Quickie plumbing question

Ok so I just finished talking to my buddy who is a CPEIT (certified plant engineer in training) who graduated from the Maratime Academy ( merchant marine engineer, and ex commercial electrician)
The power used is constant (in this application, which is a huge difference in the application that your pumps work on) there is no change in what the pump uses. And I hate to say it just because they are the same style of motors doesn't mean they are engineered in the same manner, or for the same application. Its like saying because a gas and diesel motors are combustion motors they work and were engineered the same. Not true.. These aquarium pumps draw what they draw no matter how you restrict their flow. When you mechanically restrict the flow the electric energy is now being transferred into flow and pressure in the line. Wide open the pump flows at its max so all the electrical energy is being transferred to that. Now when you decrease the flow, you are increasing the pressure. thus you are not changing your power consumption. Its just being redirected to the increase in pressure.

ok, you knew what I was talking about when I said drive, it was a general term...

now you are totally right on all this, the problem is your understanding on these pumps (we are talking small less advanced engineered aquarium pumps) is wrong. You can not change their power consumption by mechanically restricting flow inline. Application of the pump affects the pump design.

I have add a picture of the equation for General Energy (given to me by the same engineer who has taken more classes in fluid dynamics then just about everyone, and I also have a BS in mathematics)
and sorry the pic is not real great cell phone pic (im at work and no scanner)

 

Good God man, you don't need an equation, all you need is a power meter. A $40 dollar meter from Home Depot will tell you you are wrong.

I'm not a Engineer in training.... I went through the Naval Nuclear Power school 20 years ago. I have been moving water and using pumps since then. I monitor energy flows all day long.

I would love for you to tell me the difference in engineering in pumps for how these special aquarium pumps operate compared to the special pumps I seem to be using. I have told you exactly why you are wrong, yet you have no argued your case as to why you are right, and you do not understand the subject other than to ask somebody else. The equation you show does not is not being used in the proper application.

In any system energy can neither be created nor destroyed... it can only be converted. The enery a pump consumes is converted to heat and how much water it moves. A fan draws power on how much air is moved, a grinder pulls power based on how much material it grinds.

Aquarium pumps are not positive displacement pumps and can't slip. Velocity is converted to pressure in the volute. If the discharge is closed, the impeller slips in the fluid, no work is being performed other than heat being generated by friction.

So explain to me how moving water is free and requires no energy.

 

Look bro. You are not understanding what I am saying. Trying reading it, and not just assuming you are right because you move water at your work. open your mind.

First I never said moving water was energy free, so don't put words in my mouth. just because you don't want to listen to what I am saying doesn't mean you can imply that I don't know the basics. So don't treat me like some uneducated person, that has no clue with the basics of life. I can tell your ignorance from the comment of the equation. Math is life buddy, and all the button pushing you do comes from math.

Second I know exactly what you have been saying, in fact I understand the situation perfectly, its you that is not understanding. I asked my friend because he has a little more experience with the topics then either you or me. By the way the only reason he is in "training" is because he doesn't have 5 year experience, 4 but not 5. So in another year he wont be in training. You are a worker, not the person that does the equations. Thus you know what you are told. And as for the equation being wrong, you made your self clear that you really don't know what is going on. (here is a little in site on math, so I will try and talk slow for you) You can take the variable you plug into the equation, and leave the variable (its like a place holder) out that you don't know (the electrical draw). Do the math and find how it changes with different situations. Would some one with a PHD in fluid dynamics change your mind? Probably not because you must know everything about pumps and water movement because you are a worker bee at some sand plant.

Third, when you are talking about energy not being destroyed or created you are right. And as i said in my last post ( I will go slow again). When the flow is wide open (non restricted) the "electric energy" is converted to "flow energy" and "heat energy" and some "pressure energy". Now when you constrict flow (throttle back, put a valve on it) you are decreasing the "flow energy" but you are increasing the "pressure energy" and probably the "heat energy" (I will admit I am not sure on that, but I put it in there for the sake of argument) Thus, the "electrical energy" being drawn is the same, but it is being converted to different types of energy other then strictly "flow energy". At the chance of sounding redundant, I am not destroying or creating energy, it is being converted.

Fourth, you can tell me with a straight face that the pumps you are using (which by you move 40 million pounds of water) are designed/engineered exactly the same as a $100 120v pump. I don't think so, and if you really do then you are in a sad position.

Fifth, the impellers can slip, but that doesn't mean the drive mechanism is turning. The impeller is slipping on a part of the motor that is still running. Still drawing power. Unless the pump has clutch system.

Sixth, by your logic. I can take a 120v pump, throttle it back and run it off 12v system. I don't think so...

Seventh, You are not looking at in the application. What you do at work is a whole other application then that of our aquarium application. Its completly different. You can't just scale back what you do to this because its not the same. The induction motor doesn't affect the style of pump. The pump style can change with the same type of motor. The motor has nothing to do with how the water is moved.

Eighth, I am done. You are not even going truly analyze and think about anything from another point of view, so you will be stuck in what you believe. The next post on this thread you see from me will be after I have my experiments completed. (that is using a muti-meter for test draw. First run the pump wide open, and test. Then throttle is back a little, and test. Then come close to cutting off the flow completely, and then test). At the time I will either say I'm sorry your right. More likely it will be me that is right, but don't worry I won't expect you to say your sorry (your to good for it).

