Hello,
When I run an EPS I see that when my pump turns on (which is pulling from the tank in the graph below to fee the distribution system), one of my downstream PRVs doesn't seem to be breaking head. It almost looks like it is trying, rather unsuccessfully.The model setup is such that water from the tank enters the system at two locations 1st location has a PRV, 2nd location has a pressure set point of 80 psi that the pump is trying to maintain.That being said, controls do have to tell the pump to shut off if tank levels get too low; this has a higher priority.
Thoughts?
Hello Nastassja,
Check the "Status (Calculated)" of the PRV in question. A PRV only allows flow in one direction. If the hydraulic grade upstream of the PRV falls below that of the downstream, the PRV closes (and acts as a check valve) and there is no flow. Check in your model if the PRV status is showing as “closed” which obviously indicates that valve is closed.
Additionally please check if you have setup the pipe downstream correctly and the orientation of the PRV is as desired. I am sharing an article which can guide you into setting up your PRV effectively. See the article below for details;
How does the Pressure Reducing Valve (PRV) work in WaterGEMS and WaterCAD?
Hope this helps.
Regards,
Yashodhan Joshi
The pipe direction upstream and downstream of the PRV is correct and the PRV direction is correct.
The initial status is Active and the status (calculated) is closed, but according to the article that is expected "When the PRV's "Status (initial)" is set to Active, reverse flow is not allowed and "Status (Calculated)" will be set to Closed."
I did some test runs and:
When PRV 228 is Inactive the downstream pressure is 115 psi and ranges from 90.6 psi to 176.5 psi during the EPS.
When PRV 228 is Closed the downstream pressure is 101.7 psi and ranges from 90.6 psi to 157 psi during the EPS.
I looked at Test set-points as well:
When PRV is set to Active @ 0 psi, status (calculated) is Closed.
When PRV is set to Active @ 105 psi, status (calculated) is Closed.
When PRV is set to Active @ 190 psi, status (calculated) is Active.
This is not what I would expect based on the article.
Here is the graph of the PRV @ 105 psi:
If you are still have issues with this, we would likely need to see a copy of the model files.
Scott
I am still having issues with this for both Scenarios: "P1 Max Day EPS 24 hr" and "P1 Winter Day EPS".
I have uploaded the model.
Thanks!
I think I have found the issue. When the PRV-228 settings do not appear to be working it is because they are completely closed and actually receiving back pressure from the downstream end of the system. When PRV-11 is turned to active I do not see this issue anymore. Let me know if this is what you think as well once you have had a chance to see the model. Thanks!