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Old 01-21-2008, 03:56 AM   #4
NASIOC Manufacturer
Member#: 110029
Join Date: Mar 2006
Location: Sussex, England
2004 Citroen Picasso



The video showed the spread of the pressure pulses. This is a very useful data for setting the "on-demand switch (ODS). Almost all PPS (progressive Pump speed) system relies on the "ODS" to regulate or limit over pressure. Although Shurflo does not recommend the "cyclic" usage of the ODS but PPS system makers ignore it.

For this reason, knowing the peak switch of the pressure spike is very important to the system designer. This is because the "ODS" response to "peak pressure" and not "averaged" pressure as seen on a snubber pressure gauge. The nozzles see the "unsnubbed" pressure because all PPS systems do not use a " hammer arrestor" or accumulator on the delivery line.

This the very point I was trying to highlight - If the ODS is set to "trip" at 150PSI, the actual operating pressure is much lower due to the 20-30psi pressure swing. It will be worse if you account for "oscillation" due to resonance between The PPS controller and the load/reactance of pump winding.

If you look at the video, the swing of the pressure spike varies with duty cycle. You can see when the oscillation occurs, the swing can be as much as 100psi or more!

I believe your PPS controller run much high frequency than many others - avoiding the dreaded " resonance". We do design and manufacture PPS systems under different labels, I understand the design problem very well.

I totally agrees with you when you mentioned that a few WIA makers use "meaningless" terms as "150psi, 220psi 300psi etc. as a sales tools. I choose to publish your test results because your company has come across as a "no thrills" and honest WAI maker.

I have updated the pressure/flow table. and corrected the 30psi checlvalve to 20psi but upping the "minimum" onset pressure of the nozzle.
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Last edited by Aquamist; 01-21-2008 at 04:10 AM.
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