Am I creating Inner Fuel Tank Condensation?

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jefndeb

Guru
Joined
Jun 11, 2018
Messages
601
Location
US
Vessel Name
Indigo Star
Vessel Make
2006 Mainship 400
Hello,

I work at an aircraft factory and I am always running across what they consider "scrap" that I would consider "Project Supplies". :thumb: Another words I dumpster dive. In the completion center, where all the interior is installed following main production, the cabinetry, carpet, additional wiring, pretty much everything it takes to turn a metal tube to a luxury interior is installed. This includes layers of high quality burn proof sound dampening insulation of which I ran across a bunch of.

I figured I might could reduce engine noise in the cabin a little maybe by installing some of this sound dampening insulation in the engine bay area etc.

However sometimes my ideas aren't always good ones in the end but I got to thinking that in doing this could I be introducing a possible an inner fuel tank condensation problem?

I sorta understand condensation, it occurs when warmer air and colder air come together on a surface like a window and as a result the moisture in the air collects on the warmer surface.

So I am thinking this through and say a scenario would be like this-

The engine bay, initially where pretty much everything is roughly the same temp, engine block, transmission, fuel etc. Engine cranks, we get underway and engine area gets pretty hot. As it is now, we have port & starboard 150 gallon SS tanks.

Question is, by me partially covering the 2 tanks loosely with sound dampening insulation, am I increasing the possibility introducing a possible inner fuel tank condensation or not really?

Looking forward to comments...:oldman:
 

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I can't see a problem. How's the noise level?
 
Very interesting question! I can’t readily say if what you’ve done will increase the possibility, but Nigel Calder says the biggest issues with fuel tank condensation are contaminated fuel and the air vent line. Which, in the course of normal operation, brings into our fuel tanks moist, marine air.

That’s why he endorses (without any compensation) the Air Vent Dryers from H2Out. The AVD removes water molecules from the air entering the tank. We have them in our store and highly recommend their use:

https://www.pacificnwboatertested.com/products/h2out-fuel-guard-air-vent-dryers

When we made the video I was of course honored to work with him, but very impressed that he made sure to tell anyone within earshot that he was not being paid to do it. He was very concerned that his integrity and objectivity not be compromised. Made me respect him even more!
 
Moonfish said:
Very interesting question! I can’t readily say if what you’ve done will increase the possibility, but Nigel Calder says the biggest issues with fuel tank condensation are contaminated fuel and the air vent line. Which, in the course of normal operation, brings into our fuel tanks moist, marine air.

That’s why he endorses (without any compensation) the Air Vent Dryers from H2Out. The AVD removes water molecules from the air entering the tank. We have them in our store and highly recommend their use:

https://www.pacificnwboatertested.com/products/h2out-fuel-guard-air-vent-dryers

When we made the video I was of course honored to work with him, but very impressed that he made sure to tell anyone within earshot that he was not being paid to do it. He was very concerned that his integrity and objectivity not be compromised. Made me respect him even more!
Click to expand...

Thanks, Darren - that's a new one on me. The promise of the AVD seems quite meaningful in humid environments such as here in Florida, where many boats (sadly) lie idle with little changeover to the content of their fuel tanks.
 
I can see that the (sound) insulation would make your fuel tanks quieter inside, but to what purpose? Thermal insulation might also slow down temperature swings in the fuel, but again, to what purpose? The engine room will cool off faster than the fuel, which is what leads to condensation on the inside of the tank (assuming moisture in the fuel or water vapor in the air), but insulating the tanks might only slow that process. The condensation issue is best addressed by what you allow in your tanks, not what you put on the outside. I would use flameproof sound insulation against the engine room walls and forget about the tanks. The only advantage of using it on the tanks is that it is the easiest place to install.

Scrounging in an aircraft factory scrap pile reminds me of the old Boeing Surplus store south of Seattle. I found lots of goodies there. Soundproofing carpet that I put in my Volvo 1800. One inch titanium tubing that I used in place of stainless for boat stanchions. I still have goodies in my scrap pile that come in handy.
 
Marco, as I stated in my post the intent/purpose was to possibly reduce cabin noise a little, wasn't to worried but it was in the dumpster and didn't get wet so to me it was worth a look see...
 
They might be aluminum actually, my mistake...
 
I don’t see any problem with it. I am insulating my deck hatch now. The entire cockpit in my boat hinges up so there is quite a bit of area to insulate. The original sound insulation wasn’t very effective so I am putting in Soundown 2” 2 pound per square foot insulation. It has PSA on one side and I am using some metal pins that epoxy to the hatch to help hold it in place since it is so heavy.
 
From my limited knowledge & experience...
If you are interested in sound proofing the material / barrier needs to be applied to the bottom of the salon/ saloon floor. That prevents noise transfer from ER up to saloon. The other important point is the barrier needs to be continuous as a small opening will transmit much more noise that you might expect... so any seans need to be glued / taped and any openings such as hatches need gaskets for positive sealing.
I'm not sure from your pics if draping material over tanks will have any affect at all.
 
Why is stainless steel a bad choice for fuel tank material ??
 
BeeJay said:
Why is stainless steel a bad choice for fuel tank material ??
Click to expand...

My question as well. Many boats have stainless tanks, I had never before heard that was a bad thing. A bad thing I have heard is marine aluminum for water and holding tank which was common in earlier Island Packet boats and an eventual failure point that was not easy to replace.
 
Perhaps also consider mass loaded vinyl, which is available in rolls on Amazon. I’ve never used it for maritime use but it is weatherproof.

