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All nodes failed

Hello,

All junction and FH in my model are failed due to the available flow is less than the need flow. At first, the nodes passed when I input in the units demand for a few junctions, but after putting in the unit demands for all the junctions nodes, all the nodes was failed again. How do I fix it?

Thank you.

  • JP, 

    There is a section in the automated fire flow wiki that can help you with this called "Understanding why a node cannot provide the desired fire flow". The reason is likely one of the constraints that you have set on on automated fire flow window, such as 'pressure zone lower limit' or a mistake of adding the fire flow demands onto the junctions in the model and then setting the fire flow analysis to adding to the baseline demand in the automated fire flow, which would double up on the fire flow needed for those junctions. If you can't locate the reason with this wiki you might want to try posting a screen shot of your automated fire flow settings window. 

    Mark 

  • This is my constraints

  • also this is the results I got

  • Try to create a selection set of only the junctions in the model that you are trying to run a fire flow for instead of including all the junctions and hydrants. Make sure that you exclude junctions that are on the suction side of pumps. After that choose the selection set name in the fire flow alternative and run the analysis again ( I posted a screen shot of where to choose the selection set name).

    At this point it looks like hydrant H-75 is what is causing the problem here, but there are still things that are hard to tell without seeing the model. It might help if you added the following fields to your fire flow results table: 1) 'Pressure (calculated residual @total flow needed) Or Pressure (Calculated total residual lower limit)    2) Pressure (Calculated zone lower limit @ total fire flow needed)  3) Junction with minimum pressure zone @ total flow needed). The fields may be titled differently depending on the version you have. 

      

  • Hello JP,

    To add to what Mark said, there is a flextable specific to the fire flow results. The Fire Flow Results Table can be accessed through the FlexTables manager. This will include the results mentioned above.

    As mentioned above, it is possible that H-75 is reached the zone pressure constraint of 15 psi. If that is the case, it will limit the fire flow available at the fire flow node. 

    This link has further information on understanding fire flow results.

    Regards,

    Scott