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Anonymous Poster #1

# GPM Calculation

07/24/2017 7:52 AM

If I have a pipe diameter and pressure am i able to calculate the GPM's running through a pipe. ?

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#1

### Re: GPM Calculation

07/24/2017 8:05 AM

No, not just with that anyway. You need to know what length of pipe you are pumping through, what bends and restrictions are there and what the fluid is that you intend to pump (or supply through gravity). You'll also need to know the surface finish of the pipe ID (roughness).

It's been over a decade since I last did pipe calcs but I believe you can get software which is either free or relatively cheap which can model your system and give you pretty much whatever you want as an output but I believe you'll need more input info to stand any chance of getting an answer.

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#2

### Re: GPM Calculation

07/24/2017 8:15 AM

Not without details of the fluid, the length of the pipe, the number and type of bends, its relative roughness and the pressure drop along it, no. With these things to hand, it is possible: refer to Perry, "The Chemical Engineer's Handbook", any edition, or Kempe's Engineers' Yearbook, any edition.

• Pipe pressure drop versus flow-rate correlations were established by Osborne Reynolds in 1875, and this individual's name became attached to the Reynolds' Number, which is the ratio of viscous forces to inertial forces in the fluid.
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#3

### Re: GPM Calculation

07/24/2017 9:10 AM

Anonymous posters don't really do anything.

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#4
In reply to #3

### Re: GPM Calculation

07/24/2017 10:30 AM

Well... they can serve as a warning to governments and institutions to respects the rights of the individual.

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#10
In reply to #4

### Re: GPM Calculation

07/24/2017 12:48 PM

It would be nice if knowledge were free, but why does tuition keep going up?...

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#13
In reply to #4

### Re: GPM Calculation

07/24/2017 1:42 PM

I despise anarchists more even than Nazis! They should be made to submit, just like the rest of us schlubs to the laws, by-laws, taxes, and the rest, with one exception.

The exception: The people when in the course of human events, when it becomes necessary to throw off the excessive burdens of a government that has stopped listening to the people, shall have the right to rebellion, and to use arms to effect a re-balancing of the scales in favor of the people, not the few.

It would appear the blood of tyrants is getting ripe for the picking once again, at least that is what my watch says: "It's about that time."

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#18
In reply to #13

### Re: GPM Calculation

07/25/2017 4:47 AM

You might try reading Robert Nozick's "Anarchy, State, and Utopia", and possibly some writings by Goldman and Bakunin, before commenting so loosely.

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#21
In reply to #18

### Re: GPM Calculation

07/25/2017 9:31 AM

Coming from you, I take that with a grain of salt. I prefer reading Jefferson, Adams, and Franklin.

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#25
In reply to #21

### Re: GPM Calculation

07/25/2017 11:59 AM

... and Thomas Paine ? ...

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#26
In reply to #25

### Re: GPM Calculation

07/25/2017 12:10 PM

Sure, that is one of the main sources of that line of thought as intended.

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#33
In reply to #21

### Re: GPM Calculation

07/25/2017 5:54 PM

Good authors, but you shouldn't stop there.

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#28
In reply to #13

### Re: GPM Calculation

07/25/2017 1:15 PM

Hear, hear. What we need are more organized anarchists.

Anonymous Poster #3
#39
In reply to #13

### Re: GPM Calculation

07/26/2017 2:58 PM

This is an engineering forum. It is not your political soapbox.

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#12
In reply to #3

### Re: GPM Calculation

07/24/2017 1:38 PM

Apparently, neither did you.

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#5

### Re: GPM Calculation

07/24/2017 11:34 AM

There are many published nomographs for the most commonly-encountered fluids, water being the most common of course.

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#6

### Re: GPM Calculation

07/24/2017 11:44 AM

First, what does Bernouli's Equation tell you?...

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#19
In reply to #6

### Re: GPM Calculation

07/25/2017 6:08 AM

Well, for a start, it doesn't tell you much about pipe flow and pressure loss.

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#7

### Re: GPM Calculation

07/24/2017 11:49 AM
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#8
In reply to #7

### Re: GPM Calculation

07/24/2017 11:52 AM

Now, that's just showing off...

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#9

### Re: GPM Calculation

07/24/2017 11:52 AM

Here is a calculator...

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#20
In reply to #9

### Re: GPM Calculation

07/25/2017 9:11 AM

And here is another I've had good results from, add your static suction & discharge head...

Liquid Friction Pressure Loss

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#11

### Re: GPM Calculation

07/24/2017 1:37 PM

No. You still need the pressure at the other end of the pipe, DOH!

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#14

### Re: GPM Calculation

07/24/2017 4:06 PM

You can if the outlet valve is closed.....it would be zero....

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#16
In reply to #14

### Re: GPM Calculation

07/24/2017 4:43 PM

No fair, you changed the conditions.

