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Old 14-11-2016, 10:05   #76
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Re: "Worth it" to top off diesel for the winter?

Quote:
Originally Posted by Celestialsailor View Post
Here's a Youtube talking about water in diesel and how it may get in...




Guy selling a product but no calculations.

Here's an article explaining the same...
How does water get into my fuel tank

This one provides no calculations. It just repeats the old wives' tale.

Another article from Racor explaining water absorption from air heating and cooling in a tank and the importance of topping off...Yes a diesel filter company...
Racor News

Again, no calculations.

Another article of how little temperature change is needed to creat the absorption problem...
Condensation in fuel, & how to solve the problem

Again, no calculations.

One thing to remember in my situation where I found water in my tank was I use my engine a lot here in Mx. The starting, running of the engine acutually heats the diesel up as opposed to a boat that sits. So the temperature differential between the diesel and the water temperature on the keel (integral tank) is high. So a boat that sits a long time not running may not necessary have the same amount I would have. My tank may heat up 4 times a week and then cool.
This I hope sheds a little light on the topic.
It actually makes no sense if you are using the motor several times per week. Dissolved moisture passes harmlessly thru the engine and the regular refills will absorb any trace amounts that that are present continuously removing moisture.

I'll give you 10-1 odds, you got a batch of bad fuel that already had water in it or you have a leak introducing water to the tank.

See the calculations from Dockhead and from the earlier link. It's impossible to condense out 2 gal of water in a typically sized cruising boats fuel tank.

Again, anyone want to put forth calculations, I would love to see them.
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Old 14-11-2016, 10:43   #77
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Re: "Worth it" to top off diesel for the winter?

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Originally Posted by valhalla360 View Post
It actually makes no sense if you are using the motor several times per week. Dissolved moisture passes harmlessly thru the engine and the regular refills will absorb any trace amounts that that are present continuously removing moisture.

I'll give you 10-1 odds, you got a batch of bad fuel that already had water in it or you have a leak introducing water to the tank.

See the calculations from Dockhead and from the earlier link. It's impossible to condense out 2 gal of water in a typically sized cruising boats fuel tank.

Again, anyone want to put forth calculations, I would love to see them.
.;..and again...you show no numbers yourself. This reminds me of that ridiculous thread that was on CF about climate change. It never mattered about facts and numbers. The other side flat refused to believe in climate change. I see no difference here.
Both times that I had my diesel polished in Alameda, then here in Guaymas both guys state that it is usually condensation. That said, I do agree that 2 gallons indicated a second source of water and I went ahead and resealed any suspect entry points. My boat had just gone through a 100 mph hurricane and the horizontal rain very well could have entered the diesel tank vent.
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Old 14-11-2016, 10:54   #78
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Re: "Worth it" to top off diesel for the winter?

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.;..and again...you show no numbers yourself. This reminds me of that ridiculous thread that was on CF about climate change. It never mattered about facts and numbers. The other side flat refused to believe in climate change. I see no difference here.
Both times that I had my diesel polished in Alameda, then here in Guaymas both guys state that it is usually condensation. That said, I do agree that 2 gallons indicated a second source of water and I went ahead and resealed any suspect entry points. My boat had just gone through a 100 mph hurricane and the horizontal rain very well could have entered the diesel tank vent.

See the link in post 11 and dockhead's post 50 for numbers demonstrating that it's impossible.

I agree though, it does remind me of some of the eco threads where they don't care about numbers. They have a blind faith (in this case that water must be from condensation) and no amount of facts will change their position.

Still waiting for calculations showing you could get a measurable amount of water due to condensation.
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Old 14-11-2016, 11:13   #79
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Re: "Worth it" to top off diesel for the winter?

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Originally Posted by a64pilot View Post
Read this
Does An Empty Tank Condensate? Photo Gallery by Compass Marine How To at pbase.com

On the fuel vent question there are desiccant filter made for fuel vents, as the tank breathes the air is pulled into the vent and the desiccant will absorb any water vapor.

