This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Unusual Flow Results

I'm getting some unusual results and am unable to find a solution. I'm trying to better calibrate our model near an area where 2 pressure zones meet.

I've performed a fire flow analysis and tried to confirm the pressures and flow in that area.  A flow test was performed at hydrant H-1782. Just north of this test location, we have a control valve that stays closed if our north system has less pressure than our south system.(they differ by 20 psi because of tank elevations).  I've tried modeling this valve as a PRV.  We also have some isolation valves in the area and have ran the model with the isolation valves closed and get the same results.

The model predicted the following:

Static: 54.4 psi

Residual 23.3 psi

Flow: 591 gpm


Actual flow test data:

Static: 64 psi

Residual 38 psi

Flow: 1950 gpm

This tells me that the model is predicting to much head loss.  I've confirmed that the C-factors are correct, tried zeroing out the demands south of the test location thinking the demands might be too large, and checked for closed valves.  None of this seemed to help the situation.

The piping feeding this area has a 6" & 10" feeding into an 8" main which eventually increases to a 12" main.(Don't ask why)


I've attached the model for your convenience.  Any help/ideas is greatly appreciated.

2013 Water Model.zip
Parents
  • When you say that you confirmed that the C-factors are correct, how did you do that?

    I can see that the C-factors in the 8" main that feeds H-1782 are all set to 100, and as a result there is a lot of headloss in that main. Is it possible that the C-factors in those pipes should be higher (say 120 or 130)? That would make a significant difference in your results.

    Also, did you confirm that the model conditions were the same as when you did your flow test? For example, tank levels, pump status, etc. should be the same in the model as they were when you did your flow test.

    Regards,

    Mal

          

  • Mal,

    I’m running the automated fire flow analysis for my scenario run.  The C-factors are 139 for that alternative.

    Well, when I say that I've confirmed the C-factors, I mean I've looked at them to verify the values are reasonable for the pipe material and age.

    I have looked at the tank levels, pump status, etc and they are all correct for this test.  I've even tested it with tank levels to be full and the flows/HGLs are not near what the measured values are.

    I have also done other flow tests and input them into Darwin Calibrator.  Calibrator has adjusted the C-factors of the different pipe materials and demands within my constraints to achieve a relatively good fitness value.  Once this test information was completed in input into Calibrator, the fitness jumped from low double digit numbers to multiple thousands.  Something in this end of my system is throwing off the calibration of the model by a huge factor.

Reply
  • Mal,

    I’m running the automated fire flow analysis for my scenario run.  The C-factors are 139 for that alternative.

    Well, when I say that I've confirmed the C-factors, I mean I've looked at them to verify the values are reasonable for the pipe material and age.

    I have looked at the tank levels, pump status, etc and they are all correct for this test.  I've even tested it with tank levels to be full and the flows/HGLs are not near what the measured values are.

    I have also done other flow tests and input them into Darwin Calibrator.  Calibrator has adjusted the C-factors of the different pipe materials and demands within my constraints to achieve a relatively good fitness value.  Once this test information was completed in input into Calibrator, the fitness jumped from low double digit numbers to multiple thousands.  Something in this end of my system is throwing off the calibration of the model by a huge factor.

Children