Fuel Filtration Systems

[captain58sailin]

I use a "Baja" filter as my first step to keep contaminated fuel out of the tanks, then a centrifuge, then a 10 micron Racor primary, then the 2 micron secondary. I also have a self built dual Racor filter system. So far the only garbage I've gotten is in the centrifuge, which I have learned to drain prior to cranking up and going offshore. I also drain it after coming from a run. There is the smallest amount of residue that comes out when the valve is first cracked, so I only drain about a cup of fuel. I am sure it will become less and less over time as my fuel cleans up. I have old tank syndrome, which is kind of like old boat syndrome, there is some sludge at the bottom of the tank that needs removed and as long as I don't add to the problem by receiving dirty fuel, my tanks will get cleaner over time.

[Dockhead]

Originally Posted by thinwater

Except the data and calculations were ALL INCORRECT! The internet is a dubious source of information.

As a licensed tank inspector and 32-year chemical engineer I can tell you that:

a. The most serious hazard to tank inspectors is falling roof bracing, damaged by underside corrosion caused by condensation.

b. Have done testing of atmospheric condensation in fuel. Though it does require specific conditions, it is reproducible. I published on this, with pics.

c. They skipped one rather obvious detail; if a drop of dew falls from the roof into the fuel, it is trapped and does NOT re-evaporate in the morning. It is a trap. Obvious, no? There are several mechanisms that were omitted.

The petroleum industry spends real money on desicant filters. Probably a forum of sailors knows better.

That said, leaking fuel fills are the leading trouble spot. Same with big shore tanks!

Everything you write here is absolutely true.

But none of it is relevant to boat tanks, other than the bit about leaking fuel fills (which is seldom mentioned and very important).

The temperature in boat tanks does not fluctuate to the extent of above-ground industrial tanks.

It is a very straightforward calculation to see the volume of air which can be circulated by tank breathing in your boat, and how much water can be condensed in your tank as a result. It is an absolutely objective calculation based on non-controversial, commonly available facts, that is, the rate of expansion of air, and water vapor capacity of air versus temperature.

You cannot get a significant amount of condensation in a boat tank from tank breathing, and you cannot provide a calculation which shows otherwise.

Water problems in boat tanks come from leaky fuel fills (probably the great majority of cases) or bad fuel, period, not from condensation.

This is proved objectively not just by calculations, but by direct measurements in experiments performed by MaineSail.

[Kenomac]

Dockhead,

Can you please post a link to the thread I started last year on this subject. The one that shows our dual Racors and the Reverso fuel polishing system. Maybe even merge the two threads since we're discussing the same thing all over again.

Ken

[ericoh88]

Kenomac,

I enjoyed reading your post on your set up.

http://www.cruisersforum.com/forums/...on-132030.html

gts1544 - George,

While I am a newbie to sailing, I keep my ears open to fuel problems of my friend coming from "neighbouring country". Be cautious of small fuel station that offers "special" fuel. One was given such "special fuel", his newly purchased fishing power boat engine stalled right at the shipping lane! So now he use a white T-shirt as filter. If he sees any suspect of the quality he would stop the filling. Another smart boater would buy a drum of fuel and let it sit for 15 mins before starting his usual routine of dipping the pump shaft all the down until it hit bottom and lift it out about 6". This means he would return the last 6" of diesel to the supplier as a gift He would not risk ruining his day with all the crud at the bottom of the drums of umpteens years.

IMHO I would use a smallest filter as primary ie 2 or 5 micron with the vacuum gauge as a guide as to when to change the filters.

Better still install one of Seaboard Marine SMX Multi-Stage Fuel Fueltrationâ„¢ System Kits

I find the simple screw cannister on has less air leak problems of racors but I already have bought a Racor 500 for a dedicated fuel polishing system - yet to install.

hope the info is useful.

Eric

[SailRedemption]

I ordered the Fleetguard "Double Double" dual setup from Seaboard Marine

http://www.sbmar.com/smx-fueltration.php

Their filters stop water from passing where from what I read Racor doesn't. They hold more contamination and are dual stage. Also they come with vacuum gauges from Designated Engineer.

Here's my set up before I mounted it in the engine room..





- Ronnie...on the geaux

[Dockhead]

Originally Posted by Kenomac

Dockhead,

Can you please post a link to the thread I started last year on this subject. The one that shows our dual Racors and the Reverso fuel polishing system. Maybe even merge the two threads since we're discussing the same thing all over again.