Having gone through fuel "bug" problems, I will always add a Biocide, you will not talk me out of it, though many try. Where I buy fuel, every time I'm told that is a waste of money, our fuel already has it in it.
This is hardly an experiment...an empty tank inside a building. My situation is a tank surrounded by 75F water with doesel going through a recirculating system (injector pump) heated by a 200F engine. the diesel in the tank would be substantially higher than the surrounding water. Wter would condensate on the roof of the tank and later fall into the tank. One of the links i posted clearly showed this.

Quote:
Originally Posted by Dockhead View Post
Have you ever seen any numbers on this alleged mechanism?

You've got one thing right -- any "breathing" which takes place, will bring in cool air at night. It will not bring in warm air in the day time. And that is the crucial fact, because condensation occurs when you cool off warm, moist air, to a temperature below its dew point. No condensation will occur if you bring cool air into a tank, even if its very moist air, and you don't cool it off. So to condense anything out of cool night air, you will have to make it even cooler. But you are in the wrong phase of the temperature cycle to do that.



But on top of that -- even if there were some way for the fuel tank to be cooler than the cool night air -- and there is not, but suspending disbelief -- the amounts of water which can be condensed out of the volumes of air which could be breathed in are far too small.

Here is a table of water vapor capacity of air at various temperatures:

http://web.gccaz.edu/~lnewman/gph111...20of%20air.pdf

At 20C, it's 15g of water per kg of air. At 15C, it's 10g.

Air changes its density by about 1.625% between 15C and 20C. So 250 liters of air in a half-empty 500 liter fuel tank will "breathe" 4 liters of air. 4 liters of air at 20C weighs 4.82 grams. At total saturation, it can contain 0.0723 grams of water, of which 0.0241 grams of water will condense out if you cool it to 15C.

So if you do this 180 times over half a year, you will get 4.338 grams of liquid water in the fuel, assuming none of it evaporates back out.

Except that even this is completely impossible -- because the tank breathes in, as you said, then it's cold, not when it's warm. Besides that, you don't have 100% humidity every day.

Also the daily thermal cycle is overstated because the boat has thermal mass and doesn't cycle to the extent as the ambient air. My fuel tank (I measured it) never changes temperature by more than 2C.



All this shows that it is completely impossible to get a significant amount of water in your fuel, from tank "breathing" and condensation.
Again...all thats fine and dandy when there are no differential influences.

Quote:
Originally Posted by valhalla360 View Post
See the link in post 11 and dockhead's post 50 for numbers demonstrating that it's impossible.

I agree though, it does remind me of some of the eco threads where they don't care about numbers. They have a blind faith (in this case that water must be from condensation) and no amount of facts will change their position.

Still waiting for calculations showing you could get a measurable amount of water due to condensation.
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Old 14-11-2016, 11:46   #80
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Re: "Worth it" to top off diesel for the winter?

This is one of those arguments that just goes round and round. I have no formula, neither will I waste time trying to find one. After 55 years of flying, I know from experience that condensation does in fact form in fuel tanks, even those full of fuel. ALL aircraft manufacturers build in drains for each tank and the cross-over for multi-engined planes, the purpose being to allow the pilot to drain water from the tanks prior to flight. Normal situations, however, seldom produce more than a few drops of water. We have a cup with a small post in the middle that pushes up into the tank drains and activates the drain. The cup is about 2 inches in diameter and perhaps 2 inches tall. The tanks are built with sumps for the collection of condensation. My big Cessna twin has 4 50-gallon tanks plus the cross-over. Two of the tanks are aluminum, two are rubber bladders. The amount of water collected is almost always small, a few drops, but if left unchecked will build up. It does not "mix" with the gas. The engines are 520 cubic inch, 6-cylinder, fuel injected and turbocharged. 375 horsepower each. The normal amount of condensation build up is barely enough to make one of those engines more than hiccup, maybe not even that. Long term build can drown the engine. Washing the airplane can cause extra build up. I'm not aware of any boat manufacturers that have that kind of drain, so perhaps they don't find the same problem with boat engines, or they don't worry about it since you can pull over and clean the water out of a system that has stopped without crashing. Aircraft can't land on the nearest cloud. You don't have to believe me. Ask any pilot or read the Pilot's Operating Handbook for any plane. A fuel tank is a fuel tank, no matter what it's in.
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Old 14-11-2016, 12:02   #81
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Re: "Worth it" to top off diesel for the winter?

