Fire flow reqmnt for sprinklered building include sprinkler demand? 6

[NTTT]

The required fire flow can be reduced up to 75% if the building is sprinklered according to the IFC.

Does the reduced fire flow requirement include water demand for sprinkler system? or just for fire department hose streams only?

If not, what method should I use to get the value to add the the reduced fire flow requirement to perform hydraulic model? Thanks.

 

[stookeyfpe]

Which edition of the IFC? The 2003 IFC took the credit away for sprinklers in most buildings. It was given back (correctly) in the 06 IFC.

 

[stookeyfpe]

I looked at your question again and have concluded you are mixing apples with zebras.

Fire flow versus sprinkler demand are two completely different design criteria. Fire flow is based on the type of construction and the building area. It was calculated using very empirical formulas that were formulated by the Insurance Service Office in the 1950s. Basically fire flow is an estimation of how much water does one need to control a fire in a building that is not equipped with sprinklers.

Since your question indicated that the IFC is being applied, open your book and turn to page 394 (06 edition). Assume a 50,000 square foot building of Type V-A (combustible with no fire resistance) construction. The prescribed fire flow is 2,750 GPM @ 20 PSIG residual pressure for 2 hours.

Let us assume that the owner equips this same 50,000 square foot building with a NFPA 13 compliant automatic sprinkler system. I will further assume the ceiling height is less than 14 feet and that the owner will not store hazardous materials, flammable or combustible liquids, or other high challenge commodities. The assumed building will house a hair care products retail outlet. Based on this I would most likely classify the building as an Ordinary Hazard Group II occupancy using the requirements in Chapter 5 of NFPA 13.

NFPA 13 states that for an Ordinary Hazard Group II design, a minimum discharge density of 0.19 GPM/square foot over a 1,500 square foot design area is required. This equals a sprinkler demand of 285 GPM.

IFC section B105.2 in the 2006 edition states in the exception that the fire flow can be reduced by 75% but must not be less than 1,500 GPM @ 20 PSI.

So your minimum fire flow will be based on the building area, construction type and if the building is or is not equipped with a NFPA 13 compliant automatic sprinkler system. Regardless, the IFC correctly gives you a great deal of credit if the building is sprinklered. Therefore, if the building is sprinklered, your minimum fire flow is 1,500 GPM @ 20 PSI. If it is not sprinklered the fire flow is 2,750 GPM @ 20 PSI.

Your sprinkler demand question cannot be answered without more information because its design is based on storage height, commodity, roof height and the like. See Chapter 5 of NFPA 13.

I apologize for my first answer. I should have gone to bed rather than provide a more comprehensive response to the question as I have now done.

 

[NTTT]

Thank you stookeyfpe. I was looking at the 2003 IFC and now I do not have either the 06 IFC or NFPA 13 handy.

FYI. I work for a water district and we get fire flow requirements from fire departments (usually just one number i.e. 2750 gpm at 20 psi for 2 hours). Then, we (use a consultant to) perform a hydraulic model to determine available fire flow to compare with the requirements, and determine what improvements are needed to meet the flow requirements. Now, I am looking for appropriate methods to answer inquiries for flow/pressure information from fire sprinkler designers and wonder if I could use the hydraulic model to answer these questions. After a little research, I found out that the fire flow required by fire department may (not) include a demand for fire sprinkler. Then, I wonder if the hydraulic model we usually run is adequate. However, the difference could be a couple hundred gpm (+/-). And yes I try to add the apples to the zebras to cover all fire flow requirements.

Then, I conclude that the fire flow requirement of 1,500 gpm @ 20 psi in your case (sprinklered) does not include fire sprinkler demand.

Also, I should find an appropriate discharge density (0.19 in your example) and multiply it with the design area (1,500 sq.ft.) to get REASONABLE additional required flow to perform hydraulic analysis (1500 + 285 = 1,785). Note that at the very beginning of the project, we usually do not know a lot of details about the building i.e. proposed tenants, storage height, etc.

Are sprinkler heads still discharging water when the fire deparment arrive and start the hose streams? Frankly, I do not know how they operate.

Again, thank you for the information. It is very helpful and I would appreciate if you could confirm that my understanding is right or have more suggestions.

 

[TravisMack]

Here is my $0.02, and it may be worth less than that..

1st - Stookey: OH Grp II is 0.20 / 1500 - no big deal. That is per NFPA 13: FIGURE 11.2.3.1.5 Density/Area Curves.

And, as Scott said, you figure the 2 completely independently. Fire Flow is typically a requirement of 1500 @ 20 psi based on IFC tables. This does not, and is not required to include fire sprinkler demand.

The sprinkler demand - in the case of an OH Grp II requirement, would be approximately 300 gpm for sprinklers (0.2 *1500) + 250 gpm hose allowance if hydrants are taken from the supply - as is the case in most installations.

