Hello, I want to perform a flow an 1

[JimZinner]

Hello,
I want to perform a flow analysis for a proposed stormwater force-main utilizing EPANET. I have input the system with reservoir upstream of a pump, the existing pump curve, a series of pipe segments with their proposed diameters, and elevations at all of the junctions to a discharge point into EPANET. Pretty simple… I think.
I saw the following reply from a “semo” on 7-23-08 to a request for help from “brainsplease” on 1-30-08 for a similar scenario except he had 2 lift stations.
1. Use a reservoir for your pump input node. Set the head at the low water level of your wet well.
2. Set a curve for your pumps and model the pump using the appropriate curve.
3. Model your forcemain as you would waterlines.
4. Model the discharge as a reservoir with a head equal to the discharge elevation of the forcemain.
5. You can run it as static and the report will show the draw from each reservoir.
6. You need to run the system with all pumps but one off as well to see where the operating point falls on the curve when no other pumps are on.
7. No need to set demands at any nodes.
I do not have a lift station; just pumping straight out of a lake. I am not interested in the draw of the reservoir, but I am interested in the flow into the final inlet that is being pumped to. I inserted a reservoir at the discharge end of the system but it doesn’t appear the flow value is correct. I don’t have enough experience with EPANET to know how to correct the model. Is anyone interested in consulting me on this project? Please advise.
Thank, Jim Zinner

 

[trashcanman]

Please provide a flow diagram, showing all pumps, their elevation, distance from main, and elevation of connection at main. I think I can help.

 

[JimZinner]

Hello trashcanman,

Attached is a graphics input/output package providing the project plan with an aerial base, flow diagram showing all requested information including the existing pump curve. The junctions have state plane coordinates. I am not experienced enough with EPANET to provide a good input file, so I prepared snipets of each element and combined that within the package. The EPANET results provide an hourly output and the maximum flow occurs at hour 6.0; however, all I really need is a static output which I think should greatly reduce the output. I hope you can help me with this analysis utilizing EPANET so I can learn from what you provide me.

If you want to communicate outside of ENG-TIPS.com, let me know how we can trade email addresses. It appears that ENG-TIPS.com doesn't want email addresses indicated on this application due to spam and recruiters.

Thank you very much, JimZinner

 

[JimZinner]

Hello again trashcanman,
Also attached is the EPANET input file for your use.

 

[fel3]

I don't have time at the moment to dissect your model like I have done for a few others here on Eng-Tips. However, I did download your file, run it, and look at the error messages. I also took a quick glance at the data by exporting a text file. I see that the force main is all 4" and 6" pipe and that the pump is rated at 1000 gpm. If you are trying to get 1000 gpm through that system, then your pipes are too small:
-- 1000 gpm in a 4" (nominal) pipe requires a flow velocity of 25.5 fps. Assuming a H-W C of 100 (per your model, but your new pipe will likely have a C closer to 140) results in a head loss of 869 ft per 1000 feet of pipe.
-- For the 6" (nominal) pipe, it's 11.4 fps and 121 ft of head loss per 1000 feet of pipe.
This is why you are getting error messages. The WARNING message says that the pump cannot deliver the required head, which is what I figured out with my hand calcs.

You should really be targeting something closer to 5 fps, which means 8" or 10" pipe. Also pay attention to the actual diameter of the proposed pipes. Some pipe sizes and types have actual diameters that are larger than nominal and others are smaller. I use actual diameters where possible because the differences between actual and nominal can be significant. You should also consider including minor losses, at least in the piping immediately around the pump. I have had systems where the minor losses exceed the pipe losses.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[JimZinner]

Thank you very much fel3. I am not trying to maintain a certain flow, but I do want it to get the water to the discharge point. I will take a look at it in the morning. Again, thank you so much!

 

[JimZinner]

Hi fel3,
I revised my pipe diameters to have inside diameters for Pressure Class 235 psi (DR 18) per a minimum spec found online; 4.23” ID for 4” nominal and 6.09” ID for 6” nominal. I included new upstream and downstream junctions and piping located around the pump as shown in the graphics. I found my pipes were not linked to the reservoirs correctly and I had a pump speed of 1550 which I assumed was the RPMs of the motor. I removed the pump speed and the 629.32 cfs flows appear to be reasonable without increasing the pipe diameters. I have a couple of questions. Is there a way of inputting minor losses within EPANET? I see where pipes and valves have a minor loss input. Question 2: how can a static run be made to reduce the output length? Last question: Will this much head loss damage the pump?
Thank you,
Jim Zinner

 

[JimZinner]

Attached is the EPANET model input file.

 

[JimZinner]

Hi again fel3, et.al,
I've taken care of the minor losses and static run issues. Thank you for you help. I greatly appreciated it.
Jim Zinner