Hey Grady, at the factory I work at we had a 50,000 litre milk silo implode because the air inlet valve was blocked. It pulled a large vacuum then finally gave way. The resulting implosion blew the inward opening silo door off and dumped about 10,000 litres of milk over the production hall floor. It had to be cut into 3 sections to remove it and took 2 cranes to lift it out and replace it. All because of 1 blocked valve
On water mains they typically make it really difficult to close or open a valve quickly. If you have to turn ~50 whole turns you have to really try in order to damage anything.
Depends on the valves and the pressures you're working with. I have seen more lines blown out of the ground by slamming fire hydrants down by firemen though, you're right. But then I worked in a water system in the mountains where typical pressure was in the range of 250 psi with maximum pressures reaching 500 plus or minus. Makes things a little more interesting than most systems. Scary even sometimes. Large older lines are more prone to collapse, even slight sustained pressure drops. I was working in Chicago when they took down their intake line from the crib offshore and it collapsed in response, Oops. The cribs sit about a mile offshore at both of their plants. Luckily there was a second. Tough to replace a 750 mgd source quickly. lol
@@YoureASquidYoureAKid lol I left water system maint. 25 years ago and got into the control side contracting. But they certainly hadn't learned squat by the time I left there. We tried often to educate them but it seemed to be like throwing hand fulls of crap at a screen wall. Just never would stick. lol
Im on my last 2 quarters of chemical engineering and I have to admit, its pretty cool supplementing our material with your videos. They bring a new depth of appreciation outside of the classroom. Thank you for doing what you do, i honestly mean it. Thank you for giving me something new to appreciate every time you upload a video. PLEASE, keep posting. You're sculpting the minds of the next generation of engineering students
@crni195 I'm a chemical engineering student as well. You have no clue what chemical engineering is if you don't understand that we work a lot in fluid dynamics. Have you ever considered how many miles of piping are in a chemical plant? We don't just design chemical plants, though. Any sort of manufacturing process has chemical engineering involved.
bennyty no, definitely not, because he's going to need it in the long run. What he can do, however, is watching ad's. Instead of calling someone silly, you might want to use constructive criticism.
Don't forget, blue pvc glue is for non pressure applications like drainage or vents. Use green pvc glue for higher pressure or vacuum applications. Love the channel!
As a 6yr fire sprinkler service tech, I've known of these, but you using that crazy expensive clear PVC, really help me under stand the water vacuum so much more. Thanks man. I feel like I can now better explain to my customers what they are doing wrong. And have a vid I can direct them to.
As he said in the end of the video, yes, it is very important to close all valves on the fire trucks very slowly or you will risk breaking the pumps. Most of the trucks will be spraying water out in upwards of 100psi, so if you stop the water flow too fast you will most likely destroy every pipe on the truck and put it out of service for a few months. The only reason you should stop the flow quickly is if you start to lose control of the hose. And you did a great job explaining this, thank you from Manchester volunteer fire department
I am an volunteer firefighter from germany. Once we've made an exercise: we closed the valves from four waterhouses on the exactly same time, the house next to oure fireengine explodes! (before we closed the valves 2.050 litre/min on 12 bar pressure were gone out of the houses). On testings from the producer the houses held an minimum of 25 bar pressure. Greetings from germany (Please excuse my horrible english)
@ PreppingfürSchüler Wir können Sie verstehen und das ist wichtig, weil die meisten Menschen die Englisch sprechen immer wieder tun als ob es nicht zu verstehen wäre. Gruß von einem Nachbarn in Belgien 🇧🇪.
@@thomgt4 thank you very much for that info. I am in shock , in my country I can't even get a small stupid job as volunteer , firefighters are like the holly grail , no volunteer and they are military so big wages. I am literally in sock , I don't know what to do.
As a Water Distribution Employee for a Water Utility we have 26 different Fire Departments within our system. Education is the key. Both Paid and Volunteer Firefighters love to open fire hydrants as fast as possible and in turn slam them closed. Every year we have to remind them over and over please open them slowly and close slowly if you have water flowing. They can create a water hammer at their pumps just as easily as they can at the hydrants. We even have to teach them what the pressure relief valve is for on their Fire Engine pump panels. Since my job is repairing the breaks, I see this problem never going away I will be including this video along with the positive water hammer video to all the Fire Depts hopefully they will watch and remember why slow and steady is best. Some of our infrastructure dates back to 1880. We only use USA made products and materials. Sadly it’s becoming difficult to find products. They are considering now using products made in Israel and Australia. Thanks again for making great videos
As a fire fighter pumping an engine, I learned some interesting things related to this. Since we use an pump (not just system pressure), we have to be careful, that we “feel” how firm our supply line from the hydrant is so we can avoid pulling more water than the water system can supply. Also, fire hydrants require many turns to close the valve to prevent us accidentally opening/closing it too quickly which would cause problems for the municipality or whomever is supplying the water system. What is also interesting is that in dry sprinkler systems, we use a very small pressure of air to hold the valve closed against much higher pressures of water. It’s around 5:1 ratio. Maybe you could do a video talking about how this works?
Nolan Palmer nope, not necessarily. Sinkholes are caused by water under the surface where as most potholes are caused by water and mechanical forces at the surface.
There cannot be more than 100kPa vacuum (0kPa absolute), by definition. The gauge only reads over 100 kPa due to inertia in the gauge components. I'm surprised that small pipes would have a problem with 0kPa absolute, since the surface area is small. I would imagine large pipes would have a significant issue due to the surface area. Thoughts?
Haha yeah, that was the joke about it not being a scientific observation, but I don't think it came across quite as well as I planned ;) Anyway, the pressure in San Antonio that day was about 31.5", so it wouldn't be impossible. Yes, this is an issue with larger pipes. Most small pipes can withstand vacuum pressures because of their cross sectional geometry.
I'm a researcher in a lab that does a lot of work on implosion of thin shells (tubes), the dynamics behind it were described by von Mises, you should read his paper. It's a condition called dynamic instability. With the vacuum acting on the pipe (equivalent to saying the external pressure pushing in), there is, up to a certain pressure difference, equilibrium between the pressure potential loading the pipe and strain energy within the pipe material exists. The round shape is said to be an equilibrium configuration. After a critical threshold, more equilibrium configurations start to be valid for a particular pressure, the round shape is capable of balancing the load, but so is a flattened, deformed, imploded shape. Because multiple equilibria are valid, the pipe can arbitrarily jump from the round configuration to the flattened, which it does due to the slightest imperfection. The critical pressure is a function of the pipe wall's bending stiffness, which stores the strain energy. Smaller pipes (with smaller inside radii) can withstand much higher pressures because the internal moments set up by shear stresses have much less leverage to act over. So it's actually the larger pipes that are more susceptible to implosion.
@@PracticalEngineeringChannel I was disappointed. I wanted to see a pipe implode! Even if it was a thin plastic, but better if glass. :D :D Could also have shaved or sanded the sides of a section of pipe to see them collapse.