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Originally Posted by Celestialsailor View Post
This is hardly an experiment...an empty tank inside a building. My situation is a tank surrounded by 75F water with doesel going through a recirculating system (injector pump) heated by a 200F engine. the diesel in the tank would be substantially higher than the surrounding water. Wter would condensate on the roof of the tank and later fall into the tank. One of the links i posted clearly showed this.

Nope, there is only so much water in the airspace and that quantity is so small as to be irrelevant even if you somehow wrung every last water molecule out of the air. The recirculation doesn't introduce any air only replacement air based on the fuel burnt. So if you are burning 1 gal per hour, that's a volume equivalent to 1 gal per hour...again a negligible amount of water.

Again...all thats fine and dandy when there are no differential influences.

Plenty of differential influences accounted for.
You are very certain but still haven't come up with any calculations to support your position.
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Old 14-11-2016, 12:25   #82
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Re: "Worth it" to top off diesel for the winter?

Just like boats, 99% of water in the fuel of an aircraft's wings comes from leaking fuel caps.
The drains are primarily there to ensure there is no water prior to flight, water can come from many sources.
Best example was a fuel sample I pulled from an OH-58 forever ago, looked pure and clean just like it should, but something wasn't right, so I smelled it, pure water, no fuel.
The OH-58 had many drains on the transmission and engine decks and when you washed one, they often clogged, a trick Crew Chiefs learned early on was you put the hose over the bottom of the drain and blew water up the drain and that unclogged it.
Well SP-4 Rodriguez had tried unsuccessfully to unclog the fuel tank vent.
Its for that kind of impossibility that each of your tanks, your header tank and your gascolator have drains.
Just like automobiles, once in a blue moon people get water contaminated fuel, but its not from condensation. Ever drain the fuel tank on your automobile?
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Old 14-11-2016, 13:04   #83
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Re: "Worth it" to top off diesel for the winter?

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Just like boats, 99% of water in the fuel of an aircraft's wings comes from leaking fuel caps.
The drains are primarily there to ensure there is no water prior to flight, water can come from many sources.
Best example was a fuel sample I pulled from an OH-58 forever ago, looked pure and clean just like it should, but something wasn't right, so I smelled it, pure water, no fuel.
The OH-58 had many drains on the transmission and engine decks and when you washed one, they often clogged, a trick Crew Chiefs learned early on was you put the hose over the bottom of the drain and blew water up the drain and that unclogged it.
Well SP-4 Rodriguez had tried unsuccessfully to unclog the fuel tank vent.
Its for that kind of impossibility that each of your tanks, your header tank and your gascolator have drains.
Just like automobiles, once in a blue moon people get water contaminated fuel, but its not from condensation. Ever drain the fuel tank on your automobile?
Okay, so that takes us back to the round and round. And for what it's worth, I agree with you for the most part. Flying through heavy rain is another example. But how about my little experimental? It has a 10.5 gallon aluminum tank, complete with sump and drain. The fuel cap is a screw-on with O-ring, and it's underneath a panel that has to be removed to put gas in. The vent is under the belly of the plane. Again, not more than a couple of drops of water, but I have gotten that a time or two. Additionally, the plane is always hangared unless I'm flying. 'Tis a puzzlement.
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Old 14-11-2016, 13:11   #84
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Re: "Worth it" to top off diesel for the winter?

