Thread: Pumping LDH

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    Question Pumping LDH

    Recently moved and changed volly departments. Different counties, different ways of doing things. Culture shock to say the least, however the vast majority of the differences are improvements over the previous department.

    Only one of six engines in the new department has LDH, and it is the oldest ('66). The other engines are mid 80's to present. Department does not use LDH if at all possible. Got the LDH as a demo some years ago, and never returned it.

    My question regarding LDH has to do with what pressure it can be pumped at. The hose is stamped test at 200psi, however SOP says not to pump above 150psi. I am told it has to do with the couplings. Also, am told not to supply an arial device with LDH. Insist that you have to place a pumper at the turntable to boost the pressure. Anyway, is it possible that the hose is rated at one pressure and the couplings at another, and is it necessary to have a 50psi safety factor?

    Thank you all for your input.

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    Hose can be pumped up to the test pressure.

    Ask them if they remove the couplings when testing the hose. But, if their SOP says nothing above 150, you best not go above 150 without good reason.

    No LDH to feed an aerial? All mine have for supply is LDH. 1 5" line equals what, like 2 or 2.5 21/2" lines? Why use double the hose to perform 1 function? Why have increased pump pressure just to overcome the friction loss of smaller hose? 100' of 5" at 1000gals is about 8lbs friction loss. 100' of 2 1/2" at 500gals is how much more friction loss?
    "This thread is being closed as it is off-topic and not related to the fire industry." - Isn't that what the Off Duty forum was for?

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    Different manufacturer's hose have different pressure ratings. We have two different makes that have two different ratings therefore we go with the lesser of the two.

    There are more items to consider than only hose capasity. One thing iis the settings of the relief valves on your appliances. Ours are set for 175 psi therefore we do not excede 150 psi or else water's wasted. When you depend on taker shuttles, you can't afford to waste anything at all.

    Also take into consideration your pump capacity. The higher pressure you run your pump will result in less volume. We have two differnt style pumps. Twin and single stage.

    With the 1500 gpm twin stage pumps the transfer valve must be in the volume mode to achieve maximum capacity. If you pump LDH at anything over 200 psi, the motor is screaming. If the transfer valve is set in pressure, the motor will not work as hard but you'll only get half the volume of the pump rating (750gpm)

    With our single stage 1500 gpm pump, all the info is on the pump plate making the equations idiot proof: 150 psi will result in 1510 gpm. 250 psi will result in 750 gpm. If pumping at higher pressure is going to decrese the volume of water pumped, you not flowing water at maximum capacities.

    We do pressure test our LDH at 150 psi annually. If I remember correctly, that's all that's required by ISO.
    Last edited by SFDchief; 04-08-2004 at 06:59 PM.

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    The difference between 2 1/2 and 5 inch is much greater than people think. Let's use 1000 gpm being pumped 1000 feet as an example:

    5 inch hose: C(QxQ)L C=.08 gpm=1000 so Q=10 length=1000 L=10

    .08x(10x10)x10=80psi friction loss

    2 1/2 inch hose: C=2 Q=10 L=10

    2x(10x10)x10=2000psi friction loss Okay we all know thats not going to work!!

    use two 2 1/2 inch lines each flowing 500 gpm

    2x(5x5)x10=500psi I guess that won't work either

    use three 2 1/2 inch lines flowing 333 gpm

    2x(3.33x3.33)x10=221.78 0r 222psi this could work

    use 4 lines 2 1/2 inch lines flowing 250 each

    2x(2.5x2.5)x10=125psi getting close to 5 inch equivalency now

    use 5 2 1/2 inch lines flowing 200 gpm

    2(2x2)x10=80psi DING DING DING we have a winner!! Five 2 1/2 inch lines to equal the flow of a single 5 inch.

    Boy do I love figuring friction loss formulas!!

    FyredUp

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    If only we could get the explorers to look at this thread and see how much school really does matter instead of trying to figure out how to get out of homework to sneak down to the station

    I only wish I would have done better at mathwhile in school-and I was there everyday
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    Thanks for the info. Keep it coming. I was a qualified driver in my previous department and have a bit of experience pumping LDH, a little more time at the pump panel than I would have liked, but that is another story. I am still on probation with the new department, and won't be qualified here for quite some time, which is fine with me. I am trying to keep my mouth shut as much as possible, but want as much back up as I can get when we actually get in to this one day.

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    all of our trucks have LDH.........now only one has 4" ...everything else is 5". You can pump it and we use ours to feed our 85 ft quint.I would not pump it past whatever the test pressure is stamped. The only other place I know that uses NO LDH is Hwoods on these forums they use 3" and according to Harve, they have the water system to keep good pressures.
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    Okay 4 inch and 3 inch compared to 5 inch...This is gonna be fun!! I do so love math!!

    Remember 5 inch 1000 gpm 1000 feet equal 80 psi friction loss.

