Chapter 6 Calculating Required Fire Flows Flashcards
The amount of water that must be applied to a fire in order to control or extinguish it in a reasonable amount of time
required fire flow (RFF), needed fire flow (NFF)
where the benefits to determining the required fire flow
- compare available fire flow to the required fire flow, to determine if water distribution system can supply the necessary water
- deciding which apparatus and personnel need to respond
- engineers (sprinklers) need to know the flow requirements for their systems
and comparing the different methods of determining required fire flow what’s one thing to keep in mind
given the same occupancy and conditions the results determined by the three methods may vary widely…. also no method for calculating this information is ever been proven to be totally accurate…… so what the fuck
for the three methods commonly used to calculate required fire flow
- Iowa state formula
- national fire Academy formula
- insurance services office formula (ISO)
who invented the fog nozzle
Glenn Griswold, who is looking for better ways to fight oil fires as part of the Los Angeles County fire Department
who developed the indirect attack theory to battle fires on naval vessels
Lloyd Layman, his indirect attack theory was based upon atmospheric displacement of heat products by the expanding steam
the fundamental principles of Layman’s indirect attack
- indirect attack would only work in confined spaces with significant involvement
- fog stream should be placed in the upper portions of the involved space
- firefighters should not be in the space
- stream should be discharged into the area without interruption until the condensed steam that emerges has decreased considerably
Royer and Nelson founded what society
the International Society of Fire Service Instructors
who developed the ISU formula
Royer and Nelson
the ISU formula is based upon two fundamental principles
- One gallon of water will produce, 200 ft.³ of steam (with margin of error)
- One gallon water will absorb, all the heat that can be produced with the oxygen available in 200 ft.³ of normal air (with a margin of safety)
Nelson and Royer determined that ___ was the maximum time required for effective use of the adjustable fog nozzle
30 seconds, discharge times longer than that were practical only if the space in which the fire was located was not sufficiently vented
the NFA fire flow formula was developed as a quick calculation formula this formula was intended to provide a starting point for…
- deciding the amount of water required
- the apparatus needed to deliver the water
- number of companies that should be used to apply it
to the NFA advises that the formulas considered reliable only if
four floors or fewer are on fire
which formula has never been validated by scientific or practical testing
the NFA formula, the one we use
which fire flow formula is use the least
the ISO formula
what does C stand for in the ISO formula
construction coefficient, ranging from
wood frame 1.5 - fire resistive construction .6
what does A stand for in the ISO formula
area
according to the ISO formula the minimum fire flow for any structure should be….. maximum fire flow
500 GPM,… with factors applied 12,000gpm
in the ISO formula fire flow may need to be adjusted based on the level of hazard present, how is this done
+25% for high hazard occupancy
-25% for low hazard occupancy
In the ISO formula the adjusted fire flow may be reduced up to ___% for complete automatic sprinkler protection. where buildings are either fire resistive or noncombustible construction and have a low fire hazard reduction may be up to ___%
50%
75%
In the ISO formula percentage should be added to the adjusted fire flow for structures exposed within ___ft. the total percentage for all sides shall not exceed ___% of the fire flow
150ft
75%
the ISO formula is not expected to provide adequate value for
lumber yards
petroleum storage
refineries grain elevators
large chemical plants
According to the ISO form of a wood frame structures separated by 10 feet should be considered what…
one fire area
according to the ISO formula how do wood shingle roofs that could contribute to fire spread affect the fire flow
add 500 GPM
the ISO formula states continuous residences such as town houses or row houses have a minimum fire flow of
2500 GPM
according to NFPA records 90% of all fires and sprinkler buildings are extinguished by___ or fewer activated sprinklers, flowing about ___gpm
5 or fewer
8-15gpm each
NFPA standard for sprinkler systems
NFPA 13
NFPA 13 limits new sprinkler systems designed by pipe schedule to occupancies less than
5000 ft.²
two methods of designing automatic sprinkler systems
pipe schedule
hydraulic calculation
which of the two methods of sprinkler design is more common
hydraulic calculations much more common, and is the only acceptable method of design protection for special and extra hazards
benefits of hydraulically calculated automatic sprinkler systems
- system performance will still be acceptable despite using smaller pipes
- smaller pipes reduced material and labor cost for light and ordinary hazard occupancies compared to pipe schedule
- hydraulic calculated systems may use other types of pipe such as thin-walled piping, copper tubing, plastic piping which cause less friction than steel piping
what is the NFPA standard for standpipe systems
NFPA 14
if a structure is equipped with a single class I standpipe the system is required to have a minimum flow of ___, without being boosted by a fire department pumper. each additional standpipe must have an available ___ up to a maximum of____. the most hydraulically challenging discharge must have a pressure of ____.
single class 1 standpipe is required to have 500 GPM
additional standpipes must have 250 GPM
maximum flow of 1250 GPM
100psi
class 2 standpipes
- designed for use by building occupants to attack fires
-hose cabinets with 1.5” preconnected hose - flow of 100 GPM at 65 psi
no longer allowed in many jurisdictions
class 3 standpipes
combination of class I and class II systems, water supply requirements identical as class I systems
