Ted

2017-10-09 22:30:36 UTC

But I specified a centrifugal pump. Traditional.

But you refused to specify conditions.1) Duke has included the elevation or static head, but not the

friction head, which adds to the static head, and is the resistance

of the water or fluid

being pumped through the pipe filling the tank. The value of the friction headfriction head, which adds to the static head, and is the resistance

of the water or fluid

depends on the flow rate, the discharge pipe size, and somewhat on the surface

smoothness of the pipe interior. The additional friction head could easily

increase the overall head from five to ten percent higher. In poorly engineered

cases or adverse operating conditions this could be much more. In all cases the

flow rate or volume pumped per unit time would be decreased.

Friction head?? In a tank 1000 feet in diameter???? I simplified the problem

to the lowest level of complexity possible.

Duke: > Right, part of the reasonable.problem

A problem without sufficient data is next to meaningless.

Later in this post of yours, you speak of a 500' long pipe emptying

into the tank, so friction is involved.

No, I "laughed" at the idea of being concerned with line friction at 1000 ftinto the tank, so friction is involved.

diameter.

you could say the pipe had a horizontal run, but you also said that

there were no tricks.

idea. But, the pipe must run vertical, not horizontal.

You spoke of a pump rated at X gpm at P pressure. There is an

implication there that the pump is working against a 500' head.

implication there that the pump is working against a 500' head.

Okay, but another part yet of unspecified conditions.

If the pump is working constantly against a 500' head, then this

necessitates a pipe discharging at the 500' level.

That's what I said ................if............what?necessitates a pipe discharging at the 500' level.

If you say that there is no friction head, possible in a 500' tall

tank being filled from within the tank, near the bottom,

Long before a pipe came into the picture.tank being filled from within the tank, near the bottom,

to provide the static head (vertical pipe mandatory).

then the pump operates starting against a minimal head, off the tank

bottom, and the flow rate would be much greater than the 1000 gpm you cite.

bottom, and the flow rate would be much greater than the 1000 gpm you cite.

I've brought this up multiple times. You refused to comment on it.

understanding.

<ok, got to run right now> Will continue later this morning.

2) Duke did not specify what the pressure is on the inlet to the

pump. If the pump is fed from a tank, particularly a tall one with a

base at the same level,

, the volume will increase, as the inlet-outlet pressure

differential decreases. The pump may be fed from another 500? tall

tank. Even if fed from a

separate tank, with fluid fifty feet above the pump inlet, the flow rate wouldpump. If the pump is fed from a tank, particularly a tall one with a

base at the same level,

, the volume will increase, as the inlet-outlet pressure

differential decreases. The pump may be fed from another 500? tall

tank. Even if fed from a

be significantly higher. And Duke has not specified the necessity of a NPSH, Net

Positive Suction Head, to avoid pump cavitation, and pump damage.

part of the problem.

You refused to clarify specific conditions.

Me: You did? Initially? Was this before or after you said that the

answer was figured mathematically? Or when you said the answer was not

computed mathematically? Show this, please.

answer was figured mathematically? Or when you said the answer was not

computed mathematically? Show this, please.

Another refusal to clarify your problem.

And for a reasonably educated technician or mechanic, inlet conditions

are ___always___ part of the calculation.

Duke: >It would make it too complicated.are ___always___ part of the calculation.

Me: For us, generally? No.

This problem was presented to our two clowns ted and atl. Your jumping in waswelcome.

3) For me, his most grievous mistake is the omission of how the

liquid is delivered into the tank being filled. Your calculations

work for delivering the water

to the top of the tank, but you did not specify where and how the

discharge would be. You do not include another possibility. Actually

a reasonably high probability.

Now, in the big picture, that would be a reasonable consideration. However, Iliquid is delivered into the tank being filled. Your calculations

work for delivering the water

to the top of the tank, but you did not specify where and how the

discharge would be. You do not include another possibility. Actually

a reasonably high probability.

did specify attaching a centrifugal pump rated at 1000 gpm/500 ft

head to a vertical round tank 1000 ft in diameter and 500 ft tall, how long

will it take to fill the tank?

specific conditions.

In starting to fill the tank of this height, why fill from the top?

At the start, this is ?lifting? water 500? in height, and then

letting it drop to the bottom of the tank.

At the start, this is ?lifting? water 500? in height, and then

letting it drop to the bottom of the tank.

would put a pump up

in the air. Of course, if the tank was in a 500' deep hole in the ground, you

might have a point. But then you wouldn't need a pump design point of 500'

head.

