Ch4 pumping/aerial Flashcards
(105 cards)
1
Q
Water (H2O) is a compound (molecule) of hydrogen and oxygen formed when:
A
2 hydrogen atoms (H2) combine with 1 oxygen atom (O).
2
Q
What is the freezing point of water?
A
below 32 F degrees
3
Q
What is the boiling point of water?
A
212 F
*converts to gas, water vapor, or steam
4
Q
What form can water not be seen?
A
in its vapor form.
*It only becomes visible as it rises away from the surface of the liquid and begins to condense.
5
Q
What is the weight of one cubic foot of ordinary fresh water?
A
62.4 lb/ft3 (to the 3rd power)
6
Q
How many pounds does 1 gallon of water weight?
A
8.3 lbs
7
Q
What are the ways water has the ability to extinguish fires?
A
- it can cool or absorb heat from the fire
- Smoother (exclude oxygen from) fires
- used to smoother fires in combustible liquids with a specific gravity higher than 1.0 (heavier than water)
8
Q
How else may smoother a fire occur?
A
when water converts to steam within a closed space
9
Q
what does it mean if a liquid has a specific gravity greater than 1.0?
A
it is heavier than water
10
Q
Smothering fires may also occur when:
A
water converts to steam within an enclosed space.
11
Q
when water turns into steam inside a closed space, it can extinguish fire by:
A
displacing oxygen
12
Q
What characteristics make water an excellent extinguishing agent?
A
- water has a greater heat-absorbing capacity than other common agents
- water requires a large amount of heat to change to steam, allowing more heat to be absorbed from a fire
- water absorbs heat more rapidly the greater its surface area is exposed. The surface area can increase by using a fog stream or by deflecting a solid stream off an object.
- water occupies approx. 1,700 times its original volume when converting to steam at 212F, helping to dissipate heat in a well-vented room. The expansion ratio is even greater at higher temps.
- water is an inexpensive and readily available commodity.
13
Q
Why is water considered an excellent extinguishing agent?
A
it has high-heat absorbing capacity compared to other agents.
14
Q
What does water require in order to change into steam?
A
large amount of heat
*allowing more heat to be absorbed from a fire
15
Q
How can you increase the heat absorption rate of water during fire supression?
A
increase the surface area exposed to heat
16
Q
What stream patterns can increase the surface area of water for heat abosorption?
A
fog stream or deflected solid stream off an object
17
Q
When water is converted into steam at 212F, how much does it expand?
A
1,700 times original volume.
18
Q
What effect does converting water to steam have in a well-vented room?
A
it dissipates heat
19
Q
How does water’s expansion ratio change at higher temps?
A
it increases
20
Q
What are some disadvantages of using water as an extinguishing agent?
A
- water has high surface tension that makes it difficult to soak into dense materials. Mixing wetting agents with water can reduce waters surface tension and increase penetrating ability
- water may be reactive with certain fuels, such as combustible metals like sodium metal and triethyl aluminum
- waters transparency and low reflectivity create temp barrier only effective for short periods.
- frozen water causes operation problems
- water is a good conductor of electricity
- water is a relatively heavy agent, weighing 8.3 lb/gal
21
Q
What is one reason water may have difficulty soaking into dense materials?
A
its high surface tension
22
Q
What can be added to water to reduce its surface tension and increase penetration?
A
wetting agents
23
Q
What is a wetting agent?
A
chemical solution or additive that reduces the surface tension of water (producing wet water), causing it to spread and penetrate more effectively; may also produce foam through mechanical means. detergent is a mild form of a wetting agent
24
Q
why can water be dangerous when used on certain fuels?
A
it may react with combustible metals
25
what are the combustible metals that water can react with?
sodium metal and triethyl aluminum
26
what is a disadvantage of waters transparency and low reflectivity?
is only creates a short lived thermal barrier
27
how can weight of water affect a structure during firefighting operations?
it can increase the risk of structural collapse
28
what is pressure defined as?
force per unit area
29
How may pressure be defined?
pounds per sq foot (psf)
pounds per sq inch (PSI)
kilopascals (kPa)
30
Pressure is often confused with what?
force
31
what is the difference between force and pressure?
force is the total push or weight, pressure is that force spread over and area
?
32
force is a simple measure of what?
weight and its expressed pounds or newtons.
