Hello, I'm modelling a large size existing water supply network with many boosters through the network. There is also a tank with a pumping station through the network to provide water for a further network. So my question is how can I model a the the connected pumps to the storage tank?
I put the following conditions for both pumps :
If the tank level is below 10%, then pump status is OFF, else: Pump status is ON
But no flow is discharged by the pumps:
the error messages are:
Pump "PMP-22 cannot deliver flow or head."
and "Tank T1-Tech Institute 1 is full."
Tanks become full because the inflow exceeds to outflow over time. That's a trivial statement. What does it mean for you?
You need to look into increasing the outflow but if you have a fairly low demand downstream, that's not feasible. Then you can decrease the inflow. This can be done by turning off some pumps upstream of the tank or if that's not feasible, throttling the inflow to the tank using a control valve. This can also be done by shutting off inflow to the tank when it gets to about 98% full and opening it when the level drops to say 60%.
It's good to test out a lot of operational alternatives like this (e.g. peak demand/low demands, controlling inflow vs. outflow,... ) before you construct the pump station and your options become limited.
Also, what is the purpose of the tank on the suction side. Is it there to provide surge protection NPSH, or storage for the zone from which it is fed?
The overflow for that tank should be consistent with the hydraulic grade in the zone that feeds it. One way to keep it from getting stuck full, is to make it taller and consistent with that HGL. The elevation of the overflow should be consistent with the other tanks in the zone.
Dear Tom,
Sorry for my late response. Many thanks for your complete response.
Indeed the reason is storig water for the zone from which it is fed.
Also, this is an existing system that I try to model. We are not yet 100% sure about the population of the city to have the exact water demands. But we are not so far from the reality.
How can I put the control valve for the tank?
Dear Sushma, Sorry for my late response. Thank you for your response.
I made the graph, in fact the graph shows that the tank water level varies slightly. The tank has almost 3m of height with following descriptions:
And in controls I put if level is between 30% and 80% pump off and if less than 30% pump on:
Is it correct?
Could you please help?
Dear Jesse, Thank you for the response. Yes I did exactly the same. But I have still the error of Tank level full.