It comes in both a 1lb and a 2lb per square foot density. Very effective for sound blocking not absorption.
To confirm the prior post, a small gap allows half the sound to come through.
 
Last edited:
backinblue said:
My question as well. Many boats have stainless tanks, I had never before heard that was a bad thing. A bad thing I have heard is marine aluminum for water and holding tank which was common in earlier Island Packet boats and an eventual failure point that was not easy to replace.
Click to expand...



I hope someone enlightens us, l’ve read about the difficulties of many ferrous fuel tanks being replaced, but can’t recall the same of stainless steel.
 
jefndeb, Savannah huh - might that 'scrap materiel' come from a Gulfstream?? Back in my banker days I financed quite a few of those great planes.
 
I am not an expert on welding but I think that the problem with stainless steel tanks is the welding may cause areas that can rust if it isn’t properly passivated.
 
jefndeb said:
...condensation...occurs when warmer air and colder air come together on a surface like a window and as a result the moisture in the air collects on the warmer surface...Looking forward to comments...:oldman:
Click to expand...
.
[I will hold-off saying your understanding is wonk.
I acknowledge two people can have different experiences.
I hope this short treatise may offer clues to guide your new project.]
.
Here is my experience:
.
The 'cool' of it:
* Cold air is denser, unable to carry much moisture.
For example:
* Rising -- moisture-laden -- warm air always cools, creating rain and snow in high altitudes with thinner air.
That thin air is mostly-incapable of absorbing moisture (beyond saturation), so gravity assists in maintaining the balance.
.
Another example, this one closer to home:
* winters are notorious for sinus infections/influenza/pneumonia in dehydrated mucus membranes -- and chapped lips -- because the air can be very dry.
Everything floating in the air is automatically attracted to warm moist surfaces, i.e. sinus, lungs, sweaty folds.
.
An aside:
Oft-visible during the cold weather 'sick-season', each exhalation exhausts moisture in our breath, compounding our tendency toward dehydration.
.
The 'warm' of it:
* Warm air is thinner, able to carry more moisture.
An example:
* Warm surface at approximately the temperature of nearby air has little to offer as a landing zone.
The moisture may well stay saturated in the air... the temperature similarity creates little ionic attraction.
.
Inside a structure -- house, boat -- warm air 'absorbs' and holds moisture.
During winter or a chilly evening -- as this warm moist air convects near a cooler surface such as an exterior window -- the suddenly-chilled air must release its moisture.
This presents as condensation.
.
.
My opinion on your q:
I think surrounding the exterior of your room with insulation would help temper/mitigate the temperature differences inside that room.
.
I think laying insulation against an interior surface creates a concealed area for condensation to collect... probably acting as a medium for mold.
Those molds could poot airborne spores... and potentially take residence on an accommodating sinus orlung.
 
Last edited:
Large Marge said:
.
[I will hold-off saying your understanding is wonk.
I acknowledge two people can have different experiences.
I hope this short treatise may offer clues to guide your new project.]
.
Here is my experience:
.
The 'cool' of it:
* Cold air is denser, unable to carry much moisture.
For example:
* Rising -- moisture-laden -- warm air always cools, creating rain and snow in high altitudes with thinner air.
That thin air is mostly-incapable of absorbing moisture (beyond saturation), so gravity assists in maintaining the balance.
.
Another example, this one closer to home:
* winters are notorious for sinus infections/influenza/pneumonia in dehydrated mucus membranes -- and chapped lips -- because the air can be very dry.
Everything floating in the air is automatically attracted to warm moist surfaces, i.e. sinus, lungs, sweaty folds.
.
An aside:
Oft-visible during the cold weather 'sick-season', each exhalation exhausts moisture in our breath, compounding our tendency toward dehydration.
.
The 'warm' of it:
* Warm air is thinner, able to carry more moisture.
An example:
* Warm surface at approximately the temperature of nearby air has little to offer as a landing zone.
The moisture may well stay saturated in the air... the temperature similarity creates little ionic attraction.
.
Inside a structure -- house, boat -- warm air 'absorbs' and holds moisture.
During winter or a chilly evening -- as this warm moist air convects near a cooler surface such as an exterior window -- the suddenly-chilled air must release its moisture.
This presents as condensation.
.
.
My opinion on your q:
I think surrounding the exterior of your room with insulation would help temper/mitigate the temperature differences inside that room.
.
I think laying insulation against an interior surface creates a concealed area for condensation to collect... probably acting as a medium for mold.
Those molds could poot airborne spores... and potentially take residence on an accommodating sinus orlung.
Click to expand...
That may be a very wordy way of saying... when a surface temp is at or below the dew point of the adjacent / surrounding air, condensation occurs.

If air can be "thin" explain what thick air is?
It seems to me a better term is less or more dense.
The thing that confuses many is the fact that dry air is more dense that moist air... many relate moist air with it being "heavier" or more dense but the opposite is true.
 
Last edited:
Stainless is not high corrosion resistant when welded. In addition it is brittle and does not like vibration. It would be about the last material I would use for fuel tanks.
 
Marine grade SS is not made brittle by welding (if done properly). It is not a material that can be hardened with heat. It can loose corrosion resistance if overheated during welding, or if 316 is used instead of 316L. I can't see any reason not to use SS for a diesel tank, other than it will be heavy compared to aluminum.
 
Anyone have stainless diesel tank failure. Perhaps some failure reports would explain why there is a negative view to consider the product.
 
insulating your fuel tanks will keep the fuel cooler. Colder fuel entering the engine will usually result in better performance.
 
bfloyd4445 said:
insulating your fuel tanks will keep the fuel cooler. Colder fuel entering the engine will usