Another "myth to kill"??.....what makes it go???

[Egon]

If you want to know which way the effluent is flowing, just look down the pipe when flushing.

I see or is it understand.:thumbsup:

 

[AKKAMAAN]

..... one could push on a rope!:ashamed:

Pull or push doesn't matter, both are about applying FORCE...

You can push on a rope if you spray it with hair spray....stiff grade....

 

[Egon]

spray it with hair spray....

What would I have Hair spray For??:laughing:

 

[AKKAMAAN]

What would I have Hair spray For??:laughing:

stiffen the rope....so you can push it....:thumbsup:

 

[gpflepsen]

Interesting comments in this one.

In some world of dynamic modeling, pumps supply the work, or the potential to do work. In the case of positive displacement pumps (most of the hydraulic pumps we are familiar with) these are merely sources of flow. They turn and can only produce flow. More correctly, they have to produce flow. This flow is directed anywhere we want to take it, but it must go somewhere. When this flow meets resistance (i.e. a cylinder/motor/hose resistance/flow orifice) or a capacitance (accumulator) a pressure is produced proportional to the characteristic of the "load". Velocity (flow rate) is a given and pressure is determined by the outside influences. So, flow makes it go.

Conversely, centrifugal pumps are purely sources of pressure. The pressure potential is a function of the speed of the pump's impeller. This pump can only produce flow if the "loads" are sized such that the reaction is less than the pumps developed head. The pump's speed can control the pressure but the flow is conditional on the resistance seen. So, in this case, pressure makes it go.

 

[AKKAMAAN]

Interesting comments in this one.

In some world of dynamic modeling, pumps supply the work, or the potential to do work. In the case of positive displacement pumps (most of the hydraulic pumps we are familiar with) these are merely sources of flow. They turn and can only produce flow. More correctly, they have to produce flow. This flow is directed anywhere we want to take it, but it must go somewhere. When this flow meets resistance (i.e. a cylinder/motor/hose resistance/flow orifice) or a capacitance (accumulator) a pressure is produced proportional to the characteristic of the "load". Velocity (flow rate) is a given and pressure is determined by the outside influences. So, flow makes it go.

Conversely, centrifugal pumps are purely sources of pressure. The pressure potential is a function of the speed of the pump's impeller. This pump can only produce flow if the "loads" are sized such that the reaction is less than the pumps developed head. The pump's speed can control the pressure but the flow is conditional on the resistance seen. So, in this case, pressure makes it go.

Newtons first law of motion states:
"Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."
This means that, to displace (move) an object, a force have to be applied.
A hydraulic system consists of a prime mover that converts electricity or fuel? into, usually rotating, mechanical energy. A person can be a prime mover in a hydraulic system, using a hydraulic jack .
There are a few different mechanical ways to transfer this mechanical force, to an actuator, where the work needs to be done.
We start with a simple object that need to be moved, a cubic shaped box. We apply a force to the side of the box. When force is big enough to overcome the force of friction, the object will start moving (accelerating).
We can now add distance between the prime mover and the object and let a piece of lumber or a bar made of steel etc, transfer the force from the prime mover to the object. The result will basically be the same; the applied force will make the object move.
Even if we stick the steel bar through a tube or hose, the result will be the same; the applied force will make the object move.
Now if we replace the steel bar with a liquid, and a cylinder with a pump piston in the prime mover end, and a work cylinder with a piston in the actuator end, the fluid will fill the same purpose as the steel bar, it is there to transfer force.
Now, scientists have complicated things, by breaking down the applied force in a liquid into something called pressure. Pascals law states:
"Pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid."
This means that if we apply a force on a limited area, pump piston, in the confined fluid, we create a pressure that will be equal, trough out the whole confinement. This pressure can react on another limited area, cylinder piston, and create a force that can displace the object.
In this discussion we havent mentioned f��low one single time, and we have proofed that it is the f��orce (pressure) that makes it go? Newtons first law applies!
Flow is a hydraulic parameter that describes the volume of fluid that is passing a certain cross section of the fluid confinement, within a certain time unit.
Flow is part of the moving linkage, but flow is not what makes it move.
The myth is dead!!

