Running the Pump - Drafting Part 2 of 3 - The Fundamentals transcript

Hi there. Welcome back to our running the pump video series. This is actually part two of a three-part look at drafting. In part one, we took a look at the equipment and set up procedures for a drafting operation on a fire ground. Part two here, we're going to talk about the theory or the fundamentals of what makes drafting even possible along with some operational considerations and some troubleshooting tips. And then in part three, the next video, we'll actually flow some water and demonstrate some different procedures for obtaining a draft or priming our pump.

So, anyways, with that being said, let's let's get started. All right. So, when it comes to the fundamentals, I think no better place to start than describing or discussing the difference between drafting and priming. I think it's important to understand that these are two different processes with different mechanisms [clears throat] that make each of them possible. So, let's just start with drafting. Okay? So, the way I generically describe drafting is the phenomenon of drawing water up to the intake side of our impeller as the impeller is spinning and pushing water out to the discharge side of our pump.

Now, what's important to understand about drafting is at first, we have to have a wet intake side of the pump. We can't have air in there. So, when we have a wet intake and our impellers start to spin and push water out to the discharge side, it's going to automatically draw or draft water up behind it. Now, uh we could get into the weeds a little bit more scientifically on exactly how this process works, but I think this is a uh fine definition to start off with.

We have to understand that drafting is only going to occur when we have water on our intake side, our impellers are spinning, and we're pushing that water out to the discharge side. All three of these have to be uh in play in order for the phenomenon of drafting to occur. Okay, then, what is priming? Well, priming is the process of expelling air or getting the air out of our intake side of our pump and replacing that air with water.

When we talked about drafting, uh one of the things that has to happen in order for drafting to occur is I have to have water uh on the intake side of the impeller. Well, if there's air on that uh intake side, I have to somehow get the air out and replace it with water. Now, when we uh if we go back to our very first video in the running the pump series, where I talk about basic pump theory, I explain that the centrifugal pump cannot pump air.

It only pumps fluid, and for us, the fluid is water. So, if the uh impeller can't help me get the air out, I need some other means to do so. And for us, that's going to be our priming pump. Now, a priming pump is different than a centrifugal pump. One, it's much smaller. It's a tiny little pump. And two, it can pump both air and water. And what they do is they attach this uh tiny pump to the uh uh high point on our intake manifold, okay?

And on the very top of that pump is there uh whoop there's a one-way valve, all right? And when we activate that pump or we turn it on, it's going to start to pump the air out of the intake manifold. As it's pumping the air out, the pressure inside of here is going to drop. And once that pressure gets below the atmospheric pressure, the atmosphere is going to push down on the water and it's going to lift it up into uh the intake manifold.

And eventually it's going to uh replace all the air out of it. Once the air is out and it's completely full of water, this priming pump is going to start pumping the water out of that one-way valve. And that water is just going to simply fall to the ground. The reason why I'm taking the time to show you the difference between drafting and priming, as elementary as this might sound, is really to help us with the troubleshooting process.

I believe when it comes to troubleshooting, if we understand the mechanism that makes drafting or priming possible, that will help us go down the proper path to fix an issue and get back to the task at hand. We know that when it comes to drafting, it's all about water flowing through the impeller. The impeller needs to be spinning in order for drafting to occur. It has nothing to do with the priming pump. However, when it comes to priming a dry centrifugal pump, when our uh intake manifold is full of air, it now is all about the priming pump and really has nothing to do with the impellers themselves, okay?

If go to activate our priming pump and we are not seeing water come up the hard suction, it has nothing to do with the speed of the impeller. Increasing the impeller won't help us. What we have is an air leak problem. We have air getting in somewhere. >> [snorts] >> It could be a bad gasket, the threads could be loose, we could have an open intake somewhere, our master drain could be open. Anywhere that's allowing air to get into this system is going to inhibit the ability to pull a prime.

