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fire flow analysis at max hour

Hello,

i'm doing the design of potable water and fire fighting network as combined network for a new site, 

we are studying two scenarios (MAx daily + fire) and (Max hourly). because it is too big site (7,000,000 m2) the peak design is the Max hourly flow.

i'm trying to study the fire flow analysis in the scenario of (Max daily + fire) and the hydraulic of the network (pressure and velocities) in the second scenario (Max hourly)

we are proposing three main DMA's, according to my previous study in water losses management we should add the entrance of each DMA with a PRV to sustain the pressure at minimum value for better leakage management. but when i used the PRV's it affected the fire flow analysis

do i follow the right methodology for such case?

note: according to the client requirements, we are assuming fire flow at each junction of the network

Regards 

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  • Hello Ahmed,

    If I understand the issue correctly, you should make sure that the different elements in the model are assigned to the proper pressure zones. When doing the automated fire flow analysis, the program is look at the residual pressure at the fire flow node itself as well as the pressures for the junctions in the same pressure zone as the fire flow node. If you only have one pressure zone, that means that a low pressure at a distance node in a different pressure zone will impact the results.

    In steady, you should make sure you have the junctions assigned to their appropriate pressure zones, in this case likely assigned by their position in relative to the PRVs. This might help with some of the results you are seeing.

    You can find more information on setting up and using the automated fire flow feature at the following TechNote: communities.bentley.com/.../understanding-automated-fire-flow-results

    Regards,
    Scott

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  • Hello Ahmed,

    If I understand the issue correctly, you should make sure that the different elements in the model are assigned to the proper pressure zones. When doing the automated fire flow analysis, the program is look at the residual pressure at the fire flow node itself as well as the pressures for the junctions in the same pressure zone as the fire flow node. If you only have one pressure zone, that means that a low pressure at a distance node in a different pressure zone will impact the results.

    In steady, you should make sure you have the junctions assigned to their appropriate pressure zones, in this case likely assigned by their position in relative to the PRVs. This might help with some of the results you are seeing.

    You can find more information on setting up and using the automated fire flow feature at the following TechNote: communities.bentley.com/.../understanding-automated-fire-flow-results

    Regards,
    Scott

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