On Nov 17, 6:04*am, "Roger Long" wrote:
"Capt. JG" wrote

This is exactly what the guy with 30+ years of experience said on
Saturday. It was recommended to add a dual (filter)....

So you are going to add that second filter ARE you not? *In view of the high
current conditions in SF Bay and your responsibility to your students I'd
hate to be you if something happened due to fuel contamination after posting
that you were aware of this recommendation.

While you are at it, consider this:

I think my system has gotten a bad rap for complexity due to the dual tanks
which does drive up the cost and complexity a lot. *Here is what it would
look like in yours or the typical single tank boat:

http://home.maine.rr.com/rlma/1tankFOsystem.gif

The Shelco Filter was about the same cost as a Racor. *The second pump was
about 60 bucks and is also a good redundancy feature. *This redundancy would
be especially desirable in a boat with a low mounted tank that will not
gravity feed. * Otherwise, there are only one or two additional valves and a
few fittings more than in the dual filter system. The cost difference is
insignificant in boat bucks.

Fuel contamination and degradation is always going on to some extent. *This
system is constantly removing it whenever the engine is running. *The system
will filter a volume equal to the typical sailboat tank every hour of
running time. *Your dual filter OTOH is just sitting there doing nothing
useful.

Fuel flow at the tank inlet is vastly greater than in the typical system.
This increases the uptake of water and anything else floating around in the
bottom of the tank waiting for rough water and a tight spot to get sucked
into the system at the worst possible time. *Since most of the fuel is going
through the polishing filter and being returned to the tank, getting this
stuff into the fuel system is a good thing.

In the event of the primary filter (Racor on the drawing) loading up, OR the
primary fuel pump failing, just turn one valve and you are back in business
with full fuel flow. *Some tank configurations or engine driven fuel pump
problems may require partially or completely closing the second valve. *In
any event, it doesn't take any longer than switching filters.

Let's say you do pick up a load of bad fuel and calling a fuel polishing
contractor isn't an option either because you are cruising or there isn't
one as is now the case here in Portland. * (BTW, none of this has anything
to do with an old and neglected tank that has gotten thouroughly coated and
filled with slime. *That's a different issue all together.)

Duel Filter Setup:

Switch filter.
Change first filter element - 16 bucks.

Run for a while.

Repeat as often as necessary at about 16 bucks a filter element.

The only way to get fuel flow is to run the engine *That means doing these
repeated and expensive filter changes underway or with the engine running at
the dock and sucking very little fuel. *With an engine the size you have on
your boat, it will take 20 - 30 hours to run all the fuel through the
filters. *And, you have to consume it which adds to the expense.

Polishing Setup:

Turn red valve and isolation valve if necessary and deal with it when you
get back to the dock. *The high capacity of the Shelco makes its load up
time much higher than the Racor or similary filter. *You can change it's two
buck element while the engine runs on the Racor, just as on a dual filter
system if it does load up.

When you get back to the dock, you can plug into shore power and let the
polishing system run with the engine off, changing two dollar filter
elements as necessary.

Based on the amount of crud I found in my Shelco and the pristine condition
of the sediment bowl in my Racor, I would say loading up of the Racor is
unlikely in any event.

Here's a challenge. *Usually after you've taken a seminar like the one you
just did, they will entertain a few follow up questions. *Take this
schematic to your guy and let us know what he thinks.

--
Roger Long

Roger why not double the filters and install a two position Y valve
them so you can shut off the clogged filter and run through a new
instead of trying to change out while running?

"Two meter troll" wrote

Roger, why not double the filters and install a two position Y valve
them so you can shut off the clogged filter and run through a new
instead of trying to change out while running?

Did you read the post? The boat will run on the Shelco filter and polishing
pump until that filter loads up which will take a lot, lot, longer than a
second Racor to become non-functional.

Or, do you mean having 4 filters?

--
Roger Long

On Nov 17, 1:10*pm, "Roger Long" wrote:
"Two meter troll" wrote

Roger, why not double the filters and install a two position Y valve
them so you can shut off the clogged filter and run through a new
instead of trying to change out while running?

Did you read the post? *The boat will run on the Shelco filter and polishing
pump until that filter loads up which will take a lot, lot, longer than a
second Racor to become non-functional.

Or, do you mean having 4 filters?

--
Roger Long

four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

Two meter troll wrote:

four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

That would certainly increase redundancy but, so would a third set of
filters. It has to end somewhere on a 32 foot boat.

The reason filters clog up in bad weather is because the motion of the boat
stirs up the stuff that's been sitting in the bottom of the tank. The whole
point of the polishing system is to remove that stuff before you get into
bad weather. Before bad weather or going into a spot where power is vital,
it would be good to take a peek at the filter gauges to see if they show any
restriction. This would be an especially good thing to do with a new load
of fuel.

With the high capacity of the Shelco filter, it's pretty unlikely I'll be
changing elements underway.

--
Roger Long

On Nov 19, 3:28*pm, "Roger Long" wrote:
Two meter troll wrote:
four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

That would certainly increase redundancy but, so would a third set of
filters. It has to end somewhere on a 32 foot boat.

