Old diesel fuel

[thinwater]

1. Water entering your fuel from tank condensation is a myth. Maine Sail proved it through the definitive test:

http://www.pbase.com/mainecruising/fuel_tankt_condensation

He's a smart guy, but he is out of his depth on this one. I can line up refinery engineers and they will point out the errors in his testing. Personally, I spent decades inspecting tanks and I can promise you that condensation drops hanging from the ceiling is a normal thing. Rust of rafters is so endemic, the FIRST thing the code required an inspector do is decide if they might fall and hit him on the head.

Personally, I have run tests with tanks that were free vented, vented through carbon, and vented through silica gel. The differences were easily observed and quantified using ASTM methodology.

Yes, tanks can and do condense water. Not very much, and exact conditions make a difference, but not zero. That said, if you are seeing free water in your Racor, it is coming from a deck leak, not condensation. I'm talking about a few dozen grams per year, all of which may dissolve in dry fuel, not obvious amounts.

 

[Maine Sail]

He's a smart guy, but he is out of his depth on this one. I can line up refinery engineers and they will point out the errors in his testing.

Drew, please do, but lets keep in mind the intent of the experiment, the scale / scope and that boats do not have refinery size tanks on-board that are outside and fastened to a fairly stable ground/Earth substrate temp.. Please also keep in mind the statement and "net-lore" this experiment was instigated by:

"An empty tank will condensate and fill with water a full tank is far better than leaving it empty"

Thus the experiment: "Question: Does an empty marine fuel tank condensate when left empty and accumulate water?"

I chose not to use the words "fill with water" in the article title as that is simply absurd but I wanted to see if it would or could accumulate over time..

Things such as the physical installation of a marine fuel tank and a refinery or storage tank are actually quite different. For example a massive fuel storage tank here in Maine is partially below grade and mostly above grade. The below grade portion of the tank may be at 50F while the above grade portion could be at 80F, in direct sunlight. In a well designed inboard engine boat, the tank is very often isolated from the actual hull, not in direct sunlight, therefore the entire tank heats and cools more evenly with temp shifts. In the off season, on the hard, the tank is at the ambient of the vessel and with no fuel to slow the changes in aluminum tank temp, well, as I have found, no "accumulated water" as of yet.... To satisfy one readers comment about boats stored in the water, I put some pavers under the tank to slow the tank temp change response, still no water noted in this tank...

This whole discussion usually reminds me of the helicopter/plane vs. sailboat prop analogy. We were taught for years as "fact" that a locked prop creates less drag. For years and years this was taught as the golden rule when in-fact it has been proven incorrect by such institutions as University of Strathclydes Ocean Engineering Department and even by MIT. I was the first to build a test jig and actually tow a physical sailboat prop free spinning and locked through the water which also showed the "helicopter analogy" to not be a correct assumption as related to sailboat props.

This test, & I still have it on-going, simulates a winter stored empty actual marine fuel tank, because it is one. It also simulates an actual fuel vent hose, and thru-hull vent fitting, because that is what they are. Real world is what I was after. It also simulates the same height off the ground as a typical boat because the second floor of my barn is identical in height to our boats fuel tank that sits just a few feet away. The tank, which is still there, was still bone dry as of six months ago. The test even over exaggerates temperature swings, which most agree only adds to the condensation potential, because the barn has a black asphalt roof and swings can be about 5-15F (measured averages) wider than I normally measure on the boat due to hull vs. roof color. I will again check it today but I suspect I'll see the same result as I have been getting all along.

Personally, I spent decades inspecting tanks and I can promise you that condensation drops hanging from the ceiling is a normal thing. Rust of rafters is so endemic, the FIRST thing the code required an inspector do is decide if they might fall and hit him on the head.

