On Sun, 07 Dec 2003 19:41:08 GMT, Rich Hampel
wrote:

...
... take a toilet paper roll, get a container, immerse it in any oil
that you want and let it soak, then add 1" of water to settle at the
bottom of the container with the TP .... to the bottom of whatever you
contain the toilet paper, let sit a week or more, remove and examine
that the TP has fallen apart where the water has come in contact with
the TP.

Wow: now that's a test I can relate to.
If true, it would be a strong disincentive to using unbonded cellulose
media for fuel oil. Though I have mentioned that critical applications
like aero recips and tractor engines specify a water/sediment cup
before the fuel filter - still, a filter medium that will collapse in
the presence of water is a no-no.


I am uncomfortable with the "perpetual"filters which feature narrow
gaps in metal disks. And I'm uncomfortable with bonded surface
filters that will block in a fresh storm (The approach of specifying
an oversized surface filter can postpone the inevitable, it's true)

Now consider that the TP in poorly designed boat system is
held in place by a knife edge seal biteing into the end of the TP
roll........ What happens later on when there is differential pressure
across 'mush' (papier mache) being held by a knife edge seal and has a
differential pressure across it.


Depth filters are routinely used in water-purification and
air-handlers. I don't pretend to speak for *every* industry,
but I can say is this, about the car biz:
the automobile typically uses resin bonded paper surface filters in
the oil line.
Since detergent oil suppresses sludge formation, these filters could
stay in place longer than they typically survive before replacement.

Alternative media are now growing in popularity but there is little
advantage over the resin bonded paper type for lube oil filtration
IMO.
Fuel filtration, on the other hand has become much more demanding
in the mass auto market, since the advent of high pressure fuel
injection. Dual in line filters have become the norm - discarding
the first, moving second to first, and installing new second filter
is one approach to holding down costs.

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.

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.

The next reasonable step is to provide a sight glass for early
detection of water and contamination (the 'tractor' approach)

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.

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.)

These are the people who could consider fuel polishing.
So the question is: does fuel-polishing work?
I don't see how you can avoid the conclusion that a reasonable
fuel-polishing design makes things better - if not perfect.

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.

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.

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.

As a labor of love, I'll take a look around to see what industrial
depth filters may prove helpful in this application.

Brian W