The PRV structure in my system has two parallel PRVs (2" and 4"). Do I place two PRVs in parallel? or is there a way to do it more cleanly?
Also, how do I get the arrows to appear to indicate flow direction?
dculeton,
I have a few comments and a few questions for you. In the model that you provided a screenshot of it looks like the PRV’s are in opposite directions. Is that how they are in field or do they face the same direction? Is one valve smaller than the other one to handle a different flow setting? How do these PRV’s function or operate?
PRV’s in parallel can causes issues for the solver, but they don’t always. What I would try first is to model them as they are in the field. If that doesn’t seem to be working out and you are getting an unbalanced network user notification or a red notification about the network not being able to be solved then replace the PRV’s with a single effective PRV. In most cases the difference should be small, but that depends on the other conditions you have.
In the single PRV you will have to create controls that adjusts ‘setting’ attribute of the valves (either done in hydraulic grade or pressure). From what I have read usually the smaller PRV opens first and has the highest setting and when the hydraulic grade can’t be maintained the larger one opens. You might have something like “IF junction J-10 hydraulic grade < 90ft THEN PRV-2 setting = 20 psi OR IF junction J-10 hydraulic grade > 90ft THEN PRV-2 setting = 30 psi.” This is just an example and you may have more or less controls that you need. If you need some help with creating controls you can refer to our help documentation that comes with the software or you can refer to the wiki technote found here:
communities.bentley.com/.../2567.creating-controls-conditions-actions-and-control-sets-tn.aspx
I’m also not sure, which version of the software that you are using, but you also might want to check your calculation options settings (Analysis > Calculation Option) and make sure the Engine Compatibility is set for WaterGEMS 2.00.12. This is the latest version of the calculation engine and has improved handling for valves vs. the WaterGEMS 2.00.10 engine.
You can also have a look at this forum post, which has some additional information that may be useful to you. The question is not exactly the same as yours, but in his first reply a contributor to our forums, Ben Wilson, discusses PRV's in parallel.
communities.bentley.com/.../79394.aspx
Regards,
Mark
You also asked "how do I get the arrows to appear to indicate flow direction?".
In order to do that you need to do a few things. 1) Make sure you have some type of boundary condition in your model like a tank or a reservoir for a source of water. 2) Make sure the option for the "Show Flow Arrows" is set to True for your pipes. There is a wiki that shows how to do that here:
communities.bentley.com/.../how-to-display-flow-arrows-in-haestad-methods-products.aspx
3) Make sure to compute the model.
I hope that helps out.