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Thread: PRV in extended period simulation

  1. #1
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    Dec 2016
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    57

    PRV in extended period simulation

    I have a PRV set up to 45 psi.
    When I run steady state simulation works fine

    However, when I run in Extended Period Simulation (EPS) I get a problem, the downstream pressures are higher (image).
    I tried both, the initial status button (the yellow pipe) and the Attribute -> valve ->setting

    How do I set up a PRV valve for EPS?
    PRV.jpg

  2. #2
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    Innovyze Employee



    Innovyze Employee



    Join Date
    May 2015
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    Vladimir,

    PRV's run the same in steady state or EPS except that rule based controls can

    If the downstream pressure is higher than the setting and there is flow through the valve this is often an indication that either the initial status of the valve was set to "OPEN" or a simple or rule based control set the status to OPEN. When a valve has a status set to open it no longer acts like a control valve, but will be like an open pipe with headloss based on the ML coeff assigned.

    If the downstream pressure is higher than the setting and the valve has no flow, the valve is closed because this is how PRV's work. They will automatically close if the downstream pressure is higher than the PRV setting and will only open and allow flow if the downstream pressure would fall below the setting in order to maintain the pressure setting indicated:

    From the help file:
    Pressure Reducing Valves (PRV) - A PRV limits the
    pressure on the downstream end not to exceed a pre-set value when the upstream
    pressure is above the setting. If the upstream pressure is below the setting,
    then flow through the valve is unrestricted. Should the pressure on the
    downstream end exceed the pressure on the upstream end, the valve closes to
    prevent reverse flow.


    I believe from your screen capture your issue is likely higher pressure but no flow in the valve. Your setting is 45 psi but the downstream pressure is 70-90 psi so it is automatically closed to prevent reverse flow through the valve.

    Patrick


    Quote Originally Posted by Vladyman View Post
    I have a PRV set up to 45 psi.
    When I run steady state simulation works fine

    However, when I run in Extended Period Simulation (EPS) I get a problem, the downstream pressures are higher (image).
    I tried both, the initial status button (the yellow pipe) and the Attribute -> valve ->setting

    How do I set up a PRV valve for EPS?
    PRV.jpg

  3. #3
    Forum Moderator

    Innovyze Employee



    Innovyze Employee



    Join Date
    May 2015
    Posts
    417
    One last note: Check the things that are controlling the HGL downstream such as another valve possibly set to "OPEN" or something else unusually boosting the downstream HGL higher than it should be. Search for high headloss pipes as these are good indicators of accidental interties between pressure zones. If the pressures and flows were good in SS but not EPS, some setting was adjusted that would be causing the difference. This is often due an initial status or control for a pipe, valve or pump that creates a different operating condition that seen in the SS run.

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