I am using WaterGEMS to study rehabilitation options of a certain rural & urban water supply network in Tanzania. The network runs across mountainous landscape, and encompass a good number of break pressure tanks (BPT). Indeed, BPTs are preferred to Pressure Control Valves in most mountainous rural water supply schemes in the country; partly because BPT are less expensive and do not require maintenance.
My question now is: How can I model BPTs in my system? Is it right to model them as normal tanks? The problem is that these tanks are normally small in size, and they tend to overflow in the model, causing pipe disconnection. Can anyone assist me on this please?
I would also appreciate if someone can direct me to more informative resources on how to use the Darwin Designer. I tried out the help but I can't get it work.
If my understanding of a break pressure tank is correct, I believe you could approximate this with a PRV. Or, you could end the system at a reservoir at the elevation equal to the upstream HGL, then start the downstream system at another reservoir, set at the elevation equal to the tank's water surface elevation.
We have some training classes available, which cover Darwin Designer. See below for more information, or contact your Bentley account manager:
If you have technical questions or problems, you can contact technical support.
Jesse DringoliSupervisor, Bentley Technical Support Group
I once tried to use PRV but I got negative pressures at nodes located upstream of the valve. Can you please advise me on how I can set it. I am thinking that may be I got the settings wrong. I set the pressure at the PRV to be equal to 1m, which is the pressure at the outlet of the Break pressure tank (in fact, there is always 1m water column in the BPT when the water is flowing).
I initially tried reservoirs but it didn't seem to work. As I understand conceptually, reservoirs behave like additional sources in the model, which is not the case here.
Thanks also for the training link, I will browse through and I hope I will find something helpful.
As I understand break pressure tanks, they are essentially a tank element with a separate inlet (high pressure side) pipe element and out let (low pressure side) pipe element. The inlet side has a throttling control valve on it which is set to thottle the flow as the tank approaches full and shut off flow when the flow reaches a full level without overflowing.
In our upcoming release of WaterGEMS/CAD (coming out withn the week), we have a new feature on our tank element where you can specify this trottling fill valve as a property of the tank and not need a separate throttling control valve element.