IFSTA Chapter 11 Static Water Supply Sources Flashcards
Lift is the difference in elevation between _______ of the static water supply and the __________
surface
Center of the pump intake
During drafting what does the priming device do
Exhausts air from the intake hose and fire pump creating a pressure difference between the inside of the pump, the intake hose and the atmosphere
Using fire service equipment can a total vacuum be created
NO
What causes during draft for water to rise until the pump is full
Pressure outside the intake hose is higher than the pressure in the hose
What 3 factors affect the maximum height of water that can be lifted
The Angle of the intake hose
The amount of negative pressure (vacuum)
Existing atmospheric pressure (sea level or above)
Theoretical lift
Scientific height that a column of water may be lifted by atmospheric pressure in a true vacuum which is 33.9 feet
Unable to be achieved by fire apparatus
Maximum Lift
Greatest height to which any amount of water may be raised through an intake hose to the pump
Maximum lift will be affected by these conditions
Atmospheric Pressure
Condition of the pump and primer
Conditions of the intake hose, gaskets and all valves
Strength and condition of motor driving the fire pump
What height does Maximum lift approximate to
How does maximum lift hinder a draft operation
25ft
all atmospheric pressure is used to overcome the gravity pressure affecting the lift. The volume of water available for the fire pump may be too low to be of value in fire suppression
Formula to determine maximum Lift
L= 1.13 x (inHg)
L= Height of Lift
(Hg) = Inches of Mercury reading on the master intake gauge
Dependable Lift
Height in Ft
Height a column of water may be lifted in sufficient quantity to provide a reliable fire flow
Usually considered to be at least 14.7 feet
At what minimum lift are most fire department pumpers rated at and how deep is the strainer submerged
Minimum 3 ft lift from the center of a pump intake to the surface of the water through 20 ft of hard intake hose.
Strainer submerged atleast 2 feet in a water depth of at least 4 feet.
Determin NET pump Discharge pressure
Accounts for all factors that contribute to the amount of work required by a pump to produce a fire stream
NPDP (at draft)= Pump Discharge Pressure + Pressure Correction
Net Pump Discharge Pressure Correction at draft formula
PC = (Lift + Total intake hose friction loss) / 2.3
PC = (Height in feet + (2) + (1/2 ONLY for addtnl suction hose sections) / 2.3
Minimum depth/water around the barrel style strainer
2 feet