@@PracticalEngineeringChannel Correct. Small pipes don't care. We had a sewage pumping station rising main with 36" concrete lined steel (thinwall) pipes and large anti-vacuum valves. The valves used to suck in huge noisy gulps of air and leak sewage 'on the rebound' and the operators found the best way to prevent that was to shut them off, when all the objectionable symptoms miraculously disappeared. When I was asked to look at it I nearly had kittens. With the valves offline, those pipes were pulling almost a full vacuum on pump stop and how close they were coming to an incredibly expensive 'whump' I don't know. (And calculations didn't help much because the equations for collapse of a thinwall pipe under internal vacuum depend directly on the assumed eccentricity of the pipe wall). But I suspect it was much too close for comfort.
I think this is a channel that's actually trying to speak to "the back of the class". Your videos are so thoughtful, and very illuminating. You communicate things so plainly and supplement with visual aids when needed and it shows that you want your message to penetrate. You're a good dude.
I live in a small town with volunteer firefighters. I was working for our local newspaper as a photographer and was at a firefighter exercise, teaching the new folks how to handle the fire equipment. The Captain told me that the new pumper truck could collapse all the underground pipes from our fire hydrant system. It pulled more vacuum than the ancient water pipes could handle. He reminded me of when the town utility had to dig up several dozen feet of destroyed pipe pieces and replace them. Now they are VERY CAREFUL with that pumper truck!!!
In addition to water hammer, cavitation is also bad for fire trucks. When trying to discharge more water than you are taking in, vapor bubbles begin to form. When they enter the pump, they collapse back into liquid, and the shock of the tiny implosions chips away at the impeller blades.
Dan Teall. Had to look through a lot of comments before I found one that mentioned cavitation. I'm surprised that he didn't mention it in the video. Cavitation is a huge issue & has extreme power. It Deserves it's own video
The you tube video "Obere Wasserschlosskammer" demonstrates the amount of water that needs to dissipate to stop water hammer in a very large dam. The pressures involved with such a large system must be absolutely massive and your demonstration shows why it happens. Even though its on a small scale, it demostrates how much pressure or vacuum is actually created.
I was away from my phone, but just by listening i could visualize the whole thing and i can't believe i never thought of this phenomenon. Thank you for the information, now i know why old piping shakes sooo weird in old buildings
This is honestly one of my favorite youtube channels, I'm in my second year as a mechanical engineering major and am loving all of these cool fluid dynamics videos. Thank you!
The bubbles are not dissolved gases; it's actually steam. The boiling point of water drops with pressure, so under vacuum, water will actually boil. That's what causes cavitation - areas of low pressure cause water to vaporize, but the surrounding high pressure causes the bubbles to collapse.
Could be both! Even when you heat up water, the first thing that happens is that gases get out of solution with the water, and after that water itself gets over into a state of gas. The gases disolving from the water are the reason why you can make better tea if you properly cook the water as it becomes a better solvent by cooking.
You are both right. Some steam and some formerly dissolved gas. The steam would be condensed immediately when the pressure returned, but notice the haze of small bubbles? Not steam.
Great explanation, as a volunteer firefighter we are taught not to slam valves on trucks or hydrants, but I have never gotten a clear explanation of how the damage occurs. Thanks!
One gallon of epoxy costs about the same as one cubic yard of concrete. There are about 200 gallons in a cubic yard. The price of epoxy will have to come down by two orders of magnitude before it could be considered as a concrete replacement.
Awesome video like always!. Thank you for the very interesting follow up I always learn something from watching your videos. This is one of my favorite UA-cam channels keep up the great work!! :)
im a JHS student who has been inspired to learn more, and its from people like you who help me keep my burning curiosity burning as bright as possible, thankyou
If water is flowing through an inverted u shape tube and air bubbles are inside the stream, would the air build up at the top of the tube and eventually jam the stream or would the air gap just be pushed along the stream
It depends on the velocity of the fluid and the diameter of the tube. If the velocity of the fluid exceeds the rate at which a bubble will rise in the vertical section of tubing in still fluid, the air bubble will be pushed through. If not, it will rise to the high section of the inverter U.
For what it's worth, an experienced designer or pipe fabricator would never install a permanent system like that. If there must be a high point, an air release valve would need to be installed.
While pumping out my boat last night with a clear hose and a small electric pump I observed exactly the phenomena you describe. As the pump began to suck air, the bubbles accrued at the top of the loop and eventually blocked the flow. When I moved the pump to a deeper spot, the increased and airless flow was able to overcome the blockage and blow the bubbles through, and out of, the hose.
@@osubucks2010 Would you still need an air valve if the downstream pipe of the air valve is atmospheric/open-ended? Given that the end point is of a bit lower elevation.
Thank you for the experiment, it's been very useful to explain the possible effects it could cause this vacuum hammer in an oil refinery pipes, where there is no water but explosive and toxic fuels.
I wanted to see the pipe collapse. As a road designer though, these videos have been invaluable for the real visable examples of phenomena that have been largely theoretical until now. Look forward to your future demonstrations. Thank you.
Hey this video is really interesting to me for a completely different reason, and I wanted to share it. Massive wall of text incoming, about beer. I work with draft beer systems and often run by bar owners who reduce their gauge pressure if they start getting foaming beer problems. They think, "I'm getting too much air in my beer, so I should reduce the amount of air going into the beer." This is often the opposite of what they should be doing, and I've had a hard time articulating why. I was taught that this was wrong, that having pressure too low will cause it to be foamier, but I never understood the science behind it. Now, foaming beer can come from a variety of sources, but the main ones are human error, temperature, or pressure. If I pour some beer and it's foamy, I'll make sure the keg is nice and cold. if temp is good but it foams up when i pour it, now we dig into pressure. I've had most of this next part understood for a long time, but now I can communicate it. Pressure could be wrong for a variety of reasons, which causes issues with the dissolved CO2 in the beer. If the pressure is too high, more air will dissolve into the beer, and when you pour the beer it will experience a very large pressure drop when it leaves the tubing and hits the glass, causing it to foam or at least taste overly fizzy. This is often the case with the hand pumps that folks use at parties. If you catch it fast enough, you can fix it by releasing the pressure in the keg. otherwise, the keg becomes overcarbonated, and when set to the normal correct pressure, will act as below. If the pressure is too low, air will come out of solution as long as it is experiencing less pressure than what it was carbonated with, until it equalizes. This can take days, and if the bar moves through beer quickly then they will have a nonstop foaming issue until their pressure is fixed. Every time they shut off the faucet it closes hard, causing the vacuum air effect in the video at 3:10, and exacerbating the issue further. FYI we tell people to keep co2 between 12-14psi when the beer is at 36-38F. if you can't maintain a 38F minimum, then raise the pressure to 16-17 until over 42F. Above 42f you will have major unfixable foaming issues. if you use ice, you only need to keep the bottom of the keg iced down (The beer coupler with the handle goes into the top of the keg, but it actually draws from a tube that reaches a couple millimeters from the bottom)
Off Topic: I am looking for experimental data of simple pipes with T,p and massflow data for my master thesis. Anyone got an idea? Nice video by the way!
@@lordflufffluff This comment didn't really go anywhere, but I found data online probably a couple of weeks / days later :) now I'm working as a researcher on topics connected to the energy transition
With I had these demos 5 years ago when I started in the water field, knowing nothing of these concepts, learning about these things by word of mouth and cryptic mathematical reference manuals! Thanks. I'll be sure to share with the new hires!
