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Negative pressure at the Surge tower and Hydropneumatic Tank

Hi, everybody!

After run model, i see negative pressure at the Surge tower and Hydropneumatic Tank

That is mean?

+ I think the surge tank is going through the atmosphere, so why are there negative pressures?


+ Negative pressureat at the Hydropneumatic Tank is - 7m H20, may cause bladder rupture? And what should I do in this case.

Thank for all !

Parents
  • Hello Doan, 

    What kind of transient event are you modeling? Is it pump shut down? Why negative pressure is seen, depends upon many conditions in model like, size of the hydropneumatic tank and surge tank, where is it located etc. Are you modeling one-way or two-way surge tank? 

    In case of pump shut down event, when the pump trips and pressure becomes negative, water is allowed to enter the system from surge tanks to keep the water column moving. 

    Whereas for the hydrpneumatic tank when pump trips and negative pressure is seen trapped air in the vessel expands and pushes water out in system to keep the water column moving. 

    Here is technote for modeling hydropneumatic tank for your reference, if you haven't gone through it yet. 

    Modeling Reference - Hydropneumatic Tanks 

    What user notifications do you get, which might explain what is issue with the model? A copy of the model would help in this case to help you with this issue. 

    Sharing model files 

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • Hello, Sushma!

    My event is Pump shutdown. i think the size of the hydropneumatic tank (DxH = 2.7 * 10,8m) is small and the surge tank inside diameter (D600) is medium

    and tank in modeling is two way.

    I sent to you my modeling, please check and help me to clarify

    + I think the surge tank has connected to the atmosphere, so why are there negative pressures?

    + Negative pressureat at the Hydropneumatic Tank is - 7m H20, may cause bladder rupture? And what should I do in this case.

    Thank for all !

    doan.rar

  • Hello Doan,

    We have received the model and are looking into the issue.

    Thanks,

    Scott

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