Me: If we had a half-capable technician or mechanic, we wouldn't needmight have a point. But then you wouldn't need a pump design point of 500'

head.

an engineer. And I did give different consideration for pump

location, and pump heads.

Regardless of how the typical tank is filled, the most

energy efficient way is to fill the tank from near the bottom.

Duke: > Shucks, now you really let me down. A 500' filling pipe wouldenergy efficient way is to fill the tank from near the bottom.

do the job, if filled first.

Me: I'll try and make this more clear, Duke. You finally mention a

500' filling pipe, which would add a friction head. This is what I spoke of earlier.

In using this pipe to fill the tank, the pump must __always__ work

against a 500' head,

a range of flows.

Wrong. A pipe discharging into the top of a 500' high tank, fed from a

pipe starting at essentially the zero level and discharging at the 500' level, would

always have at least a 500' head, even if the flow were miniscule. As

the flow rate increases so that friction head increases to a noticeable

value the head would increase above 500'.

would use up some of the tdh..

even when the filling starts, with the level of liquid in the tank

being essentially zero, at first.

(Unless you crawfish and say the tank already has 499'or some lesser

figure, above zero feet, in the tank).

being essentially zero, at first.

(Unless you crawfish and say the tank already has 499'or some lesser

figure, above zero feet, in the tank).

Yes Yes Yes.

With a pump discharging into a point near the tank bottom, the flow

rate will be much greater than 1000 gpm. Surely you are familiar with

performance curve for pumps?

Oh, yes.rate will be much greater than 1000 gpm. Surely you are familiar with

performance curve for pumps?

refusing to specify operating conditions again arises.

You are shot down in flames. Or maybe centrifugally pumped into the

sewer system. I hope you have kept yourself company by the

regurgitation of your dodging techniques.

I'm not dodging. I'm spoon feeding you to the answer.sewer system. I hope you have kept yourself company by the

regurgitation of your dodging techniques.

Your writings here are dishonest or irrational. I suppose they need not

be entirely mutually exclusive.

Put up or shut up, Duke. Don't waste our time by your cries for

attention. You and I might have held an interesting discussion off AA.

but you're apparently not up to it. Don't bother to reply unless you

have something worthwhile to say. You haven't yet said anything

worthwhile in this thread.

Now you're trying to bail out and blame me because you still can't figure outbe entirely mutually exclusive.

Put up or shut up, Duke. Don't waste our time by your cries for

attention. You and I might have held an interesting discussion off AA.

but you're apparently not up to it. Don't bother to reply unless you

have something worthwhile to say. You haven't yet said anything

worthwhile in this thread.

the answer.

To whit, the intermediate answer I acknowledged really is 5.6 years but ONLY

with a vertical discharge pipe of approximately 500ft length and pre filled to

the top. It could be within the tank via a flanged nozzle, or up the outside up

and over.

But that's not the answer I was seeking. I did NOT say anything about a

discharge pipe and asked for an answer. This was not part of the given

information -- as you know as you tried to make it a part..

So you're still coming up short of the true answer to the problem as given. And

no fancy stuff. Just pump stuff. You're almost there, but not yet.

Does this look familiar: HP = (TDH x Q) / 3960 (for gpm)

earlier. But you'd have to know some physics to understand it. Are you able

to derive that formula, Duke?

down at some point. When input and output pressure are

both zero (both reservoirs at the same level), TDH=0, the

equation says any amount of water can be moved without

expending any energy; or, that if a finite nonzero

horsepower is applied, then you get an infinite flow

rate. Either of those situations is obviously hokum.

So you can't apply the equation from the beginning of the

tank filling operation.

The total volume of water in the tank at a point in time

is the integral of flow, Q·dt. But the flow rate depends

on TDH which depends on the volume of water already in

the tank. So now we're all into different equations,

which are clearly way over duke's addled head. Maybe Bud

could explain that to him? :)

LOL. I'm crossposting this to the group Bud monitors in case he wants tois the integral of flow, Q·dt. But the flow rate depends

on TDH which depends on the volume of water already in

the tank. So now we're all into different equations,

which are clearly way over duke's addled head. Maybe Bud

could explain that to him? :)

get involved.

Bud, in case you are interested, the subject of the thread is Re: Duke lie

0902171 - Blatantly False Witness