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Old 03-29-2019, 07:15 AM   #41
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Originally Posted by O C Diver View Post
To be clear, I have them and watch them, but it's still a pretty low quality gauge. Have seen more than one fail to read at all with a plugged filter. See Ski's comments below.



Ted
I have found fairly robust gages pretty easy to find and install - similar to any engine gages that you will want to utilize it is best to have good indicators - rpm, boost, pyro, oil pressure etc. If they seem weak or are failing they need to be replaced with a suitable replacement.
The last 10 or so vac gages I bought were very good and not too expensive at all - 2" Stainless steel case, + or -2% accuracy, and I added snubbers and glycerin filled them for better use and protection - I think they were less than $30 each at the time. Would not want to cruise without any of the gages in good working order as they are a big plus when you need them.
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Old 03-29-2019, 07:19 AM   #42
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"(the gauge is not always mounted in a location that is easy to monitor)."

If the gauge is located in the Hell Hole on top of the filter , it might be dangerous to change out the plugged filter with the engine operating.

At best it will be loud and over 100F , moving the filter bank to a location out of the HH only requires some hose.
IMO, never do anything to a running engine unless you want to lose a body part.
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Old 03-29-2019, 10:59 AM   #43
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You guys are way over-thinking this filter thing. Unless you have taken on a load of bad fuel, you can see the level of crud in a Racor in the bowl. If the engine slows uncommanded under load, flip the lever. If you haven’t changed that filter, for a while, change it in a safe place later but that gauge is adequate. ANY reading not zero and it’s time to change. Has anybody ever seen a “deteriorated” filter? Of course not; crap in an engine from a failed filter would bankrupt Racor, they don’t use any filter compound that “fails.” How else to sell filters to boat owners that only do 100 hours a year? Tell them they fail over time. Codswallop.
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Old 03-29-2019, 11:39 AM   #44
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You guys are way over-thinking this filter thing. Unless you have taken on a load of bad fuel, you can see the level of crud in a Racor in the bowl. If the engine slows uncommanded under load, flip the lever. If you haven’t changed that filter, for a while, change it in a safe place later but that gauge is adequate. ANY reading not zero and it’s time to change. Has anybody ever seen a “deteriorated” filter? Of course not; crap in an engine from a failed filter would bankrupt Racor, they don’t use any filter compound that “fails.” How else to sell filters to boat owners that only do 100 hours a year? Tell them they fail over time. Codswallop.
"ANY reading not zero and it’s time to change."
I am confused by this....
- most all vac gages I have used and installed have a 'new' reading of 2-3" , so there is no zero ever.
- a 'good' filter in use will trend thru 3-8" over use and not be near a point requiring replacement.
- at about 8" I typically plan on when to change for convenience sake and make life easier, filters reading 11-12" still do not stop my engines.
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Old 03-29-2019, 02:28 PM   #45
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"ANY reading not zero and it’s time to change."
I am confused by this....
- most all vac gages I have used and installed have a 'new' reading of 2-3" , so there is no zero ever.
- a 'good' filter in use will trend thru 3-8" over use and not be near a point requiring replacement.
- at about 8" I typically plan on when to change for convenience sake and make life easier, filters reading 11-12" still do not stop my engines.
You're correct. There will always be a baseline vacuum, usually around 7 - 10 inches of Hg when running at the operating rpm. I believe Racor says to change the filter when it gets 5 or so inches above that range.
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Old 03-29-2019, 02:50 PM   #46
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All this change or not to change IMO over looks one point. How much water is in the bowl.
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Old 03-29-2019, 03:17 PM   #47
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All this change or not to change IMO over looks one point. How much water is in the bowl.
I have never seen any water in the filter bowls - but we always had separate inline water separators for water - which were always empty as well.
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Old 03-29-2019, 08:55 PM   #48
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You're correct. There will always be a baseline vacuum, usually around 7 - 10 inches of Hg when running at the operating rpm. I believe Racor says to change the filter when it gets 5 or so inches above that range.
Always best to check the engine manufacturer's spec on maximum fuel pump lift or vacuum. An odd one is the C series Cummins which have a surprisingly low vacuum limit. Exceeding that pumps limit can damage the pump.

