FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS > Operational

Pressure for structural firefighting

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Clevelandfire 3:
I know the minimum flow rates required for structural fire fighting but can't find any up to date references regarding pressure, or am I missing the point (ie so long as flow rate is achieved then the pressure is largely irrelevant)

Dinnertime Dave:

Yes, fire service pump will increase the pressure.

SeaBass:
The dynamic pressure is critical. Too little and the throw of the jet won't be sufficient to reach the fire, too much and the branch operators will be knocked off their feet, or worse, and the water jet will feather and break up before it reaches the fire. The pump operator also needs to make allowances for the loss in pressure at the branch that will be incurred for every meter of rise, when the branch is taken aloft (0.1 bar loss per metre) as well as losses due to friction arising from the flow of water in the hose line.  The old Fire Service Manuals go into this in quite some detail, I think that it was in book 7, Hydraulics and pump operation, from memory.   

Clevelandfire 3:
someone said these days that crews need at least 5 bar at the branch to undertake gas cooling?

SeaBass:
 Five bar sounds about right. The rule of thumb for pump operators used to be to aim to provide no more than 70 PSI at the branch, which is just under five bar, and then increase or decrease as was necessary.  70 PSI with a standard, uncontrolled branch pipe and nozzle, was fine for a two person branch team, who knew what to expect, and could brace themselves for a known level of jet reaction.

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