The reason filters clog up in bad weather is because the motion of the boat
stirs up the stuff that's been sitting in the bottom of the tank. *The whole
point of the polishing system is to remove that stuff before you get into
bad weather. *Before bad weather or going into a spot where power is vital,
it would be good to take a peek at the filter gauges to see if they show any
restriction. *This would be an especially good thing to do with a new load
of fuel.

With the high capacity of the Shelco filter, it's pretty unlikely I'll be
changing elements underway.

--
Roger Long
IME the fuel polishing only works for stuff suspendid in normal
conditions; I have never seen a tank that didnt have stuff in the
bottom that only got into the filters in really bad conditions.
As you say. Me I like redundancy when I can get it.

Two meter troll wrote:

IME the fuel polishing only works for stuff suspendid in normal
conditions; I have never seen a tank that didnt have stuff in the
bottom that only got into the filters in really bad conditions.
As you say. Me I like redundancy when I can get it.

You have to remember that the polishing pump is drawing at 20 - 30 times the
rate of the normal fuel pump. That makes it much more effective at sucking
stuff up out of the bottom of the tank. With my retrofitted system, both
engine and polishing flow are drawn through the same suction. I actually
can't draw a tank quite as low with the polishing system running as I can
with just the engine drawing because it sucks air down about an inch and
into the intake.

--
Roger Long

On Nov 19, 7:28*pm, "Roger Long" wrote:
Two meter troll wrote:
IME the fuel polishing only works for stuff suspendid in normal
conditions; I have never seen a tank that didnt have stuff in the
bottom that only got into the filters in really bad conditions.
As you say. Me I like redundancy when I can get it.

You have to remember that the polishing pump is drawing at 20 - 30 times the
rate of the normal fuel pump. *That makes it much more effective at sucking
stuff up out of the bottom of the tank. *With my retrofitted system, both
engine and polishing flow are drawn through the same suction. *I actually
can't draw a tank quite as low with the polishing system running as I can
with just the engine drawing because it sucks air down about an inch and
into the intake.

--
Roger Long

Roger I do understand that and i work in an industry where fuel
polishing is SOP because we are out in it all the time. i made the
suggestion because the redundancy to me is paramount and i never ever
trust one system when i can have a backup. I am in no way knocking
your system

On Wed, 19 Nov 2008 13:18:54 -0800 (PST), Two meter troll
wrote:

four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

Since he has a single engine usually two switchable filters would
suffice.

On Nov 19, 8:37*pm, Wayne.B wrote:
On Wed, 19 Nov 2008 13:18:54 -0800 (PST), Two meter troll

wrote:
four filters. two sets paired with a y valve so you can run through
one or the other in the set. it would save you changing out filters in
bad weather (which IME is when filters clog up) or while running.

Since he has a single engine usually two switchable filters would
suffice.

his fuel polishing system disallows this if he wants a proper fuel
line pressure in all cases. his decision, his boat. pointing out
options was my idea.

Two meter troll wrote:

his fuel polishing system disallows this if he wants a proper fuel
line pressure in all cases. his decision, his boat. pointing out
options was my idea.

I appreciate the suggestions. However, for sake of discussion and anyone
looking at it for ideas on their sailboat:

(Schematic of my system he
http://home.roadrunner.com/~rlma/StriderFuelSystem.htm)

My system is a very tolerant, low pressure system. It runs from the main
tank quite well with gravity feed alone up to the mechanical fuel pump. The
mechanical fuel pump draws quite well from the low tank with the electric
fuel pump turned off but the vacuum is higher than I would like to subject
the pump to for long periods.

The pressure head at the mechanical pump inlet is the same when running off
the bypass as it is when gravity feeding from the main tank. If this should
be insufficient due to the secondary engine mounted filter starting to load
up or a fault in the mechanical fuel pump, I can gradually close the
isolation valve to force fuel to the engine at up to the full pressure that
the polishing pump can develop. This pump BTW does not have the pressure
cut off and regulation feature of a normal FO lift pump.

In a single tank installation with a bilge tank significantly below the
engines and fuel system, there might not be sufficient fuel pressure and
partial closing of the isolation valve might be necessary. In my case
though, I get normal fuel line pressure in all cases as well as the option
of increasing it.

It's worth repeating Rich H's brilliant idea for further redundancy:

The fuel polishing line runs to a small gravity feed tank that contains 1 -
2 hours of fuel. The line goes in the bottom of the tank from the polishing
system and exits the top on its way back to the main tank. A line runs from
this tank directly to the engine bypassing the engine driven fuel pump and
the vent has a valve on it. The fuel line could also bypass the engine
mounted fuel pump in some installations but not on mine since the injector
return line goes back to the filter instead of the tank, a Yanmar oddity.
This tank is constantly being filled, flushed, and renewed with just
filtered fuel that doesn't sit in the tank when the engine is running. If
all else fails, just open the supply and valves and a supply of clean fuel
sufficient to get the vessel out of trouble or change filters goes directly
to the engine.

In any event, I can change filters alternately on my system until I run out
of elements so I'm pretty well covered for the worst case situation. I've
also got those sails

--
Roger Long