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#35
In reply to #14

### Re: GPM Calculation

07/26/2017 11:58 AM

If the outlet valve was closed, then where would the flow ''go'', after the ''water hammer'' dampened down ?...

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#36
In reply to #35

### Re: GPM Calculation

07/26/2017 12:19 PM

With the information provided that is the only answer he can get - 0.

The pipe would not flow in the first, or the second place.

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#15

### Re: GPM Calculation

07/24/2017 4:14 PM

Just measure it.

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#17

### Re: GPM Calculation

07/25/2017 1:38 AM

Fluids flow under the effect of a pressure drop so knowing the absolute (gauge) pressure does not help you any assuming we are dealing with a liquid.

As noted by all our learned friends you need to measure a pressure drop between two points; then add up lengths and fittings between those two points and use a calculator from the internet to back calculate a flow based on pipe diameter and linear pressure drop (ie x.x psi per 100ft)

Personally I would look for a calculator that uses Colebrook-White and Darcy-Weisbach rather than Hazen Williams but it depends on the accuracy you need. H-W is a lot simpler!

If you have an existing system then a rough rule of thumb gives

Pipe Size (in) = SQRT (GPM/10)

which I have used for PRELIMINARY pipe sizing on many oil and gas process plant

ie GPM = 10* (Pipe Size)^2

This should just be used as sense check for the detailed calculation above as it could easily be out by 50% or more

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#22

### Re: GPM Calculation

07/25/2017 10:32 AM

Dear friend,

Theoritically you can calculate as follows:

1. You know the pressure in Kg/cm² and this can be converted in to Metres of HEAD, by the equation H (in Metres) = (10.063) x P ( in Kg/c m² ) The Head decides the velocity by the equation V² = 2 x g x H

where V is equal to theoritical velocity, im Metres/Sec.,

g is equal to the accleration due to gravity i.e 9.81 M/Sec.²,

H is equal to the Head in Metres.

2. You know the pipe dia in Metres and hence you can calculate the area in M²

Multiply area and Velocity and you will get theoritical flow in M³/Sec

This is applicable for water. If some other liquid, (with same range of viscosity) the Sp.gravity will come into picture

But in practise, the friction head loss will occur and this is to be deducted from the theoritical head.

For approximate actual discharge multiply the theoritical discharge by 0.65.

DHAYANANDHAN.S

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#23
In reply to #22

### Re: GPM Calculation

07/25/2017 10:44 AM

How do you know he is pumping to an open-ended pipe? The rest of us seem to question that aspect.

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#27
In reply to #22

### Re: GPM Calculation

07/25/2017 12:50 PM

Sorry, but that will just confuse him. It would be right for an orifice in the side of a vessel, depth H m above the orifice centre, or for an orifice in a pipe where pipe dia >> orifice dia, and differential is H m across the orifice. Coefficient of discharge is usually taken as 0.62.

The situation here is quite different. We would need to know the fall in pressure over the pipe length, as well as other details of the pipe and fluid.

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#29
In reply to #27

### Re: GPM Calculation

07/25/2017 1:23 PM

He never said if this was a California pipe, or one from the east coast, or elsewhere. LOL

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#30
In reply to #29

### Re: GPM Calculation

07/25/2017 2:06 PM

No, for all we know, it might run from California to the east coast

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#32
In reply to #30

### Re: GPM Calculation

07/25/2017 5:00 PM

I was thinking 1-1/4" OD x 5/8" wall, schedule 100,000.

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#34
In reply to #32

### Re: GPM Calculation

07/26/2017 8:39 AM

Now that is what you call a solid pipe.

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#40
In reply to #32

### Re: GPM Calculation

07/28/2017 2:40 PM

Oh Jolly! Now we have to compute the Quantum Tunnelling probabilities.

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#31
In reply to #22

### Re: GPM Calculation

07/25/2017 3:34 PM

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#24

### Re: GPM Calculation

07/25/2017 10:51 AM

No.

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#37

### Re: GPM Calculation

07/26/2017 1:19 PM

You may be confusing the rule of thumb known as Poiseuille's law that states that the rate of flow of water is proportionate to diameter of the pipe.

"Pipe cross-sectional area and flow vary with the diameter (of the pipe) squared. this means that twice the pipe diameter yields four times the flow, at a given friction loss."

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#38
In reply to #37

### Re: GPM Calculation

07/26/2017 2:34 PM

Sorry, that's all wrong! If it's laminar flow, Poiseuille's law applies, but this states friction loss is proportional to Q, and inversely proportional to dia4. So for a given ΔP, twice the pipe diameter yields 16 times the flow.

We don't know any details of the pipe, flow rate or fluid, so flow could be laminar. But in practice, it's much more likely to be turbulent. In that case flow is approximately proportional to dia2.5, so for a given ΔP twice the pipe diameter yields about 5.7 times the flow. Approximately because changing the dia changes the Reynolds no. so the friction factor could change somewhat.

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