It has nothing to do with the speed of the impeller. If we go down the path of increasing the RPMs to try to fix a priming issue, one, we're just going to waste time, but two, we could seriously damage the pump or even worse, hurt somebody. As we increase the RPMs, the impeller is spinning faster and faster. That's going to be generating more and more heat inside the pump cavity. So, that's not good. But, what if we all of a sudden do get a sudden surge of water into the intake side of the manifold?

Well, since the impellers are spinning at an unsafe speed, we're going to have significant water hammer go all the way out to the nozzle where a firefighter is standing. So, we could knock them over injuring them. At the same time, seriously damaging our pump. So, all this soapbox preaching is just to say, if we're having a hard time pull a pulling a prime, chances are it has nothing to do with the impeller whatsoever.

It's most likely because we have air getting in the system somewhere. We just simply need to slow down a little bit, try to figure out where that air is coming from and plug the hole. All right. So, just real briefly, a few of the different types of priming pumps we might encounter. Now, real quick disclaimer, I'm not an engineer or a mechanic. I don't tear these things apart. I don't replace them or fix them. I'm just going to give you a quick, uh, uh, flyby review of a few different styles that I have, uh, some experience with, okay?

So, there is oil-based uh, primers, electric primers, and air primers. Uh, all three of these do the same thing by priming our pump for us, and all three of them have an actuator of some sort on the pump panel. When we either pull or push on these actuators, that's what engages the pump and begins the priming process, okay? Our old engine 17 had an oil-based uh, priming pump. Um, it was a fine pump. It it worked well.

Uh, these are a rotary vane style pump. Um, I guess the biggest thing with these is they use oil for lubrication. Um, so our uh, inside of our pump panel, there was a little reservoir that we'd have to keep an eye on and uh, fill up with uh, priming oil from time to time. And it uses that oil for lubrication, and that oil will get depleted and uh, drip on the ground. So, I guess uh, in today's uh, standards, not exactly environmentally friendly.

Uh, but they had a signature horn or kind of a honk sound, and they're powered by an electric motor, okay? So, when we pull or activate that switch, that activates the motor, which engages the pump. All right? Um, again, I don't think those are um, bad by any means. I just don't think they're as common anymore. Uh, then our engine 29 has an electric priming pump. Um, this particular one is uh, made by Waterous. Uh, they're very similar to the uh previous one that we talked about where it's a rotary vane style pump.

And uh the big difference here is they're uh self-lubricating. It's an oil-less design, so uh there isn't a reservoir of oil that we have to keep an eye on. Uh it's more environmentally friendly. Uh but they're also powered by an electric motor. So, you can hear it when it's being activated. It just sounds different than uh that oil base. It doesn't have the same honking sound. It It just sounds differently. All right?

And then lastly uh our air priming pumps. Um our engine 19 has uh an air primer, and uh there's a few different uh brands or manufacturers of them. This particular one that I'm showing you is made by Trident. And what these do is it uses the engine's uh compressed air brake system. So, we have air already on uh the apparatus that we use for the air brakes, and it takes some of that air and it passes it through a Venturi uh nozzle.

And as that air is passing through that nozzle, it's going to draw up uh the air that's inside of our pump, uh our centrifugal pump. And uh there's no moving parts. It's self-draining, and it's very quiet. So, it's a very effective um way of priming our pump by using uh the uh air system that we already have on board. Uh what's neat with these is they do make uh auto primers. So, if you have an auto primer and it's turned on, once it detects uh air uh inside the centrifugal pump, it's going to activate uh this air priming pump and start to uh evacuate that air automatically for you.

Uh we don't have the auto primer. We have a switch like that, so we just push it and it works fine. Uh all three of these are excellent options. I'm not going to say any one of these is better than the other. Uh it's just really just an FYI, so you as a pump operator are a little familiar with some of the different types you might see out there. All right, let's talk about a few different signs or indications uh that we can pick up on that will let us know when our system is either primed or we're flowing a draft, okay?

