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Deceleration of check valve

Dear Bentley team,

We want Deceleration value for check valve, decelaraion is calculated velocity vs time graph taken from Hammer downstream of the NRV, but in graph velocity is going below the zero, we could not understand how to calculate deceleration in this case, request you to confirm calculated deceleration is correct? if wrong please provide the method.

Thank you 

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  • Hello Jayakanthan,

    This article has information on determining check valve deceleration during a transient simulation in HAMMER, but it sounds like you may need to determine why the velocity is not staying at zero.

    If the velocity becomes negative during a transient simulation and stays negative, that means that the flow reverses and stays in reverse. If such a velocity graph is from a pipe right next to a check valve, then it would suggest that the check valve is not closing. If you are using a check valve node element, check the "close time" parameter and set it to a reasonable value if you would like the check valve to close when reverse flow is first detected (see more here).

    If you're using a check valve in a pump or in the pipe itself (which should instantly close on first detection of reverse flow), then it is possible that the reverse velocity may be from the water column moving away from a vapor pocket that has formed from sub-vapor pressure conditions, or from an air pocket at an air valve. See this article for more information on how you can use profile animation to check for this.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows Products
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

    Answer Verified By: Sushma Choure 

Reply
  • Hello Jayakanthan,

    This article has information on determining check valve deceleration during a transient simulation in HAMMER, but it sounds like you may need to determine why the velocity is not staying at zero.

    If the velocity becomes negative during a transient simulation and stays negative, that means that the flow reverses and stays in reverse. If such a velocity graph is from a pipe right next to a check valve, then it would suggest that the check valve is not closing. If you are using a check valve node element, check the "close time" parameter and set it to a reasonable value if you would like the check valve to close when reverse flow is first detected (see more here).

    If you're using a check valve in a pump or in the pipe itself (which should instantly close on first detection of reverse flow), then it is possible that the reverse velocity may be from the water column moving away from a vapor pocket that has formed from sub-vapor pressure conditions, or from an air pocket at an air valve. See this article for more information on how you can use profile animation to check for this.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows Products
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

    Answer Verified By: Sushma Choure 

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