 

[gpflepsen]

Newtons first law of motion states:
"Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."
This means that, to displace (move) an object, a force have to be applied.
A hydraulic system consists of a prime mover that converts electricity or fuel? into, usually rotating, mechanical energy. A person can be a prime mover in a hydraulic system, using a hydraulic jack .
There are a few different mechanical ways to transfer this mechanical force, to an actuator, where the work needs to be done.
We start with a simple object that need to be moved, a cubic shaped box. We apply a force to the side of the box. When force is big enough to overcome the force of friction, the object will start moving (accelerating).
We can now add distance between the prime mover and the object and let a piece of lumber or a bar made of steel etc, transfer the force from the prime mover to the object. The result will basically be the same; the applied force will make the object move.
Even if we stick the steel bar through a tube or hose, the result will be the same; the applied force will make the object move.
Now if we replace the steel bar with a liquid, and a cylinder with a pump piston in the prime mover end, and a work cylinder with a piston in the actuator end, the fluid will fill the same purpose as the steel bar, it is there to transfer force.
Now, scientists have complicated things, by breaking down the applied force in a liquid into something called pressure. Pascals law states:
"Pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid."
This means that if we apply a force on a limited area, pump piston, in the confined fluid, we create a pressure that will be equal, trough out the whole confinement. This pressure can react on another limited area, cylinder piston, and create a force that can displace the object.
In this discussion we havent mentioned f瑞low one single time, and we have proofed that it is the f瑞orce (pressure) that makes it go? Newtons first law applies!
Flow is a hydraulic parameter that describes the volume of fluid that is passing a certain cross section of the fluid confinement, within a certain time unit.
Flow is part of the moving linkage, but flow is not what makes it move.
The myth is dead!!

Riddle me this...

Say I have a reservoir of fluid which I can vary the height above ground. This reservoir is connected via hose to a hydraulic cylinder. This cylinder is connected to a load of some kind, say a block on the ground. To make the block move, I'll have to raise the tank to a sufficient height to produce the pressure to overcome the friction... then the block will move. I am supplying pressure which results in motion (or flow). Ergo, pressure makes it go. Say the Pressure-Flow interaction is a linear relationship with friction,


Flow=Pressure/Friction



Here Flow is a function of the pressure, that is the pressure dictates (is in charge of) the motion. The myth is dead!

Take the tank in the example above and replace it with a positive displacement pump (spinning at a constant speed) providing a constant flow. The relationship between the motion and the pressure then becomes



Pressure=Flow x Resistance.



In this case, the pressure is a function of the Flow, i.e. the Flow dictates the pressure. The myth is alive! The flow made it go!

The two examples above are different. One has an input of flow and the other has an input of pressure. The myth is... well it depends!

 

[Redneck in training]

Riddle me this...
Pressure=Flow x Resistance.

In this case, the pressure is a function of the Flow, i.e. the Flow dictates the pressure. The myth is alive! The flow made it go!

The two examples above are different. One has an input of flow and the other has an input of pressure. The myth is... well it depends!

There is something wrong with above equation. More flow equals less pressure. The equation should be Pressure=Resistance/Flow.

 

[AKKAMAAN]

Riddle me this...
Say I have a reservoir of fluid which I can vary the height above ground. This reservoir is connected via hose to a hydraulic cylinder. This cylinder is connected to a load of some kind, say a block on the ground. To make the block move, I'll have to raise the tank to a sufficient height to produce the pressure to overcome the friction... then the block will move. I am supplying pressure which results in motion (or flow). Ergo, pressure makes it go. Say the Pressure-Flow interaction is a linear relationship with friction,

Head pressure or pressure from a prime mover powered pump does not matter PRESSURE=PRESSURE

Flow=Pressure/Friction

Please back this one up!!
In metric system I'll tell you what you just said....
Flow unit = m3/s
Pressure unit = N/m2
Friction or resistance is equal to force, actually opposing force...unit=N

so here is your equality, and I'll simplify it for you too

m3/s =(N/m2)/N
simplified step 1
m3/s=1/m2
simplified step 2
m3 x m2 x s/s = m2/m2 x s
simplified step 3
m5=s
"m5" equals time???????

Here Flow is a function of the pressure, that is the pressure dictates (is in charge of) the motion. The myth is dead!

