Chapter 5 - Principles of Water Flashcards
The ______ must understand factors that influence water supply ______ and how the availability of water for fire suppression is achieved using a variety of ______.
- driver/operator
- capability
- methods
What is the most common weapon in the FF’s arsenal?
water
You must understand why water is an effective WHAT and the physics of WHAT kind of water?
- extinguishing agent
- moving
Below 32 degrees F (0C), water becomes a solid called?
ice
Above 212 degrees F (100C) is called the WHAT of water? it converts to what? (3)
- boiling point
- gas, water vapor or steam
You can see water vapor? TRUE or FALSE
FALSE
When can you start to see water vapor?
when it rises away from the surface of liquid and begins to CONDENSE
Water is considered virtually incompressible? TRUE or FALSE
true
Does waters weight vary with temperature? YES OR NO
YES
Water’s density (weight per unit of volume) is measured in WHAT per cubic foot?
pounds
For fire protection, fresh water is considered to weigh ____lb/ft3 or ____ lb/gal.
- 62.4
- 8.3
When water smothers a fire, it does this?
excludes oxygen
Can water heat or contribute heat to a fire?
No, it cools and absorbs
What kind of combustible liquid can water smother?
those with a specific gravity greater than 1
What is the specific gravity of water?
1
Within a closed space, how might water smother a fire?
when it converts to steam
Does gas have a higher or lower specific gravity than water?
lower, .72-.76
Does Methylene Chloride have a higher or lower specific gravity than water?
higher, 1.33
Pressure in this manual means force per unit area or?
pounds per square foot/pounds per square inch
What is pressure confused with?
force
Force is a simple measure of WHAT?
weight
Force is measured in WHAT?
pounds or newtons or kilograms
What force is “force” directly related to?
the force of gravity, the amount of attraction the earth has for all bodies
If several objects are placed on a flat surface and are all the same size and weight, they exert the same WHAT on that surface?
force
What influence can cause a change in the speed, direction or shape of a substance?
force
The force exerted by water is based on the impact of its _____ within a specific area.
weight
To understand how force is determined, you mus know the _____ of water and the ____ that a column of water occupies
- weight
- height
What is the weight of 1 cubic foot of water?
62.4 pounds
How many principles of pressure are there?
6
What is determined by the pressure on the fluid as well as the size of the orifice through which it is flowing?
the speed at which a fluid travels
What is speed of a fluid often called?
velocity
Is it important to identify the type of pressure when connected to fluids? Why or why not
YES - it has a broad range of meaning
What must a driver understand before they can understand the types of pressures on fluids?
the principles of fluids
The FIRST(of 6) principle of pressure states that fluid pressure is _______ to any surface on which it acts.
perpendicular
In the first principle of pressure, if the fluid pressure was not exerted perpendicular to any surface on which it acted, what would happen to the fluid if pressure was exerted in any other direction?
the liquid would move downward along the sides and rise at the center
The SECOND (of 6) principle of pressure states that fluid pressure at a point in fluid at rest is the same _________ in all ________.
- intensity
- directions
What testing process uses the second principle of pressure (fluid pressure at a point in fluid at rest is the same intensity in all directions.
hydrostatic testing
The THIRD principle of pressure (of 6) states that pressure applied to a confined fluid is transmitted ______ in all directions.
equally
How is the third principle of pressure illustrated in the book?
All pressures will be the same if…(2)
-hollow sphere with water pump attached and series of gauges all around, all gauges will register the same with pressure
-there is no change in elevation
and
-they are on the same grade line
Why would the gauge at the bottom of a 100 ft tall standpipe read 100 psi (100psi is applied) at the top, but 143.4 psi at the bottom? (according to the 3rd principle of pressure)
because of the weight of the water in the standpipe
Why are pressure-regulating devices installed in high rise buildings?
increase in water pressure requirements necessary for the height of buildings
What does a pressure-regulating device on a high-rise do for people on lower floors?
higher floors?
- more easily control hoselines
- use higher pressure required higher
The FOURTH principle of pressure (of 6) states that in an open vessel, pressure of a liquid is proportional to its _________.
depth
Three vertical containers with different depths, but the same cross-sectional area, help describe which principle of pressure?
fourth
The FIFTH principle of pressure (of 6) states that pressure of a liquid in an open vessel is proportional to the _____ of the liquid.
density
Two vessels containing different depths of different density liquids, but the same pressure at the bottom due to different specific gravity shows what principle of pressure?
fifth
How mush denser is mercury than water?
13.55 times
The SIXTH principle of pressure (of 6) states that the pressure of a liquid at the bottom of a vessel is ________of the shape of the vessel.
independent
If the same liquid has a different shape, but the same cross-sectional area at the bottom and the same height, will they have the same pressure?
What principle of pressure is this?
- YES
- fifth
How many types of pressure should a driver be acquainted with? What are they?
6
- atmospheric pressure
- head pressure
- static pressure
- normal operating pressure
- residual pressure
- flow pressure (velocity pressure)
The depth and density of the atmospheric pressure that surrounds the earth does what on everything?
exerts pressure on everything
Where is atmospheric pressure greatest at?
low altitudes
What is atmospheric pressure at sea level?
