Practical Engineering - 2021-05-04
Explaining how pumps produce both pressure and flow with some fun water demonstrations. There’s a popular and persistent saying that pumps only create flow in a fluid, and resistance to that flow is what creates the pressure in a pipe. This video goes into some details about how two kinds of pumps work: centrifugal pumps and positive displacement pumps. Practical Engineering is a YouTube channel about infrastructure and the human-made world around us. Hosted, written, and produced by Grady Hillhouse. We have new videos posted regularly, so please subscribe for updates. If you enjoyed the video, hit that ‘like’ button, give us a comment, or watch another of our videos! CONNECT WITH ME ____________________________________ Website: http://practical.engineering Twitter: https://twitter.com/HillhouseGrady Instagram: https://www.instagram.com/practicalengineering Reddit: https://www.reddit.com/r/PracticalEngineering Facebook: https://www.facebook.com/PracticalEngineerGrady Patreon: http://patreon.com/PracticalEngineering SPONSORSHIP INQUIRIES ____________________________________ Please email my agent at practicalengineering@standard.tv DISCLAIMER ____________________________________ This is not engineering advice. Everything here is for informational and entertainment purposes only. Contact an engineer licensed to practice in your area if you need professional advice or services. All non-licensed clips used for fair use commentary, criticism, and educational purposes. SPECIAL THANKS ____________________________________ This video is sponsored by CuriosityStream. Stock video and imagery provided by Getty Images, Shutterstock, Pond5, and Videoblocks. Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License Source: https://www.youtube.com/watch?v=U6fBPdu8w9U Producer/Host: Grady Hillhouse Assistant Producer: Wesley Crump
A good rule of thumb is: "If you want an accurate one-liner saying, don`t get involved in hydrodynamics".
"Pump go glugg glugg!"
What about; "Water runs downhill"? But then, the ram pump made it run uphill. (Back to the drawing board, I'll find one).
@footrotdog see, the issue there is that drinking involves a liquid travelling through a tube and displacing other liquid thus involving hydrodynamics
@ellmann creative beat me to it lol
Fluid dynamics in general
As a professional engineer who worked at a water and waste-water utility for over 30 years, let me congratulate you for an excellent presentation. I would really like to see a future presentation on cavitation.
He did one on turbulence before I think. But obviously that's more general and not pump specific.
He has a couple vids on cavitation too
Its an interesting concept its it
a little late, but it was just beside your comment... it's a sign :D
https://www.youtube.com/watch?v=zCE26J0cYWA
I'm an electrician. Everytime I hear it's not the voltage that kills you, it's the current, I slap them in the face and tell them it wasn't my hand that hurt them, but Newton's conservation of momentum.
@The Sleeper ...funny how 60,000 volts alone, muscles seized, no permanent damage.
....60,000 volts + 1 amp = instant death.
Prove me wrong.
I'm an electrical engineer. Current is certainly what kills you. But for that current to keep flowing, a high enough voltage needs to be maintained. A Van De Graaff generator can create millions of volts, but as soon as you touch it, the voltage drops to zero and thereby cutting that current off.
@Daniel Jensen There is no simple number. It depends on many factors such as dampness of the contact points, contact pressure, etc. Those are some of the many factors that define the resistance. We know that current=voltage/resistance. To make things even more confusing, resistance is non linear, depending on voltage and changes once the current starts to flow. Bottom line: the human body is not like a theoretical resistor so trying to assess a voltage value that results in a certain current is impossible.
Not saying your wrong just saying that 1 million amps at 1 volt will literally never kill you due to electricity but maybe heat from resistance.
@ak assasin Exactly right, but of course that would only happen if the human body has a resistance of 1 micro-ohm (R = V/I). Given that the human body has a resistance that's many orders of magnitude higher that that, the only way to develop a sufficiently high current flow is to have a voltage source with a voltage large enough to develop those currents (I=V/R).
This is basically the hydraulic version of the discussion whether an electric source provides current or voltage. And as my university teacher likes to say: "what they have taught you in school might not be wrong, but the full story is a lot more complicated".
@SolventTrap dot com i think this is a really good way to put it
@NC Because it comes from decades of experience. ;-)
@SolventTrap dot com I think that's why it is said the current kills, because you always have voltage and you don't get killed when the current is zero, you short the circuit and the current spikes and you are dead. The current is the one who killed you but because there was a voltage. The same way when someone shots you, the bullet was the one that killed but only because someone pressed the trigger.
Uh yeah i mean he literally said this in the first minute of the video.....
