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    dlc
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    Default Drafting questions from a hale midship

    hopefully someone can make sense of my questions,,,,when you get the pump primed from a draft must water be dicharged to keep the draft going? if water is not needed right away do you just use the recirculator/ tank fill to keep the water moving or must you discharge a larger amount to keep the draft?

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    good question. I'll admit that I am pretty sure you need to keep water moving, but I have been taught and operated under the idea that you need to keep water going.

    If you are drafting from an open body of water (river, lake, pond etc), I point the deck gun out over it so that I can just open that up.

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    If you are able to "shut off" your incoming water (butterfly, MIV), then you should be able to do that and maintain your draft and just circulate from tank to pump and back to tank to avoid overheating your pump. If you need to switch back to drafting, open the valve then shut off your tank to pump. You may need to hit the primer if you have any leaks in your intake valve. If you have no intake valve to draft through, you need to discharge water somehow once your tank is full, either through a booster line, uncapped discharge, deck gun, or just leave your tank fill open and let it run on the ground. Either way, gotta keep water moving anytime your pump is in gear, whether running from your tank or drafting.

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    Get it moving, keep it moving!

    Milford Chief's statement is not wrong technically assuming no air entering from anywhere. But view it from a practical standpoint. You pull a prime, then open the tank to pump and tank fill. The pump that was churning what you brought in from your static source is now moving your tank water. Eventually, air is bound to find its way into the system and break your prime.

    If your system is absolutely 100% air tight (tighter than needed to pass a dry prime), you'd do better to disengage the pump.

    I was going to make a couple of other statements but I'll pass on them until (if ever) I get a chance to experiment with the scenaria.

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    Quote Originally Posted by chiefengineer11 View Post
    Get it moving, keep it moving!

    Milford Chief's statement is not wrong technically assuming no air entering from anywhere. But view it from a practical standpoint. You pull a prime, then open the tank to pump and tank fill. The pump that was churning what you brought in from your static source is now moving your tank water. Eventually, air is bound to find its way into the system and break your prime.

    If your system is absolutely 100% air tight (tighter than needed to pass a dry prime), you'd do better to disengage the pump.

    I was going to make a couple of other statements but I'll pass on them until (if ever) I get a chance to experiment with the scenaria.
    I agree with you 100%. What is your ideas? Someone way have already tried it or give us something to try.

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    Quote Originally Posted by rm1524 View Post
    I agree with you 100%. What is your ideas? Someone way have already tried it or give us something to try.
    They're actually opposites. I'm not sure which would happen but in one scenario I see the drafted water going into the tank and overflowing it.

    In the other I see tank water (positive head pressure) pushing back down the hard sleeves since they are at negative pressure.

    I'm trying to mentally sort out the physics involved, that's why I said I would want to set it up and try it first. (I actually had it keyed in to my earlier response, then took it out and replaced it with the statement about needing to try it out first.)

    Or, would there be enough of a balance that nothing would happen.

    If you want to play with it, I'd really be interested in learning what, if anything, happens.

    I wonder if our physics guru, KuhShise, would like te weigh in on this.
    Last edited by chiefengineer11; 03-09-2010 at 10:38 PM.

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    Depends on which suction you have connected and if you have an intake valve. On our pony suctions we can draw a prime and close the valves and hold the prime while circulating through the tank. On the main suction we don't have a valve so we have to send water somewhere or shut down.

    If the tank is full and we won't need the water real quick we just shut down and pull a new prime. The fast way to pull a prime in that case is to open the Tank to Pump and drop water into the entire system. Then close the valve and pull the primer as required if you pull any air back in.

    I will say it is one of the benefits with the turbo draft type units. With it connected you can pull a draft VARY fast because of the way it operates. You can also circulate water through it and hold your draft as well.

    Another NICE item is if your using a drop tank are the tanks that have a suction fitting built in at the bottom. With those you connect your suction to the fitting and with a full tank of water you can shut down and the hose usually stays full because of the water pressure on the tank.

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    A Precon on intake.

    When topped off the booster tank full, open tank to pump and the head pressure will close the Precon and hold hard suction full of water.

    When need to discharge again close the tank to pump and resume drafting.

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    Most of the time, when you draft, you are going to use that water pretty soon, once you have the pumped primed.

    Once you achieve a prime while drafting, you should, if the pump in new, be able to hold the prime without discharging any water.

    You can if you have a booster line, pull the nozzle and line over to where you are drafting and open it up and let water flow back. Or you could pull the trash line and do the same. Older pumps even in great shape will start to lose the prime in time if water is moving through the pump.

    If the weather is warm and not freezing. crack the tank fill and let water run into the tank. Yes it going to over flow, but allowing it to do so will keep the pump prime.



    We always take the "keystone", Pistion Intake off and connect the sleeve direct to the steamer intake on the right side on the rig is possible.


    Stay Safe and Well Out There....

