7. Mathematics for the driver operator Flashcards
To extinguish a fire sufficient flow must be applied to overcome the heat generated by the fire- a rate referred to
Critical rate of flow
PDP =
PDP = NP + FL
Nozzle psi
Combination nozzle or fog nozzle 100 psi
Low pressure fog 50 to 75 psi
Solid steam 50 psi
Distributor nozzle psi
100 psi
Elevated smoothbore master stream psi
80 psi
Nozzle reaction for a smoothbore
NR =
NR = 1.57 x d^2 x NP
Now is a reaction for a fog nozzle
NR =
NR = 0.0505 x gpm x NP squared
If you double the speed of water the friction loss will increase ___ times
4x
FL=
FL = C Q^2 L
Water exerts a pressure of
0.434 psi per 1 ft of water column
Elevation pressure =
EP = 0.5H
5 psi for every floor above the first
10ft per floor common
Friction loss for appliances when flowing less than 350 GPM
0
Friction loss in appliance when the flow rate is 350 GPM’s or greater
10 psi
Friction loss for all master stream appliances
25 psi
Three methods used to calculate the friction loss in lines to the Siamese connection
Split flow
coefficient
percentage
As a general rule you should not exceed a PDP __ psi in a standpipe
200 psi
Simply add ___ psi to account for the standpipe riser
25 psi
Pressure regulating valves are installed on standpipe risers where static pressure exceeds __ psi
175 psi
To determine the head pressure, divide the height of the column in feet by
2.31
Note
PDP = NP + FL
FL = C Q^2 L + AL + EP
The subtracting method determines friction loss in 2 1/2 inch hose only and for flows of __ GPM or greater
160
The fastest and easiest way to calculate the available water from a hydrant is to use the ___ method
First digit method