It helps that pressure vs flow and current vs voltage are analogous enough that you can create an electric model of a system to analyze flow and pressure. Look up Deltar sometimes, it's a computer to do just that for a big flood prevention project called delta works.
"This isn't rocket science". I'm not a rocket surgeon, but I'm pretty sure pumps and fluid dynamics are a big part of at least designing rocket engines and fuel tanks.
i heard a professor once say "come on guys, this isnt rocket science... though it is USED in rocket science"
Designing a good efficient turbo pump is like 30% of the engineering going into a rocket.
Rocket engines are all about pumps and turbines
As a chemical engineer that works with pumps on a regular basis, I enjoyed this.
As a chem eng grad I agree
Stranger on the internet is happy for you
As another engineer, I feel the need to tell everyone that I am also an engineer.
another engineer here i work in boosting station " compression 5002D turbines
As a plumber I really appreciate this video. You opened my eyes to new ideas, and I love pumps too. I work with hydronic pumps so we go for efficiency and longevity rather than high flow or head. There are issues however with placement that can impede or enhance cavitation and also entrapped air removal through traps or high points. Thanks again for all these great videos!
I’ve had a lot of friends who are engineers, i myself am a mechanic, and I always smile when i see Grady puts little eyeballs on the action pieces knowing full well how special it is for an engineer to humanize things for the rest of us emotional non-Vulcans. It’s a special breed who can bridge that gap. 🖖🏽
And amazing how much of a difference they make! 👀
Love the video. I build and maintain ponds and water features, so I really dig this. My job is often trying to find the right pump curve for the project. I'd love to see more about how the system modifies the flow from the pump with multiple discharges or varying sizes of pipes. Also, I've always wondered if the pressure from the intake of the pump modifies the flow. An example for me is submersible pumps and their depth, does that help increase the flow?
This video operates where my interest curve and the supply curve intersect.
@Jeffrey Long that's only important for youtube itself, no one cares about it
I think you mean interest curve and attention curve intersect.
@calholli I think he might be just be saying that he likes this content, it’s both interesting and available or supplied to him. Also, isn’t interest and attention about the same in this context, if something has your attention then it must have your interest or vice versa? Lol just speculating
@Jeffrey Long I think that interest is his demand curve. He is interested in this content ergo he has created a demand for it. Then the supply is this video. Just trying to overthink this, no more than a theory of his message’s meaning haha
Well done.
Even though this is aimed a lot more at civil engineering concepts, for me who is studying chemical engineering, this channel is so informative to conceptualize and understand physical setups of a bunch of engineering concepts.
Thank you for the content!
Awesome video! I am a project engineer for a large diameter(54” into 92”) sewer project where we bypass 30MGD. I just went through learning all this and this video does a great job simplifying a complicated topic.
I'm an engineer in a pump repair shop and make and fit mechanical seals to them, this video was fantastic.
Plus to prove pumps do create pressure, it's in their design, the volute has that spiral shape that once the product has been moved off the impeller eye to the walls of the volute it follows this spiral to the discharge and as the volute opens up the fluid builds up and loses flow and builds pressure before leaving the discharge, which is why the suction always larger than the discharge, to create pressure.
Very interesting! The issue is everything has exceptions. Gear pumps (and some other positive displacement pumps) are different in that they deliver a fixed flow rate regardless of fluid viscosity or system pressure and can blow out a line if there is a blockage and no relief valve. Therefore, gear pumps do only deliver flow and the pressure is system driven!
"Not a great catchphrase, but it is accurate." Spoken like a true engineer.
That was the real catchphrase all along
@seneca983 That is incorrect. Voltage is the measure of the "Potential flow" of electrons. Pressure is the measure of "resistance" to flow in a given system. They are on opposite sides of the equation.... The analogy would be voltage of a battery is equivalent to the cubic ft/sec flow rating of the pump... these are the "SOURCE", pressure is measuring the restriction to that flow source. Raise the resistance to flow and the pressure will increase proportionally. Just like putting your thumb over a water hose, it increases the pressure-- not because of more VOLTAGE--- the pump is still running at the same rate.------- its because of the increase in RESISTANCE from your thumb mostly blocking the hose. They are on opposite sides of the equation.... Not only does resistance increase pressure, it also increases the speed of flow across the restriction in a given volume. Because in a given/ set rate of flow, when you increase restriction, in order to still pump out the same flow through a smaller hole, it has to increase the pressure and speed of that flow, so the output is still the same, because the pump is still pumping the same-------- you're just getting a smaller AMOUNT of water coming out, but at a higher rate.
