3 Pump Cycling

Hi Jack,

Yes, it is possible to set up controls to alternate between pumps, though some creativity is necessary, utilizing pipe open/close status as variables. You can read details on how in this article from our Wiki: Controls for alternating or cycling between multiple pumps

Thank you Jesse,  

I used that article previously to set up the correct controls to get the model to cycle between 2 pumps but I wasn't sure how to integrate a 3rd pump that needed to turn on after the other two had cycled.  Do you have any ideas on how to get the third pump to be in corporated?

Thanks, 

Hello Jack,

For the third pump, you can use controls based on hydraulic conditions, as mentioned in referred wiki. 

Do you have any hydraulic condition like tank level or control of any other element on which operation of pump 3 depends?

If the pumps are identical, why worry about which one is running. The hydraulic results would be the same. If one is different, what is the reason the operator would run it? Build that reason into your controls.

I agree with Tom's comment about first considering whether it is hydraulically relevant to the design or decision-making.

If it really is necessary to cycle between three or more pumps, then as Sushma said, you can extend the same general concept, using two or more fictitious pipes in order to create multiple combinations of open/closed, to determine which pump should turn on next. Here is a brief example for three pumps:

• If On_condition occurs, controlpipe1 is closed and controlpipe2 is closed then turn on pump1
• If On_condition occurs, controlpipe1 is closed and controlpipe2 is open then turn on pump2
• If On_condition occurs, controlpipe1 is open and controlpipe2 is open then turn on pump3
  
  
• If Off_condition occurs and pump1 is on, then turn pump1 off and open controlpipe2
• If Off_condition occurs and pump2 is on, then turn pump2 off and open controlpipe1
• If Off_condition occurs and pump3 is on, then turn pump3 off and close controlpipe1 and controlpipe2

I have updated the related wiki article with this information

The three pump curves are roughly the same but there is one pump that pumps down an 18" force main and the other two pumps pump down a 20" force main.  Those force mains have different end points in the system.  From the Volumetric flow data they have provided it looks like they cycle to have each pump have its turn to be the lead pump.  All pumps have the same on elevation but its rare that they have more than one pump running at a time.  I am trying to accurately model the volume of flow that can be seen on the two mains that are downstream of this lift station to see if surcharging is an issue during a rain event.  I am going to attempt Jesse's reply below and will let you know how it goes.  

Thank you for your help Jesse and everyone at Bentley this did exactly what I wanted it to do and the model works much better now!

Thank you for your help Jesse and everyone at Bentley this did exactly what I wanted it to do and the model works much better now!