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Hydraulic Model Troubleshooting Guide

This page contains the following topics:

  • Introduction
  • Troubleshooting Input Data Errors
    • Common Input Data Errors
      • Series 200 Error Codes – missing or invalid data in a required field
      • Other Input Data or Connectivity Issues
  • Model Failed to Converge
    • Simulation Options for Best Convergence
    • Configuring the Full Hydraulic Status Report
    • Common Reasons for Model Instability and Troubleshooting Recommendations
      • Maximum Trials Exceeded
      • Pump Cannot Deliver Head
      • Pump Exceeds Maximum Flow
      • Variable Speed Pump (VSP) Unable to Meet Setting
      • FCV Cannot Deliver Flow
      • Disconnected Nodes or Ill-Conditioned Errors
      • Tank Closed Due to Min/Max Level Reached (Pipe Temporarily Closed)
      • Frequent Status Changes – Hydraulic Diagnostics
      • PRV Status Switching
      • Check Valve Status Switching
      • Pump Status Switching

Introduction

For troubleshooting a model that has failed to solve, it is important to understand the type of simulation failure you have experienced. Generally, a failed simulation falls into one of the following categories:

  • Input data errors (grey light)
    • Meaning: InfoWater Pro could not attempt the simulation due to incomplete data or syntax errors.
    • Behavior: Errors will either popup in a text report or display in the Message Board. No output data and no output report will be available because the simulation never began.
    • Note: It is important to have the Message Board visible at all times when using InfoWater Pro. It is enabled from the View group of the InfoWater Pro ribbon ().
  • Model failed to converge – No output (red light)
    • Meaning: InfoWater Pro attempted the simulation but failed to converge in the initial timestep. No output data will be available.
    • Behavior: There will be no output data loaded into the model but you can open the .html report to troubleshoot.
    • Note: The .html report is accessed from the Run Manager next to the Run button.

  • Model failed to converge – partial output (yellow light)
    • Meaning: InfoWater Pro partially completed a simulation but failed before reaching the final timestep. Some output data will be available.
    • Behavior: There will be output data loaded to the model for the timesteps which solved. Use the .html report or the partial output results for troubleshooting.

Troubleshooting Input Data Errors

One or more errors were detected in the input data. Run Manager shows a grey light. Errors will either popup in the .html report or be displayed in the Message Board. Make sure the Message Board is always visible when using InfoWater Pro, if it has been disabled you can toggle it back on using the button shown below in the View group of the InfoWater Pro ribbon.

Locate the error message and resolve each error one at a time. The report only shows a few errors before the program stops processing, so you may find that you resolve the displayed errors only to get new ones after re-attempting a simulation. To avoid doing this for many iterations you can use the Command Center > Tools > Engineering Validation Manager to see a complete validation report on your entire model. More information on using this tool may be found on Engineering Validation Manager.

Common Input Data Errors

Series 200 Error Codes – missing or invalid data in a required field

  • Example (in the .html report popup): Input Error 202: Pipe 12050 contains illegal numeric value.
  • Copy the Element ID and paste it into the Model Explorer or use the Search function to find the Element. Look for missing or invalid field values, in the example below Pipe 12050 is missing a Pipe Roughness, which is a required field.

  • Read more about 200 & 300 Series Error Codes on Error Codes in InfoWater Pro.

Other Input Data or Connectivity Issues

  • Example (in the Message Board): ERROR: Error 4401: missing upstream/downstream connection data for Pump/Valve elements.
  • Look for the full error text in the Message Board. Copy the Element ID provided and look for input data or connectivity errors. In the example below, both pipes connected to Pump P-160 have Pump P-160 as their downstream node so InfoWater Pro cannot ascertain which direction the pump should flow. Pipe direction (To/From nodes) is critical for pump and valve elements, or when a pipe uses Check Valve = Yes.

  • For more help on common connectivity issues, view the tutorial on Customer Success Hub – Working with Connectivity Tools.

Model Failed to Converge

When a model fails to converge, the Run Manager will show either a red light (no output) or yellow light (partial output), and the .html report may popup with error messages indicating the failed simulation. If the .html report does not open automatically, it can be opened by pressing the button in the Run Manager.

Simulation Options for Best Convergence

Some models are more sensitive and experience more instability than others. Many times, a model that fails to converge under the default settings may converge by adjusting specific parameters in the Simulation Options. By default, the Simulation Options are optimized for the fastest solution, but adjusting to the settings shown in the screenshots below will allow many unstable models to converge without significantly increasing simulation time. Read more about Simulation Options, recommended values, and term definitions on Simulation Options.

