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How is water measured for its density or weight per unit of volume?
Pounds per cubic foot
How heavy is ordinary fresh water?
62.5 lb/ft3 or 8.33 lb/gal (1 kg/L)
How does water extinguish fire?
Cools Absorbs heat Smothering
When can a liquid be smothered?
When the specific gravity of that liquid is higher than 1
As an extinguishing agent, water depends on what?
Specific heat Latent heat of vaporization Exposed surface area Specific gravity
What is specific heat?
It\'s a measure of the heat-absorbing capacity of a substsnce
What is a BTU?
It's the amount of heat required to raise the temperature of 1 lb of water 1 degree F. ( starts at 60 degrees F)
What is latent heat of vaporization?
It is the quantity of heat absorbed by a substance when it changes from a liquid to a vspor
Each pound of water requires approximately how many BTUs of additional heat to convert it into steam?
970 BTUs
The rate at which an object gives off heat depends on what factors?
Physical form Amount of surface exposed Air or oxygen supply
At 212 degrees, water expands approximately how many times than its original volume?
1,700 times
What are some obervable results of proper application of a water stream into a room?
Fire is extinguished or reduced in size Visibility in a room is maintained Room temperature is lower
What is viscosity?
The tendency of a liquid to possess internal resistance to flow
What is specific gravity?
The density of liquids in relation to water. For example, water has a specific gravity if 1, therefore anything with a specific gravity of less than 1 will float on water. Liquid with a specific gravity of more than 1 will sink and water because its heavier
What are some advantages of using water as an extinguishing agent?
Greater heat absorbing capacity Relatively large amount of heat is needed to change water into steam The greater the surface area of water exposed, the more rapidly heat is exposed Water converted to steam occupies 1,700 times its original volume Water is plentiful, and relatively inexpensive
What are some disadvantages of using water as an extinguishing agebt?
Water has a high tension ratio which makes it harder for water to soak into dense materials Water may react to certain combustible metals Water has a low opacity and reflectivity and allows gradient heat to pass easily Water freezes at 32 degrees F. Water readily conducts electricity
Define pressure
Force per unit area
What is force?
Simple measure in weight and is usually expressed in pounds or kilograms
How much does 1 cubic foot of water weigh?
62.5 lbs
What is velocity?
A speed at which fluid travels
What is atmospheric pressure?
The atmosphere surrounding the earth has depth and density and exerts pressure upon everything on earth
What is vacuum pressure?
Any pressure less than atmospheric pressure
what is head pressure?
The height of a water supply above the discharge orfice
What is static pressure?
Stored potential energy available to force water through pupes, fittings, fire hose, and adapters
What does static mean?
at rest or without motion
What is normal operating pressure?
pressure found in a water distribution system during normal consumption demands
What is residual pressure?
The part of the total available pressure not used to overcome friction loss or gravity while forcing water through pipe, pipe fittings, fire hose, and adapters
What is flow pressure ( velocity pressure)?
The forward velocity pressure at a discharge opening while water is flowing
How is flow pressure measured?
With a pitot gauge
What is elevation?
Refers to the center line of the pump or the bottom of a static water supply source above or below ground level
What is altitude?
The position of an object above or below sea level
When above sea level, the atmospheric pressure decreases approximately how much?
0.5 psi for every 1,000 feet
What are the causes of friction loss in a fire hose?
Movement of water molecules against each other Linings in the fore hose Couplings Sharp bends Change in hose size or office by adapters Improper gasket size
The friction loss in old hose may be as much as percent greater then that in new hose
50%
What are some causes of friction loss in piping systems?
Movements of water molecules against each other Inside surface of the piping Pipe fittings Bends Control valves
What characteristics of a hose layout affects the friction loss?
Hose length Hose diameter Sharp bends ( kinks) in the hose
What are the intricate working parts of the water system?
Source of water supply Means of moving water Water processing or treatment facilities Water distribution system, including storage
Where is the primary water source obtained from?
Surface water Groundwater
What are the three methods of moving water in a system?
Direct pumping Gravity system Combination system
What is direct pumping ststem?
Use one or more pumps that take water from the primary source and discharge it through the filtration and treatment process
What is a treatment facility?
A place where the water is treated to remove contaminents that may be detrimental to the health of those who use or drink it
what is a dead end hydrant?
A hydrant that only receives water from one direction
What is a circulating feed or looped line?
A hydrant that receives water from two or more directions
a distribution system that provides circulating feed from several mains is called what?
A grid system
A grid system has what components?
Primary feeders Secondary feeders Distributors
What are the two types of valves for water systems?
Indicating Non indicating
What are two common indicator valves?
Post indicator valve ( PIV) Outside Screw & yoke ( OS&Y)
Where are non- indicating valves normally installed?
Valve boxes Manholes
What are the two types of control valves?
Gate valves Butterfly valves
A water pipe that is used underground is usually made of what?
Cast iron Ductile iron Asbestos cement Steel Plastic Concrete
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