Pumping Apparatus Driver/ Operator Handbook
3rd Edition
Chapter 5 — Principles of Water
Describe the characteristics of water.
Learning Objective 1
5–1
Water is a compound of hydrogen and oxygen that can be in different states depending on its temperature.
5–2
Water density
• Weight per unit of volume
• Measured in pounds per cubic foot (kg/m3)
Weight of fresh water
• 62.4 lb/ft3
(1 000 kg/m3)
• 8.3 lb/gal (1 kg/L)
Ability to extinguish fire
• Cooling• Smothering
Driver/operators should be familiar with the characteristics of water.
5–3
REVIEW QUESTION
What are the ways that water can extinguish fire?
5–4
Identify the advantages and disadvantages of water.
Learning Objective 2
5–5
Greater heat-absorbing capacity than other common agents
Large amount of heat required to change to steam
Greater exposed surface area allows heat to be more rapidly absorbed
Steam dissipates heat in well-ventilated rooms due to increased volume
Generally inexpensive and readily available
Water has many characteristics that make it an excellent extinguishing agent.
5–6
Somewhat difficult to soak into dense materials
May be reactive with certain substances
Radiant heat passes easily through water
May create operational problems or safety hazards in cold weather
Good conductor of electricity
Relatively heavy
There are some disadvantages to using water as an extinguishing agent.
5–7
REVIEW QUESTION
What are some advantages and disadvantages of water as an extinguishing agent?
5–8
Summarize facts about water pressure and velocity.
Learning Objective 3
5–9
Simple measure of weight
Directly related to force of gravity
Expressed as• Pounds• Kilograms
Force per unit area exerted by liquid or gas
Expressed as• Pounds per square
foot (psf)• Pounds per square
inch (psi)• Kilopascals (kPa)
Pressure is easily confused with force, but they are not the same thing.
5–10
Pressure Force
Speed that fluid travels
Pressure upon the
fluid
Size of orifice that fluid flows through
Driver/operators must understand how pressure affects the rate that fluid flows through a hose or pipe.
5–11
First principle
Fluid pressure is perpendicular to any
surface on which it acts
Driver/operators must understand the principles that determine the action or pressure on fluids.
5–12
Second principle
Fluid pressure at a point in fluid at rest is
the same intensity in all directions
(Cont.)
Third principle
Pressure applied to confined fluid is
transmitted equally in all directions
Fourth principle
Pressure of liquid in an open vessel is
proportional to its depth
Driver/operators must understand the principles that determine the action or pressure on fluids.
5–13
(Cont.)
NOTE
Due to the increase in water pressure requirements necessary for the height of the building, pressure-regulating devices are installed in standpipe systems that serve high-rise buildings. These devices allow hoselines on lower floors to be more easily controlled, while allowing the high pressures required to access upper floors.
5–14
Fifth principle
Pressure of liquid in an open vessel is
proportional to density of the liquid
Driver/operators must understand the principles that determine the action or pressure on fluids.
5–15
Sixth principle
Pressure of liquid at the bottom of vessel is
independent of vessel’s shape
Greatest at low
altitudes and least at
high altitudes
Standard atmospheric pressure at sea level is
14.7 psi (100 kPa)
Commonly measured
by comparing weight of
atmosphere with weight of mercury
Readings of most
gauges in psi (or kPA)
Vacuum is any
pressure less than
atmospheric pressure
Atmospheric pressure surrounds the earth and exerts pressure on everything.
5–16
Head pressure is the height of a water supply above the discharge orifice.
5–17
Static pressure is the stored potential energy available to force water through pipes, fittings, hose and adapters.
5–18
Water supply is not moving
Static water pressure• True static pressure seldom found in
municipal systems• Considered static before it flows from hydrant
Normal operating pressure is the pressure found in water distribution systems during normal consumption demands.
5–19
Water begins flowing
Static pressure no longer exists
Consumption demands fluctuate continuously
Difference between static and normal operating pressure is friction
Water source
Water moves through pipes, fittings, hoses,
or adapters
Residual pressure is the amount of pressure not used to overcome friction loss or gravity.