True, didn't notice that line, thanks for replying! Faster instruments are probably 10x the price, not so "backyard" ;-) I was expecting a thin metal/plastic pipe that would collapse when the valve was slammed shut, just another idea for later
The return time of the wave is dependent on the length of the pipe (among other things). In a real-world sewer rising main of, say, 1000 feet in length, the pressure spikes are several seconds apart and you can easily see them on a gauge. However, it's not the negative (vacuum) spikes that are alarming, so much as the 'rebound' when the gauge needle goes off scale at +100psi and whacks against the zero stop from the wrong side :) (Yes that shouldn't happen. There was an anti-vacuum valve incorrectly set up).
Pipe engineer here - had a customer after a shutdown and drainage of pipe for maintenance try and fill the system with water from empty at full open valve and full pump. The pipe jumped about a foot and scared everyone. Luckly the pipe did not break and had sufficent flex. After the customer contacted us for a redesign they showed us the issue by turning on the pump with a full pipe. The pipe had a small vibration then settled out, no issue.
When I installed all new CPVC pipes for the kitchen and bathroom. I also used t-fittings for the bathtub and bathroom sink. Above the t-fittings I used large pipes capped off to let the air in the pipes absorb the shock when the valves were shut off.
As a pipeline hydraulics engineer who works on surge analyses daily, this video is an excellent demonstration. I’d never seen water hammer in real life before (although maybe that’s a good thing).
@2:30 You can't have a peak of more than 30 inHg of vacuum. 29.92 inHg is a perfect vacuum, or by definition, absolutely zero molecules in the area measured. The gauge spiking to over 30 inHg is just the momentum of the needle carrying it past the perfect vacuum mark. Side note: vacuum gauges are calibrated to 1 atmosphere for use on planet Earth. The only thing the gauge is measuring is pressure in relation to the pressure outside of the gauge. Hypothetically, if you pulled a perfect vacuum on Venus, the reading would peak at about 2692.8 mmHg because the atmospheric pressure on Venus is about 90 atmospheres or 90 times the average pressure on Earth. The opposite would happen on Mars where a absolute perfect vacuum would read only .177 mmHg because the atmospheric pressure on Mars is about 0.005 atmospheres. Now, pressure on Earth is not always exactly 1 atm (for which these gauges are calibrated for). If you are below sea level, it will be over 1 atm and above sea level it will start dropping off. At the summit of Mount Everest, the pressure there is approx .25 atm
Ambient air pressure was over 31" Hg that day. I made an obvious joke about how my guess was far from a scientific observation. I don't think it quite reached 30" below ambient but I think it got close.
I sort of love the fact that I didn't catch the joke in the video. It means I'm in the right place, to learn some more that I didn't know! Thanks for the video and for once, the comment section as well!
Very awesome video! How would this relate to installing new high efficiency washer/dryers that tend to shut on/off the water valve to save water (with their eco settings) - Would installing water hammer arrestors on the hot/cold spouts address the positive & negative pressures as show in this video? I just put a new washer/dryer in, and have not experienced any noises or shaking of the pipes when it runs through a cycle, i bout 2 x 20$ arrestors off amazon, but have not installed them yet - should I install them on the wall spouts or on the washer and hook the hoses up to them
The negative pressures talked about in this video are not an issue for a washer. Any arrestor device installed upstream from the valve would have no effect (on negative pressures). It is what happens after the valve that causes the negative pressure. Arrestor devices will however dampen pressure spikes cause by fast shutting valves.
It certainly wouldnt hurt to put them on if you bought them already. Some valve types are designed to shut off slowly, (Diaphragm valves with a hole of a carefully chosen size in the diaphragm) and some slam off/on (like a solenoid valve) Ive noticed some washing machines have a distinctively slow turn-off, which would reduce water hammer. Also, use the stainless braided hoses instead of the plain rubber ones to run from the wall to the machine too. When the rubber hoses fail (rubber hardens, cracks eventually) they end up bursting and dumping a lot of water. The braided stainless ones last longer as its steel rather than fiber-reinforced rubber providing the strength,.When they fail the rubber liner leaks, but as its contained by the steel, rather than bursting you get a much smaller leak which can hopefully be caught before its caused a ton of water damage. Finally, if its not in an unfinished basement where a slow leak wont hurt anything, consider a washing machine pan too. The price for all the accessory bits can add up, but $100 wont even begin to touch water damage repair if something goes wrong.
I agree with all of your information except for the hoses, all the stainless steel hoses are warrantied for 5 years, versus the rubber hoses at 7, both should be replaced at these times - i can buy the rubber ones for 1/3rd the price and set a boomerang Gmail e-mail to remind me to replace them in 6.5 years. I prefer proactive maintenance on hoses. Thank you for the information about the diaphragm valves.
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That was quite interesting, as always ! I really enjoy learning about those concepts, the clarity with which you explain them is just what I need, thanks for the great work
As a sewage pumping station designer, the negative pressures encountered on pump stop / valve closure were always a major consideration in a long rising main, and far more worry than any positive spikes on start-up. Not so much the negative pressure itself (except on very large steel mains), but the pressure drop could cause a full vacuum to appear at any high point or 'brow' in the main, creating a gap in the water column, after which all the sewage that had carried on under its own momentum would come back and slam into the fluid the other side of the gap, causing a massive pressure spike that, repeated often enough, could and did cause fatigue failures of pipelines. A pump didn't have to be stopped dead to seriously impede the flow and cause negative pressure surges. Just cutting the power would turn the pump instantly from a device propelling the flow to a severe restriction throttling the flow (as if a valve had been slammed 3/4 shut). Unlike water mains, in a sewage pumping station pump stop could happen up to 6 - 10 times per hour, so the cycles mounted up. All sorts of measures could be (and were) taken to alleviate it, including slow-stop (or VSD) on the pumps, anti-vacuum or air inlet valves into the line, check valves in parallel with the pump to allow flow to 'bypass' it, heavy flywheels between the motor and pump (that was an old-fashioned method no longer used in my time), slow-closing pump discharge valves, even a very high 'standpipe' slightly higher than the normal operating head of the system that would just allow excess to weir over back into the wet well.
Yup I was thinking the same thing, 14.7 psi = 1 atm = 29.93 inches of mercury. Vacuum is not likely to damage any pipes unless rated for no pressure or a thin walled tank like a 55 gallon drum, kinda clickbait...
@@anime2485 Just depends what your reference pressure is. If you are talking about an oil pipe 2km down on the ocean floor it's a whole 'nother ball game.
Well, is that entirely true? The way that very tall trees get water all the way to the top is through very deep negative pressures which are possible in a pure fluid environment. I'm not sure if you could recreate this effect here though
@@thomgt4 I don't think so. What you mean is probably osmosis, which can create big pressure gradients, but absolute pressure can't be less than 0 atm. Trees also start the water transport in the roots with ~ 1 atm and evaporation in the leaves leads to negative pressure - but at maximum 0 atm (but that could only transport water ~10m up) and according to the source creates an osmotic pressure at the leaf cell walls thus sucking up the water up to 100m. Source: www.scientificamerican.com/article/how-do-large-trees-such-a/
@@anime2485 Most large water mains (say over 30" diameter) are thinwall steel and can easily be collapsed by internal 'vacuum'. They usually have air valves to release trapped air but those valves also perform an even more important role of letting air in if the water pressure inside drops below atmospheric.