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Okay, so that takes us back to the round and round. And for what it's worth, I agree with you for the most part. Flying through heavy rain is another example. But how about my little experimental? It has a 10.5 gallon aluminum tank, complete with sump and drain. The fuel cap is a screw-on with O-ring, and it's underneath a panel that has to be removed to put gas in. The vent is under the belly of the plane. Again, not more than a couple of drops of water, but I have gotten that a time or two. Additionally, the plane is always hangared unless I'm flying. 'Tis a puzzlement.
That's consistent with the prior calculations shown. The calculations I did found in a worst case scenario, you might get as much as 4 grams of water over the course of a winter (it will vary based on the assumptions but never much). So if the plane wasn't turning over the fuel, a few drops is possible. But if the entire bowl is full, you better be looking for a leak or checking your supplier.

Again, there is no round and round. There are the facts and those who "believe" but have yet to put forth calculations to support their position.
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Old 14-11-2016, 13:16   #85
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Re: "Worth it" to top off diesel for the winter?

I'll second what 64pilot said.

The only times I have found water in aircraft tanks was immediately after the plane had been sitting outside in the rain. Further, these instances of water only occurred with aircraft that had poorly designed/maintained fuel filler inlets/caps.

By far the worst, was my beloved PA-23. It had recessed (into the wing) filler inlets that were perfect for collecting rainwater. A scupper and a raised lip were supposed to keep water below the level of the filler cap. Un-fortunately, the scupper was placed above the level of the raised lip. If the "expanding rubber" type filler cap was in anything but perfect condition, the water just poured into the tank.

Numerous crashes (some fatal) have occurred as a result of this design fault. One crash that I found particularly fascinating was when an aircraft up North was thoroughly inspected for purchase and found to be airworthy. During the long flight South to its new home, the blocks of frozen water (that were previously undetectable) began to melt, disabling both engines within a short time of each other.

I stored my example of this plane in a hanger. The final solution to water in tanks.

Steve
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Old 14-11-2016, 13:16   #86
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Re: "Worth it" to top off diesel for the winter?

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That's consistent with the prior calculations shown. The calculations I did found in a worst case scenario, you might get as much as 4 grams of water over the course of a winter (it will vary based on the assumptions but never much). So if the plane wasn't turning over the fuel, a few drops is possible. But if the entire bowl is full, you better be looking for a leak or checking your supplier.

Again, there is no round and round. There are the facts and those who "believe" but have yet to put forth calculations to support their position.
In the case of my experimental, your "if the plane wasn't turning over the fuel" is unfortunately quite accurate. I just don't have the time to fly it more than once every few months.
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Old 14-11-2016, 13:25   #87
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Re: "Worth it" to top off diesel for the winter?

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I'll second what 64pilot said.

The only times I have found water in aircraft tanks was immediately after the plane had been sitting outside in the rain. Further, these instances of water only occurred with aircraft that had poorly designed/maintained fuel filler inlets/caps.

By far the worst, was my beloved PA-23. It had recessed (into the wing) filler inlets that were perfect for collecting rainwater. A scupper and a raised lip were supposed to keep water below the level of the filler cap. Un-fortunately, the scupper was placed above the level of the raised lip. If the "expanding rubber" type filler cap was in anything but perfect condition, the water just poured into the tank.

Numerous crashes (some fatal) have occurred as a result of this design fault. One crash that I found particularly fascinating was when an aircraft up North was thoroughly inspected for purchase and found to be airworthy. During the long flight South to its new home, the blocks of frozen water (that were previously undetectable) began to melt, disabling both engines within a short time of each other.

I stored my example of this plane in a hanger. The final solution to water in tanks.

Steve
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Old 14-11-2016, 13:41   #88
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Re: "Worth it" to top off diesel for the winter?