 

No crap. I've had plenty of math. I know all the equations. Now it is you being condescending and think that I'm just some stupid worker that does what he is told. You have no clue what my educational back ground is or what I have done in my field. I have been more than kind to this point and have explained why you are wrong. Now you want to jump in here fresh out of school with some meaningless math degree and tell me I'm wrong and don't know crap about what I have done for my whole career. You are the one living in ignorance because you think you know something and you don't even know how wrong you are. Perhaps just perhaps... somebody actually knows something you don't. I know that sounds far fetched.... but just maybe.

Wow astounding. You argue I'm wrong when you don't even know the subject we are discussing. Do you know what the Naval Nuke School is? It is all the core course work for a Mechanical Engineering degree... minus the English. Do you know how hard it is to get into and pass? Nothing but fluid flow, thermodynamics, reactor principles, physics, chemistry, metallurgy... and they even teach you how to add two plus two. I realize it may be hard for you to think anyone can understand calculus and differential equations other than you... but get a clue Sport... you're not that special.

You are out of your league. Go ask your friend in training to have his teacher explain it to you. In you great equation you gave... that's great for flowing water... so now lets close the valve. P1 and P2 are the same...V1 and V2 are the same, gravity is the same, specific weight is the same, it's a horizontal run of pipe so height is zero or at least is the same at point one and point two...so those cancel each other out on both sides of the equation. So what are you left with..... add losses to both sides of the equation and you are left with energy added by the pump is equal to losses. Wow genius. Way over my stupid little worker head but I'll try and keep going. So what is the amount of enrgy added by the pump Sport???? What it says on the label right??? WRONG. It is the measurement of the multimeter. So what it is drawing is equal to what the losses are... which is the frictional loss to the fluid and to the bearings. Exatly what I said before..... yet now you open a valve... now you have fluid flowing.... now you have velocity... now you pump it up a height..... but according to you that is all free without one single milliamp more power being used. You will definitely get the Nobel for this breakthrough.

Voltage applied has nothing to do with the physics that govern. Same for both whether you are using 120vac or 4160vac. Motors have not changed for a hundred years. You need a voltage, a conductor, and a magnetic field. Totally straight face.

Good God Son, what the heck are you talking about.:

The impeller is physically attached to the rotor... which is physically attached to the magnet.... the rotor does not slip... the impeller can slip in th fluid in a centrifugal pump. Here is an experiment for you Sport....get your little multi meter....take the pump cover off. Hold the impeller.... and then plug it in.... tell me how many amps it draws before it cooks it self. It isn't even turning, no water is even moving...gee what could possible be bad... it should not draw any power at all.:

Your lack of electrical knowledge is astounding. Voltage is simply the potential across two points. Voltage does not change. P=I X E. E remains the same at 120v. Current changes... However... if you took a 120v motor rated at 1 amp that would be a 120watts ... but if you only had 12 v, and the magnet actually stayed locked to the frequency, then it would draw 10 amps to remain equal..... your pump would melt.

Well now I'm excited I might actually learn something. Now is your big moment to shine. I have asked you to explain... but you have not done so. Please gather your vast knowledge of fluid flow and electrical theory... call your friend if you need to... and tell me what is different between a centrifugal pump with an induction motor drawing 465 amps, at 3 phase 2400 VAC, putting out 2100 PSI at 100,000 LBS/HR....a 3 phase 480v centrifugal pump with an induction motor drawing 1 amp moving 2000 GPH.... and a single phase 120v centrifugal pump powered by an induction motor moving 200 gph. Get as many friends as you need.... I'll wait.

I'm so giddy with excitement. Golly gee... what could the results possibly be????? The suspense is killing me.

When you are scratching your head because it didn't come out how you expected.... this is what happened....with the valve closed.... your 100 watt motor pulled 60-70 watts... that is the power factor and the frictional loss..... when you opened the valve and it pulled 100watts.... that was water moving.

Now that we got that straightened out.... please tell me how throttling a pump is going to shorten it's life. I sure do appreciate you going slow for me.

 

OH my, this is gonna be fun

 

The power a centrifugal pump consumes is directly related to the work at hand. Move less water or add more head, the power consumption goes down. Positive displacement pumps are different but this is true for all centrifugal pumps.
You can demonstrate this very easy using a ball valve and a kill a watt meter (about $15 at any hardware store). I have done extensive testing on most popular aquarium pumps including Mag, Ocean Runner, Quiet One, Via Aqua, Eheim, Rio and others and it has never failed to be true.

 

You obviously don't know what you are talking about.... probably just doing what an engineer tells you to do.

 

...scale? :;D

I'm fairly sure it already was fun; he won't be back for more.

 

Who doesn't know what they are talking about?
I'll dig up my test results which I published on Reef Central several years ago. Facts don't lie.
Having worked in the pump industry for 35 years I am confident I know what I am talking about.

 

I don't think that comment was meant for you.
I hope this doesn't get closed b/c i would love to see the definitive outcome.