Blitz Attack/BTU Vs. GPM Question

[MG3610]

I was asked to figure out the following situation...

You havd 500 Gallons of tank water. You want to flow 350 GPM for 20 seconds.

How many BTUs can be absorbed?

Is this possible to answer?

[fire49]

Hope you know how to work formulas

http://www.beaumontfire.com/docs/Cha...gnment_6_1.pdf

[ffmedcbk1]

1 pound of water is raised 1 degree by 1 btu
it takes an additional 970 btu's to convert to steam
1 gallon of water = 8.34 pounds

assume starting tem is 70 degrees f

212-70 = 142 degrees or 142 btu's
970 btu's + 142 btu's = 1112 btu's
1112 btu's * 8.34 = 9274.08


350 gpm / (20/60) = 116.66666666666 [this is 20 seconds of flow at the rate of 350 gpm]

9274.08*116.66666666666666=1,0 81,976 btu's absorbed

[Bones42]

I was asked to figure out the following situation...

You havd 500 Gallons of tank water. You want to flow 350 GPM for 20 seconds.

How many BTUs can be absorbed?

Is this possible to answer?

Only if you can calculate how much water is actually getting to the fire.

[nameless]

Only if you can calculate how much water is actually getting to the fire.

Correct, we can calculate the theoretical maximum amount of BTU's that could be absorbed, but we won't know how much will actually be.

[GTRider245]

So in other words, who really cares?

[RFD21C]

I dont know any numbers, but i am willing to bet it is not as much as a properly pumped 265 GPM line from inside.

[ffmedcbk1]

put the water on the fire.... enough of it to make it go away quickly

[johnsb]

I was asked to figure out the following situation...

You havd 500 Gallons of tank water. You want to flow 350 GPM for 20 seconds.

How many BTUs can be absorbed?

Is this possible to answer?

It's only possible in a labratory setting. There are WAY to many variables to consider. Nozzle, spray pattern, materials burning, access to the seat of the fire, etc. I think GPM's are more important than timing. I'd use all of my 500 gallons for knockdown rather than saving it for overhaul. The best way to protect exposures is to knock down the main body of fire.

[Theusje]

In Euro Firefighter Grimwood says that a solid stream is at 50% and a fog stream is at 70%. That is heat absorbed per gallon. This is for interior firefighting in general.

Also in that book about fog nozzles they say that you need twice the volume of the room in steam (at 100°C) to extinguish the fire, but this is for an enclosed fire with limited vents: ship fires etc.

[FyredUp]

In Euro Firefighter Grimwood says that a solid stream is at 50% and a fog stream is at 70%. That is heat absorbed per gallon. This is for interior firefighting in general.

If we re talking about steam conversion I don't doubt this at all. But the truth is not all steam conversion is good OR beneficial to the fire fight. The stream needs to penetrate to the base of the fire and cool the burning material. Any part of the water that turns to steam before it reaches the actual burning material, UNLESS you are doing an indirect attack in a sealed compartment, is essentially wasted. And even worse than wasted, can make the area untenable from the moist heat of the steam.

I can tell you from my 34 years in the fire service that anytime I am in the fire area, and intend on staying in the fire area, a straight stream or solid bore, will be my choice for fighting fire. I started back in the day when they were teaching recruits to crawl into the fire room, put the pattern on wide fog, flop on your side or back, and whip the line around filling the upper atmosphere with fog. Guess what happened? We got steam burned every time.

Now, I am not saying that fog injected into the overhead in a pulsing manner can't be effective in specific circumstances. But that is definitely different than a fog attack on a confined fire.


Also in that book about fog nozzles they say that you need twice the volume of the room in steam (at 100°C) to extinguish the fire, but this is for an enclosed fire with limited vents: ship fires etc.


AND in order for you to build up that much steam in a room the room needs to be intact, no holes in the walls, ceiling, and the door and windows need to be intact. You inject the fog stream into the overhead and close the door and let the steam work. Then you ventilate, to the outside, because if you open the interior door you will have all that steam and heat push out right over the top of you.

Both types of nozzles put fire out every day all over the world...technique and knowing when which stream is appropriate is the key to safe and effective operations.

[L-Webb]

I have had good luck fogging the fire room when the fire is vented via a window. The air induced by the fog stream pushes the heat smoke and steam out, Now I understand that this is not a indirect attack per se. You must have control of the doorway as always.