Ken

Here it is:

http://www.cruisersforum.com/forums/...on-132030.html


The math is very simple. If your tank fluctuates by 5 degrees C between day and night, and if it is a 400 liter tank half full, it will "breathe" by 4.12 grams of air per day.

4.12 grams of air at 25C can hold maximum of .1141 grams of water vapor at saturation. At 20C this volume of air can hold .0824 grams of water vapor. So if the difference all condensed out, this would amount to .0317 grams of liquid water. This would only happen if the warm moist air were breathed in at 100% saturation, so that's a theoretical maximum.

So if this process went on for 100 days and nights, which it could not, but as a theoretical maximum, you would have 3.17 grams of condensation in your half empty 400 liter tank.

3.17 grams of water is about 0.1 ounces. The 200 liters of diesel fuel in your half-full tank can absorb up to about 100ppm of water at 25C, so roughly 32 grams of water. Most likely 3.17 grams of water will go right into solution in the diesel fuel, unless it was very wet to begin with.

That's the theoretical maximum amount of condensation you could get in a half empty 400 liter tank fluctuating 5C every day. In reality, how many nights do you have 100% humidity at all, much less during the whole time your tank is breathing in?

This also assumes that the tank itself does not change volume while warming and cooling. in reality, most tanks will expand and contract together with the fuel and air inside them, and there will be less breathing than this, or none, or even negative breathing.

[Dockhead]

Originally Posted by sailorboy1

. . . The volume of air/water isn't really an issue, the issue is that it exists and happens.. . . .

If you believe that water gets into your tank by operation of principles of physics, then it certainly is an issue.

If on the other hand, it is getting in there by magic, then it's not an issue at all

[thinwater]

Originally Posted by Dockhead

Everything you write here is absolutely true.

But none of it is relevant to boat tanks, other than the bit about leaking fuel fills (which is seldom mentioned and very important).

The temperature in boat tanks does not fluctuate to the extent of above-ground industrial tanks.

It is a very straightforward calculation to see the volume of air which can be circulated by tank breathing in your boat, and how much water can be condensed in your tank as a result. It is an absolutely objective calculation based on non-controversial, commonly available facts, that is, the rate of expansion of air, and water vapor capacity of air versus temperature.

You cannot get a significant amount of condensation in a boat tank from tank breathing, and you cannot provide a calculation which shows otherwise.

Water problems in boat tanks come from leaky fuel fills (probably the great majority of cases) or bad fuel, period, not from condensation.

This is proved objectively not just by calculations, but by direct measurements in experiments performed by MaineSail.

I stated that specific conditions are required.

Temperature. It is obvious that the temperature of a 1,000,000 gallon shore tanks is more stable than any boat. Rethink that one. Additionally, not all boat tanks are bilge tanks (mine is not), and many are affected by solar heating. Some areas see relatively stable water temperatures, while others see great fluctuation (the Chesapeake goes 31F to 85F, heavy dew every night). There is also significant air exchange through convection when there is a large air/fuel temperature differential. Thus, presumed temperature stability is not a rebuttal.

Calculation. Actually, the calculation is very complex. The ideal gas law part is easy, the vapor equilibrium and dew point parts may be above your pay grade unless you are a petroleum guy. It is NOT simple. So simplistic calculations are not a rebuttal.

Mainesail is a smart guy, but he did his work with MT tanks. I explained how that is not a relevant comparison (any condensate can evaporate if the tank is MT). I did my work with 1/2 full tanks, both with and without vent filters.

Bare in mind that the amounts of water we are discussing are tiny, only a few grams in a year. Leaks and bad fuel are MUCH larger issues. But in terms of corrosion and growing bugs, a few grams can make a difference.

You can either open your mind and spend a few dollars on prevention or not. I thought it was silly on boats at first too, until I did the math and did rigorous testing on both gasoline and diesel for a series of articles, including corrosion coupons. I was surprised, and I am just trying to share.

[Dockhead]

Originally Posted by thinwater

I stated that specific conditions are required.

Temperature. It is obvious that the temperature of a 1,000,000 gallon shore tanks is more stable than any boat. Rethink that one. Additionally, not all boat tanks are bilge tanks (mine is not), and many are affected by solar heating. Some areas see relatively stable water temperatures, while others see great fluctuation (the Chesapeake goes 31F to 85F, heavy dew every night). There is also significant air exchange through convection when there is a large air/fuel temperature differential. Thus, presumed temperature stability is not a rebuttal.

