Hi again,
In SewerCAD V8i, all necessary data (invert and ground elevations, manhole discharges) were entered but total discharge comes out higher than the entered one and system has six pumps two of which notify negative pressure.
What can be the reason of that?
Best regards,
Seylan
Kim and Tom,
Thanks for your helpful suggestions. I have handled the problem.
The behavior of the pumps is controlled by the calculation option "Use pumped flows?". If this is set to True (default), then the pumps will discharge accordign to their pump curves regardless of the loading on the station.
See the help for this setting.
Since I don't have shape file, I cannot use Load Builder and I have calculated discharges by determining population which each manhole serves. Then, I have input this population values to sanitary load control center as unit load count and I have used unit sanitary load capita based. My unit load is 0.01 L/s ad population equivalent is 1. With these values, total discharge of the pipe that has the lowest elevation and goes to treatment plant should be 11.8 L/. However, SewerCAD calculates this discharge between 33 and 45 L/s.
Is this because of the pump properties or is there any another reason?
(Note: The system has 6 pump stations.)
Sometimes this problem is due to using the ground elevation as the elevation of the pump instead of the elevation of the pump impeller. Check the pump elevation
Pumps can run with a slightly negative suction pressure as long as the head exceeds the NPSH.