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Pumping and Aerial Apparatus Driver/Operator Handbook 3rd Edition > Ch 5 Principles of Water > Flashcards

Ch 5 Principles of Water Flashcards

1
Q

Characteristics of Water

A

-Water (H20) two hydrogen one oxygen
-Freeze 32F 0C
-Liquid 32F-212F
-Boils 212F 100C
-1-gallon weighs 8.3lb
-Cools or absorbs heat from a fire as well smother (remove oxygen)
-Smoothers fires in combustible liquids whose specific gravity greater then 1
Advantages:
-Greater heat absorbing capacity
-Large amount of heat required to change to steam
-Converted to steam occupies 1700 times its original volume
Disadvantages:
-Higher surface tension makes difficult to soak
-Reacts with certain fuels or metals
-Wetting agents may be mixed to reduce its surface tension and increase penetration

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2
Q

Pressure vs Force

A

Pressure: force per unit area
Force: measure of weight in pounds or newtons

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3
Q

Principals of Pressure

A
  • First- Fluid pressure is perpendicular to any surface on which it acts
  • Second- Fluid pressure at rest is same intensity in all directions
  • Third- Pressure applied to a confined fluid is transmitted equally in all directions on same grade line
    -Example 100 feet tall 100psi top gauge is 100psi bottom is 143.4 psi because of weight of water in standpipe
  • Fourth- Pressure of a liquid in an open vessel is proportional to its depth
    -Example depth of first container 1 foot second is 2 feet third is 3 feet. Pressure in second is double the first and pressure in third is triple the first
  • Fifth- Pressure of liquid in open container is proportional to density of liquid
    Mercury 1 inch, water 13.55 inch
    Mercury is 13.55 times denser then water
  • Sixth- Pressure of a liquid at the bottom of a vessel is independent of the shape of the vessel
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4
Q

What is atmospheric pressure at sea level?

A

14.7psi
- greater at lower altitudes

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5
Q

what is a PSIG and what does it measure?

A
  • pounds per square inch guage
  • it measures PSIA( pounds per square inch absolute) which is actual atmospheric pressure
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6
Q

Vacuum

A
  • any pressure less than atmospheric
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7
Q

Perfect Vacuum

A
  • pressure of absolute zero
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8
Q

Head Pressure

A
  • Refers to the height of a water supply above the discharge
    -Example water supply 100 feet above discharge (100 ft of head)
    -Every 1-foot increase .434 psi gained
    -100 ft divided by 2.304 is 43.4 psi
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9
Q

Static Pressure

A
  • stored potential energy available to force water through pipes, fittings, hoses, and adapters
  • static means at rest, or without motion
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10
Q

Normal Operating Pressure

A
  • Pressure found in system during normal consumption
  • Friction caused by water flowing through pipes, valves is the difference between static pressure
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11
Q

Residual Pressure

A

Portion of the total available pressure not used to overcome friction loss

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12
Q

Flow (Velocity) Pressure

A
  • While water is flowing through discharge the forward velocity pressure is flow pressure
    -Use pitot tube a gauge to read
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13
Q

Pressure Loss and Gain

A

Elevation- Center line of pump or bottom of static source above or below ground
-Gain or loss in hose line due to elevation
-When nozzle above the pump pressure loss
-When nozzle below pump pressure gain
Altitude- Geographic position of object in relation to sea level
-Atmospheric pressure decreases .5 every 1,000 feet

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14
Q

Causes of Friction Loss

A

Friction Loss:
-movement of water molecules
-Inside surface of piping
-Couplings
-Bends/kinks
-Change in hose size or orifice
-Improper gasket size
Friction Loss in Piping:
-FL in older hose can be 50% greater
-Movement of molecule
-Linings of the fire hose
-Pipe fittings
-Valves
-Flush hydrants periodically

