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Old 04-04-2019, 02:26 PM   #141
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Ok, you did the first easy part. The next part is more complicated: Hygrometrics. So 5% of volume goes in or out with a 13deg swing (did not check your math, but assume it is right). Next, how much water is contained in that 5% and how much will condense out in the temp swing process?
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Old 04-04-2019, 02:30 PM   #142
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Re: "But do the math and the volume through those mechanisms is very small as a percentage of trapped air volume above the fuel level.

Nope, and I did do the math. During a single 24 hour cycle, it's between 5-16%, depending on temperature. That's actually very large. Over the course of a week or so, it's more than large enough to maintain the inside of the tank at the same RH as the outside air.

Let's walk through the math...

A 300 gallon tank that's 10% full will inhale and exhale a total of 3,050 cubic inches of air in a single 24 hour cycle where the temperature swing is a mere 13 degrees F. You're both capable of doing this math (remember to convert to Kelvin) but if you want to avoid the effort, send me a private message with an e-mail address and I will send you the spreadsheet. It's pretty simple.

Don't think of the vent hose as any kind of 'buffer'. 3,050 cubic inches is many hundreds of times the volume of air in a typical vent hose.

Remember, this happens every day, so multiply by 365 and you'll know how much water laden air you are ingesting over time. Remember, this is on a mere 72-85 degree swing.

What if we use SteveD's test conditions where he experiences...

"...temperature swings of 40F are not uncommon in 24 hrs as warm fronts move through..."

PV = nRT gives us 9,900 cubic inches in 24 hours. That's about 16% of the tank's ullage...in one day. That's six cubic feet per day and 175 cubic feet per month.

Re: "in order to generate significant condensation the movement of water-laden air into the tank has to occur".

Right...and it does. 10% per day (on average) is more than enough.

And if it weren't...there are several other factors that folks also neglect to consider. I'd be happy to explain these also, but I think PV = nRT is giving us plenty.



Good God we're doomed!


Yet there are those of us who have boats that never have water or any of the water living crud issues that if it really was that wet inside our tanks we would pumping out buckets of the stuff.


HOLLYWOOD
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Old 04-04-2019, 02:32 PM   #143
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We burn a little less than 7 gallons / hour, but of course, a lot more than that goes thru the filter every hour.

The fuel has been refreshed regularly over the 13 months since I changed the filter (422 hours x 7 gph is almost 3,000 gallons, and we hold only 1,000). But at the time the filter was changed, we hadn't put much fuel through the system in the previous year, so some of that filter's life was filtering some not-so-fresh fuel.

We've bought fuel in Nassau, Providenciales, and Salinas (PR) during that time. Since all fuel goes through the 2 micron filter before it goes into our "day tank", and that filter has never gotten really cruddy, I feel like we've never gotten any bad / dirty fuel.

As noted in the OP, the filter in the pic is 10 micron, and everything goes through 2 micron on its way into our day tank.
Ok...here's a new clue. Of the fuel we've purchased in the islands, probably 50% or more comes in from above ground or near surface tanks -- so it's 'warm' fuel. Warmer fuel holds a lot of water which has been absorbed. That means that no filter can filter it out and it cannot be seen in a fuel bowl. If that fuel was at or near it's water saturation point when you took it on (likely), then as soon as you cooled it down (by adding it to your main tank), liquid water 'fell out' (precipitated) down into the bottom of your tanks.

Re: "I feel like we've never gotten any bad / dirty fuel."

You probably didn't. Moisture saturated fuel is neither bad or dirty, but it cannot absorb any more water, so any little downward temperature change is going to cause water to drop out in the liquid phase. That's what fed the bugs (microbial slime) you found on your filter. Bugs can't grow until there is liquid water in the tank.

I think I know what you mean by "Day Tank", but others here are unfamiliar...can you elaborate? Generally, a Day Tank does not have a deck fill, is that right?
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Old 04-04-2019, 02:38 PM   #144
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Re: "But do the math and the volume through those mechanisms is very small as a percentage of trapped air volume above the fuel level.

