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EPS in WaterCAD with Booster Pump and Hydropneumatic Tanks

I'm trying to run a 24-hour EPS in WaterCAD (starting at 12 AM) for a system with a booster pump and four hydropneumatic tanks.  The initial condition is to have the booster pump turned off and the hydropneumatic tanks fully pressurized.  I've set the controls so that the booster pump turns on when the hydraulic grades in the tanks drop to a certain level and shuts off when the hydraulic grades within the tanks rise to a certain level and when the demands in the system are below a certain level.

Whenever I run an EPS, the results show that the booster pump never turns on, and I get several user notifications saying "Hydropneumatic Tank HT-1/2/3/4 is empty."  The same thing happens when I use the tanks' internal pressure as a basis for the booster pump controls.

Do you know what the problem might be?

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  • Hello Robert,

    First, you will want to make sure the properties of you hydropneumatic tank are accurate. The following link has useful information for setting up such a tank for use in WaterCAD: communities.bentley.com/.../17625.how-are-surge-tanks-and-hydropneumatic-tanks-hydro-tanks-used-in-watergems-and-watercad-models.

    Using the Gas Law method is largely recommended, so if you are not using that, take a look at this link for information on how it works: communities.bentley.com/.../17624.how-does-the-gas-law-model-work-for-a-hydropneumatic-tank-in-watergems-or-watercad.

    You may also want to review your controls. If the on/off control is too close to the top or bottom of the tank, it is possible that the program is overshooting it a little. Adjusting the on/off settings in the control may help in such a case. You may also want to try using a smaller hydraulic time step in your model, which is sometimes help for some modeling cases using hydropneumatic tanks.

    If that doesn't help, we may need to see a copy of the model files. There are two options for sharing your model on Communities, whichever you choose please be sure to zip your files first. The first option is to attach the zip file containing your model to your reply on the forum using the Advanced Reply Editor (you'll find the link below and to the right of the reply box). If your data is confidential please use the instructions in the link below to send it via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley employees. Please be sure to reply on this thread with the name of the file after it has been uploaded.

    communities.bentley.com/.../7079.be-communities-secure-file-upload

    If you upload the files to Sharefile, please post here so we know it is available.

    Regards,
    Scott

    Answer Verified By: Robert Tejano 

Reply
  • Hello Robert,

    First, you will want to make sure the properties of you hydropneumatic tank are accurate. The following link has useful information for setting up such a tank for use in WaterCAD: communities.bentley.com/.../17625.how-are-surge-tanks-and-hydropneumatic-tanks-hydro-tanks-used-in-watergems-and-watercad-models.

    Using the Gas Law method is largely recommended, so if you are not using that, take a look at this link for information on how it works: communities.bentley.com/.../17624.how-does-the-gas-law-model-work-for-a-hydropneumatic-tank-in-watergems-or-watercad.

    You may also want to review your controls. If the on/off control is too close to the top or bottom of the tank, it is possible that the program is overshooting it a little. Adjusting the on/off settings in the control may help in such a case. You may also want to try using a smaller hydraulic time step in your model, which is sometimes help for some modeling cases using hydropneumatic tanks.

    If that doesn't help, we may need to see a copy of the model files. There are two options for sharing your model on Communities, whichever you choose please be sure to zip your files first. The first option is to attach the zip file containing your model to your reply on the forum using the Advanced Reply Editor (you'll find the link below and to the right of the reply box). If your data is confidential please use the instructions in the link below to send it via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley employees. Please be sure to reply on this thread with the name of the file after it has been uploaded.

    communities.bentley.com/.../7079.be-communities-secure-file-upload

    If you upload the files to Sharefile, please post here so we know it is available.

    Regards,
    Scott

    Answer Verified By: Robert Tejano 

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