Eric Johnson (01:11)
Welcome back to Boiler Wild. My name is Eric Johnson on this podcast. Talk about boiler industry topics as well as personal development. Boiler Wild. Wild is part of the name of the podcast. Stands for work hard, invest yourself, lead others into develop yourself into a person of excellence. Always striving to get better. And if you're listening to this podcast, hopefully I share something to help you get better or think about a topic differently. Today we're going to talk about
Water hammer at the intro of this podcast. You heard a video that video is decently famous and it is a person or construction crew. There was one person in a steam vault or a vault. It is a underground concrete room with valves and pipe connections.
And this was in California, I believe, and in 2015. And they were cutting in a new section for some building and they were opening lines and the banging you hear is water hammer caused by steam. And eventually the blowout was a pipe breaking or something breaking in the vault and
the people that were saying, you should come out of there. You should come out of there. the worker was on a ladder and he was about standing about halfway out of the hole of the pipe vault when whatever broke and then the gases. So the air that was in the pipe vault plus the now steam coming out of the break.
pushed him out and there was a huge cloud and he got shoved or pushed out of the hole of the vault and landed on the ground next to it. He did walk away in the video. I don't know what the extent of his injuries were, but he got super lucky to have been halfway out of the vault when that happened. There have been other accidents where
Water hammer breaks a pipe when people are inside of a vault and they don't get out and they die because steam, one it displaces oxygen, but two just the heat of the steam will cook you and you'll get burned. And I don't know if you guys have ever had a steam burn, but I've had, you know, a little one here and there on my hand or arm. And man, when steam touch,
touches your skin. It's not like, you know, you're touching a hot stove and it's like, wow, that was hot. Like for some reason, a steam burn is just, it like just instantly cooks your skin. And if you have any amount of extended contact with steam, you are going to be in some trouble, especially if you have to start trying to breathe it. ⁓ because then it starts cooking your airways and your lungs. And it's, and it also,
⁓ Steam, if you don't know, displaces oxygen or displaces air and air has oxygen. So if you're in like a tunnel or a crawl space with steam pipes and there's a steam leak, you just need to be mindful of that, depending on how big the leak is. But you don't want to be breathing all that or down there.
an active leak. is a safety issue. I've been in a crawl space under a school once and we had a condensate line come apart and there was a lot of condensate come out and a lot of water vapor in the air and I was like, ah we should probably just like let this leak out and cool down. Like let's get out of here. We don't want to
takes any risk that we don't have to. So got out of there and let all the condensate leak out, all the hot condensate leak out and all the water vapor dissipate in the crawl space and then go back in and then fix the leak in the pipe section. But water hammer, what is water hammer? So the first thing we need to understand about water hammer is water is a fluid and fluids
are not compressible. So you you've heard of an air compressor. An air compressor is a pump and it constantly compresses air into a pressure chamber. So a tank, and then that tank can store air and that air is essentially a spring. So whether you have 10 psi of air or 100 psi of air, the tank size doesn't change.
but it keeps pushing more and more air into the tank. So it is compressing the spring. If that tank were to rupture and fail, it would explode violently and all the air would come out very quickly with a lot of energy because it acts like a spring. However, if you have water and you put water inside of a tank and you try to compress the water, you can compress it.
and get the tank to 100 psi but if the tank fails there's only going to be a small blip of pressure failure and then it'll go to 0 psi because you can't compress water so there's no stored up energy in there and that's why when you hydro a boiler and you're checking for leaks you fill it all the way up with water one so that the water will come out of leak but two there's less potential energy
when you are pressurizing water versus pressurizing air. If you were to fill a boiler halfway up with water, just the normal water line and then pressurize it with air, one, it would take way longer to pressurize it, but two, you are now stuffing way more potential energy
into that pressure vessel and if the pressure vessel were to fail or something fails like a tube leak or something now you have a lot more energy coming out and I don't know if you've ever had a airline fail on you or something come apart on an air compressor but there's a lot of energy behind that that is stored in the pipe that comes out of that line even when you
take apart a hundred foot air hose. Think about the big pop when you're taking that hose apart and then all that compressed air that's coming out of just that tiny half inch or 3 1⁄8 inch whatever air hose. So that's the number one principle for a water hammer is you cannot compress a fluid and water is a fluid. So there's two
kind of scenarios of water hammer one that is just water induced. I don't know how to say that but there's waves. So without going into a giant physics lessons there's pressure waves. So think like waves of an ocean. Those are all waves of like pressure and while you see a wave at the top of the ocean
the wave actually goes underneath the surface of the ocean. It's not just water on top moving around. The wave is on the in like under the water level where you can't see it. So if you're like along the seabed, like you can feel waves coming over you. That's a very simple term. I'm not a physics expert on waves, but you, so if you push on water,
the force of your push will get transferred through the water in a wave.