I used to do these sorts of calculations when I worked for a hydro-electric engineering company. When I first started the job out of college, the P.E. said to me, "When a 5-foot penstock explodes, it's a serious issue." That got my attention.
2:30 "I'm seeing a peak of over thirty inches of mercury". No, what you are seeing is the gage needle overshooting - then beginning to settle. The pressure spike is so short lived that the needle does not have time to settle to a reliable value. Watch how the needle bounces back and forth, the middle of the range of that bouncing is around 23 inches of mercury. Nowhere near "over 30 inches of mercury". BTW, 29.92 inches of mercury would be a perfect vacuum on a standard day.
Haha, Pressure was over 31 inches that day in San Antonio. I tried to make it clear that my estimation from the gauge was not a scientific observation.
My point is that you are not seeing a peak of over 30 inches but the result of needle overshoot due to the inertia of the mechanism caused by a transient spike. You can however still estimate the pressure of that spike (non scientifically) by averaging the swing of the needle.
Sorry dude, but you aren't getting more vacuum than the gauge shows. About 14.7 psi below atmospheric pressure is all there is to be had in vacuumland. Negative absolute pressure only means that you weren't quite there yet to begin with.
Pressure that day in San Antonio was about 31.5". I said in the video the peak looked like it was around 30" below atmospheric but that it wasn't a scientific observation.
*Not* PSI, Pounds per Square Inch, but inHg, or Inches of Mercury. Besides, he is *not* measuring open air or barometric pressure, he is measuring the pressure on a closed water system. You could draw vacuum on water until it starts to boil at room temperature, since water is incompressible.
That doesn't look like a gauge buffered with a fluid to absorb the momentum of the slingshot. Just because it is bouncing past 30 doesn't mean it is reaching 30. There is a bit of a whiplash going on. If you want to talk numbers please get better equipment in the future.
I'd love to see one on strength vs stability. How materials that are inherently strong (e.g. steel) are brittle due to instability, lack of bracing, like in wood joists and rafters. Nice vids thanks.
You are right about Firefighters, we try to close valves slowly. The only time Waterhammer is funny is when you send the Probie to get one off the Rig. Cool vid that earned a sub.
Excelente vídeo. Me ayudo mucho para entender sobre la importancia de instalación de válvulas de aire y válvulas para golpe de ariete Felicidades por tus aportaciones tan ilustrativas
I've always wondered why when I turn the water off in my shower I can hear the pipes rattling around in the wall...never would have guessed lol ty sir! Subscribed!
Finally! We've missed you! As for fluid motion, I think pumps would be an interesling topic to do a video on. You could show how chaining together pumps in series or in parallel affects the flow or how their effectivness is limited by cavitation.
![АЛАУДИНОВ у Скабеевой: эти их ВСУ нас НЕ ДОГОНЯТ 😁 [Пародия]](http://i.ytimg.com/vi/an0anqU4WGQ/mqdefault.jpg)
What topics are you interested in for 2018? More fluid dynamics? Reinforced concrete? Geotechnical?
Curing Concrete by refrigeration? (Like Hoover Dam)
Could you do one on fluid dynamics of gases (ventelation systems, tunnels, etc)?
Is grainlock something that might interest you ?
I like Tyzoids idear
Prestressed Concrete
Hey Grady, at the factory I work at we had a 50,000 litre milk silo implode because the air inlet valve was blocked. It pulled a large vacuum then finally gave way. The resulting implosion blew the inward opening silo door off and dumped about 10,000 litres of milk over the production hall floor. It had to be cut into 3 sections to remove it and took 2 cranes to lift it out and replace it. All because of 1 blocked valve
That is insane. Exactly the kind of failure that this video was talking about.
Makes a good case for redundancy, a few hundred for a second vacuum breaking system or a few hundred thousand for a new tank.
probably even the lost milk alone would've covered up the price of a redundent valve.
Oh boy you need some milk! lol (also did the milk spoil then you would have a loose version of cottadge cheese)
How did you fight off all the skeletons seeking calcium?
On water mains they typically make it really difficult to close or open a valve quickly. If you have to turn ~50 whole turns you have to really try in order to damage anything.
Me: "This thing takes forever!" *pulls out electric drill* 2000 rpm go brrrrr
Depends on the valves and the pressures you're working with. I have seen more lines blown out of the ground by slamming fire hydrants down by firemen though, you're right.
But then I worked in a water system in the mountains where typical pressure was in the range of 250 psi with maximum pressures reaching 500 plus or minus. Makes things a little more interesting than most systems. Scary even sometimes.
Large older lines are more prone to collapse, even slight sustained pressure drops. I was working in Chicago when they took down their intake line from the crib offshore and it collapsed in response, Oops. The cribs sit about a mile offshore at both of their plants. Luckily there was a second. Tough to replace a 750 mgd source quickly. lol
@@manueltodesschnitzel3097 I had the same thought. Hilarious
@@beebop9808 I'm always afraid whenever firefighter test fire hydrants because they always slam the fire hydrant off. They do not learn
@@YoureASquidYoureAKid lol I left water system maint. 25 years ago and got into the control side contracting. But they certainly hadn't learned squat by the time I left there. We tried often to educate them but it seemed to be like throwing hand fulls of crap at a screen wall. Just never would stick. lol
Im on my last 2 quarters of chemical engineering and I have to admit, its pretty cool supplementing our material with your videos. They bring a new depth of appreciation outside of the classroom. Thank you for doing what you do, i honestly mean it. Thank you for giving me something new to appreciate every time you upload a video. PLEASE, keep posting. You're sculpting the minds of the next generation of engineering students
crni195 if you knew anything about design engineering, you would know they do process and system design.
crni195 are you saying that chemical engineers have no real purpose?
Who cares what kinda of engineering he does, he obviously just enjoys learning.
+zachell1991 This.
@crni195 I'm a chemical engineering student as well. You have no clue what chemical engineering is if you don't understand that we work a lot in fluid dynamics. Have you ever considered how many miles of piping are in a chemical plant? We don't just design chemical plants, though. Any sort of manufacturing process has chemical engineering involved.
I would have liked a practical demonstration of the implosion.
I too, was hoping to see a weak piece of pipe imploded from the negative pressure.
xWood4000 ... indeed, the title sort of implied that was going to happen.
That's what caught my attention. I never thought it was an issue, at least in the residential scope I was considering.
There's a crack on the pipe...
instead you got click bait lol
Since I'm a student with no money I can't donate, but I think your channel is great. Def thumbs up every time.
If you have no money that you can't donate that means you should just donate your excess money silly.
bennyty no, definitely not, because he's going to need it in the long run. What he can do, however, is watching ad's. Instead of calling someone silly, you might want to use constructive criticism.
Don't worry bennyty, I understood your joke.
You’re donating by giving him views and likes and clicking subscribe button
Don't forget, blue pvc glue is for non pressure applications like drainage or vents. Use green pvc glue for higher pressure or vacuum applications. Love the channel!
