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principles of pressure > Chapter 5 > Flashcards

Chapter 5 Flashcards

Principle of water

1
Q

Water is considered to be?

A

virtually incompressible and it weights varies at different temperatures.

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2
Q

For fire protection purposes,ordinary fresh water is considered to weight?

A

62.4 pounds per cubic feet or 8.3 pounds Per gallon

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3
Q

force is

A

simple measure of weight and is expressed in pounds or kilograms

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4
Q

Friction loss in a water system ___as the length of hose or pipe in increases

A

Increases

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5
Q

To prevent water hammer when flowed from a master streams or hydrant opened

A

they should be partially closed,stopped ,and then closed more as a prevention measure.

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6
Q

water may be reactive with certain fuels

A

2•SODIUM METAL
3• TRIETHYI ALUMINUM
4• COMBUSTIBLE METALS

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7
Q

atmospheric pressure @ sea level is

A

14.7psi

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8
Q

any pressure less than atmospheric pressure is called

A

a vacuum

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9
Q

absolute zero pressure is called

A

perfect vacuum

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10
Q

a vacuum is needed

A

to facilitate a drafting

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11
Q

head

A

The height of a water supply above the discharge orific.

Alternate term for pressure especially pressure due to elevation.

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12
Q

for every 1 foot increased in elevation

A

0.434 psi is gained

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13
Q

static pressure

A

stored potential energy available to force water through pipes,hoses.etc

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14
Q

residual pressure

A

available pressure not used to overcome friction loss or gravity while forcing water through pipes,fittings,hoses or adapters

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15
Q

flow pressure

A

While water is flowing from a discharge opening,the forward velocity pressure

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16
Q

when measuring the forward velocity of flow pressure,what must be used?

A

a smoothbore nozzle with a pitot tube and gauge

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17
Q

above sea level atmospheric pressure

A

decreases 0.5psi for every 1000 feet

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18
Q

Fluid pressure at a point in a fluid at rest is the same intensity in all directions

A

Describes the second principle of pressure

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19
Q

Water may be used to smother fires in which type of combustible liquid?

A

Combustible liquid whose specific gravity is higher than 1 (heavier than water)

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20
Q

What describe the term elevation in the fire service

A

The center line of the pump or

the bottom of a static water supply source above or below ground level

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21
Q

What determines the velocity for a given volume of water?

A

Diameter of hose

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22
Q

The first principle of friction loss?

A

If all other conditions are the same, friction loss varies directly with the length of the hose or pipe.

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23
Q

Second principle of friction loss

A

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

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24
Q

The third principle of friction loss is

A

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

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25
Q

The forth principle of friction loss

A

For a given velocity,friction loss is approximately the same,regardless of the pressure on the water

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26
Q

The diameter of the hose determines the velocity for a given volume of water therefore?

A

The smaller the hose,the greater the velocity needed to deliver the same volume

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27
Q

The speed at which fluid travels through a hose or pipe is determined by

A

The pressure upon the fluid as well as the size of the orifice through which it is flowing.

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28
Q

The pressure upon the fluid as well as the size of the orifice through which it is flowing.

A

Pressure applied to a confined fluid is transmitted equally in all directions

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29
Q

The first principle of pressure

A

Fuel pressure is perpendicular to any surface on which it acts

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30
Q

The second principle of pressure

A

Fluid pressure at a point in fluid rest is the same intensity in all directions.

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31
Q

What principle of pressure is used in hydrostatic testing

A

The second principle

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32
Q

The fourth principle of pressure

A

The pressure of a liquid in an open vessel is proportional to its depth

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33
Q

The fifth principle of pressure

A

The pressure of a liquid in an open vessel is proportional to the density of the liquid

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34
Q

When the flow of water for fire fighting needs to be increased;

A

It is said usually acceptable to use large diameter hose to reduce friction

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35
Q

The primary water supply can be obtain from?

A

Surface water or ground water

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36
Q

What is illustrated by the second principle of friction loss

A

Friction loss develops much faster than change in velocity

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37
Q

If velocity is increased beyond practical limits the friction becomes so great that resistance agitates the entire system, and creates?

A

Critical velocity

38
Q

What describe best the term altitude in the fire service

A

position of a location or object in relation to sea level.

The location may be either above below to sea level

39
Q

Secondary feeders

A

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

40
Q

Flow pressure will always be greatest near the source of supply lowest at the furthest point in the system

A

true

41
Q

Distributors

A

Make up of a grid arrangement of smaller mains serving individual fire hydrants and blocks of consumers

42
Q

The friction caused by water flowing through the pipes,valves and fittings is the difference between static pressure and:

A

Normal operating pressure

43
Q

When does water exist in a liquid state?

A

Between 32°F and 212°F

44
Q

To convert head in feet to head pressure, you must?