    Always remembering 9-11-2001 and 343+ Brothers

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    thanks for all the good answers. more questions, when the truck is drafting , the master intake guage should change from a vaccum to psi as the primer expells the remaining air from the intake, is this correct or no?

    also when working from a booster tank , what is the procedure for switching to draft without interupting flow to handlines? the truck is a 2005 freightliner with a 1250 hale midship, id be drafting from the front intake w/ LL strainer in a 2500gal. dump tank.

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    Quote Originally Posted by dlc View Post
    thanks for all the good answers. more questions, when the truck is drafting , the master intake guage should change from a vaccum to psi as the primer expells the remaining air from the intake, is this correct or no?
    You should see any "pressure", as the water is coming in via vacuum as opposed to a pressurized source. To be honest, I don't know that I've ever looked at a master intake guage while drafting, rather I watch the water coming through the intake and make sure the master discharge doesn't drop (indicating lack of water).

    Quote Originally Posted by dlc View Post
    also when working from a booster tank , what is the procedure for switching to draft without interupting flow to handlines? the truck is a 2005 freightliner with a 1250 hale midship, id be drafting from the front intake w/ LL strainer in a 2500gal. dump tank.
    Switching back and forth isn't really practical with just a suction hose and strainer. Once you close the intake valve, any leaks will cause the water to drain out of the suction hose and you'll have to pull suction again.

    You can "cheat", however, and use a siphoned low-level strainer and charge the suction hose when you're ready to swap back to draft.

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    If you have gated aux intakes you can slowly open the gate while the pump is flowing water. the flow of water through the pump will pull the air into it, causing a vacuum. Reduce your tank-to-pump- after a bit, and eventually you are just drafting. Refill your tank just in case.

    We are a rural district w/o hydrants. We use this for switching to portatank water while flowing. The officer side of out engine has a gated Siamese on the intake steamer. we have (2) 10' section of 3" suction hose w/ cam locks, and out tender has (4) 7' sections. We thread a 2.5" fire to 3" male cam adapters into the gated intakes and can draft from the tank. you can flow about ~250gpm per intake hose like this, so we can switch from tank to 750gpm using the above method.

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    You may not get full capacity from the front intake as you would from the right side intake.

    You won't show any postive pressure on the compound gauge, you are drafting and should stay where you first got the prime, maybe about 20 pis negative pressure or what ever you had.

    You will show postive on the master pump gauge as well as the discharge[s] that you are pumping through.

    When taking water from the booster tank, in theory you are drafting too.

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    Quote Originally Posted by chiefengineer11 View Post
    They're actually opposites. I'm not sure which would happen but in one scenario I see the drafted water going into the tank and overflowing it.

    In the other I see tank water (positive head pressure) pushing back down the hard sleeves since they are at negative pressure.

    I'm trying to mentally sort out the physics involved, that's why I said I would want to set it up and try it first. (I actually had it keyed in to my earlier response, then took it out and replaced it with the statement about needing to try it out first.)

    Or, would there be enough of a balance that nothing would happen.

    If you want to play with it, I'd really be interested in learning what, if anything, happens.

    I wonder if our physics guru, KuhShise, would like te weigh in on this.
    I'm thinking that the head pressure would push the water out of the tank. It would be like a drain on a bathtub. We have a couple of guys that are starting their engine training in the next couple of months. I'll see what happens.

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    Quote Originally Posted by fireinfo10 View Post
    A Precon on intake.

    When topped off the booster tank full, open tank to pump and the head pressure will close the Precon and hold hard suction full of water.

    When need to discharge again close the tank to pump and resume drafting.
    What kind of flow can you get using a precon?

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    Quote Originally Posted by rm1524 View Post
    What kind of flow can you get using a precon?
    At one time, Precons were notorious for high friction loss. I don't know if they've changed their design to overcome that or not. Haven't worked with one in years.

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    hopefully someone can make sense of my questions,,,,when you get the pump primed from a draft must water be dicharged to keep the draft going? if water is not needed right away do you just use the recirculator/ tank fill to keep the water moving or must you discharge a larger amount to keep the draft?

    In teaching local level pump classes for 30+ years, I have not seen a single drafting set-up that was absolutely tight for air leakage. At some point either sooner or later with no water passing through the pump, air will leak into the system and collect at the eye of the impeller. Usually the leak is at the gasket where the hard suction is connected to the pump intake. There is a strain on this connection because the sleeve bends downward toward the drop tank or the water source. Additional places where air can leak into the suction side are at the coupling bowls, packing glands, relay relief valve, or drains. I teach all my students to put a nozzle on a discharge and throw water back into the water source, or connect a hose and circulate water back into the drop tank. You will need enough flow to entrain (mix) the air into the water and blow it back to the source.
    Opening the tank fill as a means of moving water will over fill the tank and put the water on the ground under the engine. Most water source draft locations are not well suited to supporting a heavy engine and the ground quickly becomes saturated preventing the engine from being driven away without help from another apparatus. Opening the tank to pump while the hard sleeve is connected simply allows the tank water to drain down the hard sleeve into the static water source. It is possible to crack the tank-to-pump valve and open the tank fill fairly wide causing a balance between the water being taken from the apparatus tank exactly matching the water refilling through the tank fill line. If you do this, never turn your back on the pump. Any changes in the water demand from the attack crew will change this balance and deplete the tank water. Once all the water is pulled from the apparatus tank, you will loose the prime and may have a difficult time getting the pump re-primed. Many tank valves have a slight leak that won’t pass much water, but it only takes a slight amount of air to prevent getting a good prime.