Um when it comes to priming our system, uh the first thing that we're going to notice is a tone change in that priming pump. All three of those priming pumps that uh I just uh showed you will have a certain sound or a certain tone to it as it's pumping air. Once all the air is depleted and it's overtaken by water, there's going to be a change in tone or pitch. That's going to be my first indication letting me know that that intake manifold is now full of water.

If I keep that switch open or I'm activating that priming pump, rather than air coming out, water's going to start coming out of that one-way valve. And that water's going to hit the ground. That's going to be my second indication that I have a primed uh pump. Now, when it comes to drafting or flowing water, uh one of the first things that we're going to notice or we should pick up on is our intake gauge will show a vacuum or a negative number.

Now, we talked about that briefly before, so uh on a digital gauge like this, okay, let me switch to orange so we can see it. That's going to start to read a negative number and on our compound gauge that needle is going to go down into a vacuum. Uh in either of those circumstances, it's only going to read a a vacuum if I'm flowing water. Now, I could have a prime system and not flowing water. These won't read uh anything negative.

So, that's just an indication that I'm actually flowing a draft, okay? And uh secondly, uh on drafting, we're going to notice our discharge gauges will will hold steady. They're not going to bounce. When we start the drafting process, if there's turbulence or air going through the system and I have a discharge open, I'm going to see that turbulence bounce uh through on that discharge needle, okay? Uh once all that air is out and I'm flowing a nice steady stream of water, that discharge gauge is going to hold steady.

Uh that's what we want to see. That's going to be an indication to me that I'm now uh flowing a nice draft. Okay, so the first key point that I want to make uh next is that we're going to lose our prime anytime our impellers are overtaken by air. All right? Now, if I'm drafting and water is flowing through the system, if I have a little bit of air inside the water, okay? The water that's being drafted will pull that uh little pockets of air, little bubbles of air along with it.

And uh we might see on our discharge gauges a little fluctuation. Uh that would be that turbulence that's going through. So, when we're drafting, we can handle a little bit of air, but we can't handle tons of air. Once the impellers are overtaken by air, we're going to completely lose our prime, and we're going to have be back to a dry pump. All right? So, uh couple places where air can get in. Obviously, uh my drop tank.

If my uh whoop, if my uh water level goes below my uh hard suction hose or that draft plate that we talked about in the previous video, air is going to be pulled in. Another uh culprit is the booster tank. All right? Uh Let's say we get on scene and we open up our tank to pump. And so, our booster tank is flowing water into our intake manifold. If we don't close that, and we're flowing water, we're drafting, we're essentially going to be drafting or pulling water out of this booster tank.

And as that level gets low enough, once the level gets below that uh intake or that pipe that's coming from it, it's going to let air come in here, and then we'll instantly lose prime. All right? So, that's a culprit that happens to people from time to time. So, you need to remember uh to close that tank to pump. All right. So, the next uh key point I'd like to talk about is cavitation. If you're unfamiliar with cavitation or what that is, I highly recommend checking out my uh uh basic pump theory video.

Uh I go into great detail of what cavitation is and how it occurs and what's happening. Um but, I basically break it down into a supply and demand issue. Cavitation is going to occur when I'm demanding more water than what there is a supply to support. Now, remember, our hard suction hose is a limiting factor here. Depending on the size or the diameter of that hard suction hose is going to uh determine the amount of gallons per minute that's able to flow up, okay?

Obviously, if I have a smaller hose, there's less gallons per minute that's even able to get into my intake. So, as I'm flowing water out of multiple discharges, I can get to a point where I'm flowing more water than what is able to get up that hard suction hose. All right? When that happens, it's going to start to cavitate. Now, the way we keep track of that is keeping a close eye on our pump intake gauge. So, this one here is a digital gauge, and as we're drafting water, and and flowing water through the impeller, if we're drafting, it's going to read as a negative number.

And once I get to -20, I'm going to start to experience the cavitation phenomenon. This here is a compound gauge. Anything above zero is reading pressure, okay? So, if I was hooked up to a hydrant, and pressure was coming in, that compound gauge is going to read as a positive, all right? And if I'm drafting, or pulling water into the intake side, it's going to read as a negative, or going to the vacuum side. inches of mercury.

