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Engineer School > Chp 5 > Flashcards

Chp 5 Flashcards

1
Q

Water properties

A

Incompressible
Weight varies at different temperatures
Weigihs 62.4 lb/ft^3 or 8.3 lb/gal

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2
Q

Waters ability to fight fire

A

Absorb heat
Smother
Smother liquid fires with density >1
Smother with steam

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3
Q

Advantages of water

A

Expands 1700x upon steam (higher at greater temps)

Cheap and readily available

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4
Q

Disadvantages of water

A 
High surface tension
Doesn't stop radiant heat
Can react with metals
Freezes
Conducts electricity
Heavy
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5
Q

Pressure

A

Force per unit area exerted by a liquid or gas

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6
Q

Force

A

Measure of impact of weight within a specific area
Moves direction of an object
1 sq” of water weighs 0.434 lbs
Column 2.304 ft high exerts 1 psi

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7
Q

Principles of pressure

A

1: pressure is perpendicular to any surface
2: fluid pressure is the same in all directions
3: Applied pressure is transmitted equally in all directions
4: Pressure in an open vessel is proportional to its depth
5: also to its density
6: Pressure at the bottom is independent of shape

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8
Q

Types of pressure

A 
Atmospheric
Head
Static
Normal operating
Residual
Flow pressure (velocity pressure)
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9
Q

Atmospheric pressure

A

14.7 psi at sea level (standard)
Most gauges are psi plus atmospheric or psig
psig is psi gauge
psia absolute is psi above a perfect vacuum absolute zero

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10
Q

Vacuum

A

Pressure that is less than atmospheric

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11
Q

Head

A

Height of a water supply above discharge
Head pressure is pressure due to elevation
0.434 psi per ft
Divide feet of head by 2.304 to get head pressure

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12
Q

Static pressure

A

Pressure in a system before it flows from a hydrant

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13
Q

Normal operating pressure

A

Pressure found in a distribution system during normal consumption demands. Since water is always flowing, basically residual pressure of a system.
Diff of static and normal operating pressure is FL

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14
Q

Residual pressure

A

Pressure at the test hydrant while water is flowing

Portion of total available pressure not used to overcome friction loss or gravity

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15
Q

Flow pressure

A

aka velocity pressure
forward velocity pressure while water is flowing from an opening
Only exerted forward not the sides because its not encased

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16
Q

Altitude

A

Geographic position in relation to sea level. Drops approx 0.5 psi for every 1,000ft change

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17
Q

Elevation

A

Gain or loss in pressure due to change in elevation from center line of the pump

18
Q

Friction loss

A

Loss of pressure created by turbulence of water moving against interior walls of the pipe

19
Q

Friction loss causes

A 
Movement of water molecules against each other
Lining of the hose
Couplings
Kinks or bends
Change in hose size or orifice
Improper gasket size
Old hose (up to 50%)
Same in piping but add valves
20
Q

Measuring friction loss

A

Coefficient of friction measured by inserting in line gauges in hose or pipe and testing difference in residual pressure

21
Q

1st principle of friction loss

A

FL varies directly with the length of hose

22
Q

2nd principle of friction loss

A

FL varies approx to the square of the increase in velocity

23
Q

3rd principle of friction loss

A

FL varies inversely as the fifth power of the diameter of the hose

24
Q

4th principle of friction loss

A

For a given velocity FL is the same regardless of pressure. Overcome by larger hose or dual lines

25
Q

Critical velocity

A

Practical limit of velocity. When agitation is he enough to cancel PDP

26
Q

Reducing FL

A

Hose length
Hose diameter
Sharp bends

27
Q

Water hammer

A

Force created by the rapid deceleration of water causing an increase in pressure

28
Q

Sources of water supply

A

Ground water: well, spring
Surface water: Lake river
Combination (rare)
Also desalination

29
Q

Means of moving water

A

Direct pump
Gravity fed
Combination

30
Q

Water treatment

A

Coagulation, sedimentation, filtration or addition of chemicals, bacteria or organisms, add fluoride or ozone

31
Q

Dead end hydrant

A

Receives water from only one direction

32
Q

Circulating feed hydrant

A

Aka looped line receives water from two directions.

Much less friction loss

33
Q

Grid distribution system

A

Primary Feeders: large pipes, widespread spacing
Secondary feeders: intermediate pipes that reinforce the grid
Distributors: grid arrangement of smaller mains serving hydrants.

34
Q

Water main valves

A

Good for isolating problems
Rarely used, test often
Indicating or non indicating

35
Q

PIV

A

Valve on underground water mains on supply main of installed fire protections systems

36
Q

OS&Y

A

Control valve for a sprinkler system

Center screw shows if open or closedCo

37
Q

Non indicating valves

A

Most common in public water distribution systems

Normally in valve boxes or manholes

38
Q

Control valves

A

Generally gate valves

OS&Y or non rising stem (should show number of turns to fully open/close)

39
Q

Water pipe

A

Usually cast iron, ductile iron, asbestos cement, steel, plastic, or concrete

40
Q

Water supply capacity

A

Average daily consumption; average daily for 1 yr
Maximum daily consumption: max 24 hr within 3 day period
Peak hourly consumption: max 1 hr amount

41
Q

Private water systems

A

Just for fire
For sanitary and fire
Or for fire and mfg
Usually separate pipes for fire protection and industrial use to save money

42
Q

Hydrant Colors

A

Light Blue: >1500 gpm
Green: 1000 - 1499 gpm
Orange: 500 - 99 gpm
Red: <500 gpm

Engineer School (21 decks)

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