Polishing diesel fuel

[wsvoboda]

Need some advice on fuel polishing kits or systems. I only have a 40 gallon tank but want to keep it clean all the time. Ideas/ advice please

[sailalfin]

I have a Perkins 4-236 (best engine in the world) which is 25 years old and plenty of hours. I have a very good furl filtering system with 2 Racor 500 filters installed so that you can route the fuel in different ways, series, parallel, isolated etc. However, the best thing I ever did for peace of mind was to fabricate a polishing system, very simple and DYS. Now I polish fuel every day while cruising. I have attached the drawing

[Diesel Polisher]

FYI - If you ever have any diesel bug problems just know that the Racor 500 series filters have very poor emulsified and free standing water removal.

[Boracay]

I checked my fuel tank by taking off the inspection cover and shining a torch (flashlight) down into the fuel. I could see various kinds of junk (mainly metal shavings from the tank construction) on the bottom.

I emptied the tank and used rags to get the bottom as clean as possible.

Other than that I use fuel treatment (algaecide) to control algae.

It may be desirable to assume that there is always some contamination in your fuel and to use a quality water separation filter.

I've installed a proper marine fuel pump and there is a secondary water separating filter on the engine.

Having spare filters and being able to "bleed" the engine quickly is highly desirable.

[GordMay]

Greetings and welcome aboard the CF, Diesel Polisher.

Can you recommend a separator/filtre that does provide emulsified and free standing water removal.

[twistedtree]

attached drawing?

[Diesel Polisher]

Cummins Fleetguard do a nice range of filters that have coalescing elements with efficiency of 95% emulsified water removal. See them here.

The other cool feature on this filter is that if the housing is mounted above the fuel tank and in vacuum. The bowl which sits on top remains empty unless the the element starts to block. As the element blocks the bowl will fill. So from a maintenance perspective it only takes a glance at the filter housing to understand the condition of the filter element.

[twistedtree]

Keep in mind that with a diesel engine you are polishing your fuel all the time that the engine is running. Diesels circulate a fair amount more fuel than they burn, returning the excess via the return line. If you dig up the specs for your engine it should tell you what the flow rate is. All that fuel runs through your primary and on-engine filters (assuming you have both, and you should) and gets polished along the way.

[Diesel Polisher]

Yes twistedtree is correct, but standard engine filters have very little capability to deal with water or a large lump of diesel bug/sludge. It's always good to have a decent sized pre-filter before your engine filters to catch the bulk of rubbish and water beforehand.

Most pre-filters on the market have limited emulsified water removal properties too. So you should consider what exactly are you trying to polish out of your fuel.

[Cotemar]

Why do cruisers polish their diesel fuel?

A marine diesel engine has a built in polishing system with a primary and secondary filter to trap and filter out water and sludge.

I have had boats for 30 years now and never needed to add a Diesel fuel polishing system to them.

[colemj]

Taking on bad fuel can overcome the relatively small primaries and secondaries almost immediately.

Sometimes fuel is not used and sits in the tank - polishing it occasionally filters out the asphaltenes that agglomerate in it over time.

Water also suspends in diesel and it is useful to get this out before it condenses and drops to the bottom. A Polishing systems typically have higher flow rates and tank inlets/returns that pick up from the very bottom of the tank and stir the tank on return.

The flow through the main filters while operating is not high enough to do any type of actual polishing - it would take continuous running of the engine for days to "polish" a 100gal tank.

Just some of the reasons.

Mark

[Cotemar]

colemj,

Good reasons for a having a diesel fuel polisher, but does it really make since on a sail boat with a small fuel tank that is already getting fuel polished every hour that its engine is running.

Don’t most full time cruisers use one of those Racor Fuel Filter Funnel - Water Separator or a Mr. Funnel when fueling up in unfamiliar fuel docks.

[DoubleWhisky]

Originally Posted by Cotemar

colemj,
Good reasons for a having a diesel fuel polisher, but does it really make since on a sail boat with a small fuel tank that is already getting fuel polished every hour that its engine is running.

Depends on the system involved Cotemar.

I have - for example - three fuel tanks, 320 liters each, 960 liters together. They are mounted in the cascade, each next two inches lower than the previous one. Fuel backing from the engine goes to the lowest one. Fuel to the engine go from the same. Polishing through the engine fuel system is not effective this way. And I use more fuel for generator rather than for the propulsion engine. And the system on the generator is even less effective than that on engine...
Ah, and this is probably not the small fuel tank You mentioned.

Regards

Tomasz

[Cotemar]

Originally Posted by DoubleWhisky

Depends on the system involved Cotemar.

I have - for example - three fuel tanks, 320 liters each, 960 liters together. They are mounted in the cascade, each next two inches lower than the previous one. Fuel backing from the engine goes to the lowest one. Fuel to the engine go from the same. Polishing through the engine fuel system is not effective this way. And I use more fuel for generator rather than for the propulsion engine. And the system on the generator is even less effective than that on engine...
Ah, and this is probably not the small fuel tank You mentioned.

Regards

Tomasz

Yes, it does make since on your large boat with large fuel tanks, but the vast majority of sailboats are in the <40 foot (<12meters) range with around 55 gal (208 Liters) of fuel.

Diesel fuel polishers make more since on trawlers also, as they tend to have bigger engines and fuel tanks.

[ontherocks83]

Cotemar, really dumb question and I apologize in advance, but what do you do with the contaminated fuel that is left in the filter after fueling? Where we fill up there is no disposal place that I know of.