Breather tube moisture trap

[thinwater]

I wonder if anybody has done some actual research? Some very rough calculations.

I have a 100 ltr tank or 0.10 of a cubic metre.

According to gegcalculators.com a cubic metre of air with a temperature of 15°C at 85% humidity holds 6.05 grams of water.

In total my empty tank could hold 0.605 grams. At 90% full is c0.55 grams.

I am sure somebody can come up the the weight of water in a raindrop.

The US EPA. Most is related to gasoline, but they now require carbon vents on most new boats with gas motors and installed tanks. See the link below for "resources."

How Can Silica Gel Have Out-performed Carbon? - Practical Sailor
EPA Mandate Sparks Fuel-vent Filter Test - Practical Sailor
Diesel Tank Vent Filters - Practical Sailor
Marine Fuel Vent Filter Maintenance - Practical Sailor
Fuel Vent Rules Are Out of Whack with Reality - Practical Sailor
EPA Needs to Revisit Fuel Vents - Practical Sailor
Fuel-vent Filter Test Resources - Practical Sailor
https://www.practical-sailor.com/boat-maintenance/reviving-fuel-filter-beads-again-and-again
https://www.practical-sailor.com/systems-propulsion/gasoline-additives-in-the-e-15-era

In the case of e10, the alcohol (hygroscopic) draws water, just like CaCl2. In the case of diesel, the amount of water depends on temperature swings and condensation in side the tank. If enough condenses to drip into the fuel, it is sealed under the fuel and stays there (a small amount also dissolves). So the math in each case is very different and very site-specific. For example, identical tanks on the same dock, one in the bridge deck and one in the bilge, will be very different.

 

[thinwater]

If you leave silica gel or any other desiccant exposed to UK autumnal / winter atmosphere it will rapidly become saturated and ineffective, a waste of time of course you could regenerate the silica gel in an oven once you know how long it takes to be deactivated, it won't be long.
Better as Sandy says just seal the vent and reduce the airspace as much as possible.

Yes, covering the vent is probably best.

No, if it is located well up the vent tube it will not saturate quickly, as you say. It will take years. We tested two boats in Seattle and a bunch in Alaska, both similar to UK climates. Testing on boats, not guessing or even calculating.

No, I do not work for any of those companies. Practical Sailor. I would have loved for it to be a gimmick I could debunk. It is not.

 

[thinwater]

Like many safety precautions, it only matters when it matters. If you use the motor enough, and water is not entering another way (vent or filler), the small amount of condensation will simply dissolve in the fuel and won't hurt a thing, and this will all seem like non-sense. If you only burn 10-20 gallons per year out of a 50 gallon tank, you will likely get some free water. Even then, the water may just sit in the tank, doing little harm, or it might grow bugs or corrode something. Or nothing.

People who sail a lot need to inspect standing rigging and replace it on a schedule. People who sail 4 times each year in less than 10 knots will never strain the rig. This is sort of the reverse case. Motors need to run. You need to either change the fuel (burn it) or store it very carefully.

 

[RunAgroundHard]

I wonder if anybody has done some actual research? ...

Not research but calculations, and see my post above where Marine How To Did experiment.

@JumbleDuck, who is a respected engineer and very clear in his facts and calculations, had something to say on this topic, and so did you, back in 2018 in this YBW thread To Top Up the Diesel Tank or Not?

Extreme case: suppose that a 100 litre tank is warmed ever day to 10oC and then cooled every night to 0oC. Total air ingested each cycle will be 10/283 x 100 litres = 3.5 litres. On average it's going in at 5oC, and if it's fully saturated will have at most 7g/m3 of water in it, so that's 7g x 3.5/1000 = 0.025g per cycle. Repeat this 150 times over the winter and your 100 litre tank has acquired a horrifying 3.7cc of water or 37ppm. As supplied diesel to standard EN-590 can come with 200ppm in it.

 

[Sandy]

The US EPA. Most is related to gasoline, but they now require carbon vents on most new boats with gas motors and installed tanks. See the link below for "resources."

How Can Silica Gel Have Out-performed Carbon? - Practical Sailor
EPA Mandate Sparks Fuel-vent Filter Test - Practical Sailor
Diesel Tank Vent Filters - Practical Sailor
Marine Fuel Vent Filter Maintenance - Practical Sailor
Fuel Vent Rules Are Out of Whack with Reality - Practical Sailor
EPA Needs to Revisit Fuel Vents - Practical Sailor
Fuel-vent Filter Test Resources - Practical Sailor
Reviving Fuel Filter Beads - Again and Again - Practical Sailor
Gasoline Additives in the E-15 Era - Practical Sailor

In the case of e10, the alcohol (hygroscopic) draws water, just like CaCl2. In the case of diesel, the amount of water depends on temperature swings and condensation in side the tank. If enough condenses to drip into the fuel, it is sealed under the fuel and stays there (a small amount also dissolves). So the math in each case is very different and very site-specific. For example, identical tanks on the same dock, one in the bridge deck and one in the bilge, will be very different.

Thanks, I shall enjoy reading those.

 

[Sandy]

Perhaps in addition to sealing the vent we should be lagging our tanks?

 

[William_H]

People who sail a lot need to inspect standing rigging and replace it on a schedule. People who sail 4 times each year in less than 10 knots will never strain the rig. This is sort of the reverse case. Motors need to run. You need to either change the fuel (burn it) or store it very carefully.

I would disagree with implications of that statement re rigging. It seems to me that it is calender life on boat in weather rather than actual sailing time that dictates when wire lets go.
ol'will

 

[thinwater]

I would disagree with implications of that statement re rigging. It seems to me that it is calender life on boat in weather rather than actual sailing time that dictates when wire lets go.
ol'will

Ummm ... No.

 

[Pye_End]

I noted a reference in 'Practical Sailor' mag to inline devices which extract water/vapour from the air passing through the tank breather tube. Silica gel is used and beneficial claims made.
Can anyone point to a similar product available in UK/Europe?

Just came across this: Below Deck Silica Gel Tank Breather/Dryer | Marine 16

Makes a DIY version attractive!

 

[Sandy]

Just came across this: Below Deck Silica Gel Tank Breather/Dryer | Marine 16

Makes a DIY version attractive!

Marine 16 do like a laugh with their pricing.

I see their Dipper is now just shy of £1,200 and then you need to add hose tails!