Fuel Filter Question
I went through this too. When I discussed it with Precision Airmotive, they replied as follows:
"We recommend a nominal 32 micron filter because the finger screen in the inlet of the servo is 70 micron and is not meant to be a primary filter. I agree that most certified aircraft should have a similar filter installed, but I have no way of knowing what they use as they are separated from us by the engine manufacturer which gives engine installation specs. Also from our experience, most do not use a sufficiently fine filter".
It's also worth noting that the finger screen in the inlet of the servo does have a bypass, and so if it gets clogged with 70 micron particles, it bypasses and lets any contamination downstream through to the spider and nozzles.
After a LOT of investigation of certified aircraft fuel systems, and available components I ended up with the following system.
Andair GAS375 gascolators (70 micron) in each wingroot
Andair fuel tank selector valve
Weldon 18000A high pressure fuel pump mounted in the usual place ahead of the selector valve in the tunnel
Falls Filtration 02W05847 main filter mounted approximately where the Van's gascolator for a carb engine is mounted right side low forward of the fireeall. This particular filter is normally used on the Beech King Air.
The specs on the filter are:
Fluid: Avgas or Jet Fuel
Flow Rate: 600 pph, using Jet fuel this works out to 85 GPH
Pressure rating:
-Operating 75 psi
-Proof 150 psi
-Burst 225 psi
Filtration:
-17 micron nominal
-33 micron absolute
Pressure drop: 0.5 psi max at rated flow
Bypass valve cracking pressure: 1.8-2.2 psi
I think most FBO fuel systems have 32 micron or better filtration, but as protection against those that don't or for fueling from a drum I prefer to have an adequate main fuel filter with good contaminant filtration and dirt holding capacity. YMMV
I'm still working on mounting all this stuff and sorry do not have pix.