Fire hose volumes

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Permalink Reply by Larry Lasich on January 20, 2009 at 9:14pm

1st. NFPA 1901 requires that all 2 1/2 inch fittings on pumping apparatus flow 250 gpm at 150 psig. So you will not be putting 250 gpm through an inch and a half line reguardless of the pressure.

2nd. If the plumbing on the pumper, the lines and the nozzle are right, you can get 150 gpm from a fog nozzle on the end of a 200 foot long hose lay.

Calculations for fire flows, engine pressure and friction loss can be found in the IFSTA Pump Operators manual.

Larry

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Permalink Reply by Scott on January 21, 2009 at 7:47am

Thanks but not what I was looking for....what I meant is the max flow a hose will flow....regardless of nozzle. Regardless of pressure there is a max flow that hose can attain.

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Permalink Reply by Charles Ziel on January 21, 2009 at 9:56am

The Houston Fire Department WEB site has some excellent formulas for calculating friction loss, GPM etc. Been a long time since I was there and used the stuff to set up some tables. If you like that sort of stuff like I did you will find it informative. Have your calculator handy, alot more fun than math class as a kid. They should have what you are looking for

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Permalink Reply by Larry Lasich on January 21, 2009 at 10:51am

That question was not in the body of your post.
Per NFPA all discharges must be able to deliver their max volume at an engine pressure of 150 psig.
That is at the discharge, so any hose or appliance needs to be factored in.
As pressure in the line increases, so does turbulence (Friction) until the friction loss gets so high it drops the flow to an unuseable level. Less pressure means greater volume. That's why a 50 psi SB gets greater flow than a 75 or 100 psi fog nozzle. No restriction and lower pressure in the line.
The only way to KNOW what you are delivering at the end of the hose is to get a flow meter and run the line. There are too many variables (your hose condition, pumper status, etc) for anyone to answer you question with anything but a "by the book" answer.

Sorry,
Larry

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Permalink Reply by Tom on January 21, 2009 at 12:42pm

Larry,

This goes back to the late 70's when I was a pump operator. We refered what you are asking as the "redline" GPM flow for the size lines we were using. The Illinios Fire Service Institute Pump Operators course was the bases for this info. You might be able to get more current info there.

Basically the redline rule of thumb was:

1 1/2 - 100 gpm
1 3/4 - 150 gpm (?)
2 1/2 - 400 gpm
3 - 600 gpm

At least this is the best my memory can come up with short of going through some of my old pump operators stuff, lots of dust involved.

Tom



Scott Wetmore said:

Thanks but not what I was looking for....what I meant is the max flow a hose will flow....regardless of nozzle. Regardless of pressure there is a max flow that hose can attain.

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Permalink Reply by troy kerckhove on January 21, 2009 at 5:25pm

It all depends on hose size, length, pressure, and nozzle. For example on my engine we have 2 different 2 inch line setups. Both are pumped at 150 psi pump pressure. One is 300 feet long with sm30 elkhart brass automatic it flows around 200gpm. The other is 50 feet with 1 1/4 smooth bore it flows 400+gpm. I know what NFPA says but it is a great blitzing line.

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Permalink Reply by Scott on January 21, 2009 at 10:22pm

Thanks Tom ...thats what I was looking for
Tom said:

Larry,

This goes back to the late 70's when I was a pump operator. We refered what you are asking as the "redline" GPM flow for the size lines we were using. The Illinios Fire Service Institute Pump Operators course was the bases for this info. You might be able to get more current info there.

Basically the redline rule of thumb was:

1 1/2 - 100 gpm
1 3/4 - 150 gpm (?)
2 1/2 - 400 gpm
3 - 600 gpm

At least this is the best my memory can come up with short of going through some of my old pump operators stuff, lots of dust involved.

Tom



Scott Wetmore said:

Thanks but not what I was looking for....what I meant is the max flow a hose will flow....regardless of nozzle. Regardless of pressure there is a max flow that hose can attain.

