Chapter 5 - Principles Of Water Flashcards
Waters freezing point
Below 32F (0C)
Waters boiling point
Above 212F (100C)
How much does water weigh?
Ordinary fresh water is considered to weigh 62.4lbs/ft 3 or 8.3lbs/gallon
Water extinguishes fire in several ways
-It cools and absorbs heat in a fire
-can smother the oxygen from a fire
-can also smother combustible liquid fires whose specific gravity is higher than 1 (heavier than water)
-smothering may also occur when water converts to steam in a closed space
Water converted to steam converts to?
1,700 times it’s original volume
Pressure
Force per unit area exerted by liquid or gas measured in pounds per square in (psi) or kilopascals (kPa)
Force
Simple measure of weight, usually expressed in pounds or kilograms
Principles of pressure
First principle
Fluid pressure is perpendicular to any surface on which it acts. A vessel having flat sides and containing water. Pressure exerted by the weight of the water is perpendicular to the walls of the container. If pressure is exerted in any other direction, the water would begin to move downward along the sides and rise at the center
Principles of pressure
Second principle
Fluid pressure at a point in fluid at rest is the same intensity in all directions. This principle is used in hydrostatic testing
Principles of pressure
Third principle
Pressure applied to a confined fluid is transmitted equally in all directions. Illustrated by a hollow sphere around its circumference. All gauges will register the same pressure, providing that they are on the same grade line with no change to elevation
Principles of pressure
Fourth principle
The pressure of a liquid in an open vessel is proportional to its depth. Illustrated by 3 containers with the same size base but have different heights. First container being a foot tall is only half the amount of psi than the second container which is 2’ and the third container being 3’ tall and being 3 times the psi of the first container.
Principles of pressure
Fifth principle
The pressure of a liquid in an open vessel is proportional to the density of the liquid. Illustrated by two containers, one holding mercury (1” deep) and the other holds water (13.55” deep) but yet the pressure at the bottom of the containers are approximately the same.
Types of principles
Sixth principle
The pressure of a liquid at the bottom of a vessel is independent of the shape of the vessel. Illustrated by observing water in several different shaped containers, each having the same cross-sectional area at the bottom and the same height. The pressure is the same in each container
What is atmospheric pressure at sea level?
14.7 psi
Vacuum
In the fire and emergency services, a pressure that is somewhat less than atmospheric pressure; a vacuum is needed to facilitate drafting of water from a static source.
Head
Alternate term for pressure, especially pressure due to elevation. For every 1-foot increase in elevation, 0.434 psi is gained. Also known as head pressure
To convert head in feet to head pressure, you must divide the number of feet by?
2.304
Static pressure
Static pressure is stored potential energy available to force water through pipes, fittings, hose, and adapters. Static means at rest, or without motion.
Normal operating pressure
The pressure found in a water distribution system during normal consumption demands is considered the normal operating pressure.
Residual pressure
Pressure at the test hydrant while water is flowing; represents the pressure remaining in the water supply system while the test water is flowing and is that part of the total pressure that is not used to overcome friction or gravity while forcing water through fire hose, pipe, fittings and adapters.
Flow pressure
While water is flowing from a discharge opening, the forward velocity pressure is considered flow pressure. Use of a pilot tube and gauge to measure the forward velocity of flow pressure. Firefighters can also calculate the water flowing if the size of discharge opening is known.
Elevation
Height of a point above sea level or some other reference point
Altitude
Geographic position of a location or object in relation to the sea level. The location may be above, below, or at sea level.
Elevation pressure
Gain or loss of pressure in a hoseline due to a change in elevation. Also known as elevation loss.
Difference between elevation and altitude
Elevation refers to the center line of the pump or bottom of a static water supply source above or below ground level. Altitude is the position of an object in relation to sea level.
Friction loss
Loss of the pressure created by the turbulence of water moving against the interior walls of the hose or pipe
Principles of friction loss
First principle
If all other conditions are the same, friction loss varies directly with the length of the hose or pipe.
Principles of friction loss
Second principle
When hoses are. The same size, friction loss varies approximately with the square of the increase in velocity of the flow. (Basically by doubling or tripling the water flow through a hose or pipe increases friction loss significantly)
Principles of friction loss
Third principle
For the same discharge, friction loss varies inversely as the fifth power of the diameter of the hose. The wider diameter of a hose the less friction loss their will be
Principles of friction loss
Fourth principle
For a given velocity, friction loss is approximately the same, regardless of the pressure on the water.
Water hammer
Force created by the rapid deceleration of water; causes a violent increase in pressure that can be powerful enough to rupture piping or damage fixtures. Generally results from closing a valve or nozzle too quickly
Direct pumping systems
Uses one or more pumps that take water from the primary source and discharges it through the filtration and treatment processes. From there, a series of pumps force the water into the distribution system
Gravity system
Uses a primary water source located at a higher elevation than the distribution system. The gravity flow from the higher elevation provides the water pressure.
Combination system
Most communities use a combination of the direct pumping and gravity systems
Distribution systems
Part of an overall water supply system that receives the water from the pumping station and delivers it throughout the area to be served
Grid system
Water supply system that utilizes lateral feeders for improved distribution.
Primary feeders
Large pipes (mains), with relatively widespread spacing, that convey large quantities of water to various points of the system for local distribution to the smaller mains
Secondary feeders
Network of intermediate sized 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 point
Distributors
Grid arrangement of smaller mains serving individual fire hydrants and blocks of consumers
Indicating valves
Visually shows whether the gate or valve seat is open, closed, or partially closed
Post indicator valve (PIV)
Type of valve used to control underground water mains found on the supply main of installed fire protection systems. The operating stem of the valve extends above ground through a “post,” and a visual means is provided at the top of the post for indicating “open” or “shut”.
Commonly used on private water supplies
Outside screw & yoke valve (OS&Y)
A type of control valve for a sprinkler system in which the position of the center screw indicates whether the valve is open or closed. Also known as outside stem and yoke valve
Non-indicatingvalves
Most common type of valves used on most public water distribution systems. These valves have no indication other than water flow that tells you that if the valve is open or closed
This is the average amount of water used per day based on the total amount of water used in a water distribution system over the period of one year?
Average daily consumption (ADC)
This is the maximum total amount of water that was used during any 24-hour interval within a 3-year period. Unusual situation, such as refilling a reservoir after cleaning, should not be considered in determining the maximum daily consumption
Maximum daily consumption (MDC)
This is the maximum amount of water used in any 1 hour interval over the course of a day
Peak hourly consumption (PHC)