where water hammer works or is most commonly heard is in a plumbing system. So in your potable water for your house, you have 80 PSI coming off your street of a one inch water line or something. And then it goes in your house and maybe gets reduced to a three quarter inch or half inch water line that goes throughout your entire house. And if you
don't have a water hammer, a rest or of enough volume. If you open up a faucet and then you were to close it really quickly, you may hear like a clunk and that is water hammer. And that is due to the force of the water, essentially piling up on itself and causing a pressure wave to go against the valve that you just closed. So you can install a
water hammer arrestor which is a tube of compressed air where you can install like an expansion tank something that has some air in it but you can install a water hammer arrestor that's pretty common and it will expand and essentially lower the pressure spike of the water. Now in the boiler room
The same thing happens for a feed water tank. So if you have a standard feed water tank, as we know, a feed water tank is not pressurized. So it's vented atmosphere. Typically a feed water tank will have a one inch to a three quarter inch solenoid valve on it that maybe is driven off a float or water level probes. But typically the solenoid valve is going to be just on off and
When you have an on-off solenoid valve, can have that valve close very quickly and it causes some water hammer and that water hammer can either have piping come apart or it can have piping swing if it's not properly supported, but it causes pressure waves. So you can do two things. You can install a slow closing solenoid valve.
So the solenoid valve, it has an option to slowly close, and this is a special solenoid valve for water. You can't convert a normal solenoid valve to a slow closing solenoid valve. They're built differently, but you can buy a slow closing solenoid valve so that the valve doesn't just quickly close, it slowly closes, which will reduce the pressure spike when the valve closes all the way, which reduces the water hammer. Secondly, you can install...
water hammer arrestor which I just talked about is a tube and it has a little air in the tube behind like a diaphragm and it allows the pressure wave of the water to pressurize the water in the little tube and that will help provide some spring action for the water and will reduce the force of the
pressure wave in the water and kind of disperse it.
That's the common water hammer on domestic or potable water pipes.
As I was doing a little bit of research on this, also saw, I guess it's a thing for firefighters. If firefighters close water hydrants too quickly, they can cause a water main under a street to rupture. And that is going to be the same principle is a fire hydrant. Say you have a four inch line connected to the fire hydrant. And if somebody were to close it really, really quickly,
and all that flow goes to basically zero. Now all that, think about like a train going on itself. So if you have a train and it's traveling down the tracks and it's a mile long, and if you were to just be able to put a force in front of the locomotive and to stop the locomotive, so whatever force that would be, if you stopped the locomotive, all the rest of the cars don't
automatically just stop, they still have forward momentum and force and mass and they're going to want to pile up on themselves. And that's essentially what happens when a train derails is yeah, the train's derailing and it's slowly slowing down, but cars just keep piling up and keep moving forward because the front of the train has stopped, but the rear still has mass.
and is moving forward and is slowly going to pile up on itself. That's kind of how water hammer works is it's immediately stopping a train and all that pressure wave of the water just keeps piling down through the water and goes and hits right at the end of the valve where you closed it quickly and causes a pop. But that pressure wave now goes back down the pipe the other way.
But that pressure spike can be a very large percentage higher than the actual residual pressure of the water. So if you have water at like hundred PSI, that pressure wave can cause like a 300 PSI spike. And that spike can cause a pipe to fail. And that's what the fire department was talking about when if you were to close a fire hydrant too quickly, were
causing that water spike in that pressure and it can find a weak spot in a water main and blow it. Now you have to have the city come out and dig up the street and fix the water main, which is never fun. So that is water on the domestic side on the potable side on the hydronic side, water hammer. Let's talk about water hammer. So when I was a service technician,
There was a site I used to go to. It had a high temperature water loop. I think they were running around 340 degrees of temperature of water and it had to be pressurized to hold it in water. But that's, don't think that really matters with the water hammer, but how this loop worked, it was pretty big loop and had pretty big pumps, but the pumps were on off. They were not VFD.
And so it had a pretty big piping and all the piping was hung in like an open warehouse. It wasn't a closed building and everything was hung. And what's why that's important is hangers really only restrict the pipe movement from going down. It doesn't reduce side to side movement and then up. So when these pumps would shut off, if somebody were to shut them off, the pump would go from a hundred percent to zero percent.