Nope, and I did do the math. During a single 24 hour cycle, it's between 5-16%, depending on temperature. That's actually very large. Over the course of a week or so, it's more than large enough to maintain the inside of the tank at the same RH as the outside air.

Let's walk through the math...

A 300 gallon tank that's 10% full will inhale and exhale a total of 3,050 cubic inches of air in a single 24 hour cycle where the temperature swing is a mere 13 degrees F. You're both capable of doing this math (remember to convert to Kelvin) but if you want to avoid the effort, send me a private message with an e-mail address and I will send you the spreadsheet. It's pretty simple.

Don't think of the vent hose as any kind of 'buffer'. 3,050 cubic inches is many hundreds of times the volume of air in a typical vent hose.

Remember, this happens every day, so multiply by 365 and you'll know how much water laden air you are ingesting over time. Remember, this is on a mere 72-85 degree swing.

What if we use SteveD's test conditions where he experiences...

"...temperature swings of 40F are not uncommon in 24 hrs as warm fronts move through..."

PV = nRT gives us 9,900 cubic inches in 24 hours. That's about 16% of the tank's ullage...in one day. That's six cubic feet per day and 175 cubic feet per month.

Re: "in order to generate significant condensation the movement of water-laden air into the tank has to occur".

Right...and it does. 10% per day (on average) is more than enough.

And if it weren't...there are several other factors that folks also neglect to consider. I'd be happy to explain these also, but I think PV = nRT is giving us plenty.
Just as a practical question …. how many seasons have you had your Bayliner and how much water did you get in your tanks? We have had boats in the NE (NY) for 30+ years now so likely one of the worst places for this type of event I would guess.
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Old 04-04-2019, 03:06 PM   #145
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I dont have to know what the stuff is. I know it is not water. I have never, in hundreds of thousands of miles driven, had water in my fuel. I dont haveto have clear fuel tanks, only clear Racors to see water. After years of boating, in all seasons, i would ecpect to see water accumulation if it was coming from condensation. So far, none seen. I think SteveD is on the right track with his investigations. As far ad practic as l sailor is concerned, i will read your links when i get a chance.
Re: "I dont have to have clear fuel tanks, only clear Racors to see water. After years of boating, in all seasons, i would ecpect to see water accumulation"

That's the source of the confusion then. You can have a LOT of water in the bottom of your tanks, and never see a drop of it in your Racor bowls. In fact, by the time you see any water in your Racor bowls, it probably means there has been liquid water building up in your tanks for a long time.

Reason: Liquid water is much heavier than diesel -- so sits on the bottom of the tank, while your pickup tubes are up an inch or so off the bottom. No water in the tubes, no water in the Racor. Even if you are sloshing the water/fuel around in your tanks (running hard on a rough day), any small amounts of water that make into the mouth of the tube are still too heavy to get sucked up to the top of the tube (24 inches give or take) so they drop back down. The only way to get water in the bowls of your Racor is to keep the pickup tube completely submerged in liquid water long enough to get it up past the 'siphon' point. Given that 6 gallons-per-hour is only about a quarter-ounce per second, there is no way to pull liquid water up 24" of a five-ounce tube unless you can keep the tube totally under the water for 25 seconds or more, so the whole 'sloshing' theory is kaput.

re: "I dont have to know what the stuff is. I know it is not water."

We all know it's not water. It's evidence of water.

It's microbial slime, waste product of microbes than cannot live (eating your fuel) unless they can find a source of liquid water in your tanks to support their metabolism. So, if you see black slime on your filters, then you have (liquid) water in your tanks, it's that simple. This is true whether you see water in your Racors or not.
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Old 04-04-2019, 03:06 PM   #146
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Old 04-04-2019, 03:15 PM   #147
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...if it really was that wet inside our tanks we would pumping out buckets of the stuff.