I don't doubt that at all.... However, I'm not testing massive storage refinery tanks just like I was not testing helicopter blades or airplane props dragged through the water when I tested actual sailboat props.. I was looking for a more real world test design parameter that would mimic an actual boat as close as possible. I suspect an actual marine fuel tank, vent hose and thru-hull fitting, stored at the same height above ground in the winter in a thermally changing environment, like a boat, is a pretty close match for this experiment to either prove or disprove that an empty marine fuel tank won't "accumulate" water even over nearly 5 years time..

Personally, I have run tests with tanks that were free vented, vented through carbon, and vented through silica gel. The differences were easily observed and quantified using ASTM methodology.

Was this done on a marine fuel tank that was stored empty and vented, as a boat would be, and you observed the tank accumulate water? As always I invite you to show up at any time of the year here in Maine, you can even surprise me, and check this tank. I had one guy take me up on my offer to see the locked prop test up close and personal (a local pilot). I have no need to make this up and as always welcome anyone to spot check my work.

As you and I discussed previously, about the H2Out product you sent me for testing, even when I left my tank "partially full" for two winters I noted no quantifiable visual changes in bead color. I thought for sure I would see changes with a partially full tank but they were not visually quantifiable. I have since gone back to draining the tank each fall as it allows me to get int there with the scope and visually inspect the tank for cleanliness and debris. As I mention in the article draining a tank is more work than most would ever do, but for me it is very simple and is just another step in winterizing...

Yes, tanks can and do condense water. Not very much, and exact conditions make a difference, but not zero.

Again, context is important here. I quantify "zero" as no change in color & no absorbed moisture on the tissue, when the inside of the empty tank is wiped with it, and yes the ceiling of the tank is also wiped, with a very technical tool (bent coathanger) to check for moisture. We need to remember the entire context of that test" does water accumulate in an empty tank". Since 2013 I still can't find evidence of wall or ceiling moisture let alone any accumulated water.

[/quote]That said, if you are seeing free water in your Racor, it is coming from a deck leak, not condensation. I'm talking about a few dozen grams per year, all of which may dissolve in dry fuel, not obvious amounts.[/QUOTE]

Bingo.. ! That said, I'm not even getting a damp tissue with this empty tank so I suspect this marine tank may be in the microgram range...

 

[JamesG161]

I did the calculations for my 50 gallon tank for my Gulf Coast temperature and humidity ranges.
One tablespoon of water maximum.

But remember when the worst situation reverses. That water will evaporate.

The myth is the worry about it with good tank filling practices and water separator.
Jim...

 

[thinwater]

Drew, please do, but lets keep in mind the intent of the experiment, the scale / scope and that boats do not have refinery size tanks on-board that are outside and fastened to a fairly stable ground/Earth substrate temp.. Please also keep in mind the statement and "net-lore" this experiment was instigated by:

"An empty tank will condensate and fill with water a full tank is far better than leaving it empty"

Thus the experiment: "Question: Does an empty marine fuel tank condensate when left empty and accumulate water?"

I chose not to use the words "fill with water" in the article title as that is simply absurd but I wanted to see if it would or could accumulate over time..

Things such as the physical installation of a marine fuel tank and a refinery or storage tank are actually quite different. For example a massive fuel storage tank here in Maine is partially below grade and mostly above grade. The below grade portion of the tank may be at 50F while the above grade portion could be at 80F, in direct sunlight. In a well designed inboard engine boat, the tank is very often isolated from the actual hull, not in direct sunlight, therefore the entire tank heats and cools more evenly with temp shifts. In the off season, on the hard, the tank is at the ambient of the vessel and with no fuel to slow the changes in aluminum tank temp, well, as I have found, no "accumulated water" as of yet.... To satisfy one readers comment about boats stored in the water, I put some pavers under the tank to slow the tank temp change response, still no water noted in this tank...

This whole discussion usually reminds me of the helicopter/plane vs. sailboat prop analogy. We were taught for years as "fact" that a locked prop creates less drag. For years and years this was taught as the golden rule when in-fact it has been proven incorrect by such institutions as University of Strathclydes Ocean Engineering Department and even by MIT. I was the first to build a test jig and actually tow a physical sailboat prop free spinning and locked through the water which also showed the "helicopter analogy" to not be a correct assumption as related to sailboat props.

