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Just as a sidenote, excavators regularly prop up onto the back tracks like this while compacting soils. So the water pressure is ~~~roughly the same as the max downward force the excavator applies during normal operations ~25-50k lbs
The tonnes is the proper designation of âmetric tonsâ
Generally Iâd prefer to work in kg. SI doesnât name the m3 so volume is awkward in SI units, but generally I prefer to stick to SI with the usual Aussie aversion to prefixes other than kilo, milli and micro.
The water has better leverage though. The weight in these is far back. Iâd guess the bucket is probably 5x further from the back roller of the tread than the CG, which would put the force of the water at âonlyâ 4 tons
Thereâs also some funky fluid mechanics going on here. Notice how the bucket doesnât really get lifted until itâs inverted? The inverted bucket is acting like the blade of a turbine, reversing the direction of the water, increasing the water pressure on the bucket further
Letâs approximate 10 te force to tilt it so easily, divide by the cross section area of the bucket and youâll get a rough idea of the pressure I guess
The pressure for most city Mains is anywhere between 60-120 PSI. This range includes coties that use specific pumps to boost pressure in certain zones. From that Hi PSI it will typically go through a reducing valve at your house to keep it between 60-80 PSI.
So like I said itâs not a pressure issue, Itâs a Volume issue. And thatâs a shit ton of water getting shot straight up
It's both. I mean you can't dunk a loader in a lake and expect it to do this despite an even greater volume of water. Needs volume, velocity and pressure
Right but the guy asked about the pressure of the water main.
Typically at a max they are ran about 120 PSI. Usually ran about 20 psi lower.
I was more or less stating in this instance the Pressure is the Static figure, whereas the volume is what is doing the heavy lifting. In this instance.
And thatâs depends on how big the break is and what size of pipe. For example 120 psi from a 3/4â water line doesnât feel great but wonât lift you off the ground.
Whereas 120 PSI from a 12â ductile main yeah thatâs going to throw things around at nearly 4700 Gal/min. Depending on pressure.
Which just doing a lesser average thatâs 80 gallons of water Per second. That would be a potential 640lbs of force /second now Iâm not a mathmagician I am just a plumber but something about that much force hitting the extended part of a Fulcrum. Would cause the excavator to move, not likely to flip it.
Kinda but not the case in this instance where you can see a water Column of decent size.
120PSI out of a 1â main is still 120 PSI. It is just more directed.
120PSI out of a 12â main is the same pressure.
Yes with reductions it will increase the perceived pressure but it will never rise above the Supply pressure. Just by restricting the flow wonât turn a 120 PSI into 300 PSI. Because the supply pressure isnât increasing when you restrict it. In fact it just gives the hose a chance to fully pressurize which is why the pressure increases.
Now if you want to increase Pressure, you need pumps, and any Pump to increase pressure reduces volume. (Pressure washers). We have a mainline Jetter which is basically a Power washer on steroids that allows us to pressurize a 1â hose up to 5000PSI and itâll drain a 1000 gallon tank in 20 minutes
Hope that makes sense.
Basically restricting the pipes wonât change the supply pressure
A break won't increase the pressure, but a nozzle will (note how much better your pressure washer works with a nozzle than without one).
The crazy part is the water is at atmospheric pressure once it leaves the pipe. From that point you are just dealing with mass and velocity.
Volume is a good way to measure mass for an incomprehensible fluid like water.
Bernouli's equation should convert either the pressure into exit velocity of the water or visa versa.
I don't have the math to be able to do it anymore but I suspect you may be short a variable to actually solve it without an estimate of one of the variables, still.
Ill operate using the back wheels as a pivot point. The point of pressure is about 10 meters from the pivot, meaning the water will be roughly a tenth of the overall pressure it has to support (approximately 205,000 N) so the water pressure must overcome at least 20,500 N. So the water pressure is over 4650 lbf. Long story short, less than youd think
I've been a water engineer for 15 years now. There's a good trick for calculating pressure.Â
Water is not compressible, therefore the energy in pressurized water equates directly to depth. If you poke a hole like this, it will spray up approximately to that depth (minus losses). You could also attach a long clear pipe and watch the water level out at the elevation of a tank or whatever source of water. We call that head in the water.Â
In the video you can see the main jet sprays about 5x the height of the excavator (admittedly 1 or 2 frames). Sany says the 210C9 is a little under 3.5m tall. That puts around 17.5m tall (60 ish feet). Jets like this lose energy to the tune of 50% so we'll call it 35m (115ft). There is 9.8kpa to the meter (0.433 psi per foot of water) so we round out to 340kpa or 50psi.Â
That's a typical design range for a local waterline (40-120 ish) and tracks with what would be our assumptions. Others have discussed moving the excavator so I won't belabor that, but safe to say it doesn't take much pressure to do some crazy things.Â
The pressure can be estimated from the height of stream above ground. Pressure = densitygravityheight. If the column of water is 100 ft height the pressure would be about 45 psi. If it's 200 ft then the pressure would be 90 psi. The force on the excavator though is proportional to the surface area of the column against the bucket and deflection angles. That's a little harder to estimate.