HOLLYWOOD

No, it only takes an ounce of two of liquid water to support a pretty ugly infestation, but you've missed most of the discussion (and the point). The majority of the water in your fuel has been absorbed by the fuel, meaning it's not a problem.


Search the thread for 'saturated' or 'precipitate' to see where the liquid phase water comes in to the picture.
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Old 04-04-2019, 03:31 PM   #148
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Just as a practical question …. how many seasons have you had your Bayliner and how much water did you get in your tanks? We have had boats in the NE (NY) for 30+ years now so likely one of the worst places for this type of event I would guess.
Currently own both the Mainship and the Bayliner.


All boats I have owned/maintained: 3 Bayliners, 4 Chris Crafts, 1 Mainship = 35 seasons. New York (WNY), Minnesota, North Carolina, Florida.

How much water? I know (assume) there is always some in there, but I always add a biocide, so I don't much care. Occasionally I will pull the tank senders and stick an endoscope in there, but I'm not looking for water, just evidence of water (microbial slime). The black slime will show up on my racor 900 elements if I have a problem.

I do NOT like the cannister type filters on the Bayliner 4788! I can't see the filter media unless I cut them open. I may replace them someday.


Anyway...Water's not the problem, it's the microbes that live off of the water and their corrosive bio-waste. Use a biocide, keep the bugs from growing, and sleep well at night.
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Old 04-04-2019, 03:53 PM   #149
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Ok, you did the first easy part. The next part is more complicated: Hygrometrics. So 5% of volume goes in or out with a 13deg swing (did not check your math, but assume it is right). Next, how much water is contained in that 5% and how much will condense out in the temp swing process?
It's not more complicated. The complicated part (apparently) is the concept of the multi-phase absorption-precipitation-absorbtion-precipitation cycle. I think I've explained this three times, but some of the skeptics still don't get it, or maybe don't believe it.

Humidity in the tank can either be (a) absorbed directly into the fuel, or (b) condense on a cold surface and then be absorbed by the fuel. Either way the fuel is soaking up the water until it can't hold anymore (becomes saturated).



I think people still have a hard time with this because they once learned that 'oil and water don't mix', which is only partially true.

Liquid water only shows up in a diesel tank after the fuel itself can't absorb any more water AND the fuel temperature subsequently drops. Then, when fuel temp rises again, fuel can soak up more water...but it 'prefers' to absorb it from the air, instead of re-absorbing the precipitate down at the bottom of the tank. In effect, the fuel is absorbing water from the air when it's warm, precipitating it to the bottom when it's cold, and then absorbing from the air again when the temp goes up and precipitating to the bottom again on the downswing.

There's a name for this cycle I learned years ago but I can't remember it...
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Old 04-04-2019, 05:29 PM   #150
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Currently own both the Mainship and the Bayliner.


All boats I have owned/maintained: 3 Bayliners, 4 Chris Crafts, 1 Mainship = 35 seasons. New York (WNY), Minnesota, North Carolina, Florida.

How much water? I know (assume) there is always some in there, but I always add a biocide, so I don't much care. Occasionally I will pull the tank senders and stick an endoscope in there, but I'm not looking for water, just evidence of water (microbial slime). The black slime will show up on my racor 900 elements if I have a problem.

I do NOT like the cannister type filters on the Bayliner 4788! I can't see the filter media unless I cut them open. I may replace them someday.