In order to do the fire sprinkler system calculations, the designer is going to want a static pressure in the lines, then a residual pressure at some flow rate. For example, you may have 80 psi static pressure, while dropping to 50 psi when flowing 1500 gpm. That is what the sprinkler guy would want to do his/her calculations.

I hope that makes some sense and adds to your clarification.

Also, yes, sprinkler heads are still discharging when the FD arrives. The sprinklers that have activated due to heat (NOT EVERY SPRINKLER IN THE BUILDING) will be flowing water until the supply is exhausted or the control valve on the system is shut down - essentially exhausting the supply.

 

[stookeyfpe]

NTTT:

Just remember that fire flow is independant of the sprinkler demand. Generally speaking, fire flow is > sprinkler demand. The exception is something like a flammable liquid warehouse or acetylene charging plant. These can have sprinkler demands on the order of 2,500 to 3,000 GPM. I am also aware of some aircraft repair hangers with hydraulic demands on the order of 5,000 GPM. These are fairly rare.

The example I used (and thanks Travis for correcting me) is probably typical for about 75% of the buildings you may see in your community. The other 25% I would estimate require larger sprinkler demands because of their storage heights. Using a conservative NFPA 13 sprinkler design based on the use of ESFR sprinklers (125 GPM / sprinkler x 12 sprinklers) + 500 gallons for hose streams, I calculated a sprinkler demand of 2,285 GPM.

So Travis, have you found where you are going to shop for your little piece of Texas tranquility?

 

[NTTT]

stookeyfpe & Travis:

Thank you very much!

I think I am confused about the word "hose streams" and how you came up with 2,285 gpm. Is it 1500 gpm fire flow + 0.19x1500 sprinkler demand + 500 hose streams?

Water used to extinguish fire in a sprinklered building consists of:

1. Fire flow, for fire hose streams connected from hydrants around the building?, obtained from IFC table, 2750 gpm reduced to 1500 gpm in the above example.

2. Sprinklers and hose allowance boosting the sprinkler system?, = (discharge density x design area) + hose allowance (250 or 500 gpm).

These two are calculated independently. However, the water district wants to confirm that there will be adequate flow for all demands (items 1 and 2) and I believe that the Fire Marshal would want to ensure that everything is covered for fire fighting.

Do you think what available fire flow Fire Marshal want to see in a Water Avaialbility Certificate? 2285 gpm or 1500 gpm? (The Certificate is required for permits i.e. building, fire, etc.) What do you see typically?

I do not know about your background but if you know of something, please let me know. Thank you.

 

[stookeyfpe]

NTTT:

The stated value is wrong. I recalculated it and I came up with 2,000 gpm:

[(125 GPM/Sprinkler)(12 sprinklers)]+500 GPM for hose stream demand = 2,000 GPM.

The Fire Department will always want at least 1500 GPM @ 20 PSI. However, in the case presented the sprinkler designer would need at least 2,000 GPM @ 20 PSI.

My experience with fire flow is that it will also be driven by the type of development. For example:

Single or multiple family dwellings: 1,500 GPM max
Light commercial: 1,500 to 2,000 GPM
Industrial park: 2,000 to 3,500 GPM

Again, I apologize for the math error.

 

[TravisMack]

stookey:

My wife is still surfing around for the DFW area. She is set on that area. I have been trying to get her to look around San Antonio and Austin areas.

 

[TravisMack]

NTTT -

I think you are still trying to add 2 things that are not additive.

If you have the non sprinklered building..say an industrial park, you must have a minimum flow at any hydrant of 2000-3500 gpm at stookey stated above.

If you have the sprinklered building, for example with ESFR heads, you would need around 1750 gpm (12 heads flowing at 1500 gpm + 250 gpm hose allowance [Stookey - it is just my day to cover your back; ESFR only requires 250 gpm hose])

Now, based on my understanding, here is how the scenario works and may help you understand....

Fire occurs in an unsprinklered building. By the time the FD gets there, the fire is raging pretty heavy and the FD will be drawing a lot of water from the municipal supply - say at 3000 gpm to attack the fire. That is where the fire flows come in to play.

Fire occurs in SPRINKLERED building. Let's assume there are ESFR sprinklers to stay with the example above. By the time the FD gets there, the fire is suppresed or contained to a relatively small area (1200 sq ft or less) and the FD only needs to draw a small amount of water (to complete the final knockdown on the fire). The hose allowance that is mentioned above accounts for the relatively small amount of water that the FD will be taking from the supply in addition to the demand from the sprinklers. So, in this case there would be about 1500 gpm flowing from the sprinklers and about 250 gpm for the FD to finish the attack.

The scenarios are 2 completely different situations to try so show how the numbers are really independent of each other.

