MATH NERDS! I need help with a pump formula!

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aclockworkorange

Dovii
MFK Member
Jun 24, 2010
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Hey guys, so I'll try to make this short. Here's a flow chart for a random pump:

0a7b3514.jpg


Let's use the bottom curve as the example.

Can anyone explain step by step how to come up with a formula where I can plug in a specific head height and get an answer as to how much flow I would get based on the chart? Is that even possible?

Thanks.
 
Hello; My take from the chart is that the horozontal line from a particular head height will cross the curve and this is the volume. For example at 6 feet height on the lower curve you get something around 2400 GPH and at 10 feet you get around 1200 GPH. You seem to be asking if an equation can be derived from the data on the chart?? I think this can be done. Sorry that I cannot create a formula on a first read. I will have to think on this one a bit.
 
You could do this, but it would only be for that specific pump. You would have to rework the formula for each and every pump out there.

I don't remember exactly how to do this, but it isn't that difficult if I remember correctly.
 
The problem is that it's not linear. If it was a straight line it would be super easy, just find the slope, the Y axis intercept is already given, etc.
 
aclockworkorange said:
The problem is that it's not linear. If it was a straight line it would be super easy, just find the slope, the Y axis intercept is already given, etc.
Click to expand...

Hello; Yes it will not be a linear equation such as Y= 2X. It will be something like Y = n X exponent2 or Y = n X exponent-2 with X being the head height and Y being the GPH. I suspect the second version with the negative exponent. Sort of guessing at this point.
 
what you have is something called a pump curve.

each pump has a specific curve that would be provided by the manufacturer that relates output against maximum head.

you generally read it by looking at the pressure head and then reading across to see what the output in gallons per minute would be pumping against that head.

notice as the pressure goes up the output in gallons per minute goes down, which makes sense.
 
aclockworkorange said:
Can anyone explain step by step how to come up with a formula where I can plug in a specific head height and get an answer as to how much flow I would get based on the chart? Is that even possible?

Thanks.
Click to expand...

Not sure I follow what you're trying to do. Do you want flows for this pump, or other pumps? Because this graph gives you the flow rates from 0 to almost 12ft. Do you need something more than 12ft?
 
jcardona1 said:
Not sure I follow what you're trying to do. Do you want flows for this pump, or other pumps? Because this graph gives you the flow rates from 0 to almost 12ft. Do you need something more than 12ft?
Click to expand...

Jeez, I guess I shouldn't have kept it short in the first post.

Guys, I'm in college, I take college level math, I'm not a moron. I know how to read the chart. I know I can approximate the gph at the head height I have by looking at said chart. I am interested in a formula for the specific chart I posted where I can plug in a specific head height (say, 7.6 feet or something) and get an answer as an academic exercise. And also for an explanation as to how you came up with that formula so I could figure it out for other pump curves if I want.
 
No I get what you're trying to do. I have no idea what the formula is, but I get it.
 
There are some programs where you plot all your data points and it try to figure out the closest formula that would create that curve. I had one like that on my graphing calculator for my calculus classes, though I've forgotten everything I learned in those classes by now.
 
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