5–20
Minus loss of pressure from friction loss or
gravity
Residual pressure
NOTE
Identify the residual pressure at the location where the reading is taken and not at the flow hydrant.
5–21
Water emitted from discharge opening that is not encased within a tube exerts
forward, not lateral pressure
Use pitot tube and gauge to measure
Used to calculate quantity of water flowing if the size of discharge is
unknown
When water is flowing from a discharge opening, the forward velocity pressure is considered flow pressure.
5–22
NOTE
When measuring the forward velocity of flow pressure using a nozzle, a smooth bore nozzle must be used with the pitot tube and gauge.
5–23
Nozzle below the pump
Nozzle above the pump
Elevation and altitude can impact output pressure.
5–24
Gain
Loss
Elevation pressure
Easier to produce
effective fire streams
Harder to produce
effective fire streams
Altitude
5–25
Click image to
play
A certain amount of pressure is lost due to friction as water moves through pipes, fittings, fire hoses, and adapters.
REVIEW QUESTION
What are the different types of pressure?
5–26
Summarize the principles of friction loss.
Learning Objective 4
5–27
First principle
If all other conditions are the same, friction
loss varies directly with the length of
hose or pipe
Second principle
When hoses are the same size, friction loss varies approximately with the square of
increase in velocity of the flow
Driver/operators should be familiar of the principles of friction loss.
5–28
(Cont.)
NOTE
Velocity is proportional to flow.
5–29
Third principle
For the same discharge, friction
loss varies inversely as the fifth power of the hose diameter
Fourth principleFor a given velocity,
friction loss is approximately the
same, regardless of pressure on the
water
Driver/operators should be familiar of the principles of friction loss.
5–30
REVIEW QUESTION
What are the principles of friction loss?
5–31
Identify how friction loss principles can be applied to the fire service.
Learning Objective 5
5–32
Volume of water
supplied into fire hose
under pressure
Volume of water
expelled from nozzle
Water requires a great deal of pressure to reduce its volume even a small amount.
5–33
Hose diameter determines velocity for a given volume of water
Be aware of how friction loss and water pressure are affected by hose length and nozzle use.
5–34
Friction loss increases as length of hose or piping increases
Flow pressure always greatest at source of supply and lowest at farthest point in the system
Nozzle is needed to shape stream for fire fighting
Decreasing amount of water flowing reduces speed of water and friction loss
If velocity increased beyond practical limits• Friction becomes so great that entire system is
agitated by resistance• Degree of turbulence known as critical velocity
Specific hose length at which reduction in flow makes use undesirable• Necessary to use parallel or siamese lines beyond
this
There are practical limits to the velocity at which a stream can travel.
5–35
• Reduce length of lay• Increase diameter of hoseHose length
• Use larger diameter for long supply distance
• Reduce hose to diameter appropriate for master stream or handline
Hose diameter
• Employ proper hose handling techniquesSharp bends
or kinks
Friction loss in a system can be reduced in several ways.
5–36
There are multiple factors that can cause a water hammer.
5–37
REVIEW QUESTION
How can friction loss caused by hose length or diameter be reduced?
5–38
Identify the principles of municipal water supply systems.
Learning Objective 6
5–39
Planning for fire protection
coverage
Fire departments
Local water departments
Fire departments must coordinate with local water departments to ensure an adequate water supply for fire protection.
5–40
Municipal water systems may be supplied by groundwater, surface water, or by a combination of both.
5–41
Surf
ace
wat
erG
roundwaer
• Rivers
• Lakes
• Water wells
• Water-producing springs
Desalinated seawater
There are three methods of moving water in a system.
5–42
Sufficient for domestic, industrial, and fire fighting demands
Sufficient to allow downtime for system repairs, alterations, or additions
Storage location and capacity mains important factors in system function
Many industries provide private systems available to fire departments
Water for firefighting may be available from storage systems
Water may be stored in elevated reservoirs to ensure the water supply when the system is inoperative.