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Old 03-30-2019, 07:23 AM   #49
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Codswallop.
Xs you gotta explain what this means.
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Old 03-30-2019, 07:27 AM   #50
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Definition of codswallop



British
: nonsense


Mr. X is from BRITISH Columbia, after all...
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Old 03-30-2019, 07:58 AM   #51
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This is often proposed in theory and seldom tested. But Maine Sail (CMS) has tested it. It does not happen, at least in his tests.
I'd seen this test a few years ago, is this the one you are talking about?

https://www.pbase.com/mainecruising/...t_condensation


Condensation and dew-points are not theories, they are laws of nature. This test is nonsense.


In the same way that an empty, open beer can will never generate condensate inside, this test was guaranteed to never generate condensate inside the aluminum fuel tank. Also, the author appears to not understand the concept of a "dew point".

Missing elements:

No thermal ballast: His tank was empty so there was nothing inside it to keep the aluminum surfaces cool as temperatures rise above and below the dew point. Next time you see condensate on a cold beer can, note how it does not immediately stop forming immediately above the liquid level. Aluminum conducts heat (and cold) pretty well.

Environment/Ambient temperature: Marine fuel tanks sit in a bilge, close to the waterline, where water temps usually keep them cooler (or warmer) than the outside air coming in through the fuel vent. All of that sound insulation under your cabin sole is also good thermal insulation. I keep a temp/humidity sensor in my bilge -- temps down there are always close to the ambient water temps and in some cases 20 degrees lower than outside ambient. Here in Florida, this means that the dew-point will coincide with the temperature of the aluminum gas tanks almost every morning, and water will condense on them because it simply must do so.

Any time a cold surface comes in contact with moisture laden air, assuming that the "cold" surface is below the dew point of the air, condensate will form. No need to waste time 'testing' this, it just IS.

Read that test again and think this through...it's quickly obvious why this test was guaranteed to generate a negative result. He just doesn't 'get' the physics here.

Now...forget about condensation for a moment. In many environments (in less humid areas), the primary way that moisture gets into fuel is by direct absorbtion of moisture from the air. The more "wet air" that your tank is breathing in, the more moisture the fuel will absorb. The more air that is in your tanks, the more the tank will breath as air expands and contracts with temperature. For me, the main reason for keeping tanks full is to make their "lungs" smaller. Less air in the tank, less expansion and contraction of air and less 'breathing'.

Condensation in the tank is a problem in some environments, moisture in the fuel is potentially a problem in all environments.

My main point is that everyone who is storing more fuel than they are burning in a month (and I think that's all of us at some point) needs to add a biocide agent, because there WILL be water in that fuel, and the bugs WILL find it.

Keeping tanks full will help slow down the absorbtion of moisture, but won't prevent it. Also, keeping tanks full will increase the total amount of moisture the fuel can hold in suspension before it begins to precipitate out and build up at the bottom of your tanks. I think it's still a good idea.
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Old 03-30-2019, 08:54 AM   #52
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I believe 90% of the water problems in diesel tanks comes not from condensation, but leaky deck fill caps or bad vent plumbing.

I have two 150gal tanks below the cockpit deck, the fills are on the tanks themselves and looking through the cap you can see the tank bottom at the low point. The vents go to a separator tank that has a low point drain. I usually keep tanks only 1/4 full most of the time to reduce weight (planing hull), only fill further as needed for trips.

In 12yrs since the build, I have had absolutely zero water in the tanks or the Racor.

If condensation was an issue, I would have seen water and I have not.

My biggest issue is condensation on the outside of the tanks when we get a warm front.
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Old 03-30-2019, 10:10 AM   #53
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Ski is correct ( you beat me to it!) internal tank condensation is immaterial. The volume of moisture in the air and the volume of air in the tank cannot support enough condensation to lose sleep over - that is also physics. Measure how much air migrates in and out with temperature change and measure how little that small amount of air can hold. Besides, the tanks are more effected by water temperature which does not fluctuate as much as air temperature. Fuel from the refinery contains water, look up the msds for the fuel; not significant unless you take the fuel high in the air to -65 degrees, then you need fuel heaters etc. Racor, if sized properly, will spin out excess water and they also have some sort of membrane/coating that works like goretex as a barrier to water. As has been stated, water gets in the tank from faulty fittings or from the marina’s tanks.

