[Sentoa] Fuel Filter Size???

[Jim Waskowich]

Recommended filtering practice is to go from coarse to fine in stages, ie 30 microns followed by 20 microns, 10 followed by 2, etc.  This maximizes the effectiveness of each stage and yields the lowest overall system pressure drop.  A vacuum gage placed after the last suction-side filter will telegraph the need for maintenance.

Jim Waskowich
Grand Adventure
NT37-142


--- On Wed, 10/15/08, Simon Bergen-Henengouwen <sbergen at cybered.ca> wrote:

> From: Simon Bergen-Henengouwen <sbergen at cybered.ca>
> Subject: [Sentoa] Fuel Filter Size???
> To: sentoa at lists.samurai.com
> Date: Wednesday, October 15, 2008, 11:31 PM
> I have been doing some research in this and would be
> interested to 
> hear any comments for or against.
> 
> I have witnessed an engine filter plug up on a Cummins 6BT
> 5.9-M 220 
> HP engine on a 2002 32' Nordic Tug.  Fortunately it
> occurred while 
> tied up and after a short ride at full power and vibration
> of a near 
> empty fuel tank before idling into the marina. After
> shutdown the 
> engine refused to start and switching the primary filter in
> the 
> lazarette did no good.  After replacing the secondary
> filter on the 
> engine it took a diesel mechanic to completely bleed the
> system right 
> up to the injectors before it would start. The secondary
> filter was 
> 20 microns and the primary filter (dual switchable filters
> in the 
> lazarette) was 30.   The problem was of course that the
> secondary had 
> plugged first and once this filter was replaced air was
> introduced 
> into the lines.This I believe is extremely difficult to
> avoid as the 
> entire filter has to be removed and a new one full of fuel
> screwed in 
> it's place. Needless to say the tank also needed to be
> cleaned 
> through fuel polishing which incidentally cost 
> $1200.  The   recommendations that I could find on the web
> is for a 
> large primary and a smaller secondary, as in this case.
> 
> This to me makes no sense. I checked with Cummins and they
> say that 
> the engine is designed for a 20 micron secondary filter. So
> why not 
> put a 10 (or even a 2!) micron at the primary and a 20 (or
> 10 if the 
> secondary is a 2) at the secondary?   This would avoid the
> normal 
> problem of the secondary plugging first and the
> accompanying air 
> problems and subsequent need for bleeding when it is
> replaced.  The 
> down side is that you will probably use more primary
> filters but I 
> would rather do that than have to bleed a system that has
> died when 
> boating in an area with high currents and ferries/container
> ships 
> bearing down, a good time incidentally for high power and 
> accompanying vibrations.  Not having a diesel mechanics
> licence I am 
> not even sure I could do it.  It would be a good video to
> put on a 
> web site.  Anyway I am planning to put a vacuum gage at the
> primary 
> filters but am wondering about filter sizes.  By the way,
> Racor now 
> has a new vacuum gage for about $100 that registers the
> highest 
> reading using a second needle. This is obviously handy as
> it can be 
> checked at the dock after a run when the engine is off.
> 
> Comments?
> 
> Simon
> 
> NT32-217 (2002)
> SINOMA