Lift Station Pump Cycling Time
Lift Station Pump Cycling Time
(OP)
I am currently designing a lift station for a small subdivision. I have calculated the flow into the wet well to be 36.4 gpm (it is a very small system). The diameter of the force main leaving the wet well is 3 inches. I was able to calculate the total dynamic head which then allowed me to choose my pump from the Flygtt pump selector. My question now is how do I go about sizing the wet well or calculating the cycle time if I have two of the same pumps which will be ran in a lead/lag system?





RE: Lift Station Pump Cycling Time
You will need to establish a peak flow rate, probably something like 3-5 times the average flow rate.
The depth of the incoming sewer needs to be determined?
What is the maximum number of starts per hour you will accept for your pumps? Probably 5 - 8 starts an hour would be a good start.
The pump performance needs to be established with one pump and two pump operation.
When you say lead/ lag do you mean duty/ standby or both pumps on duty with second pump coming on after a time or upon a certain level being achieved?
The other issue will be is whether or not you are going to use a package or precast station, or will you custom build to suit. If you are using packaged or precast then some of your dimensions will be established for you and you will need to work within those constraints.
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
RE: Lift Station Pump Cycling Time
RE: Lift Station Pump Cycling Time
Thanks for your time,
Justin Gonzales
RE: Lift Station Pump Cycling Time
If your pump station could store 100 gallons between the low level and the pump start level and flow in was 10gpm it would take ten minutes at peak flow to get the level to the point where the lead pump would start. If the pump had a capacity of 20gpm it would take 10 minutes to pump out because with the 10gpm flow in this would give it an effective flow rate of 10 gpm. Therefore in this scenario the pump would pump for 10 minutes and be off for 10 minutes which would equate to three starts per hour. Total cycle time 20 minutes
If the pump had a capacity of 100 gpm the number of starts per hour increases. It would take 10 minutes for the pump station to fill but at a 90gpm effective out flow rate the pump would only pump for a little over a minute(66 secs). Total cycle time 11.1 minutes which is 5.4 starts per hour.
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
RE: Lift Station Pump Cycling Time
Then I could easily find the LS+ (pump on) point for a given allowed starts per hour.
The math is of course exaclty as in ashtrees post above, I just couldnt do it in my head.