    Okay 4 inch: C=.2 Q=10 L=10

    .2(10x10)10= 200 psi FL in a single lay of 4 inch, only works if your hose has a working pressure of 200 psi or more

    .2(5x5)10=50 psi FL in a dual 4 inch lay


    Okay 3 inch: C=.8 Q=10 L=10

    .8(10x10)10= 800 psi FL in a single lay of 3 inch ..just don't think this is gonna work

    .8(5x5)10= 200 psi in a dual lay of 3 inch...this could work

    .8(3.33x3.33)10= 88.71, okay your gauge isn't that accurate? Let's make it 88 psi in a triple lay of 3 inch hose

    So, in order to be equivalent to 5 inch it takes two 4 inch lines or three 3 inch lines. I think I would rather lay my one 5 inch line.

    Numbers, ya just gotta love them!!

    lmrchief2,

    My Dad was a practical math guy. Even before I could read he had me out in the grocery store he owned counting chnage with him in the morning so numbers made sense to me. My math skills blossomed from there but I always give him credit for my interest and for showing me there was always more than one way to get the right answer. I am very capable of doing math in my head and that is thanks to short cuts he taught me and some I adapted for myself. I agree that perhaps a little more time spent on school now would better serve the youth of today. Both of my boys know how I feel about that. My oldest is in 8th grade and he is taking Freshman Algebra this year with plans for Geometry next year followed by Algebra 2, Trgonometry and Calculous. I think he got his math interest from me!! It may never be too late to learn but I think it may be a heck of lot easier to learn the basics when you are young.

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    FyredUp, nice job on the hydraulics!

    Now, take that information and compare it to the pressures defined in NFPA 1961 and NFPA 1962. LDH is limited to 185 psi operating pressure (NFPA 1962). The service test pressure is 110% of the operating pressure. The MINIMUM service test pressure is 200 psi. If your LDH is rated higher than 200 psi service test pressure, then you may be able to exceed the 185 psi. I would get it in writing from the manufacturer. NFPA 1962 is not so forgiving.

    The max friction loss in the 5" hose in a relay situation would be 185 psi - 20 psi (suction pressure) = 165 psi. 1,000 feet of 5" can deliver 1,436 gpm (let's say an even 1,500 gpm). Now how many 2-1/2" hose lines does it take? Since attack hose can take greater pressures, try the 333 gpm calc from FyredUp's post. This still means five 2-1/2" lines. To compare it to the same friction loss as the 5", would mean even more. Five 2-1/2" should be enough to convince them.

    Other considerations are what is the maximum needed fire flow for your jurisdiction? What is the typical water supply data. This should be factored in also. This would determine whether or not you need to place an engine at the hydrant or forward lay to the fire with the 5". The later requires less manpower, equipment and time.

    Let us know how it turns out.

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    Okay here we go!!

    1500 gpm through a single 5 inch line

    .08(15x15)10= 180 psi FL can't be done with 185 psi rated hose and leave an adequate intake pressure

    1400 gpm through a single 5 inch line

    .08(14x14)10= 156.8 okay 156 psi FL this is possible leaving 29 psi for intake pressure

    1400gpm through a single 4 inch line

    .2(14x14)10= 392...okay I don't think this will work

    1400 gpm through dual 4 inch lines

    .2(7x7)10= 98 psi friction loss this is very viable

    1400 gpm through four 3 inch lines (350 each)

    .8(3.5x3.5)10= 98 psi FL very do able

    1400 gpm through three 3 inch lines (467 each line)

    .8(4.67x4.67)10= 174.47 okay 174 this is do able with 3 inch hose, usually tested at 250 psi

    1400 gpm through two 3 inch lines

    .8(7x7)10= 392 guess this won't work

    1400 gpm throuigh five 2 1/2 inch lines

    2(2.8x2.8)10= 156.8 BINGO Equivalent of 5 inch again!!

    1400 gpm through four 2 1/2 inch lines (350 each line)

    2(3.5x3.5)10= 245 psi friction loss...no room for intake pressure


    Hey how about some 6 inch hose?

    .05(14x14)10= 98 psi FL hmmm...the same as dual 4 inch lines...

    how far can we go and not exceed 5 inch at 1400 gpm?

    .05(18x18)10= 162 psi FL at 1800 gpm over 1000 feet of 6 inch hose...

    I told you I liked math!!

    FyredUp

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    You know it is nice to see firefighters and engineers who are actually concerned about the hydraulics. It has been awhile since I've been on the forums or even worried about hydraulics, as I've been stuck in paramedic and HAZMAT Tech schooling for almost a full year now. Our department only uses LDH 5" for supply and use it as the blitz line for our monitors. Talk about a lot of water with very limited work for the pump, never have to worry about getting the pressures that high. As far as the sticks go we only run quints so usually don't have to worry about suppling an aerial device from a pumper.
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    WOW! Thats alot of numbers! Nice work FryedUp. But there's a problem with standard formula's(CQ2L or 2Q2+Q and so on). The problem is they are "standard" and can be way off especially when it's a long lay.
    The best thing to do is flow test "your" hose and get the manufacturer's testing data as stated in one post.

    Exam. one post offers: 5" - 8psi per 100' @ 1000gpm which is NFPA

    Angus Hi Vol 5" - 4psi per 100' @ 1000gpm (angus test data)

    So with a 1000' lay theres a 40psi difference.

