Hmmmm.. Interesting discussion..
My understanding is;
The negative pressure inside a chamber can never be less than –1 bar. Once you get to -1 bar, you cannot pump anything else out. This is called a hard vacuum.
Festo fittings, with the correct tube, are rated to 95% of this..
I suggest that if you were ever to take the pressure inside your tank system down to .095 bar, you would have much bigger problems then air leaks in the Festos. I reckon the tanks would collapse way before the Festos failed.
Festo fittings on the suction side of a pump work. As proven every day by thousands of modellers who have this item up stream of the pump. Successfully..
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I also understand that Festos, by their design, have larger orifices than barbed fittings.. So, (provided the fittings are not letting air in), would not the larger orifice size help to reduce cavitation issues in hi flow/large engine installs?
This is a serious question