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    more questions, when the truck is drafting , the master intake guage should change from a vaccum to psi as the primer expells the remaining air from the intake, is this correct or no?

    also when working from a booster tank , what is the procedure for switching to draft without interupting flow to handlines? the truck is a 2005 freightliner with a 1250 hale midship, id be drafting from the front intake w/ LL strainer in a 2500gal. dump tank.

    Not correct. Before operating the primer, the master intake gauge should read ZERO. After operating the primer, the master intake gauge should read a vacuum in inches that will be very close to the feet of lift between the surface of the water source and the center of the pump impeller. If your pump intake is 10 feet above the surface of the pond, when you get prime the master gauge should read about 10 inches of vacuum. Most pump manufacturers buy intake gauges with very poor resolution. That is the gauge is not really meant for you to be able to see much difference between 10 inches or 20 inches of vacuum. When you begin to move large volumes of water from draft, (supplying a deluge set) you should see the vacuum gauge move toward 30” of vacuum. There is a real amount of friction loss in the 6” hard sleeve that increases as more water is being pumped.
    Changing from tank water to drop tank water, slowly operate the front suction valve while hanging on the primer handle. Here is where the circulating hose running back to the drop tank can help. The more water you can get moving, the more air can be entrained in it. You will need to remove all the air from the hard sleeve, and it will take at least 15 to 30 seconds for the primer to do the job. Just hang in there and hold the primer valve wide open, while trying to maintain the desired discharge pressure. Sometimes it helps to keep the tank fill line open and slowly gate the tank to pump line back. If you loose the prime with firefighters in the building, DO NOT SHUT THE DISCHARGES OFF. Keep operating the primer, open the tank to pump valve and hang on the primer. As soon as you get the pressure back try to change over again. When making this change, you should be in RPM mode if you have a pressure governor. Do not operate in the set pressure mode.

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    Quote Originally Posted by chiefengineer11 View Post
    At one time, Precons were notorious for high friction loss. I don't know if they've changed their design to overcome that or not. Haven't worked with one in years.
    We had them years ago and got rid of them because of the GPM loss. I don't remember what the loss was, but it was high.

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    Quote Originally Posted by dlc View Post
    thanks for all the good answers. more questions, when the truck is drafting , the master intake guage should change from a vaccum to psi as the primer expells the remaining air from the intake, is this correct or no?
    Nope. There are only a couple times you will see the master intake gauge reading pressure if your drafting. One is if you are using a draft booster like a turbo draft. Because it uses water pressure into the venturi to force more water through the suction you usually see a few pounds of residual pressure. The other is if your draft water is located uphill of your pump. Then you get whatever pressure gravity gives you once you have pulled a prime.

    also when working from a booster tank , what is the procedure for switching to draft without interupting flow to handlines? the truck is a 2005 freightliner with a 1250 hale midship, id be drafting from the front intake w/ LL strainer in a 2500gal. dump tank.
    If your front intake is valved it's simple. Drop your tank onto the pump. Start flowing water and crack open the front intake valve with the LL under water. It will pull the air out of the suction as you pump. Keep a hand on the primer just in case you get more air than your pump can deal with. Once the line is full SLOWLY close the tank to pump. Once your operating on draft water open the tank fill some to refill the tank. If at all possible keep a full tank on the rig for emergency use. You never know when that inbound tanker has a flat tire or rolls into a ditch and causes you to need ALL the tank water for evacuation.
    If it isn't valved you don't have a choice. You need to pull a prime and get running off draft and then hope you don't run out of water in the drop tank.

    In the event that you have a full tank and are not flowing water to the fire the easy way to keep everything ready is to drop a line out to a tank fill elbow and just let the water circulate. Keeps the pump cooler and allows you to instantly open lines back up. You can idle down and still be ready to go as needed. If your pulling water from a pond or running water you can even help the fish out. Toss a monitor on the shore or open the deck gun up and dump the water back into the pond/stream DOWNSTREAM of your intake. That way you not only keep your pump operating but you aerate the water as well.

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    Default recirculate

    When we put in the low level strainer, we always connect a 1.5" to the strainer so that we can use the jet siphon to fill the suction line with water so we have no break in supply as we cut over from tank water. We the recirculate a little water back through this line.

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