POSTED ALSO IN SPREADSHEETS FORUM

[drain]

POSTED ALSO IN SPREADSHEETS FORUM
I've a spreadsheet for plotting pump curves on one chart but the problem is in adding the abscissa (x, flow) values for the same ordinate (y, head) values. The two curves are not input with common y-values. The fastest way seems to be to plot out the two pump curves on one chart then create the combined curve manually by hand with a ruler. Presentation isn't the best. Pump supplier software is geared for their pumps alone and I want to be able to superimpose a couple different mfgr's pump curves on my system curves. Any ideas?

 

[HomeMadeSin]

drain:

Maybe I'm missing the problem, but do you have both the X (flow) and y (pressure) data for both pumps? If so, just do an XY plot (if using Excel) with all X values in one column and the first pump's y data in column 2, the 2nd pump's y data in column 3. The easy way to do this is to paste the X and Y data from the first pump in the 1st two columns. Then do the same for pump 2, but aligning the X values under pump ones. Then move the 2nd y values over to the 3rd column, sort by X and plot the two series.

To do it digitally, buy the real Adobe Acrobat program that allows you to print directly to a pdf file and do so for both pumps. Then fire up Adobe Illustrator (if you have access toit) and you can scale the entities to match and even change colors!

 

[drain]

HomeMadeSin
I have two plots with different y values and common x values. But I need to add the x values together for common y-values. I don't have common y values for the two plots so I need to generate them, so I can add the corresponding x values together to get my ultimate plot. Basically, I need an algorithm to fit my existing curves so I can generate additional x and y values.

 

[HomeMadeSin]

drain:

It must be the fact that it is the end of the day. I'm not following you. I can't see the need to add x values (flow) together for common y values (head). You are looking at Pump A and Pump B for a given system curve, yes? So, you would have 3 curves on a single chart: system, pump a and pump b?

 

[drain]

Here's the data, my friend. Common flow. Different heads. Plot them out. Then generate new heads so the curves can be added together for common head.


Q H-1 H-2
0 274.3 286.5
25 271.3 283.5
50 268.3 277.4
75 262.7 270.6
100 253.6 263.0
125 241.4 254.5
150 226.5 247.5
175 207.3 238.6
200 180.7 229.2
225 147.2 218.8
250 109.7 210.3
275 201.2
300 190.5
325 179.8
350 166.7
375 153.9
400 135.9

 

[RWF7437]

Unless you're trying to operate the two pumps either in series or in parallel,there is no need to add either ordinates or absicca. It looks like you can throw away all values of H-2 smaller than 210.3. That will give you equal numbers of x-y coordinates and simplify your task. Next you need to calculate the system head curve over the same range of flows. Then you should be able to plot all three curves and find the points of intersection, i.e. the operating points for each pump.

Do we understand your question correctly ? Are you trying to operate these two pumps in series ?

 

[d23]

Drain:

I thought you were confused until I started to make a sheet for you. You are using flow as a constant number (i.e.: 25, 50, 75 etc.) and trying to vary the head. Try using the pump head as your constant number and very the flow(s) to match the constant head. I think that should work.

Let me know

Good Luck!

 

[drain]

parallel pumping is precisely the reason i want to add them.

 

[HomeMadeSin]

I think D23 has got it. Parallel pumping with two different pumps is what I missed.

 

[d23]

drain:

I don't think I explained very well. I made a quick graph sheet that will show you what I mean and it actually worked . If you would like it send me an email.

davidlsus@yahoo.com

Good Luck!
David