00:00:00.250 --> 00:00:05.520 You may know that most liquids are non-pressureable (or barely less pressure), which means no matter how much pressure you use, their volume does not change. 00:00:05.520 --> 00:00:09.830 00:00:09.830 --> 00:00:14.929 This may be really useful, as is the case with hydraulic cylinders, but this lack of "pulse" 00:00:14.929 --> 00:00:18.480 It can also lead to catastrophic failure of piping systems. 00:00:18.480 --> 00:00:22.170 Hello, I am Grady, and this is practical engineering. 00:00:22.170 --> 00:00:27.180 In today's episode, we are talking about hydraulic transmission, also known as a water hammer 00:00:27.180 --> 00:00:28.200 00:00:46.240 --> 00:00:50.860 It is easy to forget the heavy water volume because we hardly carry more than a few small amounts at a time. 00:00:50.860 --> 00:00:52.770 00:00:52.770 --> 00:00:57.220 But if you add water to your city pipelines or even just pipes in your home, it forms a very large mass. 00:00:57.220 --> 00:00:59.800 But if water is pumped into your city pipelines or even just pipes in your home, it forms a very large mass. 00:00:59.810 --> 00:01:05.080 And when all that water moves through a tube, it has a lot of momentum. 00:01:05.089 --> 00:01:10.490 If you stop this movement suddenly - for example, by closing the valve quickly - this momentum will have nowhere to go. 00:01:10.490 --> 00:01:12.450 00:01:12.450 --> 00:01:16.850 Since the water is not compressed or pulsed, it cannot be diluted. 00:01:16.850 --> 00:01:20.360 It may collide with concrete in the back of the valve and the tube walls. 00:01:20.360 --> 00:01:21.530 00:01:21.530 --> 00:01:26.840 Instead of being absorbed, this sudden change in momentum creates an increase in pressure that is transmitted as a shock event through the tube. 00:01:26.840 --> 00:01:29.350 00:01:29.350 --> 00:01:33.860 Sometimes, you will hear a shocking sound like percussion in your walls when you shut off a faucet or turn on the washing machine, hence the name Super Hamo-esque, Water Hammer. 00:01:33.860 --> 00:01:39.979 00:01:39.979 --> 00:01:45.020 Huge tubes inside your walls may look a little scary 00:01:45.020 --> 00:01:49.810 But for pipes with a large diameter that can reach hundreds of kilometers in length 00:01:49.810 --> 00:01:51.409 The increased pressure from momentum change can cause significant damage. 00:01:51.409 --> 00:01:56.240 Let's do a quick calculation: if you have a pipeline that carries water with a diameter of one meter and runs for a distance of 100 km (fairly medium-sized pipeline) 00:01:56.240 --> 00:02:02.420 , The water mass in the tube is about 80 million kilograms. 00:02:02.420 --> 00:02:05.229 00:02:05.229 --> 00:02:06.750 This is a great weight 00:02:06.750 --> 00:02:10.250 In fact, this is equivalent to about 10 freight trains. 00:02:10.250 --> 00:02:15.480 Imagine that you are the operator of the end of this pipeline and responsible for closing the valve. 00:02:15.480 --> 00:02:20.040 If you close it quickly, these trains basically collide with a brick wall. 00:02:20.040 --> 00:02:24.590 The change in pressure resulting from this sudden change in momentum can cause the tube to rupture or cause severe damage to other parts of the system. 00:02:24.590 --> 00:02:28.350 00:02:28.350 --> 00:02:32.760 In fact, there is another term when a large pressure burst occurs that causes a closed container to rupture: as a bomb. 00:02:32.760 --> 00:02:34.840 00:02:34.840 --> 00:02:36.940 The water hammer can be equally dangerous. 00:02:36.940 --> 00:02:41.370 So, how do engineers design piping systems to avoid this situation? 00:02:41.370 --> 00:02:44.140 Let's create a typical pipeline and find out. 00:02:44.140 --> 00:02:45.310 Here is my equipment. 00:02:45.310 --> 00:02:51.610 We have about 100 feet (30 meters) of water-related PVC pipes on one side and valve on the other. 00:02:51.610 --> 00:02:52.910 00:02:52.910 --> 00:02:57.819 I also have an analog and digital scale so we can figure out how to change pressure in a clear section of tubes in case anything exciting happens there. 00:02:57.819 --> 00:03:01.349 A clear section of the tubes in case anything exciting happens there. I mean exciting civil engineering, not like well-known excitement. 00:03:01.349 --> 00:03:05.690 00:03:05.690 --> 00:03:07.860 Watch what happens when this valve is closed. 00:03:07.860 --> 00:03:13.069 It doesn't look like much from the outside, but look at the data from the pressure gauge. 00:03:13.069 --> 00:03:17.620 The pressure rises to more than 2000 kPa or 300 psi. 00:03:17.620 --> 00:03:20.910 This is about 5 times the pressure of hard water. 00:03:20.910 --> 00:03:26.040 It is not enough to break the tube, it is more than enough to break this pressure gauge. 00:03:26.040 --> 00:03:30.910 You can see why the design of a pipeline or pipeline network can be more complex than it seems. 00:03:30.910 --> 00:03:31.980 00:03:31.980 --> 00:03:36.400 These pressure surges can be transmitted through a system in complex ways. 00:03:36.400 --> 00:03:41.230 But we can use this simple demonstration to show a few of the ways that engineers use to mitigate potential damage from a water hammer. 00:03:41.230 --> 00:03:43.930 00:03:43.930 --> 00:03:47.220 This is the equation for the hammer pulse pressure profile. 