report:

  1. When the simulation is complete, right-click the SHC Control simulation and select Open As.
  2. In the Select Results popup, select System Head Curve Report.
  3. Click OK.

The InfoWorks WS Pro interface, with the Select Results popup open, a callout from the SHC control object, and System Head Curve Report chosen from the list.

The report opens initially in a grid, listing the pumps used in the analysis and a summary of various parameters.

To access pump curves for selected pumps and their operating parameters:

  1. Right-click the pump station KCH2PMPFR.KCH2PMPTO.1 and select System Head Curve.

The Grid Report : System Head Curve dialog box open, with the selected pump having been right-clicked, and System head curve highlighted in the list for selection.

  1. Review the data in the PST Operation window.

The PST Operation results window open in front of the Grid Report : System Head Curve dialog box, with the pump operation options open on the left and a system head curve report open on the right. A green X is shown on the graph to mark the point of pump operation.

This output can be used to more accurately size existing or proposed pumps in the analyzed network.

The system head curve analysis can be used for individual pumps as well as multiple pumps set in parallel or in a series. A set of curves is produced for each pump in the analysis.

If a pump station with multiple pumps is being analyzed, then the simulation produces one set of curves derived from the full combined capaci