This test, & I still have it on-going, simulates a winter stored empty actual marine fuel tank, because it is one. It also simulates an actual fuel vent hose, and thru-hull vent fitting, because that is what they are. Real world is what I was after. It also simulates the same height off the ground as a typical boat because the second floor of my barn is identical in height to our boats fuel tank that sits just a few feet away. The tank, which is still there, was still bone dry as of six months ago. The test even over exaggerates temperature swings, which most agree only adds to the condensation potential, because the barn has a black asphalt roof and swings can be about 5-15F (measured averages) wider than I normally measure on the boat due to hull vs. roof color. I will again check it today but I suspect I'll see the same result as I have been getting all along.



I don't doubt that at all.... However, I'm not testing massive storage refinery tanks just like I was not testing helicopter blades or airplane props dragged through the water when I tested actual sailboat props.. I was looking for a more real world test design parameter that would mimic an actual boat as close as possible. I suspect an actual marine fuel tank, vent hose and thru-hull fitting, stored at the same height above ground in the winter in a thermally changing environment, like a boat, is a pretty close match for this experiment to either prove or disprove that an empty marine fuel tank won't "accumulate" water even over nearly 5 years time..



Was this done on a marine fuel tank that was stored empty and vented, as a boat would be, and you observed the tank accumulate water? As always I invite you to show up at any time of the year here in Maine, you can even surprise me, and check this tank. I had one guy take me up on my offer to see the locked prop test up close and personal (a local pilot). I have no need to make this up and as always welcome anyone to spot check my work.

As you and I discussed previously, about the H2Out product you sent me for testing, even when I left my tank "partially full" for two winters I noted no quantifiable visual changes in bead color. I thought for sure I would see changes with a partially full tank but they were not visually quantifiable. I have since gone back to draining the tank each fall as it allows me to get int there with the scope and visually inspect the tank for cleanliness and debris. As I mention in the article draining a tank is more work than most would ever do, but for me it is very simple and is just another step in winterizing...

Yes, tanks can and do condense water. Not very much, and exact conditions make a difference, but not zero.

Again, context is important here. I quantify "zero" as no change in color & no absorbed moisture on the tissue, when the inside of the empty tank is wiped with it, and yes the ceiling of the tank is also wiped, with a very technical tool (bent coathanger) to check for moisture. We need to remember the entire context of that test" does water accumulate in an empty tank". Since 2013 I still can't find evidence of wall or ceiling moisture let alone any accumulated water.

That said, if you are seeing free water in your Racor, it is coming from a deck leak, not condensation. I'm talking about a few dozen grams per year, all of which may dissolve in dry fuel, not obvious amounts.

Bingo.. ! That said, I'm not even getting a damp tissue with this empty tank so I suspect this marine tank may be in the microgram range...

As James calculated, this is on the order of a few teaspoons per season. Not a lot, but enough that is CAN be measured and enough to have material effects on corrosion rates. I never said or implied that easily observable amounts of water would be gained this way. In fact, I said that is always the result of a leak. I do lab work and I am used to looking for very small changes.

Yes, the actual temperatures swings matter. A boat with a large bilge tank will condense less than a catamaran (bridge deck) or power boat with a tank mounted higher. Remember that I have multihulls with bridge tanks, and friends have charter boats with deck tanks, so my interest is focused there.

Unfortunately, testing with an empty tank is inherently flawed, since the oil itself absorbs oil from the air. Water will never accumulate in an empty tank, not even at the 10 million gallon scale. The water evaporates when the sun rises. This is plainly obvious and you have seen this. On the other hand, water once absorbed into the oil stays. If in droplets, it sinks to the bottom. Even if merely absorbed, the vapor pressure is now too low to revolitilized.