@Paul Elderson The real catchphrase is the friends we made along the way.
@calholli "That is incorrect."
It is correct.
"Just like putting your thumb over a water hose, it increases the pressure-- not because of more VOLTAGE--- the pump is still running at the same rate.------- its because of the increase in RESISTANCE from your thumb mostly blocking the hose."
Here the pressure is analogous to voltage. Similarly, if you have a current source that's pushing current through a resistor and you increase the resistance the voltage over the resistor increases, just like in your hose example.
Me when I try to explain lift...
How timely. I just put a new fuel pump on my E30, just the other day.
Evidently, a few pounds of pressure loss will cause hard starting issues, poor gas mileage and weak acceleration.
It runs great now. But I must admit, the safety aspect behind submersible electronic fuel pumps still sort of baffles me.
Thanks for all the expert input, Mr. Engineer.
To expand upon the similarity between electric and fluidic systems, perhaps expression in state-space form (and the relations between aspects such as flow rate, flow resistances, capacities etc.) would be useful to show how similar they are.
This is exactly analogous to load line analysis in EE, except with flow/pressure curves instead of I/V curves. There is a reason the hydraulic analogy is such a common way to explain EE principles. Just as in EE you can have more voltage-like sources and more current-like sources, in practice all sources cap out somewhere or else would need infinite power. A voltage source has a max short circuit current, and a current source has a max open circuit voltage just like a pump has a max flow with no pressure and a max pressure with no flow.
Really, that characteristic curve seems very reminiscent of the I/V curve of a solar cell which has a similar 'knee' shape, with a max efficiency point in the middle of the knee.
Thank you for this (as always) very interesting video. It will make a good complementary video to the last videos I released for my students on my own YouTube channel, where I actually deal with fluid transfert technics, and where I even recommend a previous video of yours about ram pumps 😊.
It actually is rocket science too. The big boy rockets all use pumps for propellant flow and thrust control :)) 0:32
@Natan Getschel No doubt you are right. I was just wondering if some form of unexpected turbulence might occur with that engine configuration that I never thought of, such as the exhaust streams of the rocket engines somehow interacting with one another in the spirit of Jollyphuck's wry joke. It will be interesting to watch.
@PrimeSuperboy All main stage liquid fueled rocket engines that I'm aware of use pumps. Most are turbopumps, some like the Electron rocket use electric pumps. Some things like reaction control thrusters are simply pressure fed, but pressure fed systems are typically pretty small since you need something to replace the volume with to maintain tank pressure. It's a trade-off of pump complexity or needing an extra tank to maintain pressure.
@quintessenceSL it works the exact same, It creates a force on the air and force over area is pressure. If you think about a fan, it pushes air out one side therefore there is more air at the output so the pressure is higher but at the inlet air has been removed therefore the pressure is lower. This creates a difference of pressures which produces a flow of air. The difference with air is that it is compressable whereas most liquids aren't. That means you can only fit so much liquid in a container no matter how hard you squeeze it, but with air you can force more in and therefore the higher the pressure the more mass you have in a container. Compressors keep pushing the air in hard to fit more mass in the same space, if there is an outlet then the higher pressure air flows into the lower pressure atmosphere. As far as I know pumps like the first one he showed are more like fans and therefore good at providing high flow rates but not great pressure whereas the positive displacement pump he showed, as long as it has enough power to rotate it can produce higher pressures in a container.
@Mack Dlite yes, the OP said, "big boy rockets" implying that all space delivery vehicles use pumps.
Yeah, a huge portion of rocket science boils down to extreme difficulty pump design:
Extreme flow-rate
Extreme cold
Extreme heat
Needs to operate against back pressure sufficient to lift a building into the sky
Will often need to operate in both a vaccume and zero-g
Extremely tight tolerances
Must never require even the slightest bit of in-field maintenance.
Extreme vibration tolerance
Needs to pump and mix 2 different (and frequently not insignificatly reactive) fluids at a very specific ratio.
Oh, and while also being as light as you can make it, it also will need to be as cheap as possible because we may only need to use it 1 time before we smash your prized design into the ground or water at high speed, but if it doesn't work flawlessly, someone is likely to die.
Great video. I love the subject myself. Can you do a comparison between centrifugal pumps vs Archimedean screw type pumps?
I have seen a drainage centrifugal pump with a bore of 60 inches delivering 600 tons per minute.
Which is more efficient for drainage applications? Thank you in advance.