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Permalink Reply by Jorge Plata on April 9, 2009 at 2:38pm

Perhaps you mean Freeman's formula for SMOOTH BORE nozzles:
29.7( this is a constant found by someone (Freeman?) in math) * (square root of nozzle pressure in psi) * (friction loss of nozzle .96-.98) * (square of nozzle size in inches)
Let's use 49 psi nozzle pressure ( 7*7= 49, the square root of 50= 7.071067812) which is the ideal for smooth bore nozzles- more than that and you get much more friction and poor stream due to overpressurization, and you reach the max available flow- I don't quite understand this but it makes sense- you can't just overpressurize the line to say 200psi and expect that much more water from the same sized nozzle.
Also for this example let's say the friction loss for the "nozzle" is 0 and 1 1/2" square =9/4 so:
29.7 * 7 * 9/4 = 467.775 gallons per minute max "THEORETICAL" available water from a 1 1/2" line with a
1 1/2" nozzle. I say "theoretical" because there are probably other friction forces going on as you reach the max flow of an open-ended hose line.
For example, a 1" smooth bore nozzle at 49psi nozzle pressure gives you:
29.7 *7 * 1 = 207.9 gallons per minute flow (minus whatever friction loss is in the nozzle)

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Permalink Reply by Antiquefirelt on April 12, 2009 at 1:26am

Larry Lasich said:

1st. NFPA 1901 requires that all 2 1/2 inch fittings on pumping apparatus flow 250 gpm at 150 psig. So you will not be putting 250 gpm through an inch and a half line reguardless of the pressure.

I think you're missing something here Larry. NFPA 1901 says all 2.5" discharges must flow at least 250 gpm at 150 psi, but do not limit the flow. You can have your pumper piped any way you like as long as you hit the minimums. Point being, you can flow 250 gpm through a 1.5" line off the right discharge. The theoretical friction loss alone would be 150 psi then add your nozzle pressure in, but any class A fire pump will be able to supply the line. Not a good set up, but easily attainable. Heck we just flowed 350 gpm through an 1.75" line using a Vindicator nozzle.

As for the original question? You need to know more information than just the diameter of the hose to determine the flow. The gpm at a given psi of each nozzle is a large factor as well as friction loss in the length of the lay. The best thing you can do is get rid of the automatic nozzles which make all streams "look" great even when they're woefully inadequate.

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Permalink Reply by Larry Lasich on April 12, 2009 at 7:03am

I misspoke. In the second post I restated that you need to flow your max voulume at 150 psig.

Adam Miceli said:

Larry Lasich said:

1st. NFPA 1901 requires that all 2 1/2 inch fittings on pumping apparatus flow 250 gpm at 150 psig. So you will not be putting 250 gpm through an inch and a half line reguardless of the pressure.

I think you're missing something here Larry. NFPA 1901 says all 2.5" discharges must flow at least 250 gpm at 150 psi, but do not limit the flow. You can have your pumper piped any way you like as long as you hit the minimums. Point being, you can flow 250 gpm through a 1.5" line off the right discharge. The theoretical friction loss alone would be 150 psi then add your nozzle pressure in, but any class A fire pump will be able to supply the line. Not a good set up, but easily attainable. Heck we just flowed 350 gpm through an 1.75" line using a Vindicator nozzle.

As for the original question? You need to know more information than just the diameter of the hose to determine the flow. The gpm at a given psi of each nozzle is a large factor as well as friction loss in the length of the lay. The best thing you can do is get rid of the automatic nozzles which make all streams "look" great even when they're woefully inadequate.

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Permalink Reply by George H. Potter on April 12, 2009 at 11:53am

Scott,

Please send me your e.mail, I may have something for you. georgepot@gmail.com. The flow through any diameter of hose will depend on:

1) Type of fabrication of the hose; inner lining, outer shell, etc.
2) Discharge pressure
3) Lengh of the hose from source to discharge orifice
4) Diameter of discharge orifice

We all know that the simple nozzles hooked on the end of the 1.5" hoses in building standpipes may flow around 50 gpm while those new "hi-rise" combination nozzles can get nearly 250 gpm out. I have handled an experimental 1.5" nozzle that flowed some 400 gpm, but it never got into production

George Potter
Madrid, Spain

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Permalink Reply by Catherine on May 23, 2009 at 4:58pm

Tom got this one right. Yes there are a lot of variables depending on what you are looking for. However, you can only put so much GPM thru a given diameter. Yes it will vary depending on psi, fittings, elevation ect. But only one gallon will ever fit into a gallon jug.
But I believe that 1 3/4" is actually 250GPM
4" - 800 GPM ect.
Another good way to determine correct LDH sizes for your department. We just got a new 1250 GPM pumper but run 4" LDH. We will never pump this truck to capacity running 4" hose unless we relay off a 5".

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