In a barn is not a fair representation of a marine environment. It is protected from dew and does not see the foggy conditions that often exist only very, very near the water. This mistake was also made by the EPA when they came out with carbon filters for gasoline fueled boats. I tested carbon filters and found that in certain seasons they would get soaked with water if used on a boat, but not inside a shed even a short distance away. This was boat testing on the Chesapeake, not calculation or lab work. The amount of water was small, only a few grams, but that is more than enough to render carbon ineffective as a hydrocarbon adsorption media. It demonstrates the differences minor changes in the experimental conditions can make.

I tested with a variety of tanks sizes and conditions. Some showed no absorption. Some showed as much as 140 ppm water gain in a season, which is enough to accelerate corrosion over 10 times. This can be counteracted by additives. It is also not enough to create free water or to create visible changes in all cases, though a haze was visible in some cases in very cold weather (the haze dissipated when temperatures rose above freezing and the solubility of water increased). In a few cases a few mils of free water accumulated. But never more than a few mils in 6 months. I can see that a single test would not reliably create visible changes.

By the way, half burying a tank of any size is forbidden by code for corrosion reasons. It is very bad practice. It must be all above or all below.

The prop analogy is a straw man; a false analogy or poor comparison thrown together specifically because it can be easily torn down discredited. It is not related and many engineers every helo pilot has known this for many years. It was urban legend all along.

I'm a chemical engineer and I am very certain of these things. The theory is well known and the facts have been tested. That is that. I won't argue marine wiring since you are wise. I am similarly wise with regard to fuels. It was my career. But we agree that if someone is seeing water, with their eyes, it is not condensation.

 

[thinwater]

.. But remember when the worst situation reverses. That water will evaporate....

No, it will not. It will either be on the bottom on the tank, sealed by oil, or it will be dispersed in the oil, the vapor pressure far too low for that to happen. Get a bottle and test that theory.

It will dissolve in fresh fuel, as there is very little there.

 

[abarrow]

Old diesel fuel is fine

The best advice I had from a diesel mechanic is to not worry about it overly much. I'm in the same situation of not using my engine all that much. His recommendations were

I had the same advice from a diesel mechanic. He told me a story of a guy who bought a very old tug, drained the old diesel from it, sold it, and paid off the cost of the tug (and then some). His parting words to me were "That's what your RACORs are for. Use the fuel."

 

[jssailem]

I have been watching this thread. I have personal experience with this subject. My only difference with MainSails experience is that we leave our boat in the water over winter and our summer days are not quite as hot for as long as is experienced in Maine.

The boat I purchased in 2015 had over 150 gallons of diesel in the two tanks. The fuel was of unknown age but likely more than a year old. The simple answer was to consume the fuel with diesel selling at $4 plus a gallon. I looked into having the fuel polished... about $900. The fuel pumped and the tanks cleaned... about $2500 and I would loose the $600 of fuel.

My solution has been to have spare filters and change them frequently... about every 20 hours of engine time. And to install a Racor 500 that has made the changing process almost painless. After 2 years I have consumed the fuel, changed perhaps 8 filters, and experienced a couple of engine shut downs due to fuel starvation. I have added a combo of Star Tron/Biobor JF blend and have seen good results.

Regarding the water in tank debate. I did get water in the tank. But it came as a result of the PO not having proper "O" rings on the tank caps. My tanks have been less than full over 2 winters and there has been no evidence of water from condensation. The outside of the tanks shows similar infrared temps as the surrounding materials and there is no condensation occurring there. The tanks are vented to the outside and we keep heat in the boat to reduce the chance of damage.

Granted this has not been a scientifically controlled experiment. But it is work experience and finance management while using an old boat with a 1973 diesel motor. I have constructed a home built polishing system to address the physical material that accumulated near the bottom in my port tank. When I sucked the Starboard tank dry (engine stopped then too) I did get a little water and a combination of bacteria and fungi that showed up in the bowl of the Racor Filter. Drained that off and took of for a 200 NM trip. No fuel issues.

