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