Take the tank in the example above and replace it with a positive displacement pump (spinning at a constant speed) providing a constant flow. The relationship between the motion and the pressure then becomes



Pressure=Flow x Resistance.



In this case, the pressure is a function of the Flow, i.e. the Flow dictates the pressure. The myth is alive! The flow made it go!

The two examples above are different. One has an input of flow and the other has an input of pressure. The myth is... well it depends!

:confused2::confused2::confused2:

Come back after you have "backed up" that formula statement

 

[AKKAMAAN]

There is something wrong with above equation. More flow equals less pressure. The equation should be Pressure=Resistance/Flow.

Pressure=Resistance/Flow
N/m2=N/(m3/s)
Simplified step 1
m3 x N/m2 /(N)=N x m3/(N x m3/s)
Simplified step 2
m = s
"distance" equals "time"?????

Nope that didn't work either....back to class.....:laughing:

 

[AKKAMAAN]

There is something wrong with above equation.

I can agree one this one.....:thumbsup:

 

[gpflepsen]

Head pressure or pressure from a prime mover powered pump does not matter PRESSURE=PRESSURE



Please back this one up!!
In metric system I'll tell you what you just said....
Flow unit = m3/s
Pressure unit = N/m2
Friction or resistance is equal to force, actually opposing force...unit=N

Never said I was using SI units. The equation is a generality. Flow is proportional to pressure. The unit of resistance would have to be in terms that made sense. Actually, the units of resistance would be N-s/m^5 for this situation.

so here is your equality, and I'll simplify it for you too

m3/s =(N/m2)/N
simplified step 1
m3/s=1/m2
simplified step 2
m3 x m2 x s/s = m2/m2 x s
simplified step 3
m5=s
"m5" equals time???????

Everything cancels out, 1=1.

:confused2::confused2::confused2:

Come back after you have "backed up" that formula statement

A simple example of the above equation, although in the electric domain, would be:

Current = voltage / resistance; or V=IR

The units of resistance is volts/amps.

And Redneck, if pressure increases, flow will have to increase. Think of the electric analogy. If you increase the voltage, the current will increase. That's known as Ohm's Law.

For hydraulics, the pressure is usually proportional to the flow squared and is not a linear relationship. P=C x Q^2

Does that "back up" my formula statement? :confused2:

All I am saying is that two different hydraulic situations can be modeled, one in which pressures are an input and one where flows are the input. The resulting motions, pressures and flows are dependent upon the reactions to the inputs. And yes, Newton was also correct.

 

[mmurphy]

Hey, this is getting interesting!!!!:thumbsup:
The metric stuff is a little hard on my poor little marble!

 

[Redneck in training]

Pressure=Resistance/Flow
N/m2=N/(m3/s)
Simplified step 1
m3 x N/m2 /(N)=N x m3/(N x m3/s)
Simplified step 2
m = s
"distance" equals "time"?????

Nope that didn't work either....back to class.....:laughing:

Perhaps the relationship is more complicated but I tried conveying that if the pump delivers constant flow then the resistance will affect both flow and pressure in opposite manner. In example: Resistance rises, pressure rises, and flow goes down and vice versa. Like in Ohm law. Since the hydraulic system has energy loss the equation perhaps should be Pressure=Resistance/Flow*efficiency coefficient.
Hydraulic power=Flow*pressure*efficiency.
What makes hydraulic system work is ability of the pump to deliver certain flow while maintaining certain pressure. In theory any size of the pump will make hydraulic cylinder/motor work but it might be very slow on one extreme or uncontrollably fast on the other.

 

[J_J]

I know you guys are exercising your brain power, but most of us only know how to turn a wrench.

You can have lots of flow, and no or little pressure. Not much work can be done here. Just a little flow, and max pressure caused by high resistance will accomplished the designed work.

 

[AKKAMAAN]

Never said I was using SI units. The equation is a generality.

Does not matter what units you use....it will come out the same way.....
You stated that "Flow=Pressure/Friction"

Flow=volume per time unit
Volume is distance x distance x distance=distance^3, common std unit is inch, so it will be inch^3
Time is measured in seconds, s.
Pressure is force per area unit
Common std unit for force is pounds, lbs.
Area is distance x distance=distance^2, common std unit is inch, so it will be inch^2
Friction is a force that is opposing the a the force that tries to move an object.