Calculation. Actually, the calculation is very complex. The ideal gas law part is easy, the vapor equilibrium and dew point parts may be above your pay grade unless you are a petroleum guy. It is NOT simple. So simplistic calculations are not a rebuttal.

Mainesail is a smart guy, but he did his work with MT tanks. I explained how that is not a relevant comparison (any condensate can evaporate if the tank is MT). I did my work with 1/2 full tanks, both with and without vent filters.

Bare in mind that the amounts of water we are discussing are tiny, only a few grams in a year. Leaks and bad fuel are MUCH larger issues. But in terms of corrosion and growing bugs, a few grams can make a difference.

You can either open your mind and spend a few dollars on prevention or not. I thought it was silly on boats at first too, until I did the math and did rigorous testing on both gasoline and diesel for a series of articles, including corrosion coupons. I was surprised, and I am just trying to share.

A well-reasoned and intelligent response; thanks for that. It makes for a good debate

The more subtle effects at play are definitely "above my pay grade" -- I'm not an engineer. But the calculations I have shown will give the theoretical maxima just fine, I think. You seem to agree here:

"Bare in mind that the amounts of water we are discussing are tiny, only a few grams in a year. Leaks and bad fuel are MUCH larger issues. But in terms of corrosion and growing bugs, a few grams can make a difference."

I guess that would be the crux of the issue, wouldn't it? If we agree that tank breathing can amount to just a few grams of water a year, amounting to a few tens of PPM, could it possibly matter? When it's a fraction of the fuel's capacity to absorb water? I will certainly listen with an open mind, if you have an explanation for why that could be so.


I clean out my tank every two years. In six years, I have never found a drop of water either in the tank or in my Racors. I am pretty sure that this is because my fuel filler is (wisely; thank you Bill Dixon) located above deck level, with a positive locking cap, and behind a flap, where sea water on deck can't get at it, and because I buy fuel from carefully selected and good quality providers (a luxury not available to everyone, I realize).

I don't keep my tank full, and since it holds almost 700 liters I often go for many months without filling it. Less fuel in the tank means less fuel to absorb water, and not intentionally storing fuel for long periods means I typically have drier fuel on board.

My tank, like that of most cruisers, would hardly breathe anyway. It's not in the bilge, but it is below the waterline, with temperature much more influenced by water temp than outside air temp. Between day and night hardly a degree C of difference (judging by the temperature sensor in my engine room).

To get back to the practical side of the question.

[sailorboy1]

Originally Posted by Dockhead

If we agree that tank breathing can amount to just a few grams of water a year, amounting to a few tens of PPM, could it possibly matter?

Yes. It's a fact not a debate.

[captain58sailin]

Dockhead, I have a great deal of respect for you and your reasoning on most matters, but regarding the condensation rate on half full tanks, I will respectfully disagree. I can neither quote scientific data nor the equations you use, to counter your argument, only empirical evidence for one locale in Alaska. I have seen far more water accumulate in half full fuel tanks here than what you are saying and I will keep my fuel tanks as full as possible. I get enough condensation from the outside of my water softner tanks that are located inside my house that I have to mop the floors whenever we do laundry, granted the water temp coming out of the ground is only slightly above 32* F, and so is our sea temp. which runs from about 39* F ~ 45* F, should you be running your engine which will be putting heated fuel back into the tank, I believe you have a temperature differential that can give you a significant amount of water in your half full tanks. Regardless of your logic, I will adhere to my own and you can believe me to be a luddite.

[Dockhead]

Originally Posted by captain58sailin

Dockhead, I have a great deal of respect for you and your reasoning on most matters, but regarding the condensation rate on half full tanks, I will respectfully disagree. I can neither quote scientific data nor the equations you use, to counter your argument, only empirical evidence for one locale in Alaska. I have seen far more water accumulate in half full fuel tanks here than what you are saying and I will keep my fuel tanks as full as possible. I get enough condensation from the outside of my water softner tanks that are located inside my house that I have to mop the floors whenever we do laundry, granted the water temp coming out of the ground is only slightly above 32* F, and so is our sea temp. which runs from about 39* F ~ 45* F, should you be running your engine which will be putting heated fuel back into the tank, I believe you have a temperature differential that can give you a significant amount of water in your half full tanks. Regardless of your logic, I will adhere to my own and you can believe me to be a luddite.

Everyone has the right to an opinion, especially when it is intelligently and politely expressed like this, and I don't think you are a luddite at all.

