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  1. #1
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    Default Why 300' max hoseline when hose testing??

    I was wandering if anyone could tell me why nfpa requires a 300' maximum hoseline on a single discharge when hose testing. The most popular answer I get is because of Friction Loss. They say that if you set your pump up at 250# then you wont get 250# at the end of the line because of friction loss.
    This isn't correct. Friction loss occurs because of friction between the water and the inner jacket of the hose. If the water isn't moving there is no friction, and thus no friction(or pressure) loss.
    Hoping you guys could help

    Jeff Mitchell
    Habersham County Fire


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    I'm not dead sure, but I believe it has to do with the hose stretching under pressure. Since it is desired to have the hoseline as straight as possible, and because of friction between the hose and the ground as it stretches, longer lines mean more bending and zig-zagging and the hose grows under pressure. The 300' max. is just a way to minimize it and keep the line as somewhat straight.
    TW
    Essex Junction Fire Dept.
    Vermont

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    MembersZone Subscriber SHVFD_Asst_Chief's Avatar
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    As a follow up to this, our department is new to the 5" supply line. Does this LDH require the same testing as the other lines?

    A few of us talked about it a couple of weeks back. Some say that it needs to be tested, but I say no. My reason is that it will not be used under the same conditions as an attack line.

    Is this correct, or should we test our 5"? And if so, what pressure should it be under?

    Thanks

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    NFPA 1962 and the ISO recommend YEARLY testing of all fire hose...attack or supply, reguardless of size. NFPA 1962 sets out the recommendations how it should be done. (Including the darn 300 foot thing.)
    BB

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    MembersZone Subscriber SHVFD_Asst_Chief's Avatar
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    Thanks, I think I will get a copy of NFPA 1962 and do a little studying and present it to our chiefs.

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    Your dead on about the friction loss-friction loss involves moving water-
    The stock answer on the 300 ft -- is that its hard to burp all the air out of more than 300 ft, and trapped air will compress and give you a false reading on pressure. I always thought that was splitting hairs--- but --- by the book is by the book- on the LDH-- annual test also-lower PSI and shorter duration-- I cant remember the specs yet, but if no one posts it-- ill either remember or look it up.

  7. #7
    55 Years & Still Rolling hwoods's Avatar
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    Question Huh???

    You test hose?
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    MembersZone Subscriber ullrichk's Avatar
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    LDH needs to be tested just like your hand lines - well not JUST like hand lines. Typically its service test pressure is somewhat lower than attack lines.

    It has already been pointed out that service testing is static pressure and involves no friction loss. Having said that, I have seen people try to test LDH and attack hose at the same time by gating down the LDH discharge. A VERY dangerous misunderstanding of hydraulics.

    FWIW, there are a lot of hoses out there with "oddball" service test pressures, so check your hose to be sure. We happen to have some Neidener (sp?) LDH and handlines which has a higher than standard service test pressure.

    As for the 300ft., I'm going to take an educated guess that it's because of the potential energy of the stretched hose, and that longer lengths are inherently more dangerous.

    You do strap your parallel lays of hose together don't you?

    There's another safety requirement often overlooked in my area. That is to have a gate valve with a small hole drilled in it to limit water flow if a section of hose bursts. LODD's have happened during hose testing. Hose testing is not something to take lightly for a variety of reasons.
    ullrichk
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    Forum Member firenresq77's Avatar
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    Yes hose testing can be very dangerous. We purchased a hose tester and it works wonders. It has like 6 discharges on it so you can theoretically test 1800' of hose at one time. They are much safer because it is just enough water to fill the hoses, pressurized by a compressor, so if a hose bursts, it doesn't have the continuous pressure behind it liek you would if it was run off an engine. Plus it also doubles as a pressure washer if needed..........

  10. #10
    Forum Member Weruj1's Avatar
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    we also test our hose as well....................supply and attack ....every year !
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  11. #11
    Forum Member MIKEYLIKESIT's Avatar
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    ...and here I thought hose testing was something invented by Fire Chiefs to keep the troops occupied

  12. #12
    Senior Member Dalmatian90's Avatar
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    I believe the 300' rule is a safety thing, too. Both from potential energy stored (although that's very little with water compared to say, air, which is why SCBA bottles are hydrotested, using water instead of air to test their strength!), but also from "managing" to keep everyone safe and spot leaks, etc easily & timely.