This all pretty much applies to fan selection too! The system curve is always what catches me up. Isn't that just based on the resistance of the entire system, not necessarily the complexity? And knowing the system resistance, are there other variables that impact the system curve?
Can we take a moment to pay respects to the sheer amount of time and money spent on these models to demonstrate the concepts in these videos? They are part of the reason I love this channel so much.
Thank you for the informative video. I worked years for a plant in which we did not have a clear understanding of what pumps are capable of. We had to move 10,000 gpm of a slurry containing a crystal formation that centrifugal pumps were hard on. Plus, before we discovered mechanical seals, we were pumping 500 gpm of diluting water into the packing glands, We were burdened with having to repair packing and replacing ballraces on a crippling frequency. At the end of my time at that plant, we had new minds coming on who introduced us to eddy pumps, which changed things . I wish we had youtube and videos like yours to teach us these things back then.
"this is the first of 2 videos... let me know if you want to see more". Grady, i'd watch a video on anything that you passionately explain. You explain complex topics simply with great demonstrations. Any subject is interesting in your videos. Keep up the great work.
Honestly he could narrate paint drying, and talk about how the chemical changes to paint drying, and it would be interesting.
Same. I have absolutely no practical use for anything he explains but I still watch all his videos because it's so interesting.
Wow, the comparison to voltage/current was actually very helpful for me!!! I'm learning about electricity at the library lately, and i am shocked (lol) at how similar flow of electrons and flow of water can appear
I love how analogous hydraulics and electricty are. It's the same with electricity sources, the voltage and current form identical characteristic curve. When the circuit is disconnected there is no current and the electrodes are at the maximum voltage. When you connect resistor (or anything that takes energy) the current starts flowing and the voltage falls slightly. If the resistance is small, the current is very large and the source power can't keep up and the voltage drops significantly. Finally, when the electrodes are shorted, there is no voltage and the source supplies its maximal current.
I guess we usually talk about voltage and flow, which are kind of opposite, because the voltage of a electrical supply rarely changes very much and pumps are more often used to move water without creating very much pressure.
Awesome video, well presented, thanks so much for sharing this with all of us!
I graduated with a chemical engineering degree last year, and I've NEVER heard the saying pumps don't create pressure. We only ever ever defined pumps by their pressure differential. Once you get into compressible fluids, it's very clear how much more important a pump's pressure differential is than flow.
thanks for the graphs about the different curves! i also appreciate the video editing. you're a wonderful resource, Grady.
Love this channel. The insightful content, informative experiments, and smooth delivery. Hard to beat.
I spent almost 20 years as a mechanical engineer at various pump manufacturing companies designing/developing centrifugal pumps for the water/wastewater and chemical processing industries. This video was a great primer for people getting started in understanding pumps and fluid transfer principals. Well done. Your civil engineering videos almost make me wish I'd studied that instead!
Would like to see a more in-depth video on positive displacement pumps, mainly Triplex and plunger pump systems. We use them in HDD applications and I would love to learn more about them. Most info on them that I've found is typically related to downhole high pressure systems. Also a video on HDD design, pipe stress during pull back and other general topics related to horizontal crossings!
I work for a pump company, and I want to show this to all our customers who I swear don't understand pumps. Well done. I look forward to your future pump videos!
I'm a pump designer and I'm showing this to new engineers as part 1 of onboarding.
i work for a mechanical seal manufacturer, even less understood...feel your pain lol
@David Baucom From the pump engineer: your work is appreciated.
@Matt Golman haha thanks, it's not magic or voodoo. Understand two things about mechanical seals: all seals leak, they need to do so to work properly and pressure moves from areas of high pressure to low pressure.
Thats really all you need to know about mechanical seals, on a fundamental level.
As a physicist who buys pumps without understanding them, yes please educate us instead of talking down to us when we contact you to ask about something we don't understand. This video was valuable.
Boy do I wish we had an engineer like you, 20 years ago. I was an electrician that seemed to have absorbed/dumped into the water system where I worked. (Now retired) They had 4 vertical 1000 gallon / minute Deming pumps that outputted through 8” ID pipe, into a 14” header/collector pipe, sending water from a settling pond, ¼ mile back to the main plant. They kept adding more and more equipment, that needed cooling water, so the engineer kept adding pumps. No matter what he did, the pressure and the volume, ¼ mile away never increased. (Eventually up to 8 pumps) I tried to show him the folly of forcing more water through that same 14” pipe was futile, with an impeller driven pump, but the engineer looked at me as if I was a moron, till he finally got to see the amperage going down on each pump motor as other pumps were manually turned on. (Took 4 clamp-on's at once to visualize it)
If you would, show how an ammeter is a good tool to check and set up pumps, check wear on impellers, and the need to set the pumps at 100% load (rather than 70-80%), to get the best balance out of multiple pump systems. Some of the newer people to the field would benefit. Most people see pump curves, and just shrug their shoulders. Setting them up is fascinating though, especially when the mechanic foreman comes to you, with his budget for the year, and asks, which pump is showing the least efficiency, and you can show him with an ammeter, and a pressure gauges, which impellers are wearing the most, in parallel multi-pump systems. I’d be glad to feed you my notes, but it sounds like you have all you need.
