Polishing fuel

[catmandoo]

Can any one explain to me why there is a need to polish fuel when the fuel rack feeds excess back to the tank on most engines .
I can only surmise that its because most boats mainly use engines for manoeuvring and that after a long time in port one might have a need to filter the fuel but one does it anyway ?
I also filter all fuel before filling tank and use a biocide KATHON FP1.5

I have a motor sailer and don't see the need for such regular shenanigans

 

[pvb]

Fuel polishing is normally used as a treatment for removing established diesel bug from tanks. If you don't have a diesel bug problem, you don't need to do fuel polishing.

 

[ip485]

pvb has it. The idea behind fuel polishing is you can pick up fuel with a high water content or loads of rubbish in it, and with the dreaded bug, or because of the water, ends up with the bug. Often the worst time to fill up is when there has just been a delivery to the main tanks and all the sludge has been stirred up and the filters on the fuel dock arent doing there job properly. Also diesel can have a high level of water contamination without it being apparent. Running the fuel through a properly set up polisher will remove the contaminants, although often if the pump isnt sufficiently powerful the contaminants will have settled out to the bottom of your tank and remain then until you are out in a good blow!

Use of a good additive and always checking the fuel during filling should go a long way to preventing these problems. It is not a bad idea to have a fuel funnel with a seperator and even if you dont run all the fuel through, run some through at the start of filling to check the fuel is sound before you have poored in a few 100 gallons of rubbish.

It only takes one fill up with poor fuel to cause a load of rubbish to settle out and lots of pain getting rid of it.

You mention you filter all fuel when you fill. That is perfect, but even the largest fuel funnel cant cope with full flow output from the pumps, and taking on a few hundred gallons for larger vessels is a very long process if you run the whole lot through the funnel, well at least that is my experience.

 

[lw395]

Plenty of people have discovered the need to clean their tanks despite the engin turning over the fuel and only clean fuel going in.
It is common for yacht fuel tanks to have the pickup some way from the bottom of the tank, so water and crud can accumulate over the years.

Once 'bug' is established, it produces its own water, so the problem can escalate.
Personally I feel the most important thing is to sample the fuel from the very lowest point in the tank and remove any dirt or water.
Also, I think it's best not to store fuel for longer than necessary.

 

[Sandy]

Can any one explain to me why there is a need to polish fuel when the fuel rack feeds excess back to the tank on most engines .

This is why some sailing boats need to polish fuel. I only ever use about 30 ltr in a season.

 

[catmandoo]

Well . I have a filter funnel with water trap and I always use it when filling from cans for which I have at least 5 of 20 litre capacity . So the bowser fills the cans and I fill the tanks at my leisure through the filter funnel . . I seldom get any debris and even after 200 hours my primary filter is in good condition and I seriously consider extending its service . secondary filter is hardly coloured .
I can't see any difference between the primary filter and the polishing filter they both draw off from the same point, normally a half inch from the sump bottom and as you say sludge from the Bottom of the tank only gets to the filter in rough weather . That means you should only do your polishing in rough weather ie at sea . If not then if you do it at port then the sludge stays in the tank sump
The only way to really clean out the sump is to suck it out through a dip pipe reaching down to the very bottom of the sump if you are not lucky enough to have a bottom drain cock . I have such a dip pipe but I find it better to remove the inspection hatch and suck up the muck from the sump . e
Even draining the tank completely through the access hatch has not picked up much . Perhaps a little water from condensation and a few bits of rust . and some sticky slime and I understand that this is a result of Degradation of FAME over time rather than Diesel bug

I dose with Kathon regularly and more so when leaving a full tank over the winter and to date have had no problems since using it


I also get diesel from tankers from regular filling stations here in Leros and in the rest of the Dodecanese.


.

 

[thinwater]

This is why some sailing boats need to polish fuel. I only ever use about 30 ltr in a season.

That is classic diesel bug, slimy like snot. You need to use a biocide or change to a different one (there are carbamates and borinanes, and they target different strains, just like antibiotics).

BTW, saying you only use 30 L/season is saying you don't change your oil. You really aren't doing your fuel or engine any favors.

