Netters; I'm working through some revisions to the fuel system on N335KC and trying to learn all I can about what to place where in the fuel flow from the fuel tank forward to the top-mounted Ellison on the Great Plains 2180. I came across a YouTube video from Homebuilthelp.com where they take a Facet 'cube' fuel pump apart to see what's inside and how it works. Pretty interesting, and these are ubiquitous little pumps in the experimental aviation world. The pumping mechanism is a sort of piston that oscillates back and forth within a guide sleeve and by design, the fit of the sliding parts is quite precise in order to minimize bypass around the mechanism as it pumps. More than once in the video it's mentioned that Facet recommends that a fuel filter be installed ahead of their pumps to keep foreign matter from getting into the valve and possibly clogging or preventing the sliding parts from sliding in their sleeves and the one-way valves from closing tightly.
I don't know what the clearance between the parts is, but I'm almost 100% certain that just a finger screen won't do much to keep things out of the fuel pump that shouldn't be in it. Checking sources like Jeg's, Summit, and others who offer billet aluminum body fuel filters with replaceable filter elements and AN flare fittings on the ends, I find that there are units available that can handle 100 micron, 40 micron, and even down to 10 micron size particles. To get an idea of the relative size of such particles, grains of table salt are on the order of 100 micron particles. Household dust, which is at the lower limit of what we can see with the naked eye, are in the range of 40 microns. Getting down to the 10 micron size are talcum powder, mold spores, and red blood cells. I know I want to trap 100 micron particles before they get into my fuel pumps and anything else downstream from them and it would probably be good to take out 40 micron house dust too. Where I live (southern Oregon), it gets dry and I get quite a bit of dust in my hangar all the time. In the fire season we can also get a LOT of smoke particulates but that gets down into the 2.5 micron range. Interestingly, most automotive fuel filters, especially those for fuel injected engines, are rated down to 2.5 micron particle removal but I doubt that the clearances in the Facet fuel pumps require the same level of filtration that injectors do. I currently have a NAPA 3032 fuel filter on my fuel system. I welcome any discussion on this subject. Oscar Zuniga Medford, OR KR 1-1/2, N335KC
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