You obviouslly have a good well designed system.
For improvement I'd depend more on the polisher. That you're only
getting 200 hours on a large flow system to me indicates that you could
probably benefit from better polishing.

You might want to change your recirc. 10µM to a 5µM ... or better yet
use a 5µM 'depth filter' in that location. Youll have to do a cross
reference search (thats what the internet is for) for equivalence for
any depth type filter to be used in a Racor housing. But, be wary of
any filter that doesnt say 'absolute' or some % retention when
describing the retention rating - the single statement such as '5
microns' is a potential warning that such a filter is a 'nominally
rated' filter and may have poor % retention at 5 microns. Whats the
'turnover rate' of your onboard polisher and how often do you need to
change that filter and at what differential pressure? The 'faster'
you turnover a tank with a polishing system the better the particle
removal ... polishers are not dependent primarily on 'retention rating
of the filter' but how MUCH fuel you can turnover. For boat tanks I
usually target to turnover the 'whole' tankage in about ~1.5 - 2 hours
through the polisher.

In article , Wayne.B
wrote:

On Sat, 08 Dec 2007 19:21:04 GMT, Rich Hampel
wrote:

Most tanks need to be
cleaned out on a regular basis - saves a hell of a lot of filter cost
and hassle at the wrong time.

hope this helps.

Thanks, interesting analysis. Let me play some of this back in my
words with a couple of extra details thrown in. My 10 micron Racors
are the largest size commonly available, Filter Element: 2020TMOR.

The engine mounted 2 micron filter is maufacturer specified, and
significantly smaller than the Racors, probably about 25% in size.

The engines are DD 4-71 2 strokes rated at 280 hp each, with normal
fuel burn is in the range of 2 to 5 gph each.

I think I heard you say that this was a reasonable configuration,
i.e., tank 10 2 lift pump engine. I do have an independant
polishing loop which I use when the boat is docked for extended times.
It cycles through a large Racor 10 micron and returns to the tank.

Something must be working reasonably well because I've been averaging
over 200 hours on the 2020TMORs before replacement.

On Sat, 08 Dec 2007 23:21:40 GMT, Rich Hampel
wrote:

That you're only
getting 200 hours on a large flow system to me indicates that you could
probably benefit from better polishing.

Yes, probably true but the 200+ hours/filter that I'm now getting is a
vast improvement from where I was 3 years ago.

Thanks for your analysis.