Chapter 5 Flashcards
Principle of water
Water is considered to be?
virtually incompressible and it weights varies at different temperatures.
For fire protection purposes,ordinary fresh water is considered to weight?
62.4 pounds per cubic feet or 8.3 pounds Per gallon
force is
simple measure of weight and is expressed in pounds or kilograms
Friction loss in a water system ___as the length of hose or pipe in increases
Increases
To prevent water hammer when flowed from a master streams or hydrant opened
they should be partially closed,stopped ,and then closed more as a prevention measure.
water may be reactive with certain fuels
2•SODIUM METAL
3• TRIETHYI ALUMINUM
4• COMBUSTIBLE METALS
atmospheric pressure @ sea level is
14.7psi
any pressure less than atmospheric pressure is called
a vacuum
absolute zero pressure is called
perfect vacuum
a vacuum is needed
to facilitate a drafting
head
The height of a water supply above the discharge orific.
Alternate term for pressure especially pressure due to elevation.
for every 1 foot increased in elevation
0.434 psi is gained
static pressure
stored potential energy available to force water through pipes,hoses.etc
residual pressure
available pressure not used to overcome friction loss or gravity while forcing water through pipes,fittings,hoses or adapters
flow pressure
While water is flowing from a discharge opening,the forward velocity pressure
when measuring the forward velocity of flow pressure,what must be used?
a smoothbore nozzle with a pitot tube and gauge
above sea level atmospheric pressure
decreases 0.5psi for every 1000 feet
Fluid pressure at a point in a fluid at rest is the same intensity in all directions
Describes the second principle of pressure
Water may be used to smother fires in which type of combustible liquid?
Combustible liquid whose specific gravity is higher than 1 (heavier than water)
What describe the term elevation in the fire service
The center line of the pump or
the bottom of a static water supply source above or below ground level
What determines the velocity for a given volume of water?
Diameter of hose
The first principle of friction loss?
If all other conditions are the same, friction loss varies directly with the length of the hose or pipe.
Second principle of friction loss
When hoses are the same size, friction loss varies approximately with the “square”of the increase in the Velocity of the flow.
example 3” hose flowing 200 gpm = FL of 3.2 psi. As the flow doubles from 200-400 gpm the friction loss increases
four times
3” hose flowing 400 gpm (2×2=4) 3.2×4= FL of 12.8 psi
When the original flow tripled from 300-600 gpm the friction loss
increase nine times
3” hose flowing 600 gpm (3×3=9) 3.2×9= FL of 28.8 psi
The third principle of friction loss is
For the same discharge, friction loss varies inversely as the fifth power of the diameter of the hose.
eg. a 2.5” and a 3” hose.
The friction loss in the 3” hose is: 2.5 to the fifth power divide by 3 to the fifth power 2.5×2.5×2.5×2.5×2.5=97.66 3×3×3×3×3=243
97.66/243=0.4 that of the 2.5 hose
The forth principle of friction loss
For a given velocity,friction loss is approximately the same,regardless of the pressure on the water
The diameter of the hose determines the velocity for a given volume of water therefore?
The smaller the hose,the greater the velocity needed to deliver the same volume
The speed at which fluid travels through a hose or pipe is determined by
The pressure upon the fluid as well as the size of the orifice through which it is flowing.
The pressure upon the fluid as well as the size of the orifice through which it is flowing.
Pressure applied to a confined fluid is transmitted equally in all directions
The first principle of pressure
Fuel pressure is perpendicular to any surface on which it acts
The second principle of pressure
Fluid pressure at a point in fluid rest is the same intensity in all directions.
What principle of pressure is used in hydrostatic testing
The second principle
The fourth principle of pressure
The pressure of a liquid in an open vessel is proportional to its depth
The fifth principle of pressure
The pressure of a liquid in an open vessel is proportional to the density of the liquid
When the flow of water for fire fighting needs to be increased;
It is said usually acceptable to use large diameter hose to reduce friction
The primary water supply can be obtain from?
Surface water or ground water
What is illustrated by the second principle of friction loss
Friction loss develops much faster than change in velocity
If velocity is increased beyond practical limits the friction becomes so great that resistance agitates the entire system, and creates?
Critical velocity
What describe best the term altitude in the fire service
position of a location or object in relation to sea level.
The location may be either above below to sea level
Secondary feeders
Network of intermediate size pipes that reinforce the grid within the various loops of the primary feeder system and aid in the concentration of the required fire flow at any point
Flow pressure will always be greatest near the source of supply lowest at the furthest point in the system
true
Distributors
Make up of a grid arrangement of smaller mains serving individual fire hydrants and blocks of consumers
The friction caused by water flowing through the pipes,valves and fittings is the difference between static pressure and:
Normal operating pressure
When does water exist in a liquid state?
