Help understanding how a pump curve can show higher GPM than pipe can handle? 2

[Kiboko]

Hi everybody,

I am new to the forum and have a question that is stumping me. I was looking at a curve today

and I was wondering what the maximum GPM a 1" pipe can actually handle? According to the curve it is capable up to 100gpm, but when I look on engineeringtoolbox.com (

https://www.engineeringtoolbox.com/steel-pipes-flow-capacities-d_640.html)

It is telling me that a 2" pipe can only handle 45gpm max. It didn't have a 1" option, but I believe 25gpm was what I saw when googling the capacity of a 1" pipe.

What am I missing?

Thank you for any help able to be provided.

 

[TugboatEng]

Theoretically there is no GPM limit for pipe. Practically, there are a great numbers of limitations. #1 is erosion. Copper pipe is going to have a very low GPM limit relative to steel, to stainless steel, then plastic. The next issue is pressure drop. It takes a lot of power to push high GPM through small pipe due to pressure drop. This is exacerbated by long pipe runs. Thirdly are noise and vibration. These can both make the pipe intolerable to be around and cause fatigue failures.

There are rules of thumb and most simple piping systems are designed around an "economic velocity" but this number is conservative and can be pushed either way by specific applications.

 

[EdStainless]

The erosion will be controlled by limiting flow velocity. Cu (5ft/sec), brass, and steel will all have velocity limits.
More erosion resistant materials such as stainless steel will only be limited by the pressure drop.
I have heard high flow in high alloy piping at 50ft/sec and the noise is very loud. And the pressure drop is staggering.
With non-metallics it is not an issue of erosion but vibration.
The economics of the pressure drop will usually be the real limit to flow.
Pull out a copy of Crane's and look up pressure drop values.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Compositepro]

You appear to be showing us a pump curve. This has nothing at all to do with pipe size. The pipe is part of the system to which the pump is supplying flow. Where the system curve intersects with the pump curve is the operating point of your system and pump together.

If your system is made of one inch pipe, the system curve will look like a parabola that starts at the origin (0,0) and goes off the top of your graph at roughly about 10 GPM.

 

[LittleInch]

The pump curve has nothing to do with the pipe size and flow. It is simply the source of flow.

How much flow depends on the resistance to flow in the pipe it is connected to.

That is dependant on how long it is, what the height or pressure is at the end and anything else causing friction losses such as control valves.

The table you link is quite clear that this is simply a start point and appears to be based on a similar pressure drop.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

This graphical representation of the friction loss thru' a pipe system overlayed on a pump curve.
Trust this helps in understanding

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[1503-44]

The pump is only the battery. Dont forget the wires and resistor devices have an effect on the circuit's current carrying capacity too.

 

[Artisi]

The pipework, fittings, valves etc should all be considered in the system curve calculation, from inlet to the final discharge point.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)