Fuel often contains water in suspension, let the fuel settle, temperature drop or whatever and poof the water comes out of suspension, the water came from the fuel, just a little of course, drops not ounces.
An example is phase separation.
Its the reason during certification of an aircraft I have to heat the fuel to a certain point, then jump in and climb at max rate to the aircraft's max certified altitude.
It is really not a problem in 99% of civil aircraft, but apparently during and or before WWII the fighters performance got so good, it became an issue, and now we all have to check that block on test flights. I don't know if its low pressure, or low temperatures or both together that cause a problem, vapor lock mostly.
Worst for getting fuel in the tanks is my little C-140, the only approved factory fuel caps have two quite large holes in the caps for vents as the tanks have no vents themselves. I keep two rubber toilet plunger cups in the baggage compt, if I ever have to leave her outside, I cover the fuel caps with the rubber toilet plungers.
We have a C-210 that is bad about getting water in the left wing, comes in from the cap of course in rain, but it's a bladder tank and the bladder has I believe a wrinkle in it, cause you can pull a fuel sample and get nothing, but rock the wings pretty hard and maybe get an ounce of water, I think there is a wrinkle that traps water behind it.
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Old 14-11-2016, 13:54   #89
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Re: "Worth it" to top off diesel for the winter?

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Originally Posted by valhalla360 View Post
That's consistent with the prior calculations shown. The calculations I did found in a worst case scenario, you might get as much as 4 grams of water over the course of a winter (it will vary based on the assumptions but never much). So if the plane wasn't turning over the fuel, a few drops is possible. But if the entire bowl is full, you better be looking for a leak or checking your supplier.

Again, there is no round and round. There are the facts and those who "believe" but have yet to put forth calculations to support their position.
Diesel is hygroscopic and absorbs water from air. Its not tank surface condensation alone!
Moisture migrates from high humidity zones to low humidity zones so it keeps coming in through the vents. Not very rapidly but over time it mounts up and it doesn't take much to promote the growth of microbe colonies which plug up a fuel system.
Warm fuel is more absorbant than cold fuel so its more of a problem in the tropics.

The condensation calculations are interesting but irrelevant.
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Old 14-11-2016, 13:54   #90
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Re: "Worth it" to top off diesel for the winter?

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Fuel often contains water in suspension, let the fuel settle, temperature drop or whatever and poof the water comes out of suspension, the water came from the fuel, just a little of course, drops not ounces.
An example is phase separation.
Its the reason during certification of an aircraft I have to heat the fuel to a certain point, then jump in and climb at max rate to the aircraft's max certified altitude.
It is really not a problem in 99% of civil aircraft, but apparently during and or before WWII the fighters performance got so good, it became an issue, and now we all have to check that block on test flights. I don't know if its low pressure, or low temperatures or both together that cause a problem, vapor lock mostly.
Worst for getting fuel in the tanks is my little C-140, the only approved factory fuel caps have two quite large holes in the caps for vents as the tanks have no vents themselves. I keep two rubber toilet plunger cups in the baggage compt, if I ever have to leave her outside, I cover the fuel caps with the rubber toilet plungers.
We have a C-210 that is bad about getting water in the left wing, comes in from the cap of course in rain, but it's a bladder tank and the bladder has I believe a wrinkle in it, cause you can pull a fuel sample and get nothing, but rock the wings pretty hard and maybe get an ounce of water, I think there is a wrinkle that traps water behind it.
You mention the WWII fighters, and that has always been interesting to me. Those big, thousand + horsepower, carbureted engines, Merlins and such. When the pilot went beyond mil power into what my generation knew as kicking in the afterburners, those guys were injecting water into the engines. I'm not sure where it was introduced, the carburetor or the cylinders, but that's what they did. Yet here we are with our piston engines worrying about water. Again, a bit of a puzzlement as the king would say. And I just had the thought that perhaps we're driving the boats only guys nuts with our aviation talk. I ask their pardon.
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