So, once I get to -20, or 20 inches of mercury, that's when the cavitation phenomenon is going to occur. Now, listen closely to the sound of the pump as we reach -20, or 20 inches of mercury on a compound gauge. That change in tone is our indication that we're cavitating. So, we need to make quick adjustments cuz if we leave this go unchecked, we're going to slowly damage our impeller. Now, just keep in mind if I'm cavitating, it doesn't mean I'm out of water, okay?

I could be experiencing cavitation with a full uh drop tank. It just means that there is not enough water able to get up that hard suction hose to support uh what I'm flowing out onto the fire ground. Your job is to keep an eye on that uh intake gauge and communicate with IC or operations so that people are aware of uh where we're at with your supply level. All right. So, some operational considerations as a pump operator when you're drafting.

Uh first thing is don't be shy to use your radio. Uh let IC or let um nozzle teams know uh that you're going to be transferring from tank to pump to draft, okay? We don't want to be taken off guard all of a sudden with uh limp lines and uh no water coming out. So, just get on the radio, let us know you're going to be transferring, and then also let us know when you've obtained that draft, okay? Uh then that way everybody's in the loop and we know what's going on.

Uh next thing on this list is uh before you even start the priming process, uh just slow down for a second and take a pause for the cause. Do a 360 and check all your connections. Uh make sure all your drain valves are closed. Uh make sure your bleeder valves are closed before we even start the priming process, okay? If there's anything that's open, you're not going to be able to attain a prime. And if uh if you start that process and we can't pull a prime, I guarantee you every head on the fire ground is going to turn and look to you and you're going to wind up feeling the weight of the world on your shoulders.

Uh so it's just um good to slow down and double check all your connections. Uh next thing is don't forget to switch to RPM mode, all right? Uh in one of my previous videos, I talk about the difference between pressure mode and RPM mode um on the modern pressure governors. So if you haven't seen that or you're not familiar with why we should be in RPM mode, go check that out. But uh almost guaranteed uh if you don't switch to RPM mode, uh we might run into some issues if air is getting through the pump.

Next thing uh on this list is priming should not take more than 30 to 45 seconds. Uh a couple reasons with that. One, if we have those uh electric motors on uh a couple of those different type of priming pumps that we looked at, those motors are not meant to run for a long time. So if we run them for uh a a while, they're going to overheat and we could damage them. But the main reason uh you shouldn't uh be pulling a prime for more than 30 to 45 seconds is it just flat out doesn't take that long.

Right? If my system is air tight and my priming pump is working, it will take less than 45 seconds. So after saying that, I thought, you know, I better double check before I put this out there because YouTube uh certainly happy to let you know if you say something inaccurate. So here's some footage that I filmed from uh local dry hydrant and you can see that I have 20 ft of hard suction [music] hose plus at least a 5-ft to 7-ft vertical lift to the water table.

And I'm able to pull a prime in just under 30 seconds. [music] That's pretty cool. If it's taking longer, there's air getting into the system somewhere, and we need to start the troubleshooting process, okay? And then lastly, depending on your SO Gs, I would uh consider switching back to pressure mode after you started to draft water. Now, if your SO Gs want you to stay in RPM, that's fine, and I I would not argue with that.

But just know as a pump operator, that means you're now responsible for watching all of your discharges, and either gating or opening up those discharges depending on uh when firefighters are opening and closing uh their nozzles. Another thing that you should be aware of as a pump operator is our tank fill rate versus our fire flow rate. After we transition from tank to pump to drafting, we want to start to fill up our booster tank.

Remember, this booster tank was our initial water source for attacking the fire. But now that we transitioned to uh drafting, this is going to become our backup. If anything happens down here, we want to simply close that uh inlet and open our tank to pump back up to minimize our downtime. But the thing to consider with this is whatever the flow back into the booster tank, whatever gallons per minute this is, is going to be directly reducing the amount of gallons per minute I can put onto the seat of the fire.

