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High pressure at pump discharge in spite of delayed opening of valve & presence of HT tank

Dear Sir,

Here in this model, The Valve closing time is 45 s (linear in nature). The pressure at the pump discharge is as high as 450 m of H2O ( despite having hydro pneumatic tank). The valve opening tine of 45 s is selected considering the valve closing time (Equal valve opening & closing time) to arrest the surge pressure within the acceptable limit due to tripping.

Please ascertain the reason for such high pressure.  The model is attached for your reference.

Regards,

Sujoy De

model 11-06-2016.rar

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  • Hello Sujoy,

    I am looking at the active scenario, which involves a pump startup and the valve opening. I am going on the assumption that this is the correct scenario, since that sees the high pressure you are noting. In this scenario, the issue is related to the setup of the pump startup in comparison to the valve opening. The pump is seven seconds into the simulation. However, the valve doesn't start to open until 10 seconds after the start. The build up of pressure seems be mainly when the pump is on but the valve is still closed or is just starting to open. In this case, the hydropneumatic tank will not help much with the high pressure because it is on the other side of the valve.

    If you were to model the pump startup without the valve or have the pump startup operating rule more closely match the valve opening operating rule, you may see better results.

    Note also that the TCV is initial set as active, but the operating rule has it fully closed. You may want to start with the TCV set to be closed as well.

    Regards,
    Scott
Reply
  • Hello Sujoy,

    I am looking at the active scenario, which involves a pump startup and the valve opening. I am going on the assumption that this is the correct scenario, since that sees the high pressure you are noting. In this scenario, the issue is related to the setup of the pump startup in comparison to the valve opening. The pump is seven seconds into the simulation. However, the valve doesn't start to open until 10 seconds after the start. The build up of pressure seems be mainly when the pump is on but the valve is still closed or is just starting to open. In this case, the hydropneumatic tank will not help much with the high pressure because it is on the other side of the valve.

    If you were to model the pump startup without the valve or have the pump startup operating rule more closely match the valve opening operating rule, you may see better results.

    Note also that the TCV is initial set as active, but the operating rule has it fully closed. You may want to start with the TCV set to be closed as well.

    Regards,
    Scott
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