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  1. #21
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    There are varying reasons why fire streams can do this .... both straight stream applications and fog cones can have the same effect of creating a sort of 'blow-back' of fire under some circumstances. We use mini demonstrator 'dolls houses' to teach this effect. It can sometimes occur where water passes through the flames to hit a back wall or area of superheated fuel surface, creating a 'slug' of steam that pushes flaming combustion straight back at the nozzle operator as the superheated steam expands. There is also the potential for introducing oxygen into a fuel rich flame .... all types of stream carry some amount of air into the fire zone and if the flames are orange (oxygen deficient) there may be some sudden rapid development in the flaming combustion. Another way to cause rapid fire development (seems this might be the case in the video) is for the steam 'slug' to force flaming up into the overhead, causing some rapid mixing of the fire gases.

    This is one of the primary reasons we are teaching short burst nozzle techniques through the 3D Firefighting approach, to avoid such situations. The overhead should be taken before the base fire in this instance with one or two brief bursts used to cool and 'inert' the gases there.


  2. #22
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    TPlumb - I wouldn't mind a copy of the video clip for training purposes .... Fire4242@aol.com

  3. #23
    MembersZone Subscriber cowtown's Avatar
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    As always, thanks for the info Paul!

  4. #24
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    Paul,

    Your post is very thoughtful and descriptive of fire behavior and water application. I've never heard of the steam being referred to as a "slug". We (my friends and I) usually call it a "bump". We demonstrate the "bump" in a thermal balance fire fighting class we teach at our state academy. So I know what you are talking about in your description. Maybe, you call yours a slug because you apply more water and it moves slower than our bump.

    I think that what you are seeing in the video is air and water (steam) pushing heat into a cooler (not hot enough too burn) gas environment, thus making it ignite. As the FF's enter the room the gases are flowing (venting) over their heads. These gases (smoke)are to cool to burn, I know this because they have plenty of 02. So if they were too rich they would be burning. If not at thier heads it would be burning closer to the vent point (vent point ignition).

    When the fire fighters apply their stream, the flame (heat) pushes out to meet the flammable range gases that are underheated and heats and ignites them.

    So on to 3D pulsing. Why would I pulse into the overhead, when I can Solid or Straight Stream Indirect off the ceiling and bounce the water into the base of the fire? This action described and demonstrated many times will cool the overhead and knock the fire off the ceiling and then allow me to go Direct at the base after my bump clears the room over my head. My water application is just enough to darken the fire, not dump (slug?) the thermal balance that exists in this room.

    I'm sure we can work out a deal on the video copy. Your "Doll House" demonstration sounds interesting to me. Maybe I could get more info.

  5. #25
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    Quote Originally Posted by TPLUMB
    Paul,

    Your post is very thoughtful and descriptive of fire behavior and water application. I've never heard of the steam being referred to as a "slug". We (my friends and I) usually call it a "bump". We demonstrate the "bump" in a thermal balance fire fighting class we teach at our state academy. So I know what you are talking about in your description. Maybe, you call yours a slug because you apply more water and it moves slower than our bump.
    TPLUMB -

    .... 'slug' .... certainly not official terminology and a term I made up on the spot to try and explain the concepts. I have equally never heard of a 'bump' or 'dump' but feel that there should be an accepted term and definition of this process as it is obviously relevant to firefighters.

    I don't think we are too far out on our definitions and thought process here and I acknowledge that you too have noted (and taught) similar events whilst training at your state academy.

    Quote Originally Posted by TPLUMB
    I think that what you are seeing in the video is air and water (steam) pushing heat into a cooler (not hot enough too burn) gas environment, thus making it ignite. As the FF's enter the room the gases are flowing (venting) over their heads. These gases (smoke)are to cool to burn, I know this because they have plenty of 02. So if they were too rich they would be burning. If not at thier heads it would be burning closer to the vent point (vent point ignition).

    When the fire fighters apply their stream, the flame (heat) pushes out to meet the flammable range gases that are underheated and heats and ignites them.
    OK we are both in agreement on the 'involvement of overhead gases' in this process. I would not get into a deep discussion on whether the sudden flaming is caused by gases being brought into the right 'mix' or if the flame front from the base fire heats the gases sufficently for them to ignite. It is probably a combination of both.

    Quote Originally Posted by TPLUMB
    So on to 3D pulsing. Why would I pulse into the overhead, when I can Solid or Straight Stream Indirect off the ceiling and bounce the water into the base of the fire? This action described and demonstrated many times will cool the overhead and knock the fire off the ceiling and then allow me to go Direct at the base after my bump clears the room over my head. My water application is just enough to darken the fire, not dump (slug?) the thermal balance that exists in this room.
    There is no doubt that what you say is correct. A solid stream bounced off the ceiling will cool overhead gases to some effect and allow water to reach the fire's base. I have done this enough times myself to appreciate the effect. However, the application of smaller amounts of water in droplet form, by pulsing or bursting a fog pattern as opposed to bouncing a straight stream of the ceiling, presents far greater cooling capacity. It is more difficult to maintain the height of a smoke layer using the straight stream technique as opposed to the fog pattern using bursts or pulses. Repeated tests and scientific thermal readouts also support this 'notion' .... to the point that it almost becomes 'fact'.

