Chapter 6 What is Water and Where Does it Come From
Six principles of pressure
1) Fluid Pressures is perpendicular to any on which acts. 2) fluid pressure at a point in a fluid at rest is the same intensity and all directions. 3) pressure applied to a confined fluid from with out is transmitted equally in all directions. 4) pressure of a liquid in is proportional to its depth 5) The pressure of a liquid in an open vessel is proportional to the density of the liquid 6) The pressure of a liquid on the bottom of a vessel is independent of the shape of the vessel.
What is the atmospheric pressure at sea level(Standard atmospheric pressure)
14.7 psi
How high of a water column do you need to create 1 psi
2.304 = 1 cu/ft water is 62.4 lbs 1ft squared is 144 in (12x12) 62.4 / 144 = .0434 1 (original height of cu/ft) / .434 = 2.304 Pg 141 (171)
How much PSI is required to reduce the volume of water by 1%
30,000
How much does one cubic foot of water weigh
62.4 pounds
How much does a cubic foot of water weigh
62.5 lbs
How many gallons of water are in one cubic ft of water
7.48
Recommended size for fire hydrant supply lines in business and industrial districts
8 inches cross connecting every 600 feet. 12 inch mains maybe used not, cross connecting at frequent intervals, as large as 48 inches
How much does a gallon of water weigh
8.33 pounds
How much BTU's does 1 pound of water require to convert it to steam
970 Btu 1023 kJ
Grid system
A distribution system that provides circulating feed from several mains
Specific heat
A measure of the heat absorbing capacity of a substance
Joule
A unit of the work. 1 calorie = 4.19 joules
Perfect vacuum
Absolute zero pressure
What is a vacuum
Any pressure less then Atmospheric pressure
The recommended size for fire hydrant supply mains in residential areas
At least 6" with 8 inches cross connecting mains at intervals of no more than 600 feet
Definition of static
At rest or without motion
A fire hydrant that receives water from two or more directions
Circulating feed, or looped line
Types of water treatment
Coagulation, sedimentation, filtration, the addition of chemicals, bacteria, or other organisms,
Two ways that water extinguishes
Cooling, or absorbing heat from the fire. Smothering, excluding oxygen.
Above sea level atmospheric pressure
Decreases approximately .5 psi for every 1000 feet
Why is latent heat of vaporization significant in firefighting
Definition on page 137 For 1 gallon of water at 60°F it requires 152 (212-60=152) Btu to raise each pound of water to 212°F. So 1 gallon of water absorbs 1266 ( 152 x 8.33= 1266) BTU getting to 212°F. Water weighs 8.33 pounds. So 1 pound of water requires 970 Btu to turn to steam. So 1 gallon of water absorbs 1266 Btu plus an additional 970 Btu per lb, 8080 ( 970 x 8.33= 8080) BTU, for a total of 9346 Btu to convert to steam.
Three means of moving water
Direct pumping system. Gravity system. Combination system.
Head pressure
Divide the number of feet above the discharge orifice by 2.304 ( The number of feet that one psi will raise a 1 in.² column of water)
Flow pressure
Foward velocity pressure at a discharge opening while water is flowing
Types of control valves in water distribution systems
Gate valves, butterfly valves
Head
Height of the water supply above the discharge orifice
Critical velocity
If the velocity is increased beyond practical limits the friction becomes so great that the entire stream is agitated by resistance
Four principles of friction loss
Length of hose or pipe. Friction loss varies approximately with the square of the increase in the velocity . Friction loss varies inversely as the fifth power of the diameter of the hose. For a given flow velocity, friction loss is approximately the same, regardless of the pressure on the water.
Most flammable liquids have a specific gravity of
Less than one
Maximum daily consumption
Maximum total amount of water that is used during any 24 hour interval within a three-year period
Water is heaviest when? Water is lightest when?
Near it's freezing point. Near its boiling point.
How is water density measured
Pounds per cubic foot
psia
Pounds per square inch absolute ( aka, the psi above a perfect vacuum, absolute zero )
psig
Pounds per square inch gauge
The hierarchy of a grid system
Primary feeders, (Large pipes) Secondary feeders ( intermediate pipes that reinforce the grid within the various loops of the primary feeder system and aid the concentration of the required fire flow at any given point), Distributors (Great arrangements of smaller mains serving individual fire hydrants and blocks of consumers
Elevation
Refers to the level of the pump or the bottom of the static water supply above or below ground level
Definition of residual
Remainder or that which is left
Force
Simple measure of weight, usually expresses in pounds or kilograms
Static pressure
Stored potential energy available to force water through pipe, fittings, firehose, and adapters
Friction loss
That part of the total pressure loss while forcing water through pipe, fittings, firehouse, and adapters.
BTU
The amount of heat required to raise the temperature of 1 pound of water 1°F
Average daily consumption
The average of the total amount of water used in a water distribution system over the period of one year
Specific gravity
The density of liquids in relation to water. Liquids with a specific gravity less than one hour later than water and therefore will float in water. A Specific gravity that is greater than one are heavier and will sink in water.
Pressre
The force ER unit area exerted by a liquid or gas measured in pounds per square inch, psi, pounds per square foot, psf, or kilopascals, kPa
The difference between static pressure and normal operating pressure
The friction caused by water flowing through pipes, valves and fittings.
What is the difference between static pressure and normal operating pressure
The friction caused by water flowing through various pipes, valves, and fittings in the system.
Elevation pressure
The loss or gain that is occurred because of gravity
Peak hourly consumption
The maximum amount of water used in any one hour interval over the course of a day
Specific heat
The measure of heat absorbing capacity of a substance
Residual pressure
The part of the total available pressure not used to overcome friction loss or gravity while forcing water through pipe, fittings, firehose, and adapters.
Altitude
The position of an object above or below sea level
Normal operating pressure
The pressure found in a water distribution system during normal consumption demands
Latent heat of vaporization
The quantity of heat absorbed by a substance changes from a liquid to a vapor
How the specific heat of a substance is determined
The ratio between the amount of heat needed to raise the temperature of a specific quantity of a material and the amount of heat needed to raise the temperature of an identical quantity of water by the same number of degrees
Coefficient of friction
The rougher the inner lining of the pipe the greater the friction loss will be
What are the fundamental components of a water system
The source. Means of moving water. Water processing or treatment facilities. Water distribution systems, including storage.
Velocity
The speed at which fluid travels
Boiling point
The temperature at which a liquid absorbs enough heat to change to vapor
Viscosity
The tendency of a liquid to possess internal resistance to flow.
How to determine the amount of water that a community needs
Total amount of water needed for domestic and industrial use and for firefighting use
Who are the experts in water supply problems
Water department officials
Calorie
quantity of heat required to raise the temperature of 1 gram of water by 1°C at 1 atmosphere pressure.