As a 6yr fire sprinkler service tech, I've known of these, but you using that crazy expensive clear PVC, really help me under stand the water vacuum so much more. Thanks man. I feel like I can now better explain to my customers what they are doing wrong. And have a vid I can direct them to.
As he said in the end of the video, yes, it is very important to close all valves on the fire trucks very slowly or you will risk breaking the pumps. Most of the trucks will be spraying water out in upwards of 100psi, so if you stop the water flow too fast you will most likely destroy every pipe on the truck and put it out of service for a few months. The only reason you should stop the flow quickly is if you start to lose control of the hose. And you did a great job explaining this, thank you from Manchester volunteer fire department
And you just solved a mental issue I've had with how fluid dynamics works... Thank You!
I am an volunteer firefighter from germany. Once we've made an exercise: we closed the valves from four waterhouses on the exactly same time, the house next to oure fireengine explodes! (before we closed the valves 2.050 litre/min on 12 bar pressure were gone out of the houses). On testings from the producer the houses held an minimum of 25 bar pressure.
Greetings from germany
(Please excuse my horrible english)
Your English is fine, there are lot's of native speakers that generally have a lower standard when typing
In germany , you can volunteer??
@ PreppingfürSchüler Wir können Sie verstehen und das ist wichtig, weil die meisten Menschen die Englisch sprechen immer wieder tun als ob es nicht zu verstehen wäre. Gruß von einem Nachbarn in Belgien 🇧🇪.
@@Hi.Al. yeah you can, in the small towns the fire fighters usually are just volunteers
@@thomgt4 thank you very much for that info. I am in shock , in my country I can't even get a small stupid job as volunteer , firefighters are like the holly grail , no volunteer and they are military so big wages. I am literally in sock , I don't know what to do.
As a Water Distribution Employee for a Water Utility we have 26 different Fire Departments within our system. Education is the key. Both Paid and Volunteer Firefighters love to open fire hydrants as fast as possible and in turn slam them closed. Every year we have to remind them over and over please open them slowly and close slowly if you have water flowing. They can create a water hammer at their pumps just as easily as they can at the hydrants. We even have to teach them what the pressure relief valve is for on their Fire Engine pump panels. Since my job is repairing the breaks, I see this problem never going away I will be including this video along with the positive water hammer video to all the Fire Depts hopefully they will watch and remember why slow and steady is best. Some of our infrastructure dates back to 1880. We only use USA made products and materials. Sadly it’s becoming difficult to find products. They are considering now using products made in Israel and Australia. Thanks again for making great videos
Forms of concrete failure? ( too much sand or gravel, not enough curing time, etc)
TheMr77469 or over use of a concrete vibrators or not mixed properly
TheMr77469
And for dessert - misplaced reinforcement bars?
Also, in construction in cold climates, concrete that froze before it fully cured, and later thawed.
"No offense to the backyard scientists" says the guy literally doing science in his backyard :)
Great video btw!
Matthew Shultz I think that’s a reference to the UA-cam channel by that name.
Tony Yarusso ohhhh that makes more sense
As a fire fighter pumping an engine, I learned some interesting things related to this. Since we use an pump (not just system pressure), we have to be careful, that we “feel” how firm our supply line from the hydrant is so we can avoid pulling more water than the water system can supply. Also, fire hydrants require many turns to close the valve to prevent us accidentally opening/closing it too quickly which would cause problems for the municipality or whomever is supplying the water system. What is also interesting is that in dry sprinkler systems, we use a very small pressure of air to hold the valve closed against much higher pressures of water. It’s around 5:1 ratio. Maybe you could do a video talking about how this works?
I found this channel a couple of months ago, and every time I watch a video, I can't believe how cool it is. You're doing a fantastic job, Grady!
What about one on the formation of potholes?
Also 'washboards' for those who drive on dirt and gravel roads... and things that you can do to mitigate them (Mag chloride, various other binders)
He did one on sinkholes. Not sure if those are the same concept.
Nolan Palmer nope, not necessarily.
Sinkholes are caused by water under the surface where as most potholes are caused by water and mechanical forces at the surface.
saihenjin www.korresproject.gr
Water gets in road, water freezes, water expands, water breaks road
There cannot be more than 100kPa vacuum (0kPa absolute), by definition. The gauge only reads over 100 kPa due to inertia in the gauge components.
I'm surprised that small pipes would have a problem with 0kPa absolute, since the surface area is small. I would imagine large pipes would have a significant issue due to the surface area. Thoughts?
Haha yeah, that was the joke about it not being a scientific observation, but I don't think it came across quite as well as I planned ;) Anyway, the pressure in San Antonio that day was about 31.5", so it wouldn't be impossible. Yes, this is an issue with larger pipes. Most small pipes can withstand vacuum pressures because of their cross sectional geometry.
I'm a researcher in a lab that does a lot of work on implosion of thin shells (tubes), the dynamics behind it were described by von Mises, you should read his paper. It's a condition called dynamic instability. With the vacuum acting on the pipe (equivalent to saying the external pressure pushing in), there is, up to a certain pressure difference, equilibrium between the pressure potential loading the pipe and strain energy within the pipe material exists. The round shape is said to be an equilibrium configuration. After a critical threshold, more equilibrium configurations start to be valid for a particular pressure, the round shape is capable of balancing the load, but so is a flattened, deformed, imploded shape. Because multiple equilibria are valid, the pipe can arbitrarily jump from the round configuration to the flattened, which it does due to the slightest imperfection. The critical pressure is a function of the pipe wall's bending stiffness, which stores the strain energy. Smaller pipes (with smaller inside radii) can withstand much higher pressures because the internal moments set up by shear stresses have much less leverage to act over. So it's actually the larger pipes that are more susceptible to implosion.
@@PracticalEngineeringChannel I was disappointed. I wanted to see a pipe implode! Even if it was a thin plastic, but better if glass. :D :D Could also have shaved or sanded the sides of a section of pipe to see them collapse.
@@PracticalEngineeringChannel Correct. Small pipes don't care. We had a sewage pumping station rising main with 36" concrete lined steel (thinwall) pipes and large anti-vacuum valves. The valves used to suck in huge noisy gulps of air and leak sewage 'on the rebound' and the operators found the best way to prevent that was to shut them off, when all the objectionable symptoms miraculously disappeared. When I was asked to look at it I nearly had kittens. With the valves offline, those pipes were pulling almost a full vacuum on pump stop and how close they were coming to an incredibly expensive 'whump' I don't know. (And calculations didn't help much because the equations for collapse of a thinwall pipe under internal vacuum depend directly on the assumed eccentricity of the pipe wall). But I suspect it was much too close for comfort.
Years ago, we used to "water hammer" our house via its upstairs bathroom lever-action faucet. We never popped the pipes, but it was fun. Cheers!
I think this is a channel that's actually trying to speak to "the back of the class". Your videos are so thoughtful, and very illuminating. You communicate things so plainly and supplement with visual aids when needed and it shows that you want your message to penetrate. You're a good dude.
I live in a small town with volunteer firefighters. I was working for our local newspaper as a photographer and was at a firefighter exercise, teaching the new folks how to handle the fire equipment.
The Captain told me that the new pumper truck could collapse all the underground pipes from our fire hydrant system.