Is no one going to comment on the man who somehow thought it was safer to run towards and behind the multiton excavator that is being tossed around by the water pressure?
Pressure is atmospheric. Velocity and momentum are very high but it is commonly misunderstood but the pressure out the outlet is, for all intents and purposes, always the atmospheric pressure. Itâs like the ground in an electrical circuit.
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Just as a sidenote, excavators regularly prop up onto the back tracks like this while compacting soils. So the water pressure is ~~~roughly the same as the max downward force the excavator applies during normal operations ~25-50k lbs
I was like, what are you on 25 to 50lbs, then I noticed the K đ¤Śââď¸đđ
People who want metric but canât bring themselves to use it.
It's just 25-50 kips
Another ridiculous American unit?
1 kip is 1000 lbs because anything but metric
1 ksi is 1000 lbs per square inch
Most steel can do 50 ksi
I like to throw in 1 mip = 1000 kips but that's not a real unit. We just made it up in engineering school to make fun of kips.
Why didn't you comment it in metric form to begin with? It's superiority would surely scare this poor imperial scum into submission right?
Fear not! It's around 11-22 metric tons
Metric tons are not a unit of force. Youâve got to newton that shit.
Edit: actually, lbs and kgs are both wrong. Question is pressure, so kilopascals or pounds per square inch.
I am thinking of a browser plugin that would convert imperial units to SI (& back) on a webpage. What do you think?
Dew it
Oh the power of dividing by 2.2!
Factorial of 2.2 is approximately 2.423965479935368
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I know you're a bot, but how do fractional factorials work?
I'm using the gamma function, which is a continuation of the factorial function.
Oops, I meant beep bop đ¤
Good bot, knowledge of the Gamma function is good for the motherboard. Just be careful and dont go plugging in negative integers
One alphabet here or there!
I read it as 25lbs to 50,000lbs and thought âkind of a wide rangeâ
Well, that's the force, and then the pressure is that divided by the cross section of bucket that it's hitting
Approximately how many bananas is that?? Asking for a friend.
Bananas per square inch
Sooo... Don't wash my face in that water jet?
The excavator weighs around 21 tons.
The water has better leverage though. The weight in these is far back. Iâd guess the bucket is probably 5x further from the back roller of the tread than the CG, which would put the force of the water at âonlyâ 4 tons
Thereâs also some funky fluid mechanics going on here. Notice how the bucket doesnât really get lifted until itâs inverted? The inverted bucket is acting like the blade of a turbine, reversing the direction of the water, increasing the water pressure on the bucket further
Leverage, and not fully lifting the excavator
The water pressure mustâve at least been enough to prop that excavator up like that
Nothing gets past you.
That guy maths
Maffs, that guy maffs.
Quick maffs
I was gonna say it's pretty high, but your answer is a lot more accurate.
Precise.
It never supported the full weight.
Pressure is force per unit area.
So, the pressure wasnât enough to prop the excavator like that?
Letâs approximate 10 te force to tilt it so easily, divide by the cross section area of the bucket and youâll get a rough idea of the pressure I guess
Meh. He edited his initial response to the current âfull weightâ statement.
True. The counterweight at the rear remained on the ground, it appears.
Itâs not really a pressure equation here.
The pressure for most city Mains is anywhere between 60-120 PSI. This range includes coties that use specific pumps to boost pressure in certain zones. From that Hi PSI it will typically go through a reducing valve at your house to keep it between 60-80 PSI.
So like I said itâs not a pressure issue, Itâs a Volume issue. And thatâs a shit ton of water getting shot straight up
It's both. I mean you can't dunk a loader in a lake and expect it to do this despite an even greater volume of water. Needs volume, velocity and pressure
Right but the guy asked about the pressure of the water main.
Typically at a max they are ran about 120 PSI. Usually ran about 20 psi lower.
I was more or less stating in this instance the Pressure is the Static figure, whereas the volume is what is doing the heavy lifting. In this instance.
And thatâs depends on how big the break is and what size of pipe. For example 120 psi from a 3/4â water line doesnât feel great but wonât lift you off the ground.
Whereas 120 PSI from a 12â ductile main yeah thatâs going to throw things around at nearly 4700 Gal/min. Depending on pressure.
Which just doing a lesser average thatâs 80 gallons of water Per second. That would be a potential 640lbs of force /second now Iâm not a mathmagician I am just a plumber but something about that much force hitting the extended part of a Fulcrum. Would cause the excavator to move, not likely to flip it.
