More explanation from Laing :
Quote:
Hi David
We like it how interested and competent you handle the test!
Due to the fact that we made a lot of measurements with the same result (that what you describe as Laing DDC v2), we are quite sure that our measurement is correct and not an "optimistic" curve, as you wrote :-).
The fact that we use a second pump in our test is state of the technic. Without the second pump you never can measure at zero pressure!
You are completely right if you mention the fact of additional pressures, if you work with two pumps in series, but in a test facility you have to use a speed controlled pump, then starting the test pump, watching flow meter and pressure gage and measure the difference pressure between inlet and outlet. Okay, now you start the second, speed controled pump, adjust it exactly to the point of zero pressure (watching the pressure gage), and that's it. From this moment you can measure the max. Flow rate at zero pressure.
David, you may rest assured that we don't have any interest to disappoint anyone and I'm sure we will solve the misunderstandings.
Later I'll try to make a little drawing of our test principle, to send it to you.
For the moment, have a nice weekend,
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To understand the terms above, I gave him a quick comparison with my own measurement called V1 (the same as Laing in their first webpage) and their new graph, called Laing V2 to distinguish them (not a true V2 !) :
If the V2 curve was *true*, I should to find a flowrate higher of ~40 L/h in my low restrictive system (using PD on WB) but it's not the case :shrug: . Anyway, the little difference is not really important because pump is really silent and powerful, some L/h more or less is irrevelant.