Between 32°F and 212°F
To convert head in feet to head pressure, you must?
Divide the number of feet by 2.304 (the number of feet that 1 psi will raise a one sq inch column of water)
The maximum amount of vacuum most fire pump will develop?
Approximately 22” of mercury
Because total vacuum is not possible in field operation fire apparatus must have a maximum lift of
25 feet
After life safety, the highest priority for most wildland fire fighting operations is?
The protection of structures that are exposed to the fire.
When priming,water enters the pump because
Atmospheric pressure forces it it into the pump
A_____ gauge is calibrate to read both positive and negative pressure
compound
Switch from pressure to volume operation when
There is a reason to believe that more than half of the rated capacity of the pump will be required
Given a pump that is in gear supplied by Tank water with no discharges open,what principle of pressure is represented
Pressure applied to a confined fluid from without is transmitted equally in all directions (the third principle of pressure)
The purpose of the_____is to provide circulating feed for several mains
Grid system
In draft an operation, Pumping ability decreases when
.
The formula 29.7 (d)sq x sq of np
Flow of water in gallons per minute
For drafting purpose,lift is measured from the ____ of the pump
Surface of water to the center
NFPA requires that a pumper most pump it’s rated capacity at_____of lift
10
The friction caused by water flowing through the pipes,valves and fittings of the system is?
The difference between static pressure and operational pressure
The forward velocity pressure while water is flowing from a discharge opening is referred as
Flow pressure
Friction loss in older hose may be as much as 50% greater than in new hose
true
Friction loss develops much faster than change in velocity
Is illustrated by the 2nd principle of friction loss
The fourth principles of friction loss states that for a given velocity, friction loss;
Is approximately the same,regardless of pressure on the water
The diameter of hose determines velocity for a given volume of water
True
The smaller the hose,
The greater the velocity needed to deliver the same volume
A pressure of _____is required to reduce water volume 1%
30,000
Grid arrangement of smaller mains serving individual fire hydrants and blocks of consumers
Distributors
The speed at which fluid travels through a hose or pipe is determined by the _______ upon that fluid as well as the ____ of the orifice through which it is flowing
1•Pressure
2•Size
Any pressure less than atmospheric pressure is called _____, and absolute zero pressure is called a ___________
1• vacuum
2•Perfect vacuum
To convert head in feet to head pressure, you must divide the number of feet by _____ (the number of feet that 1 psi will raise one square in column of water).
2.304
For every 1-foot increase in elevation, ______ psi is gained.
0.434
Above sea level, atmospheric pressure decreases approximately .5 psi for every 1000 feet
.5psi for every 1,000 ft
The height required for a 1 square inch column of water to produce 1 psi at its base equals
1 foot divide by 0.434 psi/ft or 2.304 feet.
Therefore a column of water 2.304 feet height exerts pressure of 1 psi at its base
water pressure may be produced by an
1•elevated water supply
2•atmospheric pressure
3•a pump
The sixth principle of pressure
The pressure of a liquid at the bottom of a vessel is independent of the shape of the vessel.
Different ways water can be treated are
1•coagulation
2•sedimentation
3•filtration or addition of chemicals
4•bacteria or other organisms
In addition to removing things from the water,fluoride or ozone may be added
If all other conditions are the same friction loss varies directly(178)
With the length of the hose or pipe
When hoses are the same size,friction loss varies approximately(pg.178)
With the square of the increase in the velocity of the flow
For the same discharge(179)
Friction loss varies inversely as the fifth power of the diameter of the hose
For a given velocity(179)
Friction loss is approximately the same regardless of the pressure on the water
Two ways in which water has the ability to extinguish fire
Cooling and smothering
static
means at rest, or without motion
the difference between static pressure and normal operating pressure is the
Friction caused by water flowing through the pipes, valves and fittings of tge system
elevation refers
Is the Centerline of the pump or the bottom of a static water supply Source above or below ground level
when a nozzle is above the level of the pump
is a pressure gain
elevation pressure
the pressure losses or gains due to gravity
less dense atmospheric pressure______ pumper effective lift when drafting.
reduces
generally control valves in public water distribution system are
gate valves
if a control valve resist turning after fewer than the indicated numbers of turn that usually means
obstruction in the valve or it may be corroded
the adverse effect of encrustation and sedimentation can be reduced by
flushing hydrants periodically
the average daily consumption (ADC)
the average amount of water used per day based on the total amount of water used in the water distribution system over the period of one year
the max daily consumption (MDC)
is the maximum total amount of water that was used during any 24-hour interval within a three-year period
Peak hourly consumption (PHC)
the maximum amount of water used in any one hour interval over the course of a day
