Dear all,
I have a situation where pipe network is laid upto 12 overhead tanks. Now I need to design pump to feed water to this network, so that daily demands at the tanks are met. So far, what I have tried is- defined a 1 design point pump with an approximate head and exact cumulative demand of the 12 tanks. When I run the system, it gives no error and the ESRs show positive residual head. So I guess the pump is working. However, the head I entered is approximate. And I need to place purchase order for the pump. How do I know that the pump definition is optimal for the network? How do I design a pump such that I am not over-sizing / under-sizing it?
I would gladly share my model if anyone's willing to have a look at it.
Regards,
Pankhuri
Hello Pankhuri,
The model appears to compute without issue for a steady state run.
I did set the the calculations to run an EPS run as well. There were issues there, related to disconnected demand nodes. These occurred because some of the tanks upstream of the demands were becoming empty. The reason that tanks were becoming empty is because the hydraulic grade into the tank was lower than the invert of the inlet pipe. For a top fill tank, if the hydraulic grade into the tank is less than the invert elevation of the inlet pipe, the tank will not fill. The top fill tank wiki article has information on this.
So if you are planning on running an extended period simulation at some point, some review of the demands, tank input, or pump may be required.
Scott
Partial Trial Run O&M.zip
Hi Scott,
Thank you for responding.
Please find attached wtg and wtg.sqlite files. There are two scenarios, 23hrs and 16hrs pumping. I have assigned demands to a junction at outlet pipes of Tanks, instead of assigning them to the Tanks directly.
Please do have a look.
Thanks & Regards,
You can send the model us with the steps in this link.
We can make sure there are not any obvious issues, but can't really give engineering advice.
Hi @Tom & @Scott,
Based on your answers, I changed my model to reflect Tanks on discharge side of pump. Earlier, I was representing tanks as simple junctions. I made the tanks top-filled to reflect real-life situation. I think now I have a better model. The system head curve is coming out ok. However, I am still not fully confident about my design. I haven't run EPS as I haven't learnt it yet. Could any of you please take a look at my model? I would greatly benefit from a review.
This information is also documented in this wiki: General Pump Selection Process.