Thanks,
Mike
Literally had this discussion today at work (microwave waveguide system air dryer). The system has both flow meters and pressure gauges with an air compressor (piston type positive displacement pump), dew point dehydrator, and output holding tank (static head?). The system was lacking adequate pressures to function. We had the great output (unsubstantiated tank leaks) vs worn out compressor debate. Always bet on the moving part.
That look on trainee or new operators when you have them close a valve when a pump apparently doesn't deliver it's intended flow, is kinda priceless.
Almost as good as showing an engineer that reducing coolant flow over a cooler, can actually improve cooling
I work with vacuum systems like this along with high pressure water systems. I have the thought that a pump imparts energy into its medium (water, air, oil, etc.). As you showed, the rest of the system determines what the resulting pressure and flow are. A more accurate rating would be Joules or Watts.
Would you do a similar video, but on compressible fluids? I often get into confusing discussions about the air compressed system at work, and how pressure and flowrate interact.
As a mechanical engineering student, I would absolutely LOVE to see a video on pump volute principles.
Like is the rate of cross section increase linear around the volute? What is the difference between a volute and a diffuser? What is the velocity profile in a volute, etc.
As an electrical engineer, I find the electrical analog of pressure and flow (voltage and current) to be an easier way to understand pumps, but only by virtue of Ohms law, which brings the all-important resistance into the equation.
Well done! As someone who does TIC for fire pumps, this was incredibly well put together. You probably know more than I do about the topic, but I have lots of experience with pumps if you want to reach out for any info!
Fan design engineer here, awesome video! Have explained fan characteristic vs system curves many a times to customers and technicians.
Brilliantly explained. Always love your videos. Left feeling very satisfied. Amazing work
Thank you for your very clear and concise explanation of physical properties without going over the heads of the majority of viewers. I don't think that it would be detrimental to slip in just a bit of math. (gently)
How do you figure out the system curve?
We've always taught a simpler view of pumps on my firefighter course and I'd like to understand how the pumps, hoses and head height can all be worked out for the system curve
Yet again great work! Definitely want more on fluids, just added this video to my fluid mechanics playlist for my physics classes.
As always - thanks for the quality infotainment! Love the content!!!
I've been using small pumps for 20 years to watercool my computers. From aquarium pumps to dedicated WC pumps, discharge head has always been a main consideration, especially when using small diameter tubes and high restriction waterblocks.
Practical Engineering - 2021-05-04
💧 Give me your best pump mantras. I'll meditate on the best one.
📺 Don't forget to jump on this great Nebula/CuriosityStream deal. https://curiositystream.com/practicalengineering
D M - 2022-05-27
Centrifugal pumps add energy via pressure to the system. Changes in flow are perceived by changes in the system state and our end-of-pipe perspective.
Duc Tran - 2022-07-28
@Scott Tancock Hi, the impeller rotate increase velocity of fluid -> increase dynamic pressure -> so pump can increase dynamic pressure, right? The volute of pump just like an increase in area to slow down the velocity and convert bulk motion in random motion -> increase in static pressure
Duc Tran - 2022-07-28
Hi Practical Engineering, the impeller rotate increase velocity of fluid -> increase dynamic pressure -> so pump can increase dynamic pressure, right? The volute of pump just like an increase in area to slow down the velocity and convert bulk motion in random motion -> increase in static pressure. Does it make sense & logical?
DonTruman - 2022-10-18
Pumps create pressure, system determines flow.
Electricity: power source creates pressure (emf) circuit determines current.
Sanjay Patel - 2022-10-29
Pumps are fascinating. I’m a Perfusionist. We use both centrifugal and peristaltic pumps to help keep patient alive during a heart surgery. There is a fascinating history of pumps evolution from basic to implementable pumps to total artificial heart in human body. I too love ❤️ pumps. 👏👏.
Great channel, btw. 👏👏