graphing pumps in parallel

[drain]

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?

 

[GregLocock]

Make an xy chart for the first pump. Select the two columns of data for the second pump.Copy. Click on the chart.
>Edit >paste special > paste as new series, columns, categories in first column, make sure replace existing categories is not ticked. >OK

Viola

Cheers

Greg Locock

 

[drain]

Well I learned something from your method but not a solution to my problem. Your method simply places a second graph within the chart. Re read my problem. I have two plots and need to add the x values together for common y-values, and plot them. But 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.

 

[IRstuff]

There is no simple way to do this in Excel. You're basically looking for the ability to interpolate on a second set of data. In Mathcad it's quite easy, but, that's not what you want to hear.

What you'll need to do is to use the MATCH function to find the closest value and then algorithmically calculate the interpolated value for the sum. MATCH returns the position of the number that's smaller, larger or equal to the lookup value. You can then use the OFFSET function to generate the interpolation. TTFN

 

[GregLocock]

Oops. I should have read more carefully. Is a piecewise linear fit good enough? Or can you generate a good analytical curve fit? Or you could use a piecewise third order fit if you don't need the last couple of points for each pump.





Cheers

Greg Locock

 

[sprintcar]

Hey DRAIN
May I get a copy when you get it working??
Thanks! Keep the wheels on the ground
Bob
showshine@aol.com

 

[ansari1]

may i get a copy of ur spread sheet?
it will be helpful for me as im fresh graduate

Best regards:

gladiator_me@hotmail.com

ansari1

 

[drain]

Unequal pump capacity and the plotting mfgr's pump graphs. In excel, plot the mfgr's curve and put use a grid which corresponds to a fixed number you choose for the "head" units, then input the corresponding flow units so you can plot the graph.

If you have pumps in series make the flow a fixed
number and input the corresponding head units.

Alternatively, you can create an approximate pump curve using the equation H = A + BQ^2. In excel use linear regression simply by taking your Q-H data and squaring the Q. Perform the regression on the Q^2 vs H and the A, B coefficients will then fit the above equation. Substitute your H and then solve for Q.

For equal size pumps in parallel, simply multiply the flow times the number of pumps and plot.

 

[psafety]

Drain,
In Excel you'll need to select the XY Scatter plot, then connect the data-points. I had the same problem building the my graph. I use 10 data points from selected pump(s) to plot the combined pump curve and then plot my calculated system curve.

Don Coffman

 

[HamishMcTavish]

If you use the XY scatter plot you could insert a trendline and use that to generate common values. Excel will also give you a correlation coefficient to assess how good the fit is. No more things should be presumed to exist than are absolutely necessary - William of Occam