It pulled more vacuum than the ancient water pipes could handle. He reminded me of when the town utility had to dig up several dozen feet of destroyed pipe pieces and replace them.
Now they are VERY CAREFUL with that pumper truck!!!
In addition to water hammer, cavitation is also bad for fire trucks. When trying to discharge more water than you are taking in, vapor bubbles begin to form. When they enter the pump, they collapse back into liquid, and the shock of the tiny implosions chips away at the impeller blades.
Dan Teall. Had to look through a lot of comments before I found one that mentioned cavitation. I'm surprised that he didn't mention it in the video. Cavitation is a huge issue & has extreme power. It Deserves it's own video
Seen a few sewage pump impellers 'eaten' by cavitation.
The you tube video "Obere Wasserschlosskammer" demonstrates the amount of water that needs to dissipate to stop water hammer in a very large dam. The pressures involved with such a large system must be absolutely massive and your demonstration shows why it happens. Even though its on a small scale, it demostrates how much pressure or vacuum is actually created.
I was away from my phone, but just by listening i could visualize the whole thing and i can't believe i never thought of this phenomenon.
Thank you for the information, now i know why old piping shakes sooo weird in old buildings
This is honestly one of my favorite youtube channels, I'm in my second year as a mechanical engineering major and am loving all of these cool fluid dynamics videos. Thank you!
The bubbles are not dissolved gases; it's actually steam. The boiling point of water drops with pressure, so under vacuum, water will actually boil. That's what causes cavitation - areas of low pressure cause water to vaporize, but the surrounding high pressure causes the bubbles to collapse.
Could be both!
Even when you heat up water, the first thing that happens is that gases get out of solution with the water, and after that water itself gets over into a state of gas. The gases disolving from the water are the reason why you can make better tea if you properly cook the water as it becomes a better solvent by cooking.
You are both right. Some steam and some formerly dissolved gas. The steam would be condensed immediately when the pressure returned, but notice the haze of small bubbles? Not steam.
Great explanation, as a volunteer firefighter we are taught not to slam valves on trucks or hydrants, but I have never gotten a clear explanation of how the damage occurs. Thanks!
This is absolutely fascinating.
Please do a video about epoxy resin's engineering properties and if it might eventually replace concrete.
this. i always wonder about this when i see people using resin in their wood works.
One gallon of epoxy costs about the same as one cubic yard of concrete. There are about 200 gallons in a cubic yard. The price of epoxy will have to come down by two orders of magnitude before it could be considered as a concrete replacement.
there's no way resin is going to replace concrete
What a loaded question dude
+Harman Robotics Or the price of concrete would have to go up by two orders of magnitude :P
This is so interesting! I love your channel. When ever I watch your videos I always learn something new!!!
Gradys a youtuber who has an acute awareness of youtube itself. Thats one of the reasons I love this channel.
Fantastic demo ! The gasses coming out of solution near the valve was amazing. Messrs Boyle and Charles would be proud of you ! 🇬🇧👍
I love these videos. Never stop.
Bobby Patton
Water hammer FOREVER 😜
Do ram pump
Excellent demonstration; good for anyone working with piping, fluids, the home plumbers...!
excellent video. this is exactly why we open and close valve SLOWLY! LADWP regulators here and LAFD please don't touch our valves!! keep them coming.
Awesome video like always!. Thank you for the very interesting follow up I always learn something from watching your videos. This is one of my favorite UA-cam channels keep up the great work!! :)
@2:50 I think the haze is actually vaporization of water due low pressure(cavitation), not dissolved gases
I don't think the pressure got quite that low.
Imran is correct. The guage clearly shows that momentarily pressure dropped below 10kPa, water vaporize into steam at room temp.
im a JHS student who has been inspired to learn more, and its from people like you who help me keep my burning curiosity burning as bright as possible, thankyou
I would REALLY have liked a practical demonstration of the implosion
Grady, you make really cool videos. I really like learning from them. :D
If water is flowing through an inverted u shape tube and air bubbles are inside the stream, would the air build up at the top of the tube and eventually jam the stream or would the air gap just be pushed along the stream
The Spherical Earth the air would just be pushed through
It depends on the velocity of the fluid and the diameter of the tube. If the velocity of the fluid exceeds the rate at which a bubble will rise in the vertical section of tubing in still fluid, the air bubble will be pushed through. If not, it will rise to the high section of the inverter U.
For what it's worth, an experienced designer or pipe fabricator would never install a permanent system like that. If there must be a high point, an air release valve would need to be installed.
While pumping out my boat last night with a clear hose and a small electric pump I observed exactly the phenomena you describe. As the pump began to suck air, the bubbles accrued at the top of the loop and eventually blocked the flow. When I moved the pump to a deeper spot, the increased and airless flow was able to overcome the blockage and blow the bubbles through, and out of, the hose.
@@osubucks2010 Would you still need an air valve if the downstream pipe of the air valve is atmospheric/open-ended? Given that the end point is of a bit lower elevation.
Thank you for the experiment, it's been very useful to explain the possible effects it could cause this vacuum hammer in an oil refinery pipes, where there is no water but explosive and toxic fuels.
I wanted to see the pipe collapse. As a road designer though, these videos have been invaluable for the real visable examples of phenomena that have been largely theoretical until now. Look forward to your future demonstrations. Thank you.
Your channel is getting huge, and that makes me very happy ^_^
Is it pulling out dissolved gasses or is the water briefly boiling due to the vacuum?
I'm not sure what 57 people have to dislike about this. This is good stuff, I don't see a lot about fluid mechanics like this on YT.
Hey this video is really interesting to me for a completely different reason, and I wanted to share it. Massive wall of text incoming, about beer.
I work with draft beer systems and often run by bar owners who reduce their gauge pressure if they start getting foaming beer problems. They think, "I'm getting too much air in my beer, so I should reduce the amount of air going into the beer." This is often the opposite of what they should be doing, and I've had a hard time articulating why. I was taught that this was wrong, that having pressure too low will cause it to be foamier, but I never understood the science behind it.
Now, foaming beer can come from a variety of sources, but the main ones are human error, temperature, or pressure. If I pour some beer and it's foamy, I'll make sure the keg is nice and cold. if temp is good but it foams up when i pour it, now we dig into pressure.
I've had most of this next part understood for a long time, but now I can communicate it.
Pressure could be wrong for a variety of reasons, which causes issues with the dissolved CO2 in the beer. If the pressure is too high, more air will dissolve into the beer, and when you pour the beer it will experience a very large pressure drop when it leaves the tubing and hits the glass, causing it to foam or at least taste overly fizzy. This is often the case with the hand pumps that folks use at parties. If you catch it fast enough, you can fix it by releasing the pressure in the keg. otherwise, the keg becomes overcarbonated, and when set to the normal correct pressure, will act as below.
If the pressure is too low, air will come out of solution as long as it is experiencing less pressure than what it was carbonated with, until it equalizes. This can take days, and if the bar moves through beer quickly then they will have a nonstop foaming issue until their pressure is fixed. Every time they shut off the faucet it closes hard, causing the vacuum air effect in the video at 3:10, and exacerbating the issue further.