00:03:47.220 --> 00:03:52.720 We will not do any calculus here, but the terms of this equation show the parameters that can be set to request the return of these harmful forces. 00:03:52.720 --> 00:03:56.080 00:03:56.080 --> 00:04:00.760 The first is clear: it is the speed at which the fluid moves through the tube. 00:04:00.760 --> 00:04:02.209 00:04:02.209 --> 00:04:06.890 Reducing this is one of the simplest ways to reduce the impact of a water hammer. 00:04:06.890 --> 00:04:10.680 Speed is the function of the flow rate and the size of the tube. 00:04:10.680 --> 00:04:14.940 If you are designing a pipeline, the flow rate may be steady, so you can increase the size of your tube to reduce the speed. 00:04:14.940 --> 00:04:17.920 00:04:17.920 --> 00:04:22.139 The tube may be smaller in cost, but the flow velocity will be higher which may cause problems in the water hammer. 00:04:22.139 --> 00:04:24.199 00:04:24.199 --> 00:04:29.780 In this case, the tube size is fixed, but I can reduce the flow rate to reduce the speed. 00:04:29.780 --> 00:04:34.030 Every time I decrease the speed and the valve closes, the resulting increase in pressure decreases. 00:04:34.030 --> 00:04:35.260 00:04:35.260 --> 00:04:41.000 After that, you can increase the time when the change in momentum occurs. 00:04:41.000 --> 00:04:46.130 A common example is the addition of flywheels to pumps that spin more slowly rather than stopping suddenly. 00:04:46.130 --> 00:04:48.330 00:04:48.330 --> 00:04:51.650 Another example is just to close the valves more slowly. 00:04:51.650 --> 00:04:56.310 If you gently close the valve instead of letting it close, the pressure change is more accurate. 00:04:56.310 --> 00:04:57.680 00:04:57.680 --> 00:05:03.030 On large pipelines, engineers not only design components but also develop requirements for operating equipment. 00:05:03.030 --> 00:05:05.440 00:05:05.440 --> 00:05:10.020 This will always include rules about the speed of opening or closing valves to avoid water hammer problems. 00:05:10.020 --> 00:05:12.840 00:05:12.840 --> 00:05:18.210 The final parameter that we can adjust is the velocity of sound through the fluid, also known as the wave propagation speed. 00:05:18.210 --> 00:05:19.460 00:05:19.460 --> 00:05:23.840 This describes how quickly the pressure wave propagates across the tube. 00:05:23.840 --> 00:05:29.520 A wave wave is an indirect measure of the system's elasticity, and can depend on the compression of fluids, tube material and even whether it is buried in the ground or not. 00:05:29.520 --> 00:05:34.320 00:05:34.320 --> 00:05:36.070 00:05:40.759 --> 00:05:46.199 It has got a flexible PVC tube placed on the floor freely to move 00:05:46.199 --> 00:05:48.740 It really helps reduce the size of the water hammer. 00:05:48.740 --> 00:05:53.800 I can increase the flexibility even further by adding an anti-surge device. 00:05:53.800 --> 00:05:58.110 This contains an air chamber that can absorb some shocks and reduce pressure rise even further. 00:05:58.110 --> 00:05:59.380 00:05:59.380 --> 00:06:04.930 Anti-boom devices are very common in piping systems, and can be as simple as a spring-loaded valve that opens if pressure increases. 00:06:04.930 --> 00:06:08.139 00:06:08.139 --> 00:06:14.199 In urban water distribution systems, water towers help control current increase by allowing the free surface to move up and down, while absorbing sudden changes in pressure. 00:06:14.199 --> 00:06:19.600 00:06:19.600 --> 00:06:24.639 Plumbing is one of the unrecognized innovations that made our modern society possible 00:06:24.639 --> 00:06:25.770 00:06:25.770 --> 00:06:30.490 When you take advantage of the energy of the water by putting it in tubes, it is easy to completely dampen this energy. 00:06:30.490 --> 00:06:32.250 When you take advantage of the water energy by putting it in tubes, it is easy to completely dampen this energy. 00:06:32.250 --> 00:06:37.160 Water can be rough like concrete when it is trapped, and if it is narrowed by two hard things together, something will eventually collapse. 00:06:37.160 --> 00:06:39.270 00:06:39.270 --> 00:06:43.930 If you are an engineer, your job is to ensure that it is not the expensive infrastructure that you designed. 00:06:43.930 --> 00:06:45.479 00:06:45.479 --> 00:06:50.639 Part of this means being able to predict hypertension due to water hammer and design systems that can mitigate any potential damage that might result. 00:06:50.639 --> 00:06:55.699 00:06:55.699 --> 00:06:58.930 Thanks for watching, and let me know what you think! 00:06:58.930 --> 00:07:01.430 Thanks Blue Apron for sponsoring this video. 00:07:01.430 --> 00:07:05.889 Blue Apron provides all the fresh ingredients you need, just to your doorstep, just right 00:07:05.889 --> 00:07:10.050 The right proportions for creating delicious recipes at home. 00:07:10.050 --> 00:07:13.759 We really love it at our house, and we have a lot of fun cooking these meals together 00:07:13.759 --> 00:07:15.980 (Never mind eating them). 00:07:15.980 --> 00:07:19.890 If this sounds like something you want, the first 100 people click on the link 00:07:19.890 --> 00:07:23.370 In the description you will get 3 free meals with first order. 00:07:23.370 --> 00:07:25.659 Once again, thank you for watching, and let me know what you think!
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