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Message: 15
Date: Mon, 3 Jul 2006 09:58:01 -0700 (PDT)
From: Peter Pisciotta <>
Subject: T&T: 10/2 vs 2/2 redux
To: TrawlerList TrawlerList
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> Somewhere there must be a
> manufacturers rationale and test
> results that support the staged
> filter method and that it is not
> based on old stationary engine history
We already know a 2-micron filter will clog a lot
faster than a 10-micron filter - ask anyone on this
list who runs 2-micron primaries for validation -
chances are, they've had to change their primaries
while underway. Question is: is there benefit to
running 2/2 filtration (2-micron primary, 2-micron
secondary) over 10/2 (so-called stepped filtration,
the industry standard)?
I'll pose this question to the 2/2 folks: the fear is
having the eingine-mounted filter clog underway and
then have to replace, prime, and re-start the engine
(the "Oh my gawd" factor).
I'm not so sure that is the big "fear".
But is there any
first-hand, real-life experience to back this up? I
mean, is there actually gunk that gets past a
10-micron primary and clogs a 2-micron secondary
between service intervals?
Based on what has been posted here, it looks like what I thought I knew was true. The engine mounted filters (on a Lehman at least) are NOT 2 micron filters.
Personally, I've never had
it happen, but concede it's possible so the question
becomes does that risk outweigh 1) vastly increased
liklihood of 2/2 clogging (monitoring is, after all, a
manual process and glass bowls eventually get foggy);
It's hardly a "vastly increased" risk of clogging if you just increase the size of the filter body you use when you step down in micron size elements.
And as far as the plastic bowls getting cloudy, mine are well over 10 years old and fine. So that's a bit of a non-issue. And one that's easily over come in any case by just replacing a cloudy bowl.
2) risk of possible engine damage due to elevated
vacuum and fuel temps; and finally 3) the remarkably
consistent guidance of billions of dollars of R&D and
warranty dollars?
But the 2/2 position seems so, well, logical - where's
the flaw? I suspect the answer lies in the microscopic
nature of the particles. We are worried about the
stuff we can see (fuel tank gunk - rust, dirt, water,
asphaltines, etc). The engine manufacturers are
worried about microscopic-sized particles. At that
level, they're okay with 10/2 filtration (in fact,
they recommend it). Sure, a 2-micron filter will
filter out the big crud, but unless the filter is very
large, it will load-up and clog, placing a burden on
the engine (their concern) and potentially cause the
engine to starve/die mid-ocean (my concern). According
to the experts (and my personal experience), using a
properly maintained 10/2 system will not cause the
2-micron secondary to clog and an unexpected engine
stop, but using a 2/2 system may.
So, I think I've laid out the 10/2 position pretty
well, albeit belabored (its not a simple position).
I'll look for the 2/2 folks to move past logic and
post their actual experiences with clogged 2-micron
secondaries when installed in a 10/2 system. Depending
upon that outcome (as I said, I've never had it
happen), I'll have to weigh that evidence with the
liklihood of having a 2-micron primary clog in a 2/2
system. I think that's the heart of the decision, at
least for me.
I think the bottom line is bigger particals can lead to increased wear. (Hence bypass oil filtration.) So why risk it when it's really easy to reduce the risk.
The vacuum increase and fuel temp. are other nonissuses, at least on the low HP engines most trawler types use, from what I've seen.
In the end I think both schools of thought work just fine. Just as long as you change you filter elements on a regular basis.
Capt. Bill
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