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Pressure Reducing Valve on Transmission Line

Dear Bently Team, 

I am designing a water supply system. System consists of 100 km pipeline. Dam is the source of water, transimission line will supply water from Dam to a reservoir at down through gravity. The difference between normal level and lower water level of Dam is150m. Can I install Pressure reducing valve at upstream and set my hydraulic Grade level at the lower water level of dam so that pressure doesn't exceeded in the pipeline. 

I am looking forward to your reply 

Thanks and Regards,

Syed

Parents
  • Hello Syed,

    You mentioned that you want to supply water from the dam to the reservoir downstream via transmission line. How are you modeling dam is it a reservoir element ?

    About reservoir to which water is supplied from dam, is it a limited storage or unlimited source of water? It could be a tank element if you are storing water in it. If it is a tank then it will define the HGL in that area. Are you modeling steady state or EPS system? 

    Is it an existing system or you are modeling a new system?

    If you set the Initial HGL setting at PRV = lower water level of dam, the model will try to reduce the HGL on downstream side as per the mentioned settings, however HGL at upstream reservoir element ( DAM) will be = normal level of dam. Do you want to reduce the HGL by 150 m downstream in that case to lower the pressure in pipeline? 

    Are you done with modeling part, do you see the higher pressures in the system downstream so you want to reduce it by modeling PRV? Please elaborate your modeling to help you further. A sketch also would be helpful to understand your system. 

    How does the Pressure Reducing Valve (PRV) work in WaterGEMS and WaterCAD? 

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • Thanks for your reply. 

    Yes I am modelling dam as reservoir and downstream point as node. Downstream reservoir would be used for storage too 

    I have already prepared model. I am uploading this file for better understanding. 

    Thanks,

    Syed

  • Hello Syed, 

    If you set HGL initial setting at PRV = lower water level of Dam -150m , you will be able to reduce the HGL / pressures downstream, however please check PRV specifications to understand its limits and what it can do on field. 

    However in your model, the end junctions are giving negative pressures if you install PRV at some point, as you mentioned they are points of storage, if you replace nodes with tanks and as it is steady state simulation, HGL = initial elevation at tank will be maintained at tank in the model. You should try to model as it is on field to have similar results.  

    What kind of project it is, as there is huge differences in the elevation? I discussed with one of my colleague he suggested about having micro hydro plant or using pump as turbine to generate some energy , if not already considered. 

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • Thanks a lot for your quick response. 

    I have simulated this model at the lowest water level, pressure ranges are acceptable but if I simulate my model when dam is full which 400m then I will get very high pressure in my system. I would like to fix HGL 250m upstream with the help of PRV. This PRV will reduce pressure when dam is full. I would like to know PRV would be good option or there is an other alternative. 

    Thanks,

Reply
  • Thanks a lot for your quick response. 

    I have simulated this model at the lowest water level, pressure ranges are acceptable but if I simulate my model when dam is full which 400m then I will get very high pressure in my system. I would like to fix HGL 250m upstream with the help of PRV. This PRV will reduce pressure when dam is full. I would like to know PRV would be good option or there is an other alternative. 

    Thanks,

Children
  • Hello Syed,

    A PRV would introduce a headloss that can decrease the hydraulic grade. Will there actually be one in the system to decrease the hydraulic grade by this amount? If not, what is expected to happen when the dam is at the higher elevation?

    Regards,

    Scott

  • If you do actually have a valve in the real system that closes/throttles to control the downstream pressure, then based on your description it should work in this situation. If it is not working as expected, please provide a copy of the model for review and reply with the name of the file: Sharing Hydraulic Model Files on the OpenFlows Forum


    Regards,

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

  • Thanks Scott for your reply.

    If Dam is full, I am getting more than 300m pressure at junctions and when is at lowest level of water results okay. 

    The reason of installing PRV at upstream to use lower pressure rating of pipe otherwise higher pressure rating will be required.

    I will attach both models for your review.

    Thanks,

    Syed Ahmed.

  • Thanks Jesse,

    I have uploaded model for your review

  • You have uploaded 2 models one for 250 elevation at dam and other for 400 m, however in none of them PRV seems to be used upstream.

    As we have mentioned in previous replies if you have a valve in the real system that closes/throttles to control the  downstream pressure then you introducer PRV in the model.

    In your model if you install PRV upstream you will get negative pressures (depending on PRV initial HGL set) at dead ends, as pressure / HGL is already reduced downstream and dead ends have higher elevations again, so try to model elements as they are on filed. 

    Also is your level at dam is not constant, generally average water level is considered however here it is large difference in levels of 150 m.

    If you want to check pressures for 2 different reservoir levels you can use physical alternative and 2 scenarios and model them in one model only rather than creating 2 models. In one physical alternative reservoir level can be 250 and another it can be 400 m. You can try introducing reservoir pattern if required. 

    Scenario and Alternative Management 

    Regards,

    Sushma Choure

    Bentley Technical Suppport