Anyway...Water's not the problem, it's the microbes that live off of the water and their corrosive bio-waste. Use a biocide, keep the bugs from growing, and sleep well at night.
I bought one of our Bayliners that previously sat on the hard for 3 seasons so the fuel was at least 3 yrs old - 20% in the tanks. Was a 4588 with the 252 gallon tanks which has easy access to each tanks senders to pull unlike the 4788. One "O" ring had completely failed and we had just about 15 gallons of water in that tank - pumped it out with a vane puppy pump and a length of soft copper ice maker line snaked into the tank. the other tank had no water whatsoever after 3 years sitting in Haverstraw NY on land.
FWIW - never had a cannister filter on any Bayliner(4) , but we do not think the Racors are that robust nor have large capacity so we add spin on bulk filters prior to the Racors like sbmar recommends.
We did check occasionally for water with water paste on a 'stick' while boat was rocking in a slip or tied to the dock - no evidence of water.
We do have a borescope but it never was able to be that valuable for this type inspection.
Have not added biocide ever except after that tank was drained after sitting with water at the bottom.
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Old 04-04-2019, 05:44 PM   #151
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It's not more complicated. The complicated part (apparently) is the concept of the multi-phase absorption-precipitation-absorbtion-precipitation cycle. I think I've explained this three times, but some of the skeptics still don't get it, or maybe don't believe it.

Humidity in the tank can either be (a) absorbed directly into the fuel, or (b) condense on a cold surface and then be absorbed by the fuel. Either way the fuel is soaking up the water until it can't hold anymore (becomes saturated).
Actually, it is more complicated. I understand the physics well regarding moisture transport. You state that humidity in the tank ullage space can either absorbed into the fuel or condense on another surface. Actually there is (c), as the tank warms, the humidity in the air is expelled with the air. It does not necessarily condense. Diesel is not hygroscopic, unlike ethanol gas.

There will be a small air exchange during thermal cycles, but the water in that air does lose its moisture unless it crosses the saturation line while in the tank. That is not a common situation.
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Old 04-04-2019, 06:46 PM   #152
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Boating, huh? I joined because I thought there might be some boaters on here, but now I’m afraid there actually are.

Kill me now, I’m drawn to this thread like a moth and the poppyco never mind I’m just going to kill myself.
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Old 04-04-2019, 06:46 PM   #153
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WTH? No, diesel is VERY hygroscopic...

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...Diesel is not hygroscopic, unlike ethanol gas....
What? Of course it is...


LMGTFY
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Old 04-04-2019, 06:52 PM   #154
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Old 04-04-2019, 06:55 PM   #155
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.


Anyway...Water's not the problem, it's the microbes that live off of the water and their corrosive bio-waste.
Water is the problem, without it there are no microbes.
Perhaps fix the problem instead of applying the repeated bandaid biocide temporary fix.

Quote:
Use a biocide, keep the bugs from growing, and sleep well at night.
Nah, I'd rather stop the water, keep the bugs from growing, spend the money saved on beer and sleep even better at night.
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Old 04-04-2019, 07:06 PM   #156
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We've bought fuel in Nassau, Providenciales, and Salinas (PR) during that time. Since all fuel goes through the 2 micron filter before it goes into our "day tank", and that filter has never gotten really cruddy, I feel like we've never gotten any bad / dirty fuel.

As noted in the OP, the filter in the pic is 10 micron, and everything goes through 2 micron on its way into our day tank.
How does the 2 micron filter look after a season or two?
Crude and water? How many gallons do you carry?
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Old 04-04-2019, 07:14 PM   #157
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Good God we're doomed!


Yet there are those of us who have boats that never have water or any of the water living crud issues that if it really was that wet inside our tanks we would pumping out buckets of the stuff.


HOLLYWOOD
At some point, debates with someone who can never be wrong, no matter how far up their kazoo their heads are, or how politely you try to explain why they are mistaken, become psychological studies into narcissism.

I'm spending my time explaining epistemology to my cat. Greater chance of a break through.
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Old 04-04-2019, 08:27 PM   #158
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Good God we're doomed!
:iagr ee:
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Old 04-05-2019, 08:31 AM   #159
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I personally think this "discussion" is excellent.
However I am still going to change my filters once per season just because.
And I like it when they look like this:
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Old 04-05-2019, 08:46 AM   #160
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What? Of course it is...


LMGTFY

Which brand of biocide do you use 'all the time"?
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