 

[thinwater]

I had the same advice from a diesel mechanic. He told me a story of a guy who bought a very old tug, drained the old diesel from it, sold it, and paid off the cost of the tug (and then some). His parting words to me were "That's what your RACORs are for. Use the fuel."

Exactly. Most engines don't run enough. I'm always amused when someone had trouble with 2-4 year old fuel. Often they are proud of how little they have used (they are sailors). Some have had operation problems, and that I can empathize with. But you change your oil every year, regardless of hours. How stable do they think fuel is?

 

[Maine Sail]

Unfortunately, testing with an empty tank is inherently flawed, since the oil itself absorbs oil from the air.

Drew, you really should have read the link; Does an Empty Tank Condensate? before you told everyone;

He's a smart guy, but he is out of his depth on this one.

Of course you then said this:

Water will never accumulate in an empty tank, not even at the 10 million gallon scale. The water evaporates when the sun rises. This is plainly obvious and you have seen this.

Umm thanks...... (wink) That is all the article was about, storing a tank empty......

On the other hand, water once absorbed into the oil stays. If in droplets, it sinks to the bottom. Even if merely absorbed, the vapor pressure is now too low to revolitilized.

Yes exactly but that is not what the article and test was about. I have emptied my boats tanks every winter for over 30 years. I don't store them full or half full only empty, except for the two winters I was testing the H2Out, as you and I have discussed.

In a barn is not a fair representation of a marine environment. It is protected from dew and does not see the foggy conditions that often exist only very, very near the water.

If you'd read the article you would have seen that I live about 100' from the ocean. My boat is sitting on the hard 4' from the barn and less than 100' from FOGGY Casco Bay. Considering our boats tank does not ever see dew, because it is below deck, that point is pretty moot for this experiment. the test and experiment had nothing to do with storing a tank full or half full only about storing it empty.

Both our boat, you can see her fuel vent 4' from the test tank, and the empty tank, are about 100' from Casco Bay. There are many days during the year when we can barely see the barn from the house. I was not testing this in Iowa.. (grin)

This mistake was also made by the EPA when they came out with carbon filters for gasoline fueled boats. I tested carbon filters and found that in certain seasons they would get soaked with water if used on a boat, but not inside a shed even a short distance away. This was boat testing on the Chesapeake, not calculation or lab work. The amount of water was small, only a few grams, but that is more than enough to render carbon ineffective as a hydrocarbon adsorption media. It demonstrates the differences minor changes in the experimental conditions can make.

Mistake? Agai, the test tank and our boats tank vent and the test tank are within 4' of each other, both tanks stored empty just feet from the ocean and both inside a structure with wide temp swings but both vented to the outside atmosphere...

I tested with a variety of tanks sizes and conditions. Some showed no absorption. Some showed as much as 140 ppm water gain in a season, which is enough to accelerate corrosion over 10 times.

Empty tanks, like the one in the article??

This can be counteracted by additives. It is also not enough to create free water or to create visible changes in all cases, though a haze was visible in some cases in very cold weather (the haze dissipated when temperatures rose above freezing and the solubility of water increased). In a few cases a few mils of free water accumulated. But never more than a few mils in 6 months. I can see that a single test would not reliably create visible changes.

Are you're saying I should put additives in an empty tank to prevent corrosion?

By the way, half burying a tank of any size is forbidden by code for corrosion reasons. It is very bad practice. It must be all above or all below.

I don't doubt that at, and believe you to be 100% correct on this. My statement was simply based on one I drive by regularly. It appears, though I may be completely wrong, to sit on Earth with an Earthen berm partially encasing the lower portion.

The prop analogy is a straw man; a false analogy or poor comparison thrown together specifically because it can be easily torn down discredited. It is not related and many engineers every helo pilot has known this for many years. It was urban legend all along.

In the context of the article on an "empty tank" it is a very similar mistaken belief that an empty take will fill with water. I see them as similar but mistaken viewpoints.