Configuring the Full Hydraulic Status Report

If the model still fails to converge after setting the Recommended Simulation Options for Best Convergence, then a more thorough review of the .html output report is required. The first step is to make sure that the report is configured to show as much troubleshooting information as possible in the Report Options settings, accessed from the Run Manager. The important changes are to set Hydraulic Status to “Full,” and Generate Warning Messages is checked as shown below:

The Full Hydraulic Status Report generally contains the following information:

  • Network Summary Table (if checked in Report Options)
  • Simulation date and important parameters from Simulation Options
  • Relative flow change for each trial
  • Element status changes
  • Total supplied, demanded, and stored flow after each timestep balances
  • List of status changes after each timestep balances
  • Warnings or Error messages (if present) will be displayed for the timestep at which they occurred
  • Use Ctrl+F to search for important text in the report (such as “Warning” or “Error”)

Common Reasons for Model Instability and Troubleshooting Recommendations

This section discusses the most common reasons for model instability (simulation failed to converge), and recommended troubleshooting steps. It is important that you have already read and implemented the recommendations in Simulation Options for Best Convergence and Configuring the Full Hydraulic Status Report. Connectivity issues or bad GIS data brought into the model can cause many of the problems described below, if the model has not already undergone a connectivity review it may be an important first step. Learn about how to do a model connectivity review with the tutorial on Customer Success Hub – Working with Connectivity Tools.

Maximum Trials Exceeded

This is a general warning that occurs when InfoWater Pro is unable to reach the convergence goal within the specified number of trials. It is important to note that when this warning is present, the results may not be accurate.

  • Example: Maximum trials exceeded at 20:00:00 hrs. System may be unstable
  • Recommendations: This is a general warning that indicates overall system instability. Troubleshooting will require a more in-depth analysis of the .html report. Look for elements with frequent status switching or search for more specific Warning/Error messages. See sections below for specific troubleshooting on each error message.

Pump Cannot Deliver Head

This occurs when the pump reaches its shutoff head, meaning the head required is greater than the maximum head on the pump curve (at flow = 0).

  • Example: Caution: Pump U7000 closed due to its inability to deliver head at 0:00:00 hrs
  • Recommendations: Check the pump curve and ensure the head conditions upstream and downstream make sense for your system. Ideally your pump will be setup using a Multiple Point Pump Curve with accurate data from the pump manufacturer. Read more about Pump types.

Pump Exceeds Maximum Flow

This occurs when the pump is operating past the last point of its multi-point curve. In order to satisfy the hydraulic equations, InfoWater Pro extrapolates an extension of the pump curve using the last two points input for the multiple-point pump curve, but this may or may not be realistic.

  • Example: WARNING: Pump CWBP_1 open but exceeds maximum flow at 5:20:00 hrs
  • Recommendations: Check the pump curve to ensure the head and flow conditions are comparable to available field data. Consult the pump manufacturer to determine whether the program’s extrapolation of any pump curve is reasonable.

Variable Speed Pump (VSP) Unable to Meet Setting:

This warning indicates that the VSP cannot maintain the required setting. InfoWater Pro will try to meet the setting using as many pumps as allowed in the VSP Parallel Count and the min/max speed settings.

  • Example: VSP Run Warning 413 for pump -187059: maximum pump capacity insufficient to meet target at time 45:30:00
  • Recommendations: Make sure the VSP control settings are reasonable for the pump station. Multiple pumps at the pump station should be accounted for in the VSP “Additional Parallel Pump(s)” count (parallel count = 3 means 4 total pumps at the station can run simultaneously to meet the setting). Make sure the minimum and maximum pump speeds are reasonable and the pump curve is accurate (cross-reference with manufacturer’s pump data). If using Remote Junction Pressure control, make sure that the specified Junction is not influenced by other pressure settings (a PRV or other VSP can fight for control). Read more about Variable Speed Pump Controls.

FCV Cannot Deliver Flow:

This occurs when there’s not enough head upstream to drive the set point flow through the flow control valve. The valve will still open to provide what flow it can which may be adequate for balancing the model.

  • Example: Caution: FCV TBP_30 open but cannot deliver flow at 18:30:00 hrs
  • Recommendations: If this is an unexpected condition, check for reasons why the upstream head is not sufficient to achieve the desired flowrate.

Disconnected Nodes or Ill-Conditioned Errors

This occurs when an area of the network with demand becomes isolated from supply and InfoWater Pro cannot satisfy the demands. Similarly, you may get an “Ill-Conditioned” error whenever InfoWater Pro cannot trace an area back to a known HGL. Often disconnection warnings will occur for many elements simultaneously, a Selection Set called “DISCONNECTED_ELEMENTS” should automatically be created to help you troubleshoot.

