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Fuel transfer/polishing pump
This is starting to look more like the pleasure boat with diesel power
application. But cars don't typically have to deal with the shaken-up sediment load - and it is this that has been a continual preoccupation in this newsgroup thread. It is this that this trhead is addressing. We have a diesel bus for our business and have had no problems with the fuel problems we have had on our boat. Preoccupation seems to have a negative connotation in that it generally infers that the issure is not necessarily real or is blown out of proportion. For people who are willing to consider reasonable approaches to diesel fuel handling (and gasoline for that matter) there can nobody who can pick fault with using a sampling valve at the low point of a fuel tank. This can save so much grief from water and visible contamination that it represents ultra-cheap insurance. Unfortunately, a sample valve at the low point in a fuel system is very much in violation of CG rules. That said, my tanks have them and I wouldn't be without them. The next reasonable step is to provide a sight glass for early detection of water and contamination (the 'tractor' approach) The transparent bowl in a Raycor fills that bill. For people who just cannot fit a drain/sampling valve in a sump (though they cost under $20 typically) and have some reason to avoid a sediment/water sight cup then using a pair of surface filters offering large area and rotating them will save most engine outs - but not all. For people who must do all they can to eliminate engine stoppage from fuel contamination, then fronting a fuel system with a depth filter that won't itself break down is cheapish insurance. I haven't surveyed depth filters in this application recently - but the ones that no expert could not reasonably object to would be built something like this: layered stockinette knit, string bobbins. In reviewing what I have written here today, I see I have omitted any mention of fuel polishing - which is where the thread started. Here's my personal opinion on this: boaters and sailors will know if they are likely to get fuel contamination - it only takes one nasty experience. The realistic view is that it is not 'if' but 'when'. Bad fuel can be obtained anywhere. But what is the reality it that fuel can go bad just sitting in the tanl. So the best supply of fuel in the world will become bad. Sailboats are especially prone to this since we tend to use little fuel. They will think that if they replaced all fuel tanks and took on only clean dry fuel, they could avoid another scare - but that's not practical for most (and even those who did could still find water in the fuel - temperature cycling in a ventilated tank can *deposit* water in the fuel, for sure.) Water is easily removed by a normal Raycor. It's the water that provides the interface for critters to grow that becomes the problem. These are the people who could consider fuel polishing. So the question is: does fuel-polishing work? Yes. I don't see how you can avoid the conclusion that a reasonable fuel-polishing design makes things better - if not perfect. Nothing is perfect, that is fur shur! So I would not want people to confuse the idea of polishing fuel with the idea of paper depth filters - the two ideas don't have to go together. It seems to me you can polish perfectly well with surface filters. It appears you can. But the filters do not last nearly as long. Arguably, the surface filter, which might block with sediment is *still* OK in a (by-pass) fuel polishing layout. If it blocks - so long as you know it, it does not stop you dead (yet) so long as you get some warning that the bypass is blocked and the same is likely to hit the main fuel filtration soon. My vision of a polishing systemn is that it is iundependent of the engine system. But I suspect that the engine system will block prior to a polishing system if the polishing system is not adequate. What you positively don't want is a main fuel feed blocking. So strangely enough, I think a depth pre-filter is *most* helpful here. And it is reasonable to take account of objections to unbonded paper filter media if they can decompose in water. Ithink a separate polishing system is better. Prefiltering may lead to lift-pump failure as things clog up. As a labor of love, I'll take a look around to see what industrial depth filters may prove helpful in this application. Thanks! Much appreciated! Brian W |
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