    Exam. 1 3/4" 100' @ 200gpm

    NFPA = 62psi
    Angus = 45psi
    Ponn = 27psi

    So my point is test "your" hose and make pump charts that fit your dept.'s needs.

    Service test pressures: 200psi is standard for 5" but there are 300psi versions (supply line)

    About the 2 stage pump: volume vs. pressure. You will not lose 1/2 the capacity of the pump if it is in pressure.
    Also the "rated capacity" plate on the pump panel refers to NFPA 1901 testing. The test is preformed at a 10' draft with 20' of suction hose. 150psi = 100% (165psi "overload" = 100psi) 200psi = 70%
    250psi = 50%. The pump can pump well over "rated" capacity from a pressurized water source with the proper hook up. Our Waterous (single stage) 1250gpm pump produced 2200gpm from a +3000gpm hydrant.


    CaptD

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    Exclamation

    We do not use LDH except with Large Satellite Cos. and Airport situations (JFK Hosewagon). Also every Engine Co has a 35 ft. connection of what you guys refer to as LDH.

    Someone mentioned they found exception with using multiple hoses for supply. Using two lines provides redundancy that provides a safety factor. This is a sound practice and well proven tactic. Our supply lines are 3 1/2" hose. We supply our Tower Ladders with 3 1/2" hose. Preferably from the same source and we prefer to use 2 hose lines. Reduces friction loss and thus lower Pump Discharge pressure and also is good just in case one line should burst.

    We do have rules for pumping hoses...we DO NOT Supply Standpipes over 250 psi. Unless a High Pressure Engine is being used with special hose and multiple precautions are taken.

    Not sure about your pumps but the Rule of Thumb when relaying or supplying Sprinkler Siameses in many Depts is to Pump at or around 150 psi because you get the maximum volume. That might be the cause of a misunderstanding in the procedures.

    FTM-PTB
    Last edited by FFFRED; 04-19-2004 at 08:18 PM.

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    DRA177...

    Absolutely correct, every manufacturer has their own "standard" friction losses they advertise for their hose. None of them are to be taken literally and if you desire to know exactly you should flowmeter the line and see exactly what is happening friction loss wise. The formulas are nothing more than a place to start.

    For us our piston intake relief valves are preset at 100 psi. We try to maintain 20 psi residual coming into the pump. This has worked very well for us.

    FFFred...

    If that works for you fantastic. We have guys on my volly FD that as soon as they can need to get back to work. We need to pick up in a timely manner so they can go. We use a single lay of nitrile rubber 5 inch hose. We hose it off, if needed, and put it right back on the engine. We annually hose test the stuff and reliability is not an issue for us.

    FyredUp

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    Using two lines provides redundancy that provides a safety factor. This is a sound practice and well proven tactic.
    True - that's why we lay dual 5's.

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    Laying 2 lines only offers redundancy and a safety factor if both lines have the ability to be shut off at the hydrant in the case of failure.

    Example: You lay two 5" lines lines from a hydrant in a forward lay. Let's call them A & B. Unless they both have valves at the hydrant allowing them to be shut off individually there is no safety or redundancy. If line A breaks you will immediately lose that flow to your engine and the overall flow will be greatly reduced because more water will flow out of the open hose than through the one still intact. If line A has a valve attached to the hydrant we can close the valve and full flow will return to the second line. In the mean time we can replace the broken section and go back to dual lines supplying the engine. If there is no valve, I suppose you could clamp the line, if you are lucky enough to have an LDH clamp, but if the first length from the hydrant broke you can't replace it without shutting down the hydrant. The same scenario would be true if line B broke and wasn't valved.

    FyredUp

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    Arrow

    In my former depts we always had a LDH clamp. It would only make sense if you have LDH...you should have the clamp.

    I am going to clear up my statement...I was refering to suppling a Tower Ladder, Akron New Yorker or something like that, as refered to in the orginal post. Not a Hydrant to fire senario.

    FTM-PTB

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    Default Re: Pumping LDH

    Originally posted by WBFD324


    My question regarding LDH has to do with what pressure it can be pumped at. The hose is stamped test at 200psi, however SOP says not to pump above 150psi. I am told it has to do with the couplings. Also, am told not to supply an arial device with LDH. Insist that you have to place a pumper at the turntable to boost the pressure. Anyway, is it possible that the hose is rated at one pressure and the couplings at another, and is it necessary to have a 50psi safety factor?

    Thank you all for your input.
    I think you need to look at the aerial device and determine what the piping is set up like, or do you use hose up to a pipe? Our telesquirt requires about 150 PSI to flow 1000 GPM. Remember 150 PSI to flow 1000 GPM, add the friction loss (8 PSI per 100') that lets you supply through about 400' of 5" hose to the aerial if you limit your max pressure to 185 PSI (less 15Lbs from 200 for safety)

    LDH comes in two families...Supply and Attack. Supply is a 200 PSI Test, Attack is 300 PSI. It is usually recommended to pump 15 PSI less than the service presure for a safety margin.
    Last edited by MG3610; 06-01-2004 at 05:20 PM.

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