  • Example: WARNING: Node J-1054 disconnected at 20:00:00 hrs
  • Recommendations:
    • Search for the node ID provided or use the DISCONNECTED_ELEMENTS Selection Set in the Domain Manager to locate all disconnections.
    • InfoWater Pro will try to list which elements caused the disconnection, but in some cases more investigation is required.
    • Review surrounding elements for a source of the disconnection, often caused by an empty tank, a valve or pump that is closed due to poor operational controls, or a pipe closed by controls or Check Valve direction.
    • Verify that demands are assigned to the correct Junctions, for example a Junction on the suction side of a pump should not have demand allocated to it.

Tank Closed Due to Min/Max Level Reached (Pipe Temporarily Closed)

When tanks reach their minimum or maximum level, InfoWater Pro temporarily closes the connecting pipe(s) which often causes other issues that prevent model convergence.

  • Example: In the screenshot below, Tank RIDGECREST reaches empty and InfoWater Pro closes two connecting pipes resulting in negative pressures at demand nodes and a pump that can no longer deliver head.
  • Recommendations:
    • Open a Tank Group Graph to plot the %-Full for all active tanks to identify those approaching empty or full. Alternatively, you can search the report file for “temporarily closed” key words.
    • Tanks should never be set to Initial Level = Minimum or Maximum Level. Setting the Initial Level close but not at the limit will allow greater flexibility and better stability.
    • Review controls on elements regulating tank levels. Controls should always activate before the tank reaches its min/max levels.
    • Check pressure zone boundaries for elements that are erroneously open which could allow too much flow into a lower pressure zone and cause a tank to fill when it should not.

Frequent Status Changes – Hydraulic Diagnostics

Usually accompanied by a Maximum Trials Exceeded warning, this issue is one of the more difficult convergence failures to troubleshoot as it is not flagged with a specific Warning/Error message but requires in-depth reading of the report. In InfoWater Pro 2023.2 and newer, the Hydraulic Diagnostics tool was added to count status changes for each element and display them in a sortable list in the Message Board – this can make it much easier to find problematic elements. The tool is enabled in the Report Options dialogue. For specific guidance on each element type switching, see sections: PRV Status Switching, Check Valve Status Switching, Pump Status Switching.

PRV Status Switching

Pressure Reducing Valves (PRVs) can show frequent status switching between active and closed when they are competing for pressure control with another nearby model element. This is very common in multiple-PRV valve pits and can indicate a real-world problem where the physical valves are also fighting for control due to their set points being too close to each other.

  • Example: see screenshot below for run report showing PRV switching or use the Hydraulic Diagnostics tool to identify these elements.
  • Recommendations:
    • Valve pits with multiple PRVs should have setpoints separated by at least 5-10 feet of HGL. Note that HGL = [Valve Elevation] + [Setpoint Pressure converted to head, i.e. 2.31 ft/psi].
    • Consider adjusting each pressure setpoint incrementally between 0.25 and 0.5 psi.
    • Verify that the valve elevations in the model accurately represent the elevation in the field.
    • Smaller valves should have higher Minor Loss assigned to it to help InfoWater Pro decide which valve to use for higher flow.
    • Recommended Simulation Options for Best Convergence are particularly important for this issue.
    • Consider modeling a multiple-valve pit as one valve with a Direct-Acting Flow Regulator (DAFR) Curve Control.

Check Valve Status Switching

Check Valves can open and close quickly based on pressure changes in the network which can exacerbate control instabilities.

  • Example: The screenshot below shows a common example where a pump is using a pressure-based on/off simple control which is combining with nearby check valves to switch back and forth between high and low pressure conditions.
  • Recommendations: Review operational controls around the switching check valves and adjust to reduce instability. Consider whether the check valve is necessary as using too many check valves can cause model instability.

Pump Status Switching

Pumps can switch between open and closed quickly depending on the operational controls used or other pump properties.

  • In the screenshot below, Pump U7026 is repeatedly switching between open and closed and the model is unable to converge.
  • Recommendations:
    • Review operational controls on the pump. A common problem is using pressure-based controls for both on/off settings on the pump, especially when no tank is present which can lead to rapid pressure fluctuations. Where applicable, controls based on tank levels are more stable. Another option is to use a pressure setting for the pump ON condition but use an alternative approach (such as low flow) for pump OFF condition. Rule-Based Controls can also be used to turn the pump off which adds a natural delay since Rule-Based Controls only kick in after convergence is reached.
    • Check to make sure that the specified Pump Curve has a shutoff-head value (head at 0 flow). InfoWater Pro will turn the pump off when the operating point is to the left of the curve, so a curve not going all the way to 0 flow will cause instability. Consult manufacturer’s pump curves for shutoff head values.

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