And then there were also check valves in the system and the pump would shut off immediately, which would is basically like stopping and closing a valve. And then the check valves would slam closed and there would be this giant bang and a series of bangs after that. And they're like, Hey, every time we shut off our pumps in our system, there's these giant bangs and
They're like, what is going on? And the pipes would swing. You could see all the pipes swinging in the ceiling. That is from water hammer. And you don't want that. So you can avoid that by slowing down the pumps slowly with a VFD. So instead of turning it from off or on to off, you can slowly ramp it down, which is basically like slowly closing a valve. It's going to not allow a
very large pressure spike when you do shut off that flow 100%. But it's something to be mindful of in a hydronic system. That's what's happening if you do find that. But the main topic of today is water hammer that is caused by steam. So that is the one that can kill you. That is the one when people talk about water hammer around boilers, they're typically talking about water hammer caused by steam.
And that is what was the start of the video, the audio from that. If you want to look it up, you can find it online, but water hammer from steam is very, powerful. So what happens is you will have a couple scenarios, but one will be, say you turn off a system and the system goes to zero pressure, whatever.
Condensate that's in the pipes has drained out to what it can but there's still low points with water in it and Now that there's no pressure. There's nothing to push the water out and up into the condensate lines and You know say we've shut off the steam system for the summer whatever so we come in on in the fall And we start everything up
And the boilers start making steam. So now you have this gas going down these pipes and it may find or will find all the low spots and all the low spots will typically still have water in it. If somebody didn't go around and individually drain each low spot of the system and it will find those low spots or sags in the piping between hangers and stuff. And the velocity of the steam traveling over those low spots will start picking up the water.
and I'll start pushing the water into a wave and that wave will eventually seal the pipe into a water slug and that water slug becomes very high speed due to the velocity of the steam and will get pushed down the pipe until there is a change of direction of the pipe so like a 90 or something but that water slug doesn't just like whip around the 90 and keep going it's going to hit that 90 like a hammer and just
bang right into that 90. And that's what you hear when you are starting up a steam system is that bang of the like ting, ting. Some of it, some of it you may hear will be from just thermal warmup of the pipes. But if you're hearing banging and the pipes are moving, that is from water hammer. And you may be thinking to yourself, you're like, man, well, steel pipes, you know, I understand like a steel pipe isn't that flexible.
and you know, a four inch pipe, that's pretty strong. Like how much force can it be? Well, I'll tell you what, you look at a four inch steel pipe and you're like, can I bend this? Can I move this? How much movement can I give to this? Not much, because you as a human can't produce a lot of force. I'll tell you what, I was in a basement one time and there was this boiler system. I was starting up.
And it was, I was bringing it back from a failure, double failure of the boilers. And it was a pretty large building and I didn't know anything about the building as far as like where stuff was. Basically just both boilers failed. I just had to get the boilers running and I was slowly warming up the system, but I guess not slow enough. And let me tell you, that four inch pipe started banging and started swinging and
it was moving at least five feet on the hangers. And when you see four inch pipe swinging five feet one way and the other and banging,
makes you realize how much energy is in the water hammer and the steam. you know, shutting down the boilers and, you know, letting it subside and then trying to find a drain where it was banging really bad and moving this pipe. And luckily nothing broke. Everything was fine. Got the system up and running again. But yeah, there was, there was another site I used to go to all the time where
They, some reason, didn't have a drain for hundreds and hundreds of feet in this steam line. It was like an eight or 10 inch steam line that went through a cold warehouse. And yet there was a dip because the steam line went way, way up, like 30 feet went over, but then dipped down under and then ran for whatever amount, 50 feet, and then went back up so that there was a big U in it. But they didn't have any
way to remove the con say and when you when you started that system up man you cracked this like 10 inch valve on the header and just a tiny little crack in the valve and you would just hear boom boom boom and you would see this giant pipe just swinging in the ceiling. I'm like hey like is this normal. They're like yeah yeah you just got to go super slow. That's normal. Takes a while to get the system.
I'm like, this is not normal. It may be normal to you, but this is not safe. But ⁓ you're just the lowly service technician at that point. There's not much I could do. It's not like I would be able to shut down their whole facility. ⁓ We got it up and running, but it's very unnerving. And you should always be mindful of your safety. In that case, it was up above. Nobody was.
