Thread: drafting

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    Default drafting

    ok when drafting. please correct me if i am wrong. when you want to establish a draft from a dump tank or dry hydrant or whatever, before you pull the primer first you must get the water thats already in the pump out. because if the pump has water in it when you go to pull the primer it wont suck because of the water already in the pump. second when pulling a draft i have noticed that especially from a dry hydrant with a significant lift, that i can get water into the pump without any discharges open BUT as soon as i slowly open one i will sometimes loose prime. when i pull the primer with a discharge slightly open i can usually keep a steady flow. also another question if a tank to pump operation is going and you need to swith over to a draft without losing prime what is the best way.

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    Default Re: drafting

    Originally posted by engineer54
    before you pull the primer first you must get the water thats already in the pump out. because if the pump has water in it when you go to pull the primer it wont suck because of the water already in the pump.
    First time I ever heard that. The presence or lack of water in the pump has no significant impact on what happens when creating suction (vacuum, negative pressure, whatever) on the intake portion of the plumbing. You lose prime, you prime again, but you don't drain the pump. In your theory, you might lose your prime at the moment you finally got water to the pump!... If your primer can't push the pump water out of the way (assuming it is "in the way" on your pump's design), how will it ever draw all that water up the hard suction?
    Originally posted by engineer54
    second when pulling a draft i have noticed that especially from a dry hydrant with a significant lift, that i can get water into the pump without any discharges open BUT as soon as i slowly open one i will sometimes loose prime. when i pull the primer with a discharge slightly open i can usually keep a steady flow.
    Check for leaks on the suction side and make sure your fittings are tight. A little air leakage might be tolerated until the demand to lift the water and charge a line is too much for the pump to maintain. Perhaps your lift is simply too great. Don't run your primer pump continuously you'll burn it out, not designed for constant running.
    Originally posted by engineer54
    also another question if a tank to pump operation is going and you need to swith over to a draft without losing prime what is the best way.
    There really isn't a graceful easy way to do that but it is not impossible, just remember that you can't allow any air into the pump.... you could try to balance your pressures to let water run down your hard suction to push the air towards the drop tank and then increase suction to draw it back in (remember pumper training when they teach you how to hook up additional intakes while the pump is engaged?), but if you don't do it enough you won't fill the hard suction all the way and remove 100% of the air and then you won't be able to get instant suction. Then you wasted your time and dumped what water you had in your tank out the hard suction. Sounds like if you're switching from on board tank to drop tank, you're out of water anyway and can't afford to let it flow out to the drop tank. Don't dink around... tell your hoseline crews they'll lose water for a minute or so while you switch over.

    Hope others have more to add. Someone correct me if you disagree.

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    Last edited by RLFD14; 07-17-2005 at 01:16 AM.
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    Most of the time, if you have water in the pump, it's going to go down the suction tube when you open the intake. But, you can prime with water in the pump. The primer pulls all of the air out, so most of the time, there'll be some air in there anyway.

    On any sort of lift, once you get water into the pump, it shouldn't hard to keep it there, regardless of whats open or shut. Now, you can max this water supply out(you'll know, because your gauge will bury itself down around 30 inches of mercury, regardless of lift. Once you're there, you're at the maximum that you can achieve with that setup.) If you're losing prime, generally, you got a leak somewhere.

    Finally, the way that I do it, you slowly open your intake valve on the hard tube while slowly gating back the tank to pump. Does NOT work on top mount pumps. An in-line primer would be ideal in this situation. This method takes PRACTICE, don't expect to do it right on your first try.
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    Default Re: Re: drafting

    Originally posted by RLFD14
    First time I ever heard that. The presence or lack of water in the pump has no significant impact on what happens when creating suction (vacuum, negative pressure, whatever) on the intake portion of the plumbing. You lose prime, you prime again, but you don't drain the pump.
    If you have a positive displacement primer, it doesn't care what's in the pump. If you have a vacuum primer (as in manifold vacuum) then there's a check valve that shuts down the lift before water can get into the motor. In that case, your pump would need to start dry.
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    Default Re: Re: Re: drafting

    Originally posted by ullrichk
    If you have a vacuum primer (as in manifold vacuum) then there's a check valve that shuts down the lift before water can get into the motor. In that case, your pump would need to start dry.
    I learned something new today, then. Is this universally true? I spent two years as a DNR firefighter (fleet of skid-mount pumps in the back of pickup trucks) and all our pumps had vacuum primers.... we were not taught to drain the pump before establishing a prime, and I was always successful getting a prime and never bothered to drain the pump. Maybe my memory has fogged?
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    I doubt that it's universally true. My only experience with vacuum primers is on older apparatus. I've got a nice cutaway drawing of one somewhere, but I have no idea where.

