41523 "PEAK" "Pump" "1725" "PMP-17" (N/A) "Maximum relative speed factor must be greater than zero." Pressure Engine

Hello Peter,

There is a property field in the pump properties when you are using a variable speed pump for "Relative Speed Factor (Maximum)". Make sure this is set to a non-zero value. This would be set to whatever value makes sense for the pump, but is typically no higher than 1.0, which would indicate a full speed pump.

Regards,

Scott

Greetings,

Thanks for your prompt reply.

Kindly note that the button of relative speed factor (maximum) is not shown in my ribbon as shown in the below screen shot.

Hello Peter,

What version of WaterGEMS or WaterCAD do you have? I see the maximum relative speed factor field in the latest version (build 10.03.00.69). If you can upgrade to the latest version, that would be a good idea. 

Another thing you can try is to open the pump flextable and add the Relative Speed Factor (Maximum) field to the flextable by clicking the Edit button in the flextable, then adding the field from the Available column. This link has further details on editing the properties available in the flextable.

Regards,

Scott

Hi Peter, I suspect you may be using SewerCAD or the GVF-Convex solver in SewerGEMS, as I am able to reproduce the hidden max RSF field when using the fixed flow option. We will look into that, but a workaround is to change to "fixed head", enter a value", then switch back to fixed flow. Or, use the fixed head option and select the wetwell as the target element with "control node on suction side?" set to "True" (to maintain a constant level, flow in=flow out).

However, if you are trying to use the VSP option in order to force the model to produce the flow that you want, this may not be the best approach. The VSP option will automatically adjust the speed of the pump in order to achieve the desired flow or head. If your actual pump does not change speed, then the results will be skewed.

Generally speaking a pump will operate where the pump curve intersects the system head curve (read more about this here) So, the operating point depends on the downstream system. If your pump is producing more flow than expected, this could be due to downstream headloss being less than the real system, but there are a number of other possible things that influence this. For example a bad assumption or a data entry mistake in the downstream roughness, minor loss, diameter, gravity network interconnection elevation, etc.

If you have other pumps manifolded downstream, their operation will also impact the operating point of the pump in question.

Hi Scott,

Can you please send me a write up about  the usage of the Sewercad software