Flashcards in Essentials Ch 16 Deck (39):
The primary way that water extinguishes fire is by:
Absorbing heat which creates a cooling effect
_______ _____ is the amount of energy required to increase the temperature of a substance by one degree.
_______ ____ ____ ______ is the amount of heat required to convert unit mass of a liquid into a vapor without a temperature change.
Latent heat of vaporization, water has a latent heat of vaporization of 970 Btu/lb
Does a solid stream evaporate quicker than a fog stream?
No, solid stream of water has a smaller surface area (similar to a log)and absorbs heat less efficiently.
When flowing a stream into an upper heated layer, the water ________, the hot gases are _____ and the upper layer ______.
Evaporates / cooled / contracts
What's the most common example of loss of pressure in a hoseline?
Friction loss between the pumper and the nozzle (friction loss).
A _____ ______ is a stream of water or other extinguishing agent after it leaves a fire hose nozzle until it reaches the desired target.
Fire streams are classified into one of three sizes:
Low volume streams (less than 40 gpm)
Handline streams (40 - 350 gpm, 1 1/2" - 3" size)
Master streams (more than 350 gpm - nozzle pressures of 80 to 100 psi)
The volume of water discharged is determined by the design of the _____ and the _____ ______ at the nozzle.
Nozzle / water pressure
To be effective, a fire stream must deliver a ______ of water sufficient to ____ ____ _____ than the fire generates it.
Volume / absorb heat faster
The minimum flow rate at which extinguishment can be achieved is:
Critical flow rate
The major types of fire stream patterns are:
A stream that stays together is a _______, produced from a ______ _____ nozzle.
Solid stream / smooth bore nozzle
Characteristics of solid streams include:
Good reach and stream penetration
Stream produced at low nozzle pressure
Produces less steam conversion
Provides less heat absorption per gallon
More likely to conduct electricity
Four critical elements of a fire stream:
Pressurized device (pump)
Means of delivery (hoseline)
Dish charge device (nozzle)
The ____ _____ point of a stream can be observed as the distance where it begins to lose its forward velocity.
Break over point
A ____ _____ is a fine spray composed of tiny water droplets. ____ ____ are used to produce fog streams and designed to permit adjustment of the top to produce different fog stream patterns.
Fog stream / fog nozzle
The desired performance of a fog stream is characterized by the amount of:
Heat that it absorbs and the rate by which the water is converted into steam or vapor
Fog streams have the following characteristics:
Fog stream patterns can be adjusted
Used for hydraulic ventilation
Used for vapor dispersion
Used for crew protection
Reduce heat by exposing the max water surface for heat absorption
Cool the hot gases
Shorter reach than solid/straight streams
More affected by wind
May disturb thermal layering
May intensify fire by pushing fresh air into the fire area
A _____ _____ pattern is a semi solid stream that is produced by a fog nozzle.
A _____ ____ is a fire stream that has been broken into coarse lay divided water droplets by specialized nozzles (cellar nozzles, piercing nozzles and chimney nozzles
Where will you use a broken stream?
Attics, cocklofts, basements, and other confined spaces
There are five limiting factors that affect the reach of a fire stream:
Water velocity (60 - 120 ft/second at 25-100psi)
Fire stream Pattern
Water droplet friction with air
Ideal angle for greatest horizontal reach for a fire stream is:
45º angle, 30-34º provide the maximum effective horizontal reach
Both categories of nozzles (straight tip - smooth bore and spray nozzles - fog nozzles) perform three main functions:
Controlling water flow
Shaping the fire stream
NFPA 1963 - Standard for Fire Hose Connections
Characteristics of smooth bore nozzles:
Operate at low nozzle pressures
Are less prone to clogging with debris
Can be used to apply compressed air foam
May allow hose lines to kink due to pressure loss
Do not allow for deletion of different stream patterns
Characteristics of fog nozzles are:
Discharge pattern can be adjusted
Provide protection to firefighters with wide pattern
Used for a variety of applications
Offer a variety of nozzle choices
Used to apply certain types of foam
There are four basic types of fog nozzles:
Basic fog nozzle
Constant gallonage fog nozzle
Constant pressure (automatic fog nozzle)
Constant/select gallonage fog nozzle
What are the three type of nozzle control valves?
The counter force directed against a person holding a nozzle by the velocity of water being discharged:
Nozzle reaction - caused by velocity, flow rate and discharge pattern of stream
In general, fire fighting foam works by forming a:
Blanket of foam on the surface of burning fuels - both liquid and solid
Foam extinguishes and/or prevents ignition in several ways:
Separating - creates a barrier between the fuel and the fire
Cooling - lowers the temperature of the fuel and adjacent surfaces
Smothering - prevents air from reaching the fuel and mixing with the vapors and prevents the release of flammable vapors reducing the possibility of ignition (reignition)
Penetrating - lowers the surface tension of water and allows it to penetrate fires in Class A materials
Class B foams is especially effective on the two basic categories of flammable liquids:
Hydrocarbon fuels and polar solvents
Class B foams are used on hydrocarbon fuels such as:
Petroleum based combustible/flammable liquids that float on water:
Class B foams are used on polar solvents such as:
Flammable liquids that mix readily with water:
The mixing of water with an appropriate amount of foam concentrate to form a foam solution:
There are four basic methods by which foam may be proportioned:
Foam application techniques:
Roll On Method
Bank Down Method