FYI we tell people to keep co2 between 12-14psi when the beer is at 36-38F. if you can't maintain a 38F minimum, then raise the pressure to 16-17 until over 42F. Above 42f you will have major unfixable foaming issues. if you use ice, you only need to keep the bottom of the keg iced down (The beer coupler with the handle goes into the top of the keg, but it actually draws from a tube that reaches a couple millimeters from the bottom)
I spend most of my days fixing the damage caused by this phenomenon
Off Topic: I am looking for experimental data of simple pipes with T,p and massflow data for my master thesis. Anyone got an idea? Nice video by the way!
How did it go?
I am an engineering student.
@@lordflufffluff This comment didn't really go anywhere, but I found data online probably a couple of weeks / days later :) now I'm working as a researcher on topics connected to the energy transition
@@eL3ctric cool.
@@eL3ctric Look at Geberit Mapress datasheet.
@@garagentor1855 oh shoot! So close man! Only three years behind
Very very sincere outro. I'm not a patreon supporter but now I want to be. You're doing good things Grady, THANK YOU.
With I had these demos 5 years ago when I started in the water field, knowing nothing of these concepts, learning about these things by word of mouth and cryptic mathematical reference manuals! Thanks. I'll be sure to share with the new hires!
Doesn't your mechanical gauge suffer from momentum effects? It looks like it's minimum time to get a reading isn't fast enough to measure this
Yes definitely. That’s why I joked about it not being a scientific observation
True, didn't notice that line, thanks for replying! Faster instruments are probably 10x the price, not so "backyard" ;-) I was expecting a thin metal/plastic pipe that would collapse when the valve was slammed shut, just another idea for later
The return time of the wave is dependent on the length of the pipe (among other things). In a real-world sewer rising main of, say, 1000 feet in length, the pressure spikes are several seconds apart and you can easily see them on a gauge. However, it's not the negative (vacuum) spikes that are alarming, so much as the 'rebound' when the gauge needle goes off scale at +100psi and whacks against the zero stop from the wrong side :)
(Yes that shouldn't happen. There was an anti-vacuum valve incorrectly set up).
Appliance solenoid valves open and close very quickly, like in a dishwasher or washing machine.
It's all fine when you have enough of a buffer to prevent damage. Long lengths of flexible pipes are great accumulators
Pipe engineer here - had a customer after a shutdown and drainage of pipe for maintenance try and fill the system with water from empty at full open valve and full pump. The pipe jumped about a foot and scared everyone. Luckly the pipe did not break and had sufficent flex. After the customer contacted us for a redesign they showed us the issue by turning on the pump with a full pipe. The pipe had a small vibration then settled out, no issue.
Excellent !
I wouldn't have thought that the negative pressure gets to 1 bar. Thank's for another great video. :)
That sound title's crooked on purpose?
All I paid attention to was the crooked pieces of acoustic foam.
When I installed all new CPVC pipes for the kitchen and bathroom. I also used t-fittings for the bathtub and bathroom sink. Above the t-fittings I used large pipes capped off to let the air in the pipes absorb the shock when the valves were shut off.
As a pipeline hydraulics engineer who works on surge analyses daily, this video is an excellent demonstration. I’d never seen water hammer in real life before (although maybe that’s a good thing).
@2:30 You can't have a peak of more than 30 inHg of vacuum. 29.92 inHg is a perfect vacuum, or by definition, absolutely zero molecules in the area measured. The gauge spiking to over 30 inHg is just the momentum of the needle carrying it past the perfect vacuum mark.
Side note: vacuum gauges are calibrated to 1 atmosphere for use on planet Earth. The only thing the gauge is measuring is pressure in relation to the pressure outside of the gauge. Hypothetically, if you pulled a perfect vacuum on Venus, the reading would peak at about 2692.8 mmHg because the atmospheric pressure on Venus is about 90 atmospheres or 90 times the average pressure on Earth. The opposite would happen on Mars where a absolute perfect vacuum would read only .177 mmHg because the atmospheric pressure on Mars is about 0.005 atmospheres. Now, pressure on Earth is not always exactly 1 atm (for which these gauges are calibrated for). If you are below sea level, it will be over 1 atm and above sea level it will start dropping off. At the summit of Mount Everest, the pressure there is approx .25 atm
Ambient air pressure was over 31" Hg that day. I made an obvious joke about how my guess was far from a scientific observation. I don't think it quite reached 30" below ambient but I think it got close.
I sort of love the fact that I didn't catch the joke in the video. It means I'm in the right place, to learn some more that I didn't know! Thanks for the video and for once, the comment section as well!
Very awesome video! How would this relate to installing new high efficiency washer/dryers that tend to shut on/off the water valve to save water (with their eco settings) - Would installing water hammer arrestors on the hot/cold spouts address the positive & negative pressures as show in this video? I just put a new washer/dryer in, and have not experienced any noises or shaking of the pipes when it runs through a cycle, i bout 2 x 20$ arrestors off amazon, but have not installed them yet - should I install them on the wall spouts or on the washer and hook the hoses up to them
The negative pressures talked about in this video are not an issue for a washer. Any arrestor device installed upstream from the valve would have no effect (on negative pressures). It is what happens after the valve that causes the negative pressure. Arrestor devices will however dampen pressure spikes cause by fast shutting valves.
It certainly wouldnt hurt to put them on if you bought them already. Some valve types are designed to shut off slowly, (Diaphragm valves with a hole of a carefully chosen size in the diaphragm) and some slam off/on (like a solenoid valve) Ive noticed some washing machines have a distinctively slow turn-off, which would reduce water hammer.
Also, use the stainless braided hoses instead of the plain rubber ones to run from the wall to the machine too. When the rubber hoses fail (rubber hardens, cracks eventually) they end up bursting and dumping a lot of water. The braided stainless ones last longer as its steel rather than fiber-reinforced rubber providing the strength,.When they fail the rubber liner leaks, but as its contained by the steel, rather than bursting you get a much smaller leak which can hopefully be caught before its caused a ton of water damage. Finally, if its not in an unfinished basement where a slow leak wont hurt anything, consider a washing machine pan too. The price for all the accessory bits can add up, but $100 wont even begin to touch water damage repair if something goes wrong.
I agree with all of your information except for the hoses, all the stainless steel hoses are warrantied for 5 years, versus the rubber hoses at 7, both should be replaced at these times - i can buy the rubber ones for 1/3rd the price and set a boomerang Gmail e-mail to remind me to replace them in 6.5 years. I prefer proactive maintenance on hoses. Thank you for the information about the diaphragm valves.
Thanks for shouting out my profession dude! Water hammer and not slamming valves shut was hammered into our heads day 1 of fire academy
as an architecture student some of your video really interest me. please make more that has some connection with the field of architecture.
Phenomenon... dooo dooooo do do doo... Phenomenon? ...dooo do do dooo... Phenomenon! ... Doo do doo-do-do doo-do-do dooo do-do doo-do-do daaah da-da-dada-daaaa!
I was going to have a comment like this!
I’m glad someone else thought the same thing!
That's my saying everytime I hear that word! Like mahnamana.
Why Picard...why.
Treblaine -- So, this is the "Phenomenal man"? Haaah! I love it
I've seen a similar effect where there will be a big bubble trapped in the hose before it gets forcefully pushed out by the outgoing water
That was quite interesting, as always !