    We do test our hose annually (well, once in a while it goes two years...). We have a hose tester and use it for the small lines.

    LDH we do vary from the spec in the length -- we carry over 6500' of 5" and another 1500' or so of 4". The 5" is mostly in 200' lengths, coming off a reel and the setup/pickup time if you tested it in individual lengths gets to be quite a bit. So we compromise, so the 4" is tested in 300' runs, but we make a 6500' lay with the two 5" trucks and test it in one shot.

    Remember, for safety, fill the hose with discharge open...but then gate it back to almost closed before bring up to test pressure. Water is (virtually) incompressible, so if your discharge is gated back the pressure comes up quick, but you won't have a lot of moving water which is what makes a burst so dangerous on water hoses.

  13. #13
    MembersZone Subscriber ullrichk's Avatar
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    As a point of clarificaion, when I made the statement about potential energy in the hose, I was referring to the "stretch" of the hose and the possibility of backlash in the event of failure. As has been pointed out, water is essentially incompressible and doesn't store energy in this case.
    ullrichk
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    Unless your LDH is high pressure you have to test at 200#>s for 5 minutes

  15. #15
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    You test hose?
    Over here in Oz, it is a requirement under the Australian Standards for 12 monthly testing- and by the sounds of these posts, it is similar for you guys. I take it, that you guys don't, hwoods?

    ...and here I thought hose testing was something invented by Fire Chiefs to keep the troops occupied
    Hose testing is for the troops. ROLLING the hose is for the probies!! (Especially 64mm or 90mm Duraline!)
    Luke

  16. #16
    55 Years & Still Rolling hwoods's Avatar
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    Red face Well.............

    I was stretching humour a bit. Yes, we do test hose, but not on a rigid schedule. But then, we don't do anything on a rigid schedule. We currently have a ISO class IV and there are too many things beyond our control to allow much improvement in the future. ISO is the only reason known to me to do redundant things like testing hose. Stay Safe....
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    MembersZone Subscriber mcaldwell's Avatar
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    Default

    I see a lot of guys running in circles questioning the science or reasoning behind some of the little details in the NFPA guidelines. It should be noted that while many of those "little details" are the result of exhaustive experience, science, and testing, just as many are essentially pulled out of the air.

    For the most part, don't stress yourself out over why, just go with it and know you are following the best guidelines we currently have. There may not even be a real reason why exactly 300' is the best/max length to test, it may just have been considered the most managable by the NFPA board at the time.

    I really do think they play rock-paper-scissors to decide this stuff sometimes.
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  18. #18
    Forum Member Fire304's Avatar
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    Originally posted by VollieFireman
    Does this LDH require the same testing as the other lines?
    The most common failures we find are pin holes and blisters in the hose (from the little dragging which always happens when laying and charging) and hose slipping out of the couplings. Had a brand new, fresh out of the box hose blow out of its coupling last year on the acceptance testing.

    As for the pressure, its supposed to be marked right on the hose. The FD I'm with now doesn't use it, but another FD had attack LDH on some of the trucks which is rated 400psi, so it had to be tested seperately from the supply line, and could not be mixed up on the truck.
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  19. #19
    55 Years & Still Rolling hwoods's Avatar
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    Talking I'm Back.........

    I've checked with a couple of people who were involved with our hose test last year, and they have advised that the Handlines are pulled just as they would be for a Fire, and tested with the nozzle on the line, and the valve cut back to almost nothing. The 3" supply line is in 2 800ft beds, and both lines are laid out completely, coupled to discharges on the right side of the pump, (operator is on the left) A nozzle is placed on the ends and after the hose is filled with water, the gate is cut back and pressure run up. Never had a problem. Stay Safe....
    Never use Force! Get a Bigger Hammer.
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    Asst. Chief John R. Woods Sr. 1937 - 2006

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  20. #20
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    I was under the impression that the reason for the 300' maximum length was due to the stretching of the hose holding pressure in the line. If the hose bursts, all of the stored pressure in the hose (from that stretching) comes out through that hole, possibly whipping the hose (and its associated coupling, if close enough to an end) around and into nearby personnel. If you have less than 300' of line, there's some energy stored, but not a lot. If you have 1000' of line on the ground, thats a lot of water thats going to come out of that line.

    Along those lines, thats why you're supposed to use a special gate valve when hose testing...there's a 1/4" hole in the gate so you can pressurize the line, but not flow a ton of water through it if there's a break.

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