| Applies To | |||
| Product(s): | SewerGEMS, SewerCAD | ||
| Version(s): | V8i, CONNECT Edition | ||
| Area: | Modeling | ||
| Original Author: | Mark Pachlhofer, Bentley Technical Support Group |
The flow out of my pump is zero, but the pump is set to ON and is active. I don't know why the pump isn't working. How do I fix this?
Check the "Relative Speed Factor (Initial)" property for your pump and make sure it is set to 1. Some older versions of SewerCAD for example used zero as the default initial relative speed factor, which essentially means the pump is off.
Also, a pump can turn on and have zero flow if is is operating at its shutoff head. This can happen if the pump curve's head at zero flow is less than the head needed to overcome the static and dynamic lift. First compare the pump maximum head to the difference between the upstream and downstream boundary hydraulic grades. For a SewerCAD (GVF-Convex solver) model, the difference would be the invert of the pipe that connects to the downstream receiving manhole minus the upstream wetwell initial elevation.
A pump in a SewerCAD model can also operate at the zero flow point if you are trying to use an air valve at a downstream high point and all pumps are initially off. For more on this known issue, see the item called "Pump won't turn on if initially off" in the following article: Troubleshooting Air Valves at High Points with the GVF Convex (SewerCAD) Solver