So, this can be a little bit of a balancing act. You don't necessarily want to open that all the way up because that can be upwards of 500 plus gallons per minute. That's drastically reducing the amount of gallons that I can use to attack the fire. So, this is going to be a coordination between you and the tactics that are going to be laid out by your IC or your operations team lead. So, uh this is just something to be mindful of.

This can lead to a much larger passionate conversation in YouTube land. So, I'm just bringing this out as something to be aware of, okay? All right. So, I thought I'd just take a couple uh minutes and talk about dedicated intake primers and the distinct advantages that they offer us. All right. And to do so, I thought we'd take a look at our engine 19, which has a rear intake primer. So, if you're not familiar with it, the way these work is we uh install a second primer on a specific intake on the outside of that intake's valve.

So, let's take a look at this uh pump diagram that I drew here. All right. Here is my uh intake manifold like this. And this is that main primer that we've been talking about all along. That's what I would use to uh prime the system all the way up to the impellers. Now, here is my rear intake. So, this is a long pipe, long stick uh that's going out to the rear of my engine. And this represents uh my electronic valve.

Right? Uh so, I right now my valve is closed. And what we can do is have a dedicated primer that is installed on the outside of that valve. So, uh and that primer is going to have its own actuator. And so, when I uh activate this primer, I'm going to draw water all the way up to uh this rear valve. Now, and that'll look something like this, all right? Now, you notice that my intake manifold is still dry because my valve is closed.

So, what we do to avoid any uh possible air locks in our system is before we open this, we're going to activate uh this main primer and we'll create a vacuum inside of here. So, when I open this, water's just going to instantly rush in and it'll look something like this. So, now you can see my uh valve is open, water's coming from my uh rear uh drop tank all the way up to my uh pump and if my impellers were spinning, I'm now going to start flowing water and I can send it out to a discharge, right?

So, uh what is the main advantage or how can I use this on an actual fire ground? Let's imagine we get on scene and we're attacking a fire and before we have our drop tank set up, we're going to pull a handline and we're going to start fighting that fire off of our booster tank. Remember, we got a 1,000 gallons on board, so we can pull this handline, open up our tank to pump and start flowing water out of here. So, that uh booster tank is coming into my intake manifold like this.

So, while that's happening, we'll set up our drop tank, hook up our hard suction hose and then before we open up this valve, we can activate this rear primer, bringing water all the way up to this valve, which will now kind of look like this. I have my uh booster tank. I'm fighting uh fire out of that booster tank with that water out of this nozzle. And I have this rear area or this rear stick now completely primed. So, all what I have to do is open this, and it's going to look uh something like this.

So, now that this is open, I am now drafting water all the way from this rear uh uh drop tank, out the pump, out of that uh hose, out of that nozzle, and fighting the fire. The only thing I have to remember here is I have this booster tank still open. And we talked about that previously. If I don't close this uh booster tank, this is eventually going to run dry, and that's going to allow air into my system. Once air gets into my system, I'm going to lose prime.

But, you can see here a distinctive advantage of having a dedicated uh primer like this. I can transition from tank to pump to a draft without any interruption to the uh fire flow or the water that's coming out of that nozzle. Okay, so in conclusion, like I've said before, it's not about if there'll be issues, it's about when there's issues. Will you be able to identify it, quickly fix it, and get back to the task at hand?

As a pump operator, the last thing you want to do is panic. When we panic, small little issues turn into big problems, and big problems can easily turn into a large epidemic. And when we have large epidemics, things either break or even worse, somebody gets hurt. So, just uh remember, just slow down, think about the problem at hand, and ask yourself, "What is the issue and how can I fix it?" So, anyways, thanks again for watching.

Uh I hope you're finding this stuff helpful. Uh leave any questions or comments you have for me below, and we'll catch you on the next one. Thanks. I just don't have a tool.