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15
Q

Principles of Friction Loss

A
  • First- If conditions are the same friction loss varies directly with length of hose
    -Example: 100ft has 10psi friction loss 200ft has 20 psi friction loss
  • Second- Hoses same size, friction loss varies approximately with the square of increase in velocity of flow
    -Example: length of 3 in hose flowing 200gpm has loss of 3.2. as flow doubles from 200gpm to 400gpm friction loss increases four times (2²=4). When tripled 200gpm to 600gpm friction loss increase nine times (3²=9).
  • Third- For same discharge, friction loss varies as the fifth power of diameter of hose
    -Friction loss will decrease when diameter of hose increases
    -4-inch supply instead of 3-inch equates to 76% reduction ( (2.5)⁵/3⁵ = 97.66/243 = .4)
  • Fourth- For a given velocity, friction loss is approximately the same regardless of the pressure on the water
    -Example 100gpm passed through 3 inch in certain time water must travel at a specified velocity. Four 1 ½ inch hoses are needed to flow 100gpm at same velocity as a single 3 inch
  • *Diameter of hose determines velocity to get the same gpms (smaller hose, greater Velocity needed to get same volume)
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16
Q

Reducing Friction Loss

A
  • Hose length- Reduce the length of lay and increase the diameter
  • Hose diameter- Using larger diameter hose for a long water supply
    -May be reduced to appropriate diameter
    -Should not be increased so much becomes difficult to handle
  • Critical Velocity- Friction becomes so great that resistance agitates the entire stream
  • Sharp bends (Kinks)- Avoided by proper hose handling
17
Q

Water Hammer

A
  • Sudden stopping of water moving through hose or pipe resulting in energy surge in opposite direction
  • Force create by the rapid deceleration of water
  • With large volumes of water, can damage the pump, appliances, hose, or water system itself
  • Closing a valve or nozzle to quickly
  • Prevent by slowly closing nozzles and valves
18
Q

Principles of Municipal Water Supply

A
  • principal function is to provide potable water
  • When a large volume of water is needed, request water department to increase water pressure
  • Primary water can be obtained from:
    -surface water- rivers and lakes
    -ground water- water wells or springs
19
Q

Means of Moving Water

A
  • Direct Pumping- Take water from primary source and discharge it through filtration and treatments
  • Gravity System- Water source at higher elevation
    -sufficient when source is located several hundred feet higher
    -least common
  • Combination System- Most communities use this
    -elevated storage tanks supply the gravity flow
20
Q

Water Distribution System

A
  • Receives water from pumping station and delivers it throughout the area
  • Dead end Hydrant- receives water from one direction
  • Circulating Hydrant- receives water from two or more directions
  • Grid system- Utilizes lateral feeders for improved distribution
  • Primary Feeders- Large pipes with relatively large spacing
  • Secondary Feeders- Intermediate sized piped that reinforce the grid
    -Aid the required fire flow at any point
  • Distributors- Smaller mains serving individual fire hydrants
21
Q

Water Main Valves

A
  • Provide a means for controlling flow of water through the distribution piping
  • Operate once a year
  • Two types of indicating valves (Show whether gate or valve seat is open, closed, or partially closed) (usually in private systems):
    -NOT common in municipal water systems
    -Most commonly found in private systems
    -Post Indicating Valve- Hollow metal post attached to valve housing
    • Indicates if open or shut with words
      -Outside screw and yoke- Control valve for sprinkler system
    • Center screw indicates if valve is open or close
    • Threads out valve is open
  • Non-indicating Valves- most common in public (municiple) water distribution
    -Usually gate or butterfly valves (butterfly better for long periods of inactivity)
    -can be rising or non-rising stems
    -Non-rising- stem gate valves should be marked with a number for how many turns necessary to completely close valve
22
Q

Underground water pipes are usually made of:

A

cast iron, ductile, iron, steel, plastic, or concrete

23
Q

Water System Capacity (Consumption)

A
  • Average daily consumption ADC- Is average amount of water used per day based on total water used in distribution system over one year
  • Maximum daily consumption MDC- Total amount of water used in 24-hour interval within a three-year period
  • Peak hourly consumption PHC- Maximum amount of water used in 1-hour interval
24
Q

Private Water Supply

A
  • Get water from municipal water supply systems
  • Used for one of the following purposes:
    -Provide water strictly for fire protection
    -Provide water for sanitary and fire protection
    -Provide water for fire protection and manufacturing process
  • Prevent cross contamination
    -may have non-potable water
  • If there is question about the reliability, departments should make arrangements to augment private water supply for large scale operations
    -relaying from municipal source
    -drafting

Pumping and Aerial Apparatus Driver/Operator Handbook 3rd Edition (20 decks)

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