Sorry you didn’t like codswallop. How about poppycock? Horsefeathers? Truck; that’s probably Mark Twain?

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Old 03-30-2019, 10:14 AM   #54
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I've two thread related questions. What micron rating is OP's filter in the picture with the first post? He says both 2u and 10u are used. Secondly, is the filter pictured before or after the onboard day tank?

Two likely irrelevant comments. I've first hand knowledge of a Nordhavn 55 that had all it's fuel tanks, including the day tank, completely "bug" fouled due to old fuel loaded on from a South of the border location. Secondly, spin on 30u filters, from a shore location I'm familiar with, routinely pass 20,000 to 30,000 gallons before they are changed on an approximate monthly timed, not loaded, basis.

Lastly, can a tank and filters grow cultures by merely sitting if tanks and fuel are "bad" due to water, age or bad shore fuel to begin with.
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Old 03-30-2019, 10:32 AM   #55
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I've two thread related questions. What micron rating is OP's filter in the picture with the first post? He says both 2u and 10u are used. Secondly, is the filter pictured before or after the onboard day tank?

Two likely irrelevant comments. I've first hand knowledge of a Nordhavn 55 that had all it's fuel tanks, including the day tank, completely "bug" fouled due to old fuel loaded on from a South of the border location. Secondly, spin on 30u filters, from a shore location I'm familiar with, routinely pass 20,000 to 30,000 gallons before they are changed on an approximate monthly timed, not loaded, basis.

Lastly, can a tank and filters grow cultures by merely sitting if tanks and fuel are "bad" due to water, age or bad shore fuel to begin with.
"Lastly, can a tank and filters grow cultures by merely sitting if tanks and fuel are "bad" due to water, age or bad shore fuel to begin with."
Fuel can degrade over time with no microbial action and form long chain hydrocarbons as a result - it takes years,
Fuel can support microbial action if there is a fuel/water interface in the storage area of the fuel - that can develop much quicker.
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Old 03-30-2019, 10:32 AM   #56
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Ski is correct ( you beat me to it!) internal tank condensation is immaterial. The volume of moisture in the air and the volume of air in the tank cannot support enough condensation to lose sleep over - that is also physics. Measure how much air migrates in and out with temperature change and measure how little that small amount of air can hold.
A shore based tank farm or large yacht tanks can indeed grow water. Once into multi ten thousand or larger sized tanks condensation protocols and equipment are in place. For those of us that have purchased large volumes of fuel it is real world monitoring issue. BTW, physics doesn't apply - try chemical thermodynamics instead

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Old 03-30-2019, 11:30 AM   #57
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Diesel fuel absorbs a LOT of water before you ever see it...

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Originally Posted by Ski in NC View Post

...If condensation was an issue, I would have seen water and I have not.

My biggest issue is condensation on the outside of the tanks when we get a warm front.

Hmmm...how is it that you think water can be condensing on the outside of the tanks, but not on the inside? Wet air meeting cold metal = condensation, period.



The reason you are not actually be seeing the water is because it has not precipitated out yet. Just like air, diesel fuel will "absorb" water, up to it's saturation point. Like in air, the amount of water the fuel can hold is temperature dependent. Diesel fuel can absorb a LOT of water before it 'condenses' (the more accurate term is 'precipitate') in the bottom of your tank, which will happen at the 'dew point' of the fuel-water mix.



The best write-up I've seen on this is here:


==============================================



"Diesel can hold water in solution but it doesn't condense out of solution due to gravity, it condenses out due to a drop in temperature, just like water condenses out of air. Diesel #2 holds about 120 parts per million of water at body temperature but can only hold about 40 ppm at 4 degrees Celsius. If you fill up your tank on a warm summer day, even if the diesel is dry, it'll start absorbing water from the air (via the tank vent) until it reaches its saturation point around 120 ppm.

