Part 1 (Ch. 1-3) Principles of Water and Water Flow

Question 1

Basic characteristics of water

Answer 1

• 2 parts Hydrogen, 1-part Oxygen
• Exist in liquid states between 32212 F, boiling point will decrease slightly when above sea level
• Incompressible in liquid state, 1 cubic foot water has 7.48 gallons water
  -750 gal tank’s about 100 cubic ft
• 8.34 lbs per gallon
• Densest near freezing, lightest near boiling

Question 2

Basic Extinguishing Properties of water

Answer 2

• Waters primary method of fire extinguishment is cooling
• also by smothering

Question 3

Law of Specific Heat

Answer 3

• Substances ability to absorb heat
• BTU= Amount of heat needed to raise the temp of 1lb of water 1* F
  -takes 142 Btus to get from 70* to boiling point
  -another 970 Btus to turn to steam
  -Specific Heat chart- comparing how effective other substances absorb heat compared to water

Question 4

Law of Latent Heat of Vaporization

Answer 4

• Amount of heat water can absorb when turning to steam
• The more steam produced the greater heat absorption will be
• 1 Part water will convert to 1,700 parts steam
  -can be greater in extremely hot atmospheres
• Water absorbs more heat the larger surface area contact become

Question 5

Advantages/Disadvantages of Water for FF

Answer 5

• Advantages:
  -greater heat-absorbing capacity, Cheap, readily available, non combustible, in compressible,
• Disadvantages:
  -Reacts with certain materials, surface tension, can freeze, doesn’t adhere to surfaces

Question 6

Five (6) Basic Principles of Pressure

Answer 6

• Principle #1 Pressure at a point in liquid is applied equally in every direction
  -Pascals Law, pressure from weight transmitted in all directions,
  -6th principle would be same with addition of stating pressure applied perpendicular to every surface it touches
• Principle #2 Pressure applied in a confined liquid from external source will be transmitted equally in all directions without reduction in magnitude
• Principle #3 Pressure created by liquid in an open container is directly proportional to the depth of the liquid
  -1 cubic foot of water weighs 62.4lbs, area of its sides are 144 inches squared, so a 1ft of water exerts 0.433 psi (2.31ft exerts 1psi)
  -Pressure = Force/Area
  -62.4lbs/144in2 = 0.433psi
• Principle #4 Pressure created by a liquid in an open container proportional to its density
  -Water is density of 1, all other liquids compared to density (1) of water
  -Pressure=(w)(h)
• Principle #5 Pressure at the bottom of a container is not affected by the shape or volume of container

Question 7

Head

Answer 7

Pressure expressed in units of feet of water instead of PSI

Question 8

Potential Energy

Answer 8

• Static body of water such as hydrant system has two sources of potential energy
  -#1 Potential energy due to elevation
  -#2 Potential energy due to external pressures sources such as a pump
• PE=(w)(h)

Question 9

Principles of Kinetic Energy

Answer 9

• Conservation of Energy
  -Energy in hydraulic system cannot be created or destroyed, it only changes back and forth between potential and kinetic.
  -Total energy will always remain constant
  -Total pressure will be the same at any point in a system as long as not flowing
• Conservation of Matter
  -matter can neither be created nor destroyed
• Principles of Water Flow
  1. If pipe or hose remain constant water velocity in system remains constant
  2. Increase in pipe or hose creates reduces velocity
  3. Reduction in pipe or hose creates increased velocity
  4. If pipe of hose size remains constant water will flow same velocity up or downhill

Question 10

The Principle of Pressure

Answer 10

• Atmospheric Pressure
  -Atmospheric pressure is Highest at low altitudes (below sea level California Death Valley)and lowest at High altitudes (Mount Everest)
  -Base Standard Atmospheric pressure is 14.7PSI (Sea Level)
  -For every increase of 1,000ft above sea level PSI drops 0.5psi (of little consequence up to 2,000ft)
  -Low Atmospheric pressures make drafting harder
  -No perfect vacuum ever created
• Head Pressure ,m
  -Pressure created by water at height above discharge
  -= elevation(ft)/2.31
• Static Pressure
  -Pressure in water system before water flows from a hydrant considered static pressure
• Normal Operating Pressure (NOP)
  -Pressure found in distribution system during normal consumption demands
  -Static Pressure – NOP= Result of FL from water flowing
• Residual Pressure
  -Amount of pressure remaining in system while water flowing
• Flow Pressure
  -Amount of water flowing through a discharge

Question 11

4 Principles of Friction Loss

Answer 11

• Principle #1- Amount of FL directly proportional to the length of hose or pipe
  -Longer lay means more FL
• Principe #2- FL varies approximately with the square of the increase in velocity of the flow
  -Increases at a higher rate
  -More GPM in same size hose means more FL
• Principle #3- FL varies inversely as the 5th Power of the diameter of hose
  -Smaller diameter hose means more FL because of more surface contact
• Principle #4- For a given flow velocity, FL is approx. same regardless of pressure on water
  -Increased psi does NOT create increase in FL
• Darcy-Weisbach Formula- More accurate/ used by engineers
• Hazen-Williams Formula- Used by fire protection industry