Ch 7. Theoretical Pressure Calculations Flashcards
Why must driver/operators know the amount of friction loss and pressure lost in the fire hose?
To effectively provide water for fire streams
What two characteristics of fire hose must be known to calculate friction loss?
Length and diameter
The combination of friction loss, elevation pressure loss, and loss associated with appliances is referred to as:
Total pressure loss
What are the two ways of determining friction loss?
Calculations in performing tests
What is the formula for determining friction loss?
FL = C x Q2 x L
When jurisdictions perform their own tests for friction loss coefficients, testing should be conducted using:
Actual hose that will be used during firefighting operations
When determining friction loss coefficients, how many types of hose should departments test at one time:
Only one type of hose at a time
When testing for friction loss coefficients, departments that use a Pitot tube should use what type of nozzle?
A smoothbore nozzle
When testing friction loss coefficients, departments that use a flow meter should use what type of nozzle?
Any type of nozzle
What is the assumed appliance loss when flowing less than 350 GPM?
0 psi
What is the assumed appliance loss when flowing greater than 350 GPM?
10 psi
What is the assumed appliance loss for all master stream appliances, regardless of the flow that will be used?
25 psi
Why is it important to factor in friction loss for Handline nozzles?
It is a very significant factor in pressure loss and must be taken into account
Elevation pressure is created by elevation differences between:
The nozzle and the pump
The CUSTOMARY formula for elevation pressure loss is:
0.5 x height in feet
(.434 x height in feet for theoretical)
The METRIC formula for elevation pressure loss is:
10 x height in meters
The CUSTOMARY formula used to determine elevation pressure in a multistory building is:
5 PSI x (number of stories -1)
The METRIC formula used to determine elevation pressure in a multistory building is:
35 Kpa x (number of stories -1)
When determining friction loss in multiple hose lines of equal length and who’s diameters are the same, it is necessary to perform calculations for:
Only one line
When the diameters of hose lines very, friction loss calculations must be made for each hose line, and then said based on the:
Higher pressure
In order to avoid having two different nozzle pressures when using a wye, it is important that the two smaller attack lines wyed from the supply line are:
The same length and diameter
Friction loss is approximately 25% less than that of a single hose line at the same nozzle pressure when:
Two hose lines of equal length are Siamese to supply a fire stream
Jurisdictions are likely to have predetermined pressures when connecting to the FDC to supply a _______?
Standpipe
When an incident may require the use of multiple hose lines of the same or different diameter that are of unequal length, friction loss must be calculated for:
Each hose line supplied by separate discharges to individual nozzles
When using a manifold appliance and the hose lengths are unequal and/or the diameter is different, total pressure loss in the system is based on:
Highest pressure loss of any of the lines
What is the appliance loss of a master stream device?
25 psi
When calculating total pressure loss for elevated waterways, the driver operator must consider:
Pressure loss in the aerial device
Pump discharge pressure equals the sum of what three factors?
Friction loss, nozzle pressure loss, elevation pressure loss
What is the pump discharge pressure formula?
PDP = NP + FL + EL + AL
Or
PDP = NP + TPL
Pump discharge pressure should be calculated and set based on:
The hose line with the greatest pressure requirement
What is the safe and efficient nozzle pressure for a solid strong nozzle (handline)?
50 psi
What is the safe and efficient nozzle pressure for a solid stream nozzle (master stream)
80 psi
What is the safe and efficient nozzle pressure for a fog nozzle?
100 psi
(50 for Akron Assault)
The formula for net pump discharge pressure is:
NPDP = PDP - Intake reading
Friction loss is caused by a number of factors including the condition of the hose and couplings as well as any kinks in the hose line. However, what is the primary consideration in determining friction loss?
The primary consideration is the volume of water flowing per minute.
What is the only truly accurate method for determining pressure loss in a particular hose lay?
The only truly accurate method involves measuring the pressure at both ends of the hose line and subtract in the difference