33
The measurement of force directly relates to?
the force of gravity or the amount of attraction the earth has for all bodies.
34
If several objects of the same size and weight are placed on a flat surface, they all:
exert the same force on that surface.
*if they are stacked on top of each other, the force remains the same but the pressure increases bc the surface area has reduced.
35
What can force cause in a substance?
a change in speed, direction, or shape of a substance.
36
What determines the force of water within a specific area?
water's weight within that area
37
to determine water's force, what 2 factors must be considered?
weight of water and height of water column
38
In the American system, what is the approximate weight of 1 cubic foot (1ft3) of water?
approx. 62.4 lb
39
how many square inches are in 1 sq ft of water?
144
40
What is the pressure at the base of a 1-in square column of water that is 1 ft high?
0.434 psi
41
What is the weight of 1 cubic foot of water?
62.4 lb
42
what is velocity?
speed at which a fluid travels through a hose or pipe.
The pressure upon that fluid, as well as the size of the orifice through which it is flowing, determines velocity
43
What are the 6 principles of the various types of pressure ?
1. perpendicular exertion
2. equal pressure transmission
3. density
4. intensity
5. depth
6. shape
"People Eat Donuts In Deep Silence"
Breakdown:
P – Perpendicular exertion
E – Equal pressure transmission
D – Density
I – Intensity
D – Depth
S – Shape
44
what determines the velocity of water flowing through a hose?
the pressure on the fluid and the orifice
45
What is perpendicular exertion ?
fluid pressure is perpendicular (at right angles) to any surface on which it acts.
46
pressure always acts in what direction to the surface it touches?
perpendicular (right angles)
47
What is intensity in the pressure principle?
in terms of fluid pressure, resting fluid holds the same intensity in all directions.
48
Which principle states that pressure in resting fluid is the same in all directions?
intensity
49
What principle is used in hydrostatic testing?
intensity
50
What is the pressure principle equal pressure transmission?
pressure applied to a confined fluid transmits equally in all directions.
51
In a confined system, how does pressure transmit?
equally in all directions
52
If gauges are placed around sealed sphere and water is pumped in, what will they show?
equal pressure at all points as long as they are all on the same grade line with no changes in elevation.
53
If a pump applies pressure to a standpipe, will the pressure at the top and bottom be different? why?
Yes, bc the top of the standpipe would read what PSI the DO is applying. The gauge at the bottom will read higher bc of the water weight in the standpipe.
54
What is the pressure principle: depth?
the pressure of a liquid in an open vessel is proportional to its depth.
Pressure increases with depth. The deeper the water, the greater the pressure at the bottom.
55
What is the pressure principle: density?
The pressure of a liquid in an open vessel is proportional to the density of the liquid.
Denser liquids like mercury exert more pressure than less dense liquids like water.
56
What is the pressure principle: shape
the pressure of the liquid at the bottom of a vessel is independent of the shape of the vessel.
The shape of the vessel DOES NOT affect the pressure at the bottom as long as the height and cross-sectional area is the same.
So a tall narrow tank and a short wide tank with the same height and same base area will have the same pressure at the bottom.
57
What does the 4th principle depth pressure state?
pressure in an open container increases with depth.
58
If the depth of water in a container is tripled, the pressure at the bottom will be:
tripled
59
What does the 5th principle of pressure explain? density
pressure in a liquid depends on the density of the liquid.
60
What does the 6th pressure principle (shape) state about the shape of a container?
pressure at the bottom is independent of the containers shape.
61
What are the types of pressure encountered in water supply systems? DO's should understand them bc of the affect they have on the delivery of water to the fireground.
1. atomospheric pressure
2. head pressure
3. static pressure
4. normal operating pressure
5. residual pressure
6. flow pressure (velocity pressure)
7. pressure gauge readings and increments
62
What is atmospheric pressure?
pressure that surrounds the earth has depth and density
The weight of the atmosphere pressing down on the earth.
63
where is atmospheric pressure the greatest and the lowest?
at low altitudes =greatest
at high altitudes = lowest
64
What is atmospheric pressure at sea level?
14.7 psi
65
What is considered standard atmospheric pressure?
14.7 at sea level.
66
What is head pressure?
height of a water supply above the discharge orifice.
*water supply 100ft above the hydrant discharge opening, is referred to as 100ft of head.
