On Sun, 9 Dec 2007 06:33:45 -0800 (PST), RichH
wrote:

OK Brian, ........... lets not get carried away.....

by depth filtration I dont mean toilet paper and kitchen towel
rolls.
....
Assuming that the pressures are kept low enough to keep these 'items'
from unloading they are not a 'graded pore density' ... meaning that
the average pore size is uniform throughout the matrix .... by depth
filtration I mean a statistical graded pore density filter media in
which the statistical 'pore' size gets smaller and smaller as you get
deeper into the filter matrix.

Hehe..... you're softening, but it takes a while.

You make one point that seems contentious:

You think that a depth filter that captures
particles of decreasing size as a function of depth, is a
filter whose pore sizes are actually decreasing
with depth.
It ain't necessarily so. I assert that a depth filter of
constant pore size has just this characteristic also.

Of course, I am open to contrary evidence.
Do you have a pointer?

:-)

Regards


Brian W
p.s. I found your Tampax depth filter comment both pertinent and
amusing - can't recall the edge seals, but the excellent depth filter
I used to fly with had just this kind of fabric structure. Total
hours on that engine were around 8000 when I sold it running strong
with about 1000 hours on it since last major.