Chapter 6, What Is Water/Where Does It Come From? Flashcards
At what temp does water exist as a liquid?
Between 32 degrees F and 212 degrees F.
At what temp does water exist as a solid?
Below 32 Degrees F, it converts to ice.
At what temp does water exist as a gas?
Above 212 degrees F, it converts to steam.
How is water’s density (weight per unit of volume) measured?
Pounds per cubic foot.
When is water heaviest?
Close to its freezing point.
When is water lightest?
Close to its boiling point.
For fire protection purposes, what is the weight of water?
8.33 pounds per gallon.
What 4 things does water need, as an extinguishing agent?
Specific heat, latent heat, exposed surface area, specific gravity.
What is specific heat?
A measure of the heat absorbing capacity of a substance.
What is a BTU?
British thermal unit, amount of heat required to raise the temp of 1 pound of water 1 degree F (starting at 60 degrees F).
What is a joule?
A unit of work that has taken the place of the calorie in SI heat measurement (1 calorie =4.19 joules).
What is latent heat of vaporization?
The quantity of heat absorbed by a substance when it changes from a liquid to a vapor.
What is boiling point?
The temp at which a liquid absorbs enough heat to change to a vapor.
What is the exposed surface area?
The exposed surface of a spilled liquid (the speed at which water absorbs heat increases in proportion to the surface exposed to the heat).
If water is divided into many drops, what happens to its rate of heat absorption?
It increases hundreds of times.
How much does water expand at 212 degrees F, and why is that important in fire fighting?
It expands 1700 times. It is important because
- it absorbs more heat faster
- displaces hot gases/smoke
- in some cases, smothers fire
Why is it necessary to adequate ventilation when using a fog stream in a direct attack?
Prevents steam from rolling back over and around the hose team.
What are the 3 main results of the proper application of a water fire stream into a room?
- fire is extinguished/reduced
- visibility maintained
- room temp reduced
What is viscosity?
The tendency of a liquid to posses an internal resistance to flow.
What is specific gravity?
The density of liquids in relation to water (water is given a value of 1. Fluids with less specific gravity than 1 will float on water, more than spec grav of 1 will sink).
What are advantages of water as an extinguishing agent?
- greatly absorbs heat
- greater surface area of water, the faster heat absorbs
- water to steam conversion (1700 times)
What are some disadvantages to using water as an extinguishing agent?
- high surface tension (hard to soak into dense materials)
- water reactive to certain metals
- water freezes (a problem in certain jurisdictions)
- conducts electricity
What is pressure?
Force per unit area (expressed in pounds per square foot or pounds per square inch, or kilopascals).
What is force?
A measurement of weight, expressed in pounds.
What is velocity?
The speed at which a fluid travels.
Where is atmospheric pressure at its greatest? At its least?
Greatest in low altitudes. Least in very high altitudes.
What is the most common way of measuring atmospheric pressure?
Comparing the weight of the atmosphere to the weight of mercury (in a thermometer, the greater the atmospheric pressure, the taller the column of mercury).
What is atmospheric pressure at sea level?
14.7 psi (standard atmospheric pressure).
What is psig?
Pounds per square inch gauge (psi plus atmospheric pressure as read on a gauge).
What is psia?
Its the notation for actual atmospheric pressure (pounds per square inch absolute).
What is vacuum?
Any pressure less than atmospheric pressure.
What is a perfect vacuum?
Absolute zero pressure.
What is negative pressure?
Gauge readings less than 0 psi.
What is head, in the fire service?
The height of a water supply above the discharge orifice.
How do you convert head to head pressure?
Divide the number of feet by 2.304 (the number of feet that 1 psi will raise 1 square inch column of water).
What is static pressure?
Stored potential energy available to force water through a hose (pressure in a water system before water flows from a hydrant).
What is normal operating pressure?
Pressure found in a water distribution system during normal consumption demands.
What is residual pressure?
That part of total available pressure not used to overcome friction loss while forcing water through a hose (remaining pressure).
What is flow pressure?
It is that forward velocity pressure at a discharge opening while water is flowing.
What is elevation?
It refers to the center line of the pump or bottom of a static supply source above/below ground.
What is altitude?
Position of an object above or below sea level.
What is elevation pressure?
Pressure loss and pressure gain.
What is friction loss?
That part of the total pressure lost while forcing water through a hose.
What causes friction loss in a fire hose?
- movement of water molecules against each other
- hose lining
- couplings
- sharp bends
- change in hose size by adapter
- improper gasket size
Where is flow pressure strongest and weakest?
Flow pressure is greatest near the supply source, lowest at farthest point in the system.
What characteristics of hose layouts affect friction loss?
- hose length
- hose diameter
- sharp bends
What is water hammer?
The back pressure from suddenly water moving through a hose (energy surge transmits in opposite direction).
What are the components of a water system?
- source of water supply
- means of moving water
- water treatment plant
- water distribution system
Example of surface water.
- rivers
- lakes
Example of groundwater supply.
- water wells
- water producing springs
What are the 3 methods of moving water in a system?
- direct pumping system
- gravity system
- combination system
What is direct pumping system?
It pumps directly from the water source to the distribution system.
What is a gravity system?
Uses a primary water source located at a higher elevation than the distribution system (the elevation provides the water pressure).
What is a combination system?
A combination of direct pumping and gravity, used to allow water storage during low-demand periods.
What is the fire departments main concern regarding treatment facilities?
That a maintenance failure, natural disaster, or fire could disable the pumping station.
What part of the overall water supply system receives water from the pumping station, and delivers it throughout the area served?
Water distribution system.
What is a fire hydrant that receives water from only one direction called?
Dead end hydrant.
What is a fire hydrant that receives water from 2 or more directions called?
Circulating feed or looped line.
What is a grid system?
A distribution system that provides circulating feed from several mains.
What does a grid system consist of?
- primary feeders
- secondary feeders
- distributors
What is a primary feeder?
Large pipes (mains) that carry large amounts of water to various points of the distribution system, to send to smaller mains.
What is a secondary feeder?
Network of intermediate sized pipes that reinforce the grid within the loops of the primary feeder system.
What is a distributor?
Grid arrangement of smaller mains, serving individual hydrants.
What is the recommended size for hydrant supply mains in residential areas?
At least 6 inches.
What is the minimum recommended size for hydrant supply mains in business/industrial areas?
8 inch main, with cross-connecting mains every 600 feet.
What size mains are used on principal streets?
12 inch.
What is the main function of water main valves?
To provide a means for controlling the flow of water In the distribution system.
What are the 2 types of valves in a water system?
Indicating valve and non-indicating valve.
What is unique about the indicating valve?
It visually shows whether the gate/valve is open or closed.
What are the 2 common types of indicating valves?
Post indicator valve and outside screw and yoke valve.
Identify the post indicator valve.
Its a hollow metal post attached to the valve housing (the valve stem inside the post has the words “open” and “closed” on it).
Identify the OS&Y valve.
It has a yoke on the outside with a threaded stem that controls the opening or closing.
Where are non-indicating valves in a distribution system normally located?
Normally installed in valve boxes or manholes ( most common valve used on distribution systems).
What are the 3 basic rates of consumption?
- average daily consumption (ADC): average total water used in distribution system in 1 year.
- maximum daily consumption (MDC): max water used during any 24-hour period interval within 3 years.
- peak hourly consumption (PHC): max water used in any 1-hour interval over the course of a day.
Where are private water supply systems most commonly found?
On large, commercial/industrial/institutional properties.
What are the 3 reasons private water supply systems exist?
- provide water solely for fire protection
- provide water for sanitary and fire protection
- provide water for fire protection and manufacturing