    It is not possible to RAISE a smoke layer using the straight stream method but this can be achieved by 'pulsing' a fog pattern.

  6. #26
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    Paul,

    What do you mean RAISE the smoke layer?

    When I think about fog into the overhead, I know it cools the gases but don't those gases just get pushed out by the heat behind them? If they are pushed out, then the gases are now new hot gases. How many times do I repeat this process before I decide to put the fire out? Do you have some online video I can watch?

  7. #27
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    Paul,

    I kind of agree with


    However, the application of smaller amounts of water in droplet form, by pulsing or bursting a fog pattern as opposed to bouncing a straight stream of the ceiling, presents far greater cooling capacity.
    If the room is up to a certain temperature. So that the water can turn to steam. But why am I cooling the overhead gases? To get access, so that I can make a shot on the fire. Do I have ventilation? The easiest way to cool gases is to remove them.

    But I don't agree with

    It is more difficult to maintain the height of a smoke layer using the straight stream technique as opposed to the fog pattern using bursts or pulses.
    Maybe it's just an operator thing, equipment or a water flow issue? Like your pulsing technique, I also have a valve and can shut my water down too.

    I'm confused as to which "notion" you are calling "fact".
    Repeated tests and scientific thermal readouts also support this 'notion' .... to the point that it almost becomes 'fact'.
    And certainly I would like to see the scientific thermal readouts and repeated tests. Any test can prove any point, the objective test is the important test.

    Thanks for the discussion.

  8. #28
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    Quote Originally Posted by TPLUMB
    Paul,

    What do you mean RAISE the smoke layer?
    Yes .... a correctly applied pulsing water-fog pattern can actually RAISE the smoke layer and thermal interface (thermal balance line) .... we are able to achieve this regularly and students are instantly impressed as to how a nozzle can control this smoke layer when they truly believed that only a venting action could do such a thing!

    No I don't have any online videos for you to view it unfortunately. The process is dynamic in that the smoke layer is constantly changing in it's make up in a burn facility. We can cool the overhead gases with a few droplets of water (sometimes a beer glass full) and the gases contract .... yes they shrink .... and the smoke layer rises! Then the fire heats the gases again and a few seconds later it drops again. But if we were to continue the cooling process we can get it to rise several inches before moving onto the base fire.

    'The easiest way to cool gases is to remove them' .... yes I agree .... but venting at the wrong time or at the wrong location can sometimes cause the fire to develop beyond the capability of the hose-line in use.

    There is a whole host of scientific research from respected bodies that demonstrates how fog patterns (when pulsed) can control the smoke layer by cooling the gases but seeing it is believing .... it's then when the 'notion' becomes a fact. You cannot possibly control the smoke in this way using a straight stream.

    Always enjoy debating with an informed opinion. Thanks.

  9. #29
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    Can tell much from the short clip....here are a few of my observations.

    -It doesn't appear he aimed the nozzle up initally. It is best to aim high when initating the advance into a room with fire. Basic and established rules for the nozzle man.

    -If that is a fog tip on the end(as it appears to be a half-open fog stream)...and the fire appears to be in the far corner of the room with no ventilation behind him...I have personally seen fire pushed around quickly and dangerously by fog streams when there is no or a lack of adequate ventilation. He might have hit it low and pushed it up over his head with plenty of entrained air behind the fog stream.

    To all you fog advocates...Is this where your "protection" fog will prevent you from getting burned? Best of luck.

    As for Class A foam...this is far from a ringing endorsement! Use water...it has worked well for 200+ years and it is FREE!

    Utilize the reach of the stream...it will increase the safety of your operations.

    Thank god the brothers got down low when they did! Always enter low...don't walk in standing up like an Azzhole...get down.

    FTM-PTB

    PS-This appears to be a controled environment (hense the camera angle inside) therefore it is unlikely there were any flamable liquids or gasses involved. I doubt gasoline gomez left a present for these guys.
    Last edited by FFFRED; 12-19-2005 at 05:20 PM.

  10. #30
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    FFFRED,

    Can't blame the nozzle, right? It's the operator.

  11. #31
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    Paul,

    Thinking back to something I read. Smoke doubles with a 459 degree increase in heat. So maybe what you are saying about the smoke contracting maybe true.

    The venting conerns you bring up are valid for someone that does not know the limitations of their water flow, needs training on location of fire and ventilation techniques. Fortunately, I do not fit that description.

    Getting back to pulsing, When do you do this? Every fire? Do you have any ventilation when you pulse or are you going into the room closing the door behind you? Have you experimented with different fuel loading?

    Thanks
    Last edited by TPLUMB; 12-19-2005 at 07:53 PM.