But all fancy things aside you are right, The straight stream is the safest way.

I just like to practice different things.

[Theusje]

Both types of nozzles put fire out every day all over the world...technique and knowing when which stream is appropriate is the key to safe and effective operations.

You are correct, I have nothing to add.

[Miller337]

It's only possible in a labratory setting. There are WAY to many variables to consider. Nozzle, spray pattern, materials burning, access to the seat of the fire, etc. I think GPM's are more important than timing. I'd use all of my 500 gallons for knockdown rather than saving it for overhaul. The best way to protect exposures is to knock down the main body of fire.

You almost got a gold star. You made one mistake, you now have your b@tt in a burning thing with no water and it is now time to take that forementioned body out. A little water for that trip is almost always a good idea.

[RFDACM02]

It occurs to me reading some of the posts here, that we as the Fire Service are making significant advances in using scientific method to prove or disprove some of our past tactics and practices. But, 99% of the time we'll not be able to give a "correct" answer here in cyberspace. Fires are dynamic occurrences and while even if we could identify the exact formula to make them go out in the most efficient manner, we'll never have all the variables in time to use the one correct method for the given occurrence.

So, hit it with all you got? Yep, sometimes. Or hold the fire in check and reserve water? Again, maybe this is the right answer. I think that most experienced fire officers would have a hard time putting to paper ever detail of their size-up that affects their tactical decision making, it's just not that simple.

[Theusje]

In Euro Firefighter Grimwood says that a solid stream is at 50% and a fog stream is at 70%. That is heat absorbed per gallon. This is for interior firefighting in general.

Also in that book about fog nozzles they say that you need twice the volume of the room in steam (at 100°C) to extinguish the fire, but this is for an enclosed fire with limited vents: ship fires etc.

I have to explain the number by Grimwood some bit as I didn't say what they represented.

The percentages are about the effectiveness of cooling hot smoke. Smoke cooling, no fire or flame. This is before flashover and to progress in a hallway, with no fire or very little fire in the smoke layer. A pulse of straight stream turns 50% of it's water into steam and a fog pulse 70%.

To extinguish a fire don't use a fog nozzle while you inside the fire room: Left for Lobster!

[johnsb]

You almost got a gold star. You made one mistake, you now have your b@tt in a burning thing with no water and it is now time to take that forementioned body out. A little water for that trip is almost always a good idea.

I didn't say I was IN the burning building. If I have a large body of fire, and I am going to use a "Blitz" style attack, I will be using a deck gun or large handline and not venturing more than a few feet inside the egress. Around here a blitz attack is used to knock down a large body of fire that can be (in the judgement of the first in crew) knocked down significantly with the tank water until a water supply can be established. Obviously if you have more than you can knock down with your tank, different tactics are in order. I maybe should have elaborated on my post a little, but you are right that you don't want to be in a burning building without water, especially with a lot of burning contents.

[MemphisE34a]

It occurs to me reading some of the posts here, that we as the Fire Service are making significant advances in using scientific method to prove or disprove some of our past tactics and practices. But, 99% of the time we'll not be able to give a "correct" answer here in cyberspace. Fires are dynamic occurrences and while even if we could identify the exact formula to make them go out in the most efficient manner, we'll never have all the variables in time to use the one correct method for the given occurrence.

So, hit it with all you got? Yep, sometimes. Or hold the fire in check and reserve water? Again, maybe this is the right answer. I think that most experienced fire officers would have a hard time putting to paper ever detail of their size-up that affects their tactical decision making, it's just not that simple.

I agree with you EXCEPT I would not limit being able to prove our tactics or practices to cyberspace. There are a great many firefighters that have absolutely no idea when, why, how, or where they do things other than it being just what they have always done. And an even higher number of Administrators!!

[RFDACM02]

I agree with you EXCEPT I would not limit being able to prove our tactics or practices to cyberspace. There are a great many firefighters that have absolutely no idea when, why, how, or where they do things other than it being just what they have always done. And an even higher number of Administrators!!

At the rate we're going, new officers will have a Tactics App in their smartphones for determining how to proceed. Maybe they'll take a photo upload it to the web and someone in Emmitsburg will email them an IAP.

[Spencer534]

At the rate we're going, new officers will have a Tactics App in their smartphones for determining how to proceed. Maybe they'll take a photo upload it to the web and someone in Emmitsburg will email them an IAP.

Too funny!