What youâre missing is that the main is not functioning as intended.
Pressure also has to do with pipe size/opening. What is 120 PSI in a 1â pipe is substantially higher when being forced through a smaller opening.
Think when you put your finger over the water hose. Your decreasing size of opening and increasing pressure.
Kinda but not the case in this instance where you can see a water Column of decent size.
120PSI out of a 1â main is still 120 PSI. It is just more directed.
120PSI out of a 12â main is the same pressure.
Yes with reductions it will increase the perceived pressure but it will never rise above the Supply pressure. Just by restricting the flow wonât turn a 120 PSI into 300 PSI. Because the supply pressure isnât increasing when you restrict it. In fact it just gives the hose a chance to fully pressurize which is why the pressure increases.
Now if you want to increase Pressure, you need pumps, and any Pump to increase pressure reduces volume. (Pressure washers). We have a mainline Jetter which is basically a Power washer on steroids that allows us to pressurize a 1â hose up to 5000PSI and itâll drain a 1000 gallon tank in 20 minutes
Hope that makes sense.
Basically restricting the pipes wonât change the supply pressure
A break won't increase the pressure, but a nozzle will (note how much better your pressure washer works with a nozzle than without one).
The crazy part is the water is at atmospheric pressure once it leaves the pipe. From that point you are just dealing with mass and velocity.
Volume is a good way to measure mass for an incomprehensible fluid like water.
Bernouli's equation should convert either the pressure into exit velocity of the water or visa versa.
I don't have the math to be able to do it anymore but I suspect you may be short a variable to actually solve it without an estimate of one of the variables, still.
Makes sense
Some water mains run at 200+. I learned this by a 100# gauge instantly breaking when checking.
Thank you
Yeah but it doesn't take 21 tons of force to lift it from the bucket.
Ill operate using the back wheels as a pivot point. The point of pressure is about 10 meters from the pivot, meaning the water will be roughly a tenth of the overall pressure it has to support (approximately 205,000 N) so the water pressure must overcome at least 20,500 N. So the water pressure is over 4650 lbf. Long story short, less than youd think
Makes sense. Also, isn't there the additional backpressure created due to the bucket's concave surface, pointed out by u/start3ch?
Yeah, which would lower the required pressure even more, but tbh thatâs beyond my physics level so far
Easily more than 4.Â
I spent 15 years as a utility inspector and am trained in civil engineering. I have seen breaks of a similar magnitude but nothing quite as big.
Based purely on vibes, 130 psi with enough supply to sustain it (perhaps gravity fed from a reservoir).
I had a 14t cat hold a bucket on a 45psi main, 24â diameter with a 12â round hole and lots of supply. It didnât move like this!
Finally someone who answered a pressure question with a pressure answer.
I've been a water engineer for 15 years now. There's a good trick for calculating pressure.Â
Water is not compressible, therefore the energy in pressurized water equates directly to depth. If you poke a hole like this, it will spray up approximately to that depth (minus losses). You could also attach a long clear pipe and watch the water level out at the elevation of a tank or whatever source of water. We call that head in the water.Â
In the video you can see the main jet sprays about 5x the height of the excavator (admittedly 1 or 2 frames). Sany says the 210C9 is a little under 3.5m tall. That puts around 17.5m tall (60 ish feet). Jets like this lose energy to the tune of 50% so we'll call it 35m (115ft). There is 9.8kpa to the meter (0.433 psi per foot of water) so we round out to 340kpa or 50psi.Â
That's a typical design range for a local waterline (40-120 ish) and tracks with what would be our assumptions. Others have discussed moving the excavator so I won't belabor that, but safe to say it doesn't take much pressure to do some crazy things.Â
The pressure can be estimated from the height of stream above ground. Pressure = densitygravityheight. If the column of water is 100 ft height the pressure would be about 45 psi. If it's 200 ft then the pressure would be 90 psi. The force on the excavator though is proportional to the surface area of the column against the bucket and deflection angles. That's a little harder to estimate.
There's two things you learn when you work with water a lot.
First off, there's not enough information here.
Second, it's probably 200psi.
Is no one going to comment on the man who somehow thought it was safer to run towards and behind the multiton excavator that is being tossed around by the water pressure?
Some people are unaware that you can actually win a Darwin award at any time.
Iâm appalled. Everyone giving answers and not a single person mentions that a free jet has no pressure. And you call yourselves engineers lol
!!!Pedantry Warning!!!
Pressure is atmospheric. Velocity and momentum are very high but it is commonly misunderstood but the pressure out the outlet is, for all intents and purposes, always the atmospheric pressure. Itâs like the ground in an electrical circuit.