Hopefully that helps to clear up some of the differences for you.

 

[stookeyfpe]

Travis:

Good job. I had those words in my head but you did a better job. I think I was spooked by math errors and you correcting me on NFPA 13 (note to self - read the standard before posting).

You will like the Metroplex. Just gravitate towards Fort Worth. I always liked that side of town.

When you decide to begin the hunt, e-mail me and I will make a trip up from Austin so I can meet you. We can have our own fire protection Pat's Pub in Fort Worth. And buddy I do have a great steak house in Fort Worth. Best in the state...my treat. Heck, I will give you a star just so you can remind me about it next year.

Come home to Texas brother. You will do well here...

 

[thebabe]

I am working on a housing project in NYS with 8-9 buildings which are multi family residential in scope. Based on the height of the buildings and the number of stairwells, the maximum fireflow for the standpipes would be 1250 GPM. Is this added to the sprinkler demand, hose stream, hydrant flows, or what. In other words, what is the maximum fireflow required for this project? Is it the 1500 GPM mentioned for residential projects, or is the standpipe demand an added factor? Thank you for your input.

 

[TravisMack]

thebabe:

As stated above, they are all separate entities and the water supply needs to be sized to supply each independently.

1 - Site fire flow requirements: This is often found in the IFC or whatever fire code you fall under. It is typically something like 1500 gpm @ 20 psi at any hydrant on property for a residential complex.

2 - Standpipes: You need to figure out if you have manual or automatic standpipes. If automatic, you need to be able to supply 100 psi @ 250 at the topmost outlet, 250 at the next outlet and 250 for each additional standpipe to a total of 1000 gpm for a sprinklered building. If it is a manual system, then you still need the same flows, but the FD pumper truck will provide the pressure. This will coincide with the site fire flow requirements, but they are not addititve.

3 - Sprinkler system: For a residential system, assuming NFPA 13R, you flow 4 heads at a max of 20 gpm each for a total of 80 gallons. With a 13R system, you then figure a domestic demand to add to the common point of domestic / fire lines. This may be a couple hundred gallons, depending on the domestic fixtures and the loads as illustrated in NFPA 13R. Remember, you only have to figure 1 area in 1 building going off at a given point in time. You do not calculate 4 heads on each floor in each building at one time.

Again, each of these are independent and not additive.

 

[stookeyfpe]

The State of New York uses the NY Uniform Fire Code, which is the 2003 edition of the IFC. The state does not post all of its amendments on-line so I am unsure if the Appendix Chapter on fire flow is adopted.

If you can tell me the construction type and the height and area of the largest building in the complex, I can tell you the required fire flow.

Travis, you sure are racking up some stars...

 

[TravisMack]

Stookey:

I only care about getting to the Lone Star

Looks like I will be there in Jan for a scouting trip. I will let you know when I get the dates firmed up.

T

 

[thebabe]

in response to stookeyfpe, the largest building will be four floors with three staircases, and a total area of approximately 700,000 sq.ft. also to travismack: i always thought standpipes were 500 GPM for the first and 250 each additional with a max. of 1250. thanks again for your input and help.

 

[TravisMack]

thebabe:

5-9.1.2* Hydraulic Calculation Procedure.
Hydraulic calculations and pipe sizes for each standpipe shall be based on providing 250 gpm (946 L/min) at the two hydraulically most remote hose connections on the standpipe and at the topmost outlet of each of the other standpipes at the minimum residual pressure required by Section 5-7. Common supply piping shall be calculated and sized to provide the required flow rate for all standpipes connected to such supply piping, with the total not to exceed 1250 gpm (4731 L/min).

I was assuming 250 at the top floor and 250 at the next floor down for a total of 500 gpm flowing through the most remote standpipe.

I don't know if that makes more sense or just makes it more confusing.

 

[stookeyfpe]

Babe:

You didn't provide me a construction type. However, your building area and height tells me that the building is sprinklered in accordance with the 2003 IBC, which is the adopted building code in the state of New York. I am going to assume that it is steel construction and the steel has no fire resistance.

Based on my description of the construction, it is assigned as Type 2B construction. Based on the construction type and building area the fire flow is 2,000 GPM using the requirements in Table B105.1 and applying a 75% reduction in fire flow because the building is sprinklered. See 2003 IFC, section B105.2, exception.

Please confirm the type of construction and that the building will be protected throughout by an automatic sprinkler system. If not, you got a much larger problem.

 

[thebabe]

response to stookeyfpe: the buildings will be Type 2A construction and will be fully sprinkler protected. is the max fire demand still 2000 GPM, and if so, how does that break down? (1000 standpipe,250 hose stream, etc.?) THANK YOU!

 

[stookeyfpe]

Fire flow is completely different than sprinkler demand. You are mixing the two together. Look closely at what has be written in this thread.