Your statement "Flow=Pressure/Friction" can be expressed like this...
volume/time=(force/area)/force
or
inch^3/s=(lbs/inch^2)/lbs
and it will come out as
inch^5=s.......:thumbdown:

Flow is proportional to pressure.

proof it or take it back!!

The unit of resistance would have to be in terms that made sense. Actually, the units of resistance would be N-s/m^5 for this situation.

Don't go public with that one....LOL....:thumbdown:

Everything cancels out, 1=1.

Did not! :thumbdown:

A simple example of the above equation, although in the electric domain, would be:

Current = voltage / resistance; or V=IR

The units of resistance is volts/amps.

I love hydraulic-electric analogies!:thumbsup:
But they have to be used carefully, a std electric system is almost always constant pressure (voltage) and closed loop. I just dont see how electric analogy will save your day here.....the amps is flow and the voltage is the pressure, the resistance is the load........it is the voltage that drives the amps through the circuit. Voltage is the "force".....force makes it, the amps, go.

And Redneck, if pressure increases, flow will have to increase.

I am OK with that!

Think of the electric analogy. If you increase the voltage, the current will increase. That's known as Ohm's Law

.
I am OK with that too!

For hydraulics, the pressure is usually proportional to the flow squared and is not a linear relationship. P=C x Q^2

Does that "back up" my formula statement? :confused2:

I am confused too....:confused2:

All I am saying is that two different hydraulic situations can be modeled, one in which pressures are an input and one where flows are the input. The resulting motions, pressures and flows are dependent upon the reactions to the inputs. And yes, Newton was also correct.

If we use a combustion engine, the source for the prime mover force is in the combustion room, converted from chemical energy stored in fuel and oxygen. The rest of the drive chain can be considered part of the load, piston, crankshaft, pump shaft, gears, fluid, piston, piston rod,linkage and finally "the bucket", that lift the load.
Flow is just something that happens (action or reaction) in the drive chain.....flow is just moving fluid....like the moving piston rod.....but just because the fixation that hydraulics is "complicated", we think that flow is magic.....no one ever calls that the "flow" of piston rod "makes it go"...inch^3 per second of solid steel.....which is an equivalent call to that "flow makes it go".....

Myth dead now?

ps. Glad you accepted that Newton was correct!!:thumbsup:

 

[AKKAMAAN]

Perhaps the relationship is more complicated but I tried conveying that if the pump delivers constant flow then the resistance will affect both flow and pressure in opposite manner.

If there is a constant flow, how can resistance affect flow other than if some flow gets diverted through PRV or internal/external leakage??

In example: Resistance rises, pressure rises, and flow goes down and vice versa. Like in Ohm law.

You just stated flow was constant.

Since the hydraulic system has energy loss the equation perhaps should be Pressure=Resistance/Flow*efficiency coefficient.

If you try to make the analogy with Ohm's law the formula would be Pressure=Resistance x Flow or Flow = Pressure/Resistance

Hydraulic power=Flow*pressure*efficiency.

OK!

What makes hydraulic system work is ability of the pump (and the prime mover) to deliver certain flow while maintaining certain pressure. In theory any size of the pump will make hydraulic cylinder/motor work but it might be very slow on one extreme or uncontrollably fast on the other.

OK! too...

 

[Egon]

Everybody bored today with nothing useful to do?:laughing:

Just remember water runs downhill and you can't push on a rope and all will end well.

And when a line breaks there's usually a mess regardless of units!:thumbsup:

 

[dcyrilc]

Everybody bored today with nothing useful to do?:laughing:

Just remember water runs downhill and you can't push on a rope and all will end well.

And when a line breaks there's usually a mess regardless of units!:thumbsup:

Yea, yea, yea... you had to remind me that I have a loader line leaking, didn't ya?:laughing:

How you doin' tonight Egon?

 

[kennyd]

Everybody bored today with nothing useful to do?:laughing:

Just remember water runs downhill and you can't push on a rope and all will end well.

And when a line breaks there's usually a mess regardless of units!:thumbsup:

You can't nail Jello to the wall either:laughing: