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
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,
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
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley 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.
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
Thanks Sushma for your review and reply.
Can I simulate system when reservoir is full i.e 400m with PRV settings of 250m HGL. Is this scenario practically possible for a new system?
I don't see why this would not work in a model. You would simply add a PRV downstream of the reservoir with a hydraulic grade setting of 250 meters. This will be adding a lot of headloss, so would want to make sure that an actual PRV is practical and able to do this in the real system.
Scott
To expand, here are some screenshots of your "250" model where I inserted a PRV downstream of the reservoir, set the PRV HGL setting to 250 m and set the reservoir elevation to 400 m. You can see from the profile that the PRV throttles to bring the HGL down from 400 to 250. If you were to change the reservoir elevation to 300 m it would still do the same thing (bring the 300 m down to 250.)
Thanks a lot Jesse.
That's really helpful and I was looking for this. I will incorporate this setting in my design. Thanks for Sharing this information.
Syed.