If the amount of flow through a relay operation needs to be increased, depending on the size of the supply hose and fire flow requirements, at least one of the three considerations must be met:
> The diameter of the supply hose or the number of hoselines must be increased
The pump discharge pressure of the pumpers involved in the relay must be increased
More pumpers must be added to the relay to overcome friction loss or elevation
Fire department pumpers are rated to flow their maximum volume at ____ psi, ___ percent of their maximum at ___ psi, and ___ percent of their maximum at ___ psi at draft.
100% at 150 psi
70% at 200 psi
50% at 250 psi
Formula for Relay Distance:
P = R/D + 1
P = Total # of Pumpers R = Relay Distance D = Distance from Tables 12.1a or 12.1b
is rounded up to the whole number.
Apparatus equipped with pressure governors should be set in the ______ mode when acting as the attack pumper and in the _____ mode while working as a relay pumper.
For “relay pumpers” equipped with an adjustable intake relief valve, they should be set to ___ psi about the static pressure of the water system to which it is attached or ___ psi above the discharge pressure of the previous pumper in the relay.
“Attack pumpers” equipped with an adjustable intake relief valve should be set between ___ and ___ psi to establish a stable operating condition.
50 and 75 psi