Near it and I was in a different room. You could still hear it. But like if the piping were to fail I wouldn't get hurt because I'm not in the in the vicinity of it But if I was in an enclosed room or enclosed crawlspace or a vault and there's water hammer and stuff like that Yeah, i'm out of there and that's what happened in the first video So you always need to be mindful of it and don't ever let somebody tell you that oh, that's normal that happens all the time like
you need to take calculated risk. understand everything isn't going to always be perfect, but there's a reason why you start up systems slow. So that's the first type of water hammer. The second is when steam collapses between water. So you'll get a steam bubble in a pipe and the steam will suddenly collapse and create a pressure vacuum.
and quickly draw the water together. And that water is essentially a mini explosion. That's kind of what cavitation is also in a pump, is you get little pressure bubbles and those little pressure bubbles are small collapses and vacuums and explosions inside the impeller of the pump. And it sounds like you end up pumping marbles. So how to avoid
water hammer on a steam system. Number one, go slow. So I had a college professor for controls and we were talking about steam valves and steam control and all this stuff. And he's like, the number one rule of steam. And everybody was like throwing out all this stuff. And he's like, no, number one rule is go slow. Whenever you're doing something with steam, go slow. So if you have like a large header valve and you want to close it or you want to open it on a steam line,
You open it slowly. You don't just whip a header valve closed or whip it open. ⁓ I'll tell you another story. So I was starting up a another boiler plant after a shutdown and it was only two boilers at this point, two of the four. So two are running, We were like at header pressure. But one of the boilers that it was not
cut into battery so it wasn't open to the main system, but it had gotten up to pressure. And the plant manager that was like undoing all the locks for me, he is like, ⁓ let me open this valve. And he just swung this gate valve on this chain open super quick, crazy. And I was like, no, no, no, no, no, but too late.
and the water and the pressure, the water hammer from the boiler of that instant velocity and the differential between the pressure in the boiler versus the pressure in the header created a water hammer and it blew and stretched the bonnet of the non-return valve to where
the gasket blew out and the non return started leaking like crazy. Luckily the bolts didn't shear off or the valve body didn't fail, but the, all the bolts stretched and
Essentially we had to close that gate valve again and shut down the boiler and cool it and wait for the steam pressure to go away in order to replace the non-return So that is one example of going slow when you open a system. You will also...
Notice, and they'll be on larger systems, you may have warming lines. So you'll go to a valve and it'll be like a 10 inch gate valve. And then you'll see a little like one inch bypass around the gate valve. That is a warming line. And that allows you to open up that one inch line, which is going to be a very small amount of flow versus opening up a 10 inch valve. But that warming line will start being able to warm up
or allow steam to be introduced into the downstream piping while not opening that 10 inch valve and barely cracking it so that you wear out the seat. So that is what warming lines are and they can be used a lot. They are very helpful. Not a ton of them are installed. Not a lot of people know to install them, but if you are warming up a system,
and you have to crack open a 10 inch gate valve, when you crack it, that steam is going to wear out that seat and that valve is eventually not going to seal anymore. So that's why you want to open a warming line valve and wear out that valve one if you do, but that one inch valve or whatever size that valve will be, will be able to have a smaller amount of steam flow that's controlled.
versus trying to control it with a large valve.
number two on water hammer is if you're starting up a system to avoid it.
You need to go around and manually drain all the low spots. So if you're starting up a system, you should want to open, typically all the low spots of a system have manual drain valves and you're to open up the valve, nothing's going to come out and you're going to say, there's no water. Well, stick a coat hanger or long screwdriver up there. There's probably sediment in the valve and then you'll get water to come out. And obviously make sure there's no pressure on the system. You know, we're not, we don't want live steam behind this.
but you're going to have water come out. if you drain all the low spots of the system and you make sure that there's no water coming out and then you start the boilers up or you start cracking open the valves of the system and then you start having steam come out of that drain. Now you can close the drain and you now have proved that you don't have water between the boiler and where that drain is and that you're not holding anything and
you're going to typically avoid water hammer. If you don't drain all the low spots of the system, the steam will cause all that water to eventually start moving around and it'll probably form water hammer. Now I personally have never seen a pipe or valve come apart from water hammer, but I have seen a lot of water hammer happen, but, I've also seen pictures of water hammer. So I've gotten lucky in that sense.
