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PRV setting can not be maintained?

Hello,

I am facing a problem to set my PRV in the network. I have a network whose topography is a bit sharp and the difference in levels is high. I am fixing PRVs as the pressure exceeded 6 bars. but at some location it seems the PRV just does not produce the required pressure. 

I have attached my model as wMODL.zipell.

regards 

Parents
  • Hello Ahmed,

    Which scenario are you using?

    The only scenario that isn't set to perform a fire flow analysis is the "Peak hourly demand", but when I compute this scenario, there aren't any user notifications and the PRV results are shown below. None of the PRV pressures exceed 6 bars for that steady state scenario.

    It appears you are using version 08.11.06.113?

    Are you using WaterGEMS or WaterCAD?

    What patch set version do you have applied? You can find the date of the applied patch set by going to Help > About WaterGEMS/WaterCAD. The date will appear on the lower-left corner of the about dialog.

     

    Regards,

    Craig Calvin

    Bentley Technical Support

  • Hello Craig,

    I am using waterGems 08.11.06.113 applied patch at 1/27/2016.

    I am computing the fire scenario. and when i try to fix PRV like at J-82 first of all the pipe is seemed to be closed. and the pressure downstream the PRV does not maintain at the pressure value set.
Reply Children
  • "I am computing the fire scenario."

    The model you provided contains 4 fire flow scenarios. I'm not sure which you are referring to.

    "when i try to fix PRV like at J-82 first of all the pipe is seemed to be closed."

    There are pipes allowing the flow to bypass the PRVs.

    For Example:

    I set the scenario "average daily demand" to compute hydraulics only and computed.

    PRV-1 is set to maintain a downstream hydraulic grade of 104.77m, but is closed after computing.

    The "Hydraulic Grade (To)" (hydraulic grade at the exit of the valve) is 113.77m and the "Hydraulic Grade (From)" (hydraulic grade at the entrance of the valve) is 120.02m.

    The valve's "Status (Calculated)" is set to Closed because it is trying to lower the downstream hydraulic grade to 104.77m. However, upstream of the PRV pipe P-165 allows the flow to bypass the valve which is why the PRV can't lower the downstream pressure down to 104.77m.

     

    Regards,

    Craig Calvin

    Bentley Technical Support

  • Hello Ahmed,

    In most fire flow runs the majority of PRVs (except PRV-3) are inactive since their set pressures are too high (the system has naturally lower HGLs in high flow situations).
    You may want to consider combining PRV-1 & PRV-2.

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • Hi Craig,
    that applies the concept of DMA for pressure management. because whenver I try to fix PRVs at some point in the network the flow bypasses my PRV and I don't get the satisfied result.
    could you advise me in case I want to lower the pressure in the Blue marked nodes without unsatisfying the fire flow analysis?

    by the way the design scenario is Maximum daily + fire

    Thanks
  • Hello Sushma,

    I am trying to minimize the pressure at the lowest part of the network using PRVs but it seems that could not help much in this loop system and the network should be based on DMA concept. do you agree?
  • Use the pressure zone manager tool to lay out and view the pressure zones. Use color coding to visualize which elements are in each zone. If large areas are the same color then it means you have bypasses around the PRVs which is not desirable. Close the isolatin valves and pipes to isolate each zone.