14.7 psi
Atmospheric pressure at sea level, 14.7 psi is considered what kind of atmospheric pressure?
standard
What is a common way to measure atmospheric pressure?
comparing the weight of the atmosphere with the weight of mercury
When looking at a vertical cylinder of mercury, the taller the column of mercury the ________ the atmospheric pressure is.
greater
1 psi pressure makes a column of mercury 2.04 inches high. If sea level pressure is 14.7 psi, how tall will the column of mercury be?
2.04 inches X 14.7 psi = 29.9 inches tall
The reading of most pressure gauges are psi in addition the existing ________ pressure.
atmospheric
How do distinguish pressure gauges from actual atmospheric pressure?
psig
vs
psia
What is the actual atmospheric reading?
psia (pounds per square inch absolute)
What is the reading of most pressure gauges?
psig (pounds per square inch gauge)
What is psi above a perfect vacuum?
absolute zero
For the purpose of this text, psi means WHAT?
psig
A gauge reading 10 psi at sea level, actually means 10 psig plus the ________ pressure of 14.7 psi. This pressure is not normally accounted for, as the gauge is calibrated to _____ at ambient pressure.
- atmospheric
- zero
10 psig is _____ psig at sea level.
24.7 (14.7 psi + 10 psig)
What do you call any pressure less than atmospheric pressure?
a vacuum
What is absolute zero pressure called?
a perfect vacuum
When a gauge reads 10 inches of Hg of vacuum on the compound gauge, it actually indicates ___ ____ atmospheric pressure.
less than
What does “head” refer to in the fire service?
the height of a water SUPPLY above the discharge orifice
For every 1 foot increase in elevation to a water SUPPLY, _ _ _ _ _ psi is gained (head)
0.434 psi
If the water is supply is 100 ft above the hydrant discharge opening, this is referred to as ____ ft of head.
100
To convert head in feet to head in pressure, you must divide the number of feet by _ _ _ _ _ (the number of feet that 1 psi will raise a one square inch column of water.
2.304
What is the water flow definition of static pressure?
stored potential energy available to force water through pipes, fittings, hose and adapters
The word static means…
at rest, or without motion
How can water pressure be produced?(3)
elevated water supply
atmospheric pressure
pump
If the water is not moving, this is called _______ pressure.
static
Is true static pressure found in municipal water systems? A. always B. never C.seldom D.there are no municipal water systems AND....why
C. seldom
because there is always some flow in the pipes due to normal use
Is the pressure in a system before it flows from a hydrant, even if it is municipal, considered static for fire service purposes?
YES
The pressure found in a water distribution system during normal consumption demands is considered the ____ _____ pressure.
normal operating
Technically, as soon as water flows through a distribution system, the water is no longer has WHAT?
static pressure
What causes water flow in a distribution system to increase and decrease accordingly?
consumption demands
The difference between static pressure and normal operating pressure is the ________ caused by water ______ through pipes, valves and fittings.
- friction
- flowing
______ _______ is the portion of the total available pressure NOT used to overcome friction loss or gravity while forcing water through pipes, fittings, hoses and adapters.
residual pressure
What does residual mean?
the remainder or what is left
During a flow test in a water distribution system, the ________ represents the pressure left in the system near the vicinity of one or more flowing ________.
- residual
- hydrants
Where should you identify the residual pressure? A. the flow hydrant B. open hydrant (s) C. nozzle D. pumper outlet
B. open hydrant(s)
What will reflect the water flowing from the open hydrant, other water consumption demands and the size of the pipes?
residual pressure
While water is flowing from a discharge opening , the forward velocity pressure is considered _____ pressure.
flow
Because a stream of water is emitted from a discharge opening is not encased within a _______ it exerts forward, but not lateral ______.
- tube
- pressure
What do you use to measure the forward velocity of flow pressure?
pitot tube and gauge
If using a pitot tube and gauge, a you know the size of the discharge opening, what can you calculate?
flow in gpm
What type of nozzle must be used with a pitot tube and gauge?
smooth bore
Even though elevation and altitude are used interchangeably, is there a distinction made in the fire service?
YES
Elevation refers to the center line of the ____ or the bottom of a _____ water supply source above or below ground level. (height of a point above sea level or some other reference point.)
- pump
- static
What is referred to as the position of an object in relation to sea level? (geographic)
altitude
Pressure losses or gains due to gravity are called what?
elevation pressure
How does altitude impact the production of fire streams?
atmospheric pressure drops as height above sea level increases
Between sea level and approximately what feet is atmospheric pressure drop of little consequence?
2000 ft
For effective fire streams above 2000 ft, what does atmospheric pressure do to fire department pumpers?
they must work increasingly harder to produce pressures for effective fire streams
What reduces a pumper’s effective lift when drafting?
less dense atmosphere
How much approximately does atmospheric pressure decrease for every 1,000 ft above sea level?
0.5 psi
Friction loss is an important factor in ______ a fire pump and producing an _____ fire stream.
- operating
- effective
The common term for pressure loss due to friction is….
friction loss