67
How do you convert head height measurements to head pressure in the american system of measurement?
(0.434 x height)= psi
The result is head pressure in psi
68
What is static pressure also known as?
hydrostatic pressure
69
What is static pressure (hydrostatic)?
stored potential energy available to force water through pipes, fitting, hose, and adapters.
70
What does static mean?
at rest or without motion
71
What may produce water pressure? but if it is not moving,then it is static pressure?
an elevated water supply, atmospheric pressure, or a pump
72
true static pressure is seldom found where? why?
municipal water systems bc some flow in the pipes always occurs due to normal water usage .
*However, the pressure in the system before it flows from a hydrant is considered static pressure for FD purposes.
73
What is normal operating pressure?
the pressure found in a water distribution system during normal consumption demands.
It fluctuates continuously, causing water flow to increase or decrease
74
The friction caused by water flowing through the pipes, valves, and fittings of the system creates what?
the difference in pressure between static pressure and normal operating pressure.
75
What is residual pressure?
leftover portion of the total available pressure that is not used to overcome friction loss or gravity while forcing water through pipes, fittings, hose, or adaptors
76
During a flow test in a water distribution system, the residual pressure represents what?
the pressure left in the system near the vicinity of one or more flowing hydrants.
77
The residual reading in a flow test of the distribution system will reflect what?
the water flowing from the open hydrant(s), other water consumption demands, and the size of the pipes.
78
What is flow pressure considered?
velocity pressure
79
What is considered flow pressure?
while water is flowing from a discharge opening, the forward velocity pressure is considered flow pressure.
80
Pressure created by water moving out of a discharge outlet?
flow pressure
81
Why does flow pressure exert forward pressure?
bc the stream of water emitted from the discharge opening is not encased within a tube.
82
How is forward velocity of flow pressure measure?
a pitot tube and gauge .
83
What needs to be known in order to get GPM via a pitot tube?
the size of the discharge.
84
When measuring the forward velocity of flow pressure using a nozzle, which one needs to be used?
a smooth bore nozzle must be used with the pitot tube and gauge.
85
What is any pressure below atmospheric pressure called?
a vacuum
86
The readings of pressure gauges on a pumper are in:
PSI for positive readings
Inches of mercury (Hg or VAC) for vacuum readings.
87
What is a compound gauge?
has the ability to read above and below zero
*compound gauge: pressure gauge capable of measuring above and below atmospheric pressure; commonly used to measure the intake pressure on a fire pump
88
The possible swing of the needle on a guage in the vacuum range is:
relatively small
89
in the fire service, head pressure refers to:
the height of water supply above the discharge opening
90
What is the pressure in PSI created by a water tank 100 ft above a hydrant?
43.4
(.434 x 100) = psi
0.434 x height = head pressure in psi
91
which pressure is measured when water flows through pipes during regular use?
normal operating pressure
92
What does residual pressure represent in a flow test?
leftover portion of the total available pressure that is not used to overcome friction loss or gravity while forcing water through pipes, fittings, hose, or adaptors.
93
what type of gauge shows both above and below atmospheric pressure?
compound gauge.
94
gauges on a pumper display a reading that does NOT include:
existing atmospheric pressure
95
gauges on a pumper are calibrated so that zero is:
atmospheric pressure
96
Psia is what? and what do those readings mean?
Pounds per square inch absolute
Psia readings indicate a pressure above a perfect vacuum or absolute 0
97
Elevation and altitude are NOT the same thing in the fire service, but as far as the pump is concerned, the two can be expressed as a comparison to:
the centerline of the pump.
98
Elevation refers to:
the height or the drop when comparing the centerline of the pump to the nozzle
99
Altitude refers to:
the elevation of the centerline of the pump above sea level.
100
Pressure loss or gain due to gravity is called:
elevation pressure
101
Altitude impacts the production of fire streams bc:
atmospheric pressure drops as the height above sea level increases.
102
the drop of atmospheric pressure between sea level and approximately ________ ft is of little consequence
2,000 ft
103
above the height of 2,000 ft, the lessening of atmospheric pressure means:
fire dept. pumpers must work increasingly harder to produce the pressure required
The difficulty is bc the less dense the atmosphere pressure reduces a pumpers effective lift when drafting.
104
Above sea level, atmospheric pressure decreases approx. _________ for every 1,000 ft
0.5 psi
105