There's a fairly long post on biocides here:
http://sail-delmarva.blogspot.com/p/diesel-biocides.html

 

[paulieraw]

This is why some sailing boats need to polish fuel. I only ever use about 30 ltr in a season.

A picture speaks a thousand words. That is pretty grim.

 

[macd]

BTW, saying you only use 30 L/season is saying you don't change your oil.

I may be missing something, but would you care to explain the logic that caused you to reach that conclusion?

 

[lw395]

Well . I have a filter funnel with water trap and I always use it when filling from cans for which I have at least 5 of 20 litre capacity . So the bowser fills the cans and I fill the tanks at my leisure through the filter funnel . . I seldom get any debris and even after 200 hours my primary filter is in good condition and I seriously consider extending its service . secondary filter is hardly coloured .
I can't see any difference between the primary filter and the polishing filter they both draw off from the same point, normally a half inch from the sump bottom and as you say sludge from the Bottom of the tank only gets to the filter in rough weather . That means you should only do your polishing in rough weather ie at sea . If not then if you do it at port then the sludge stays in the tank sump
The only way to really clean out the sump is to suck it out through a dip pipe reaching down to the very bottom of the sump if you are not lucky enough to have a bottom drain cock . I have such a dip pipe but I find it better to remove the inspection hatch and suck up the muck from the sump . e
Even draining the tank completely through the access hatch has not picked up much . Perhaps a little water from condensation and a few bits of rust . and some sticky slime and I understand that this is a result of Degradation of FAME over time rather than Diesel bug

I dose with Kathon regularly and more so when leaving a full tank over the winter and to date have had no problems since using it


I also get diesel from tankers from regular filling stations here in Leros and in the rest of the Dodecanese.


.

Fair comment, but a lot of yacht tanks don't have anything resembling a sump.
Our polishing rig gets right to the bottom corners of a tank.
If you have a sump with a dip tube going right to the bottom, you are better placed than most.

The other difference is our (fairly mickey mouse) polishing rig runs at a couple of litres per minute, compared to a couple of litres per hour for the engine, so the fuel in the tank does move around a lot more.
We check our tank twice a season. We find maybe a teaspoon of water. We've not seen any black mess for years now on our boat, and we don't use a biocide. fuel is a mix of UK red, UK road and French.

 

[RichardS]

I may be missing something, but would you care to explain the logic that caused you to reach that conclusion?

I think that perhaps he means "saying you only use 30 L/season is like saying you don't change your oil" but if you only use 30L a season then you only use 30L a season so I'm not sure what you're supposed to do about it?

Richard

 

[thinwater]

I may be missing something, but would you care to explain the logic that caused you to reach that conclusion?

I miss-typed that. I meant to say it is"like" not changing your oil. Fuel and gasoline are not really very stable stored in typical fuel tank conditions (exposed to air, water, copper alloy fittings, and bugs) and should not be stored for over a year. It will cause trouble. So burning through the tank 1-2x every season is simply good boat maintenance. Case in point; the Chevy Volt forces the driver to run the engine a certain amount to burn through the gas and circulate the oil.

(Copper alloys. The installation instructions for standby generator fuel systems and good engineering pracice forbid the use of brass in diesel systems because is a breakdown catalyst.

http://sail-delmarva.blogspot.com/2015/06/are-we-cause-of-fuel-breakdown.html

ASTM D975 Appendix X2.7.2: Fuel Storage Conditions
Copper and copper-containing alloys should be avoided. Copper can promote fuel degradation and may produce mercaptide gels. Zinc coatings can react with water or organic acids to form gels which rapidly clog filters.

Cat installation guidance.
http://pdf.cat.com/cda/files/3375312/7/Diesel+Fuel+Diesel+Fuel+Systems+LEBW4976-04.pdf

Material. Black iron pipe is best suited for diesel fuel lines. Steel or cast iron valves and fittings are preferred.
CAUTION: Copper and zinc, either in the form of plating or as a major alloying component, should not be used with diesel fuels. Zinc is unstable in the presence of sulfur, particularly if moisture is present in the fuel. The sludge formed by chemical action is extremely harmful to the engine’s internal components.