5–43
Water is treated to remove contaminants that may be detrimental to people’s health.
5–44
Coagulation
Sedimentation
Filtration
Addition of chemicals, bacteria, other organisms
Plan for potential shortfalls
• Maintenance failure
• Natural disaster
• Loss of power supply
• Fire
Fire departments must be aware of situations with water treatment plants that could affect water supply.
5–45
Ability to deliver adequate quantity relies on capacity of network of pipes
Friction results in reduction of pressure
Grid systems provide circulating feed
Should have sufficient supply for routine consumption and fire protection
The distribution system receives the water from the pumping station and delivers it through the area served.
5–46
Should be located at frequent intervals in grid
system
Should be operated at least once a year
Need for valve rarely occurs
Spaced so that a minimum portion may be isolated
for repair or maintenance
Provide hydrants with individual control valves
Water main valves provide a means for controlling the flow of water through distribution piping.
5–47
Records locations of all valves
Inspects and operates valves
yearly
Water departments must have the ability to promptly operate valves during an emergency or equipment breakdown.
5–48
Indicating valves
Shows whether valve seat is open or closed
Usually in private fire protection systems
Post indicator
valve (PIV)OS&Y valve
Valves for water systems are broadly divided into two main types.
5–49
Nonindicating valves
Most common in public systems
Normally in valve boxes or manholes
Can be opened with special socket wrench
NOTE
Fire department policy may prohibit firefighters from operating the control valves of a water distribution system. For jurisdictions where it is permissible to operate these valves, firefighters should be familiar with the opening direction of nonindicating valves, as they may open clockwise or counterclockwise. Consult the local water authority before operating these valves.
5–50
• Similar to OS&Y valve
Rising-stem type
• Gate lowers to control water flow as valve nut is turned by valve key
• Should be marked with number indicating number of turns to completely close
Nonrising-stem type
Control valves in public water distribution systems are generally gate valves.
5–51
Properly installed valves
• Necessary to close off one or two hydrants while single break is repaired
Less advantages if all valves are not maintained and kept fully open• High friction loss caused by partially open valves• Closed valves may not be noticeable during ordinary
domestic water use• Difficulty obtaining water for fire fighting
Proper valve installation and maintenance can effect fire department operations.
5–52
Underground water pipes may be made of many materials and be suited for a variety of conditions and pressures.
5–53
Made of
• Cast iron• Ductile iron• Asbestos cement• Steel• Plastic• Concrete
Reinforced when in
• Unstable or corrosive soils
• Difficult to access areas
(Cont.)
Underground water pipes may be made of many materials and suited for a variety of conditions and pressures.
5–54
Internal surface
• Offers resistance to water flow
Factors affecting water flow and
friction loss
• Encrustation of minerals on interior
• Sedimentation• Reduced by flushing
hydrants periodically
Average daily consumption
(ADC)
Maximum daily consumption
(MDC)
Peak hourly consumption
(PHC)
Rates of consumption can be used to determine the adequacy of the water distribution system.
5–55
REVIEW QUESTION
What are the various means of moving water for a system?
5–56
Describe private water supply systems.
Learning Objective 7
5–57
Purp
oses Strictly for fire protection
Sanitary and fire protection
Fire protection and manufacturing
Private water supplies may be found in larger properties or in some residential developments.
5–58
Design similar to municipal systems
May be supplied from municipal or own water supply source
Usually maintain separate piping for fire protection and domestic/industrial services
Private and municipal systems may work independently or together to distribute water to an area.
5–59
NOTE
Private water supply systems that rely solely on the municipal water distribution system as their water supply source are subject to service interruptions in the event that the municipal system experiences a failure.
5–60
Relay water from municipal water supply system
Draft from reliable static water source close to the scene
Fire departments should make arrangements to augment private water supplies if necessary.
5–61
REVIEW QUESTION
What are the purposes of a private water supply system?
5–62
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