I've never had a failure due to water hammer, but that is not a reason to be complacent. But I would, if I could always drain at least close to the boiler room, you know, on the header and everything, if it's a drop in header, would always drain the water out of all the low spots so that I know I am starting fresh with fresh empty pipes and not.
bunch of water pooling around when I'm trying to control and warm up the system. And the number three is go slow when you're introducing the steam. this is basically what I've already said, but if you start up a boiler, you're probably going to warm up the boiler slowly due to thermal shock. But even if you have a boiler that can go zero to 105 minutes,
You don't want the boiler to zero to 105 minutes if you don't have pressure on your system. So you are going to slowly start your boiler started in low fire and slowly introduce steam to your system and slowly warm it up. This gives all the piping time to expand. This gives any little water spots time to get pushed out or pushed down the pipe into
drain spots and then go through steam traps or to get pushed out of drains that you've opened. This gives you time to go slow. If you just go 100 % and open up the valves and you're producing a ton of steam, you are now pumping a ton of energy into piping that you are not sure the state of and all that energy shock can cause thermal stress and or water hammer.
that can then pull the piping apart and find the failures of the piping. So go slow with your boilers, lock them in low fire, slowly introduce pressure to a system and you'll hear all the clinging and clacking of most systems. Some of that will be, once again, water hammer, but also some of it will be just metal moving and the thermal stress of the metal, which
is not can't really be avoided but if you were to once again just send a boiler to high fire on a cold steam system you are asking for trouble you may get away with it a bunch of times you know try to save money or the customer says hey we really need this but you will have issues you always want to start up especially larger larger facilities you always want to start them up very very slow slowly warm up this
Facility and once you start getting 20 30 psi into your piping now you can start increasing The firing rate of the boiler a little bit because now you already have a decent amount of pressure The steam is warming things up stuff is moving around any constate is moving around with that initial 10 to 20 psi Is where you're gonna find any weak spots in your piping that's
I'm not saying that you're just going to crank it to a hundred, but you can slowly increase it because some systems are a little bit bigger. And if you just have a boiler and low fire, it will never basically produce any meaningful amount of pressure in the system and you'll never get to set point. So you need to turn it up a little bit, but you're to want to go slow and don't be surprised on a super large system when it takes hours to warm it up.
correctly, but going slow and doing it right and making sure you don't have catastrophic failures is always better than going quickly and being reckless and having a catastrophic failure. But if you are looking at a new new steam system or one that you're not familiar with, you always want to examine the low spots. You want to always want to make sure your drip legs are correctly sized. There's formulas for sizing
drip legs for like your header piping and all your piping. So if you have like a 20 inch header on your steam system, you can't just tap a one inch line into the bottom of it and say, oh, the water is going to drain out the water with the velocity of the steam is just going to go right over that. Now I believe at 20 inch, you don't have to put in a line size. You only line size it up to a certain amount, but it should be at least
whatever it is, I believe it'd be like 14 inch or something like that. There's a formula, but you want to line size your drip legs up to a certain size and then it becomes a certain percentage of the piping. I don't have that in front of me right now, but that is the ⁓ most common issue with the steam system that is installed. Or if you have like a straight run on hangers or it's supported from the bottom,
And you'll see like little up and downs in the pipe that is bad because all those little up and downs, because it's not supported correctly, will cause little water pools to always form. And even if the system is on, Constate will form those water pools and eventually it'll form a big enough of a puddle that the steam will push that big puddle out and it will constantly cause water hammer and wet steam issues.
Getting water out of your steam system or getting, I guess the correct term is condensate, getting condensate and evacuating condensate out of the steam system is critical for proper steam quality.
So that's all I have for water hammer. That's a quick overview. If you didn't already know about water hammer of hydronic systems, domestic water systems, steam systems, that is water hammer. Water introduces pressure waves into piping and it will blow apart piping, especially
when you least expect it. So always be mindful of that. Never let anybody tell you that water hammer is normal because it is not. Some is to a very, very minor extent. And I don't know how to quantify that, but some of it is just unavoidable, especially when you're starting up a system and can't drain it all the way. on a working system, water hammer is not normal.
But if you are starting up a system and it starts banging pretty good and you're not able to get away from the piping, you're close to it like you're in the danger zone. Get away from the piping, stop what you're doing, shut down the steam, figure out where your water is, get it all drained out and start up slower the next time to minimize the banging of the water hammer because you do not want that piping to come apart. Trust me.
You will have a bad day. Everybody will have a bad day and the repair will take three times as long versus just doing it correctly. So if you have any comments on this episode or any other episode, please DM me on LinkedIn or email me eric.johnson at boilearn.com If you enjoyed this episode or any other episode, please rate the boiler wild podcast five stars.
I appreciate you for listening and stay wild.