Let that fuel sit in your tank until it gets close to freezing outside and the diesel will be able to hold only about a third of the water it could when warm so the water will condense out as a separate liquid phase. It's only after condensation that it drops to the bottom of the tank due to gravity and the difference in density between water and diesel. The 80 ppm difference between diesel's water saturation at body temp and its saturation close to freezing equates to about 0.3 ml of water per gallon of diesel. If your tank is 100 gallons, you're talking about 30 ml of water, which is about an ounce. If you're on a trawler with 1600 gallons of diesel, you're talking about one beer can worth of water in your tanks.

If the tank were sealed and you brought the temp back up, the water would dissolve back into the fuel. However, the tank is vented so it has access to relatively moist air, which will supply water to the fuel at the same time the water at the bottom of the tank is dissolving back into the fuel, so you'll never get it all back into solution and you'll end up with residual water at the bottom of the tank.

By the same reasoning, you absolutely can get condensation on the tank walls from the water in the air. All it takes is warm, moist air coming in contact with the cold walls of the tank. When that happens, the air will cool near the tank wall, lose its ability to hold as much moisture, and it'll condense out on the surface. This can happen if you're out on a hot, humid day and your tank is colder than the surrounding atmosphere due to its close proximity to cold water on the other side of the hull.

Bottom line, if you can arrange to use all your fuel up without giving it a chance to cycle from warm to cold, you won't get much condensation due to water dropping out of the fuel but you're still vulnerable to water condensing out of the air if you can't keep the tank close to the same temp as the air at all times. In practice, it's virtually impossible to assure both conditions so you just have to live with water in your tanks via good water separators to handle emulsified water, filters that are designed to absorb dissolved water, and biocides that'll kill the bugs that want to grow at the water/fuel interface in the tank.


==================================================


Keeping diesel tanks full stops condensation T or F? - Fix It Anarchy - Sailing Anarchy Forums
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Old 03-30-2019, 11:40 AM   #58
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Greetings,
Mr. X. You're quite welcome. I do have some facility in translating 'Merican to Canadian...
What REALLY burns my biscuits is foyer. It's NOT pronounced the same as lawyer it's pronounced foy-eh. Oh...saloon!
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Old 03-30-2019, 11:52 AM   #59
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This topic comes up periodically. Here is what I’ve gathered over the years.

- Use a vacuum gauge with a drag needle. If it suddenly jumps up a few mmHg over the normal set point, maybe time to change your filter.

- Racor’s waterblock treatment on their filters will age out. While hard to find, I’ve seen the information from Racor that says that the filters should be changed yearly simply because they become less effective at blocking water.

- I don’t worry about condensation in my tanks. I live in a climate that has cool and very wet winters. I also live in an area that tends to have very clean fuel. I’ve never seen any water in the bowls of my Racors. When I change my filters, they aren’t as black as the OPs, but you can certainly see they are dirty.

- Despite the issue about the water block treatment above, I am currently changing one the two filters in my dual housing each year. I change the filter that was used during the year and then switch to the filter that was changed last year. I used to change both every year but decided that was probably overkill.

The “best” practice would be to change both every year as I did for years on my last three boats. FWIW, never in that time on any of those boats did I ever see a vacuum rise above the 1-3 mmHg present with a new filter. If I didn’t have a dual filter, I would still be changing it yearly regardless.
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Old 03-30-2019, 12:02 PM   #60
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Ok, we are talking yachts here, or whatever we have that approximates a yacht: as your tank empties it draws in air from the breather. The air has an amount of water in it that may or may not condense out, depending upon temperatures. Your fuel, in your tanks, has pretty much a constant temperature because it is a large volume and it’s sitting in the ocean, which has very little temperature change. If it is possible for ambient air to circulate around the outside of your tank, you will probably get some condensation right after fuelling unless it runs a long way in a hot pipe! Inside the tank, only the water that came with the fuel is in there and if you agitate the fuel, which most of us don’t as we don’t use our boats much, the fuel stays in suspension. The air in the tank will be mostly affected by the temperature of the fuel, which varies little in practice, and so only a small amount of the air goes in or out of the vent, therefore the amount of saturated air being reintroduced is minimal. Ambient air temperature matters little.

The water that arrives from the refinery has enough moisture in it to support bacterial growth but only in perfect conditions for the bacteria, hence the biocides some add to their fuel. I never have had any growth in my location in 15 years and have Never used a biocide.

The answer to the question is technically true but also immaterial to a recreational boater.
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