I really enjoy learning about those concepts, the clarity with which you explain them is just what I need, thanks for the great work
As a sewage pumping station designer, the negative pressures encountered on pump stop / valve closure were always a major consideration in a long rising main, and far more worry than any positive spikes on start-up. Not so much the negative pressure itself (except on very large steel mains), but the pressure drop could cause a full vacuum to appear at any high point or 'brow' in the main, creating a gap in the water column, after which all the sewage that had carried on under its own momentum would come back and slam into the fluid the other side of the gap, causing a massive pressure spike that, repeated often enough, could and did cause fatigue failures of pipelines.
A pump didn't have to be stopped dead to seriously impede the flow and cause negative pressure surges. Just cutting the power would turn the pump instantly from a device propelling the flow to a severe restriction throttling the flow (as if a valve had been slammed 3/4 shut). Unlike water mains, in a sewage pumping station pump stop could happen up to 6 - 10 times per hour, so the cycles mounted up.
All sorts of measures could be (and were) taken to alleviate it, including slow-stop (or VSD) on the pumps, anti-vacuum or air inlet valves into the line, check valves in parallel with the pump to allow flow to 'bypass' it, heavy flywheels between the motor and pump (that was an old-fashioned method no longer used in my time), slow-closing pump discharge valves, even a very high 'standpipe' slightly higher than the normal operating head of the system that would just allow excess to weir over back into the wet well.
the gauge is tricking you. you literally can't pull more than 30 in\hg of vacuum as that's literally a perfect vacuum.
Yup I was thinking the same thing, 14.7 psi = 1 atm = 29.93 inches of mercury. Vacuum is not likely to damage any pipes unless rated for no pressure or a thin walled tank like a 55 gallon drum, kinda clickbait...
@@anime2485 Just depends what your reference pressure is. If you are talking about an oil pipe 2km down on the ocean floor it's a whole 'nother ball game.
Well, is that entirely true? The way that very tall trees get water all the way to the top is through very deep negative pressures which are possible in a pure fluid environment. I'm not sure if you could recreate this effect here though
@@thomgt4 I don't think so. What you mean is probably osmosis, which can create big pressure gradients, but absolute pressure can't be less than 0 atm. Trees also start the water transport in the roots with ~ 1 atm and evaporation in the leaves leads to negative pressure - but at maximum 0 atm (but that could only transport water ~10m up) and according to the source creates an osmotic pressure at the leaf cell walls thus sucking up the water up to 100m.
Source: www.scientificamerican.com/article/how-do-large-trees-such-a/
@@anime2485 Most large water mains (say over 30" diameter) are thinwall steel and can easily be collapsed by internal 'vacuum'. They usually have air valves to release trapped air but those valves also perform an even more important role of letting air in if the water pressure inside drops below atmospheric.
You may not be wasting water, but you're wasting 50 feet of garden hose :P
I hope he had surge reducers between the house and the valve in the video
I'd love to see some of these experiments redone with softer and thinner piping; raw numbers just dont hit the same as seeing a hose explode
I used to do these sorts of calculations when I worked for a hydro-electric engineering company. When I first started the job out of college, the P.E. said to me, "When a 5-foot penstock explodes, it's a serious issue."
That got my attention.
2:30 "I'm seeing a peak of over thirty inches of mercury". No, what you are seeing is the gage needle overshooting - then beginning to settle. The pressure spike is so short lived that the needle does not have time to settle to a reliable value. Watch how the needle bounces back and forth, the middle of the range of that bouncing is around 23 inches of mercury. Nowhere near "over 30 inches of mercury". BTW, 29.92 inches of mercury would be a perfect vacuum on a standard day.
Haha, Pressure was over 31 inches that day in San Antonio. I tried to make it clear that my estimation from the gauge was not a scientific observation.
My point is that you are not seeing a peak of over 30 inches but the result of needle overshoot due to the inertia of the mechanism caused by a transient spike. You can however still estimate the pressure of that spike (non scientifically) by averaging the swing of the needle.
Sorry dude, but you aren't getting more vacuum than the gauge shows. About 14.7 psi below atmospheric pressure is all there is to be had in vacuumland. Negative absolute pressure only means that you weren't quite there yet to begin with.
Pressure that day in San Antonio was about 31.5". I said in the video the peak looked like it was around 30" below atmospheric but that it wasn't a scientific observation.
*Not* PSI, Pounds per Square Inch, but inHg, or Inches of Mercury. Besides, he is *not* measuring open air or barometric pressure, he is measuring the pressure on a closed water system. You could draw vacuum on water until it starts to boil at room temperature, since water is incompressible.
That doesn't look like a gauge buffered with a fluid to absorb the momentum of the slingshot. Just because it is bouncing past 30 doesn't mean it is reaching 30. There is a bit of a whiplash going on. If you want to talk numbers please get better equipment in the future.
What if you sponsored him instead of just complaining. The idea of this video is not exact digits but getting the idea. Moron
Charles Cox .
As a plumber I have used these videos to educate apprentices and start a dialogue . Great work.
I'd love to see one on strength vs stability. How materials that are inherently strong (e.g. steel) are brittle due to instability, lack of bracing, like in wood joists and rafters. Nice vids thanks.
Really liked this follow up. Fluid dynamics are fascinating to me, but really, seems like anything you make a video on is interesting.
I have a manual toilet valve and I have been closing it decently fast. Glad I read this to save the pipes!
You are right about Firefighters, we try to close valves slowly. The only time Waterhammer is funny is when you send the Probie to get one off the Rig. Cool vid that earned a sub.
i think these videos need to be much longer, you are a great presenter and teacher !
Thanks for the follow up! It was great to see what happens to the other side of a closing valve.
This video will help me save alot of money on equipment thank you man for a bit of physics.
Thank you, I'm a retired fire fighter instructor and this is an excellent explanation.
Excelente vídeo. Me ayudo mucho para entender sobre la importancia de instalación de válvulas de aire y válvulas para golpe de ariete Felicidades por tus aportaciones tan ilustrativas
Collapsing a pipe with a valve, sounds like a summary of a first date.
More fluid mechanics. Your channel is just delightful.
Oh my god, I just watched this video, and I really appreciate You walking along the 50-foot garden hose.
The water hammering videos have been fascinating!
I just love how every single one of your video are so fascinating
I've always wondered why when I turn the water off in my shower I can hear the pipes rattling around in the wall...never would have guessed lol ty sir! Subscribed!
You’re providing valuable information in a top tier presentation
Nice shoutout to FloridaMan aka The Backyard Scientist! Mutual subscriber here.
That's what I like to see, two problems and two solutions. Excellent! Thank you.
Love your videos!! They make my 40 min drive everyday more enjoyable by being able to learn more about topics I have been curious about. Thanks!
Man you got my sub when you showed the credits. to give credit to everyone evolved says alot.
Great engineering practicals with demonstrations..
Finally! We've missed you!
As for fluid motion, I think pumps would be an interesling topic to do a video on. You could show how chaining together pumps in series or in parallel affects the flow or how their effectivness is limited by cavitation.
Great explanations. I am glad there are people like you on youtube instead of all those prank videos . Keep going!
All your vids are clear, pertinent and we'll presented.
Very good to know, heard about vacuum breakers for steam systems