  12. #32
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    Quote Originally Posted by TPLUMB
    Paul,

    Thinking back to something I read. Smoke doubles with a 459 degree increase in heat. So maybe what you are saying about the smoke contracting maybe true.
    Oh it's true alright, we are able to do this every time in training. HERE is a link to the MATHS

    Quote Originally Posted by TPLUMB
    The venting concerns you bring up are valid for someone that does not know the limitations of their water flow, needs training on location of fire and ventilation techniques. Fortunately, I do not fit that description.
    The truth is, the vast majority of firefighters do not practise sound venting techniques because they are not well trained or have little 'real fire' experience. Even many experienced firefighters I have worked with failed to grasp the basics of smoke and fire dynamics. Make a vent opening and fire and heat will most likely head for that point. If you make that opening between you and the fire or near or behind you, things are likley to get a little hot. The fire will burn with greater intensity and you will need more water to suppress it. A review of 'typical' firefighting actions demonstrates that most firefighters don't work with that understanding. If you vent a window in a fire room will the conditions improve or get worse? The answer is both The temperatures will reduce for a few minutes (broadly speaking) but the heat flux will increase! This affects the capability of your flow-rate.

    Quote Originally Posted by TPLUMB
    Getting back to pulsing, When do you do this? Every fire? Do you have any ventilation when you pulse or are you going into the room closing the door behind you? Have you experimented with different fuel loading?
    No it is not done at every fire but the techniques are used a lot for cooling or 'inerting' the overhead; raising the smoke layer; or suppressing volumes of fire gases that are burning off .... a stairshaft fire is a 'classic' situation. There are limitations in using this approach .... maximum area (floor involvement) and flow-rates are recommended. The fuel-load factor is related to two things .... 1) The fuel load itself is accounted for in the limitations concerning floor area involved in fire; 2) The rate of heat release is accounted for in the flow-rate in use.

    This is a complete training program and it can't be taught from a book not even mine! It needs hands on experienced instructors to take you through the various stages of CFBT (Compartment Fire Behavior Training) to appreciate the benefits of 'pulsing' or 'bursting' fog nozzles (two different things).

    And you're correct .... it's not the nozzle it's the operator at fault

  13. #33
    MembersZone Subscriber Golzy12's Avatar
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    I want to take that class, it's hard to believe that my firefighter 1 book only had like 4 pages about actually attacking the fire, I felt it was lacking in that area, this discussion is filling in some of the grey areas.

  14. #34
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    Quote Originally Posted by Golzy12
    I want to take that class, it's hard to believe that my firefighter 1 book only had like 4 pages about actually attacking the fire, I felt it was lacking in that area, this discussion is filling in some of the grey areas.
    That's great to hear Golzy that you are keen to advance your knowledge and skills. We have tried to include a massive amount of information in the 420 page manual HERE but like anything you need real 'hands-on' to grasp the basics. We cover everything from opening the door; to advancing in; to nozzle techniques using both straight stream AND fog patterns; to observing how a fire behaves under different venting profiles.

    Nobody has invited me to the USA next year but I will be at FDIC Canada if you can get there in June.

  15. #35
    Forum Member PattyV's Avatar
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    Have to say, top discussion you guys got going here. Im learning quite a bit from it.
    "There are only two things that i know are infinite, the universe and human stupidity. And im not so sure about the former."

    For all the life of me, i cant see a firefighter going to hell. At least not for very long. We would end up putting out all the fires and annoying the devil too much.

  16. #36
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    No I don't have any online videos for you to view it unfortunately. The process is dynamic in that the smoke layer is constantly changing in it's make up in a burn facility. We can cool the overhead gases with a few droplets of water (sometimes a beer glass full) and the gases contract .... yes they shrink .... and the smoke layer rises! Then the fire heats the gases again and a few seconds later it drops again. But if we were to continue the cooling process we can get it to rise several inches before moving onto the base fire.
    What about the steam created?

  17. #37
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    Quote Originally Posted by ThNozzleman
    What about the steam created?
    The steam expansion is countered by the cooling effect which causes the fire gases to contract. The secret is not applying too much water and even then the droplets must not be too large. The ideal application causes evaporation in the gases, as opposed to droplets evaporating on hot surfaces, such as hot walls and ceiling, by at least a 2-1 ratio.

    Thats where nozzle 'pulses' or 'bursts' beat a constant flow, which would have the opposite effect and cause the steam expansion to be greater than the gas contraction. The result then would be a lowering smoke layer and a disruption of the thermal balance .... possibly even a thermal inversion.

  18. #38
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    Paul,

    Have you done the pulsing with high pressure fog?

  19. #39
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    Doesn't the pulsing of the nozzle cause a water-hammer? Or multiple mini-water hammers? For a 1-second burst the line is only open/closed once whereas with 2-3 Hz pulses the line is open/closed 2-3 times in quick succession.

  20. #40
    EuroFirefighter.com PaulGRIMWOOD's Avatar
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    Oldman 21220 - When the techniques originated in Sweden they used low-pressure (100psi) 1.5" hose-lines. We developed the concept further in the UK through the 1980s to suit our 3/4" high-pressure (500psi) booster lines. However, we are now using the methods on both low and high pressure systems.

    As long as the droplet ranges are similar the only advantage in high-pressure deliveries are in the velocity of the stream - which enhances the cooling effects.

    Voyager 9 - We have not experienced water hammer using low pressure lines but the high pressure delivery has caused minor problems that were solved using specific engineering design solutions.

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