A

Divide the number of feet by 2.304 (the number of feet that 1 psi will raise a one sq inch column of water)

45
Q

The maximum amount of vacuum most fire pump will develop?

A

Approximately 22” of mercury

46
Q

Because total vacuum is not possible in field operation fire apparatus must have a maximum lift of

A

25 feet

47
Q

After life safety, the highest priority for most wildland fire fighting operations is?

A

The protection of structures that are exposed to the fire.

48
Q

When priming,water enters the pump because

A

Atmospheric pressure forces it it into the pump

49
Q

A_____ gauge is calibrate to read both positive and negative pressure

A

compound

50
Q

Switch from pressure to volume operation when

A

There is a reason to believe that more than half of the rated capacity of the pump will be required

51
Q

Given a pump that is in gear supplied by Tank water with no discharges open,what principle of pressure is represented

A

Pressure applied to a confined fluid from without is transmitted equally in all directions (the third principle of pressure)

52
Q

The purpose of the_____is to provide circulating feed for several mains

A

Grid system

53
Q

In draft an operation, Pumping ability decreases when

A

.

54
Q

The formula 29.7 (d)sq x sq of np

A

Flow of water in gallons per minute

55
Q

For drafting purpose,lift is measured from the ____ of the pump

A

Surface of water to the center

56
Q

NFPA requires that a pumper most pump it’s rated capacity at_____of lift

A

10

57
Q

The friction caused by water flowing through the pipes,valves and fittings of the system is?

A

The difference between static pressure and operational pressure

58
Q

The forward velocity pressure while water is flowing from a discharge opening is referred as

A

Flow pressure

59
Q

Friction loss in older hose may be as much as 50% greater than in new hose

A

true

60
Q

Friction loss develops much faster than change in velocity

A

Is illustrated by the 2nd principle of friction loss

61
Q

The fourth principles of friction loss states that for a given velocity, friction loss;

A

Is approximately the same,regardless of pressure on the water

62
Q

The diameter of hose determines velocity for a given volume of water

A

True

63
Q

The smaller the hose,

A

The greater the velocity needed to deliver the same volume

64
Q

A pressure of _____is required to reduce water volume 1%

A

30,000

65
Q

Grid arrangement of smaller mains serving individual fire hydrants and blocks of consumers

A

Distributors

66
Q

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

A

1•Pressure

2•Size

67
Q

Any pressure less than atmospheric pressure is called _____, and absolute zero pressure is called a ___________

A

1• vacuum

2•Perfect vacuum

68
Q

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).

A

2.304

69
Q

For every 1-foot increase in elevation, ______ psi is gained.

A

0.434

70
Q

Above sea level, atmospheric pressure decreases approximately .5 psi for every 1000 feet

A

.5psi for every 1,000 ft

71
Q

The height required for a 1 square inch column of water to produce 1 psi at its base equals

A

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

72
Q

water pressure may be produced by an

A

1•elevated water supply
2•atmospheric pressure
3•a pump

73
Q

The sixth principle of pressure

A

The pressure of a liquid at the bottom of a vessel is independent of the shape of the vessel.

74
Q

Different ways water can be treated are

A

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

75
Q

If all other conditions are the same friction loss varies directly(178)

A

With the length of the hose or pipe

76
Q

When hoses are the same size,friction loss varies approximately(pg.178)

A

With the square of the increase in the velocity of the flow

77
Q

For the same discharge(179)

A

Friction loss varies inversely as the fifth power of the diameter of the hose

78
Q

For a given velocity(179)

A

Friction loss is approximately the same regardless of the pressure on the water

79
Q

Two ways in which water has the ability to extinguish fire

A

Cooling and smothering

80
Q

static

A

means at rest, or without motion

81
Q

the difference between static pressure and normal operating pressure is the

A

Friction caused by water flowing through the pipes, valves and fittings of tge system

82
Q

elevation refers

A

Is the Centerline of the pump or the bottom of a static water supply Source above or below ground level

83
Q

when a nozzle is above the level of the pump

A

is a pressure gain

84
Q

elevation pressure

A

the pressure losses or gains due to gravity

85
Q

less dense atmospheric pressure______ pumper effective lift when drafting.

A

reduces

86
Q

generally control valves in public water distribution system are

A

gate valves

87
Q

if a control valve resist turning after fewer than the indicated numbers of turn that usually means

A

obstruction in the valve or it may be corroded

88
Q

the adverse effect of encrustation and sedimentation can be reduced by

A

flushing hydrants periodically

89
Q

the average daily consumption (ADC)

A

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

90
Q

the max daily consumption (MDC)

A

is the maximum total amount of water that was used during any 24-hour interval within a three-year period

91
Q

Peak hourly consumption (PHC)

A

the maximum amount of water used in any one hour interval over the course of a day

principles of pressure (17 decks)

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