    In principle, though, water in the motor is a bad thing, so there's got to be some mechanism keeping it out.
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    When going from truck tank to a draft I do the same as Spartan. Spartan, why would we not be able to do this on top mount pumps? Once I have the draft I open the tank fill a little to put water bank in my tank. Water in the pump does not matter. Actually a flooded pump may stop a small air leak problem if one of you valves leak thru a little.

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    ullrichk, rlfd: Our brush truck has a vacuum primer on the skid unit. We can do it with water in the pump, too. Our brush truck's primer is the most efficient primer we have, and you can get an ungodly lift off of it.

    Shank: We have Kochek piston intake valves on all of our LDH intakes. That means, to gate that back, I have to be standing with my hand on the handle. To gate back my tank to pump, I'd have to be standing at the pump panel. You see the dilemma?
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    Pretty good reason. We use 3 in. hard line so I do it all from the panel. Big fire two tanks a 3 in. in each tank. Just was not thinking of the big valve.

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    Honestly, the easiest way to get better at drafting, transitioning from tank water to drop tank water, etc. is to practice, practice and practice some more. A few months ago I was teaching some newbies pump ops and for the life of me I couldn't get the d#mn pump primed, even though I had done it twenty times over the weeks prior for other classes. I swear its almost a voodoo art, say a little chant, burn some incense, and spritz some essential oils into the drop tank before starting. Another guy primed it right away, and in the following evolutions the rest of the day I had no trouble helping the students get a prime from absolutely nothing...

    Truth be told, the easiest way to quick and dirty get a pump primed for us is to slowly open the intake valve for wherever you're sucking the water from, dump some tank water into it to push the air out that way, and throttle up the pump. 99% of the time, I can have a primed pump in a few seconds. Saves on replacing the primer pump oil too! I'M KIDDING THERE!!!

    What's funny is that my department hadn't drafted on a fire for YEARS and in the last month we've had to set up dump tanks and a tanker shuttle for a pretty rough MVC and fire on an interstate, and yesterday our guys relay pumped for half a day at a mutual aid fire from a river. I'm sure glad we still teach the guys to draft...
    Last edited by npfd801; 07-19-2005 at 05:31 PM.

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    I've never heard of emptying the pump either. In fact, I was taught that if you lose your primer pump, dump your remaining tank water into the pump and subsequently the suction hose to help establish the 'water column', idle the hell out of it and open a discharge and you will be flowing water very quickly.

    Steve
    Last edited by smchilds20166; 07-19-2005 at 04:50 PM.

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    Because something wasn't adding up in my own mind about my earlier comment, I inquired about why we did things that way (at my old department).

    The essential detail missing is that the primer was plumbed to the top of the pump casing. While the pump was spinning, any water remaining in the pump housing would be slung toward the primer, shutting it down prematurely. If the pump was not spinning, there was no risk of shutdown as gravity keeps the water below the primer plumbing until all the air is evacuated.

    So in addition to not being universally true, it may be true in only a very few cases. Sorry if I caused any confusion.
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    Default drafting

    ok let me see if i can explain it better. when i go to draft from a dump tank and there is already water in the pump when i idle up to pull the primer it shows a positive discharge pressure. when i pull the primer nothing seems to happen since there is already positive pressure. we have a positive displacement priming pump. rotary vane. so i usually crack the tank refill to get rid of the water so then i can pull a draft. my question is if i already have positive pressure when i go to pull the primer is it possible to pull the primer and get rid of the air in the suction line, and not lose prime once i open a discharge.anyone with any information on any drafting procedures please feel free to email me. thanks

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    Ullrichk: Makes sense. Old American LaFrances(back in the 40s), along with other manufacturers, used vacuum primers like that. There was a floater inside that would close off the exhaust whenever the water had flooded the pump. Problem was, without regular operation, the floaters could stick. Well, floater sticks, and cold water was injected directly into the engine. Bad deal.....


    Engineer: Our tanker has a Waterous pump on it with a rotary vane primer. Priming procedure is the same. Run it up to 100RPMs, even if there's water in the pump, open the intake. It SHOULD flood the line and you can try to switch over without using the primer. If not, pull the primer and it should pick it up. Your primer might be shot if it's not picking up...

    Also, once you're primed, (obviously) never open another suction unless you're going to be shutting the operating down to reprime because you'll suck air and lose prime. Other than that, you may have a loose valve or something somewhere. I honestly don't know what the problem is, maybe the truck should be looked at.
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    On the river(Mississippi and Ohio),we'd use a bucket of water poured into the pump for prime and another bucketfull poured to seal the threads on the hose connection until the water started flowing.Unless he was joking with me,I was surprised when our engineer said that he'd never heard of doing that.
    I know that pumpers have priming units but someday you might have to use a portable pump and be away from the bottle of dish detergent to seal the threads with.

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    We had an extra primer installed on our engines, outside the steamer intake valve for use when drafting from a drop tank. While flowing from tank on engine, the suction hose can be primed. The switch from the tank to the drop tank is as easy as opening the intake valve. No loss of pressure, no air in pump.The guys on the hose never know you switched.

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