I'm a chemical engineer and I am very certain of these things. The theory is well known and the facts have been tested. That is that. I won't argue marine wiring since you are wise. I am similarly wise with regard to fuels. It was my career. But we agree that if someone is seeing water, with their eyes, it is not condensation.

I am well aware of that and your points were spot on with regard to tanks with fuel in them....... The problem is you were arguing a point I was not trying to make then 100% agreed with what I wrote in the end... (grin)

 

[JamesG161]

That water will evaporate.

Sorry, but I am not "out of my depth" in this.

It is called "solubility". My best information says water will dissolve in diesel fuel at about 4000 ppm in warm weather.

During the tank's low humidity cycle, water will Diffuse to the surface from which is was dissolved.
Then evaporate in order to maintain dissolved water equilibrium in the diesel, at that temperature. Thus reverses the path of input.
____

since the oil itself absorbs oil from the air. Water will never accumulate in an empty tank

Say what?
________

My solution has been to have spare filters and change them frequently... about every 20 hours of engine time. And to install a Racor 500 that has made the changing process almost painless.

I do same, but just monitor the filter. Although I have 5 spares aboard because of the myth.
_____
Best idea is to fill your diesel tank to near full after use, install a fuel water/particle separator, monitor the filter cartridge, get fuel from reputable source [mine adds a biocide], don't run your tank below 5 % and have fun sailing.
________
My Aluminum Diesel tank does not oxide with moisture in the fuel. Nor will the injectors with dissolved water.

Jim...

PS: I have been monitoring the Racor Diesel Cartridge for 2 years, never seen separated water or even a change in the vacuum gauge reading at high RPM. I even use the "flashlight beam" test for haze, no beam seen. For me, pleasure sailing myth busted.

 

[thinwater]

Please folks, calm down. This is just an educational forum. No one should feel pressed.

Mainesail:

• Emptying tanks for the winter is a very unusual practice. I'm sure it works, but I doubt 1% of the readers of this thread do that.
  
• 100' from the ocean in barn is very far. I would argue that 20' and right at ground level might be too far. Given the time, I believe over the course of a season this would be provable. A simple example is that you won't get dew inside a barn.
• No, I never tested with empty tanks. What would be the point, since we know empty containers lack the chemistry to draw water?
• Obviously I was not talking about additives in empty tanks. You knew this.
• That tank is not sitting in an earthen birm. In fact, I can see the floor to shell seam. That is an API 653 tank sitting on top of a gravel pad, the purpose of which it make certain that water does not lie against the underside of the tank. The installation appears well engineered. I've inspected hundreds like that, inside and out ( I am a licensed API tank inspector). You could take a closer look or you could ask them.

James:

• Diesel may dissolve up to 500 ppm in solution by ASTM specification. I've run these test hundreds of times, generally by KF. Most will hold considerably less before precipitating. The actual water content typically varies from 50-150 ppm. Anything that increases dissolved water tends to increase corrosion rates. This is specifically true if the fuel has any contact with seawater (chloride) or sulfur, even very low ppm levels. This is well established among corrosion engineers.
• If diesel can dissolve water, is it not obvious it can also absorb it from the air? It is the same chemistry. You cannot have one without the other. The more it can dissolve, the more it can absorb. This is an identity among all materials.
  
• If there is any salt in the tank at all, or any sulfur, the aluminum will oxidize and corrode. I've inspected aluminum tanks with holes in the bottom from interior corrosion.

I'm talking about a very subtle effect that is not easy to see. No free water will be seen. It is easy to ignore or deny. If you burn through a few tanks each season you will never notice. I'm not saying anything different from what you have observed with your eyes. Thus, there is no conflict in experiences.

 

[MitchM]

i've had 40 years of owning diesels on 3 boats. we top up the fuel and keep the tank always at least 7/8 full . we totally fill the tank to full at haul out , through a baja filter with fuel from the local high - volume diesel provider. we add cetane boost and store n start before the the last run in to the fuel dock before haul out. our tank bottoms are still testing clean each year, here on the greatest of lakes.