But the mechanisms by which condensation is formed are pretty easy to understand. If you think about it, I think you'll agree that it is hard to credit how much condensation can occur inside tanks. It's totally different from your water softener tanks, which are ice cold on the inside, and which have warm moist air circulating around the outsides of them all the time. It's not the temperature differential by itself but circulation of moist air which is required to get water vapor into your tanks. How is that happening? Then the temperature of that saturated air has to be reduced enough to make the water condense out of it.

If you are getting "significant amounts" of water in your tanks, it is hard to explain (or rather, impossible) how it could possibly come from condensation. It is far more likely that it comes in through a fill cap (are yours mounted flush with the deck?) or a vent (where is yours located?).

Having more fuel in your tank rather than less could help because more dry fuel can absorb more water than less fuel (its capacity is still only tens of PPM, however, unless it's bio-diesel).


My own anecdotal evidence is this -- my father subscribes to the "keep the tanks full" religion, and religiously tops off his tanks after every even weekend of sailing. He has been plagued with diesel bug for decades and is always fighting it, dosing the tank, having the tank cleaned, struggling with clogged filters, etc. He goes through probably a case of Racor filters every season.

I don't subscribe to this, and keep my tank mostly empty much of the time, especially during winter since I don't have access to cheap fuel when I'm not doing trans-Channel runs to Guernsey.

I do open up and clean my tanks every two years, and check the Racors every time I start the engine. Never had a drop of free water in the tank or the Racors, despite the notoriously dripping wet climate around here. I don't actually change the Racor filters more than once every two years -- there's never anything in them.

Now that doesn't prove anything -- just anecdotal. Just two data points. You can make of it what you will.

[Nicholson58]

Look into a bypass filter system. After main pump failure last summer, We are adding FRANZ filters to the sumps on the main engine & generator as well as for the fuel system. These are used on over the road trucks and commercial vessels as an add-on to the standard filter systems. Filtration os to about 1 micron. Users of these on class 8 trucks claim 100,000 miles without oil changes and crystal clear oil. Googele Bypass oil filters and study this a bit. Good posting on the trawlers forum. You will need a tiny circulation pump for the fuel system (about 40 gallon/hour). If you set it up well, your engines will only take oil from the filtered stream. Other users say that after several months, the insides of the fuel tanks become spotless.

You should be aware that the Racor filters we all use have an internal bypass relief valve so that once the filter becomes plugged dirty oil bypasses the element.

550 dollars to rebuild my main pump would have easily paid for the new filters for the entire boat.

[captain58sailin]

The primary difference in what you do and what I do regarding the operation, is I keep my tanks full and you keep yours empty. I do not have a problem with water in my tanks, I believe due to the same diligence that you have regarding your racors etc... I am religious about checking the bowls of my filter housings and draining a cup of fuel from my centrifuge prior to start up and use. I also use a vacuum gauge on my filter housings. In the environment where I live, work and play, I have never had a fuel related failure; to do so, could easily become a life threatening adventure, which I am absolutely phobic about. I can't argue your science, and I do understand the equations, I was raised to keep fuel tanks full and have yet to find a significant reason not to do so. The other part of the deal is I have only once come into the spring with a tank full of fuel that was worth less than when I bought it in the fall. In the spring when money is usually tight, it is good to be able to get my first few fishing openers in without having to pay for fuel right away.

[Dockhead]

Originally Posted by captain58sailin

The primary difference in what you do and what I do regarding the operation, is I keep my tanks full and you keep yours empty. I do not have a problem with water in my tanks, I believe due to the same diligence that you have regarding your racors etc... I am religious about checking the bowls of my filter housings and draining a cup of fuel from my centrifuge prior to start up and use. I also use a vacuum gauge on my filter housings. In the environment where I live, work and play, I have never had a fuel related failure; to do so, could easily become a life threatening adventure, which I am absolutely phobic about. I can't argue your science, and I do understand the equations, I was raised to keep fuel tanks full and have yet to find a significant reason not to do so. The other part of the deal is I have only once come into the spring with a tank full of fuel that was worth less than when I bought it in the fall. In the spring when money is usually tight, it is good to be able to get my first few fishing openers in without having to pay for fuel right away.

I would love to have a full tank of fuel in the spring! Unfortunately I can relate to the idea of a full tank of fuel having capital value

However, I live on board during the winter, so the cheap fuel I bring back from Helgoland in the fall gets burned up in the Eberspaecher and genset over the winter. No reason to refill the tank for $1500-odd, when I can do it for half that in Helgoland or Guernsey That's the main reason why my tanks are mostly empty by spring