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EPANET 2.2 flow rate shows higher than pump capacity

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Asisraja D

Asisraja D

Mechanical
Jan 3, 2024
159
Dear professionals
i have asked fire hydrant line questions here before as you guys told i have tried epanet 2.2 software for modeling our fire hydrant system piping.
i will give you the details i have taken to draw them below:
1.)Pump capacity - 137 m3/hr
2.)Pump head - 70 meters
3.)Line size - 150 mm
4.)H-W roughness - 100
5. Flow units - CMH
6.)Single period analysis
7.)Reservoir total head - 6.5 meters.
i am getting 1300 CMH as flow rate at first link and i have few question about basic stuff in epanet
1.) Why cant i draw straight lines in epanet like Autocad ?
2.) if i position tank or receiver above the link (pipe) i am getting zero flow in pipe ? i don't know how this software works basically

i have attached the link for .map file with this, review my modeling if possible.


please bear me if i test your patience and help me with your guidance.



i am very basic in pipe network modeling plz anyone help me to correct my modeling.
 
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I am not looking at your data file, but ...

You have 6.5 m elevation head.
Your pump head capacity is 70m.
I did not estimate head loss in your 6", but
I think it is probably much less than 70-6.5 =63.5m.
So you need to provide a total of 70m head loss before the pump will flow 137m3/h.
Right now your pump is very far out to the right of its BEP operating point, so head produced is closer to 6.5m, rather than 70 m. That causes flow to be very high. Pump is running nearly wide open.

Tell me what the pipeline friction head loss is at 137m3/h. It should be around 63.5m. Install a pinch valve at the pipeline entry into the reservoir and, if you need more head loss, start closing it until flow drops to 137m3/h.


--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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Hi,
Share with us the pump curve! I doubt you get 1300 m3/h or a velocity of 20 m/s, even your system is going to the far right.
Start with basic.
Pierre
 
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Fire systems need a certain head or pressure at the hydrant or fixed spray. You don't mention what the pressure is and you might need to model that.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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1503-44 sir
I didn't calculate pipe friction loss but i gave the value as 100 for HW equation in epanet.

But I have doubt in elevation head vs node elevation? What does it mean ?
My reservoir overall height is 7.3 from ground level if so how much elevation should I need to provide?

From tank suction nozzle the pipe delivery line height is 2 meter from ground level. (Is this node elevation?)

 
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pierreick sir
The pump curve which I provide here is 137 m3/hr and 70 meter as head.
In software I included as CU1 in pump browser area.
 
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LittleInch sir
We need 7 to 10 barg at line pressure in fire hydrant system.
 
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I can't read your *.map file.

Please post your pump curve data here.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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Hi,
Same comment as Mr 44, I cannot read the document. Supply the pump curve as a pdf doc.
My experience with hydrant, discharge pressure is about 12 bars, check with your fire brigade or insurance broker.
Pierre
 
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Well with a pump only delivering 70m diff by read you're not going to get 10 bar at the hydrant

And barely get 7 bar at the furthest hydrant.

How are you modeling this pressure requirement?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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You can not supply the minimum equipment and expect to get the performance required by your system.

Thanks for the pump curve. How did you enter the curve into EpaNet?
If you do not enter the curve correctly, you will get unpredictable and unreliable results, like 1300 m3/h. I think you have to look at that Epanet pump curve data requirements and the data you entered. Maybe you just entered the one (pump's rated operating) point on the curve?

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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1503-44 sir
I did only one point for pump curve but we didn't order the pump from any vendor so we did not get the pump curve.

Ok I will start from basic of including pump curve.
 
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If you do not have the exact pump curve, you must find a similar model and use the substitute curve until the design is confirmed when final vendor data is received.

When EpaNet does not get a curve, it seems to result in the maximum flow that can pass through the pipes at the operating point head, even though the pump cannot supply such flows.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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1503-44 SIR
That is good idea to try in this and i will try asap and update the results.
 
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Even if its basic try 0 flow, 80m head, 137, 70m, 180, 60m or maybe 55.

At least it will give the program something to go on rather than only one point.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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