 

[rotrax]

Old info.

Contempary diesel fuels do not carry anywhere near as much Sulphur as old generation fuel. I go back to DERV fuel used in agriculteral vehicles, plant and also London Black Cabs with the infamous 2.2 and 2.5 BMC diesel units.

I have used a 10mm copper pipe as a connector in a marine diesel fuel line for many years without any trouble. It is as as clean as the day I fitted it, inside and out.

My experience goes back to the '60's, when it was a problem.

 

[Sandy]

BTW, saying you only use 30 L/season is saying you don't change your oil. You really aren't doing your fuel or engine any favors.

Er, um. Where did I say that?

The boat was new to me and came with a full tank of fuel. Because I use so little, just to get in and out of the river, I am quite certain the fuel had gone well past its use by date. Until very recently I understood that diesel did not have a shelf life, but it looks that this is no longer the case.

I may be missing something, but would you care to explain the logic that caused you to reach that conclusion?

Yes I was just a tad confused about that comment as well. The old Volvo Penta gets its annual service no matter how much I've used it. Thank goodness my motor car does not need such regular oil changes.

 

[thinwater]

Calm. I miss-typed one thing and admitted as much hours before. Calm.

Diesel and fuels have had stability problems since way back, and the problems have not entirely faded. For example, cross contamination (common) with ethanol and biodiesel at the transportation level has introduced new instabilities, including an increased tendency towards infection, such as this. You can burn through your diesel every year or not. You can accept some kindly offered suggestions or not.

I don't understand why a few more engine hours is a big deal for a regular sailor and I believe the engine will probably last longer with a better warm-up and some hours operating under proper load.

 

[RichardS]

Calm. I miss-typed one thing and admitted as much hours before. Calm.

Indeed. My post #11 seems to have been written in invisible pixels.

Richard

 

[Sandy]

Calm. I miss-typed one thing and admitted as much hours before. Calm.

No worries...

The winters work has been interesting, the tank has been removed and steam cleaned, the fuel lines replaced and a new primary filter fitted (due to the old one being in a silly place behind the engine and under a bunk). The new top loader is now in an easily accessible place in the engine compartment.

The UK has a dyed fuel (less tax) that I am convinced sits about in marina tanks for decades before being sold to unsuspecting pleasure sailors. Thus I have moved to full tax fuel from my local filling station and am planning to run with just what I need on-board with a 20 liter spare which can be used in the car.

 

[lw395]

Old info.

Contempary diesel fuels do not carry anywhere near as much Sulphur as old generation fuel. I go back to DERV fuel used in agriculteral vehicles, plant and also London Black Cabs with the infamous 2.2 and 2.5 BMC diesel units.

I have used a 10mm copper pipe as a connector in a marine diesel fuel line for many years without any trouble. It is as as clean as the day I fitted it, inside and out.

My experience goes back to the '60's, when it was a problem.

You're normally the most relaible on engines, but to be accurate, DERV is road fuel, not the red stuff used in agriculture etc. The clue is in the acronym.
There are plenty of recent papers from fuel companies adviding against copper and brass etc in diesel systems, I'm not so sure about zinc.
The zinc/sulphur problem may be separate from the copper problem with modern diesel.

 

[lw395]

No worries...

The winters work has been interesting, the tank has been removed and steam cleaned, the fuel lines replaced and a new primary filter fitted (due to the old one being in a silly place behind the engine and under a bunk). The new top loader is now in an easily accessible place in the engine compartment.

The UK has a dyed fuel (less tax) that I am convinced sits about in marina tanks for decades before being sold to unsuspecting pleasure sailors. Thus I have moved to full tax fuel from my local filling station and am planning to run with just what I need on-board with a 20 liter spare which can be used in the car.

Likewise, we make a point of only buying fuel we will use in the next few months at worst.
We carry a sensible reserve in sealed cans.
Low engine hours need not mean old or suspect fuel.

 

[Cornwallsailing]

Depends where are you are in the world too. Sailing around Asia like the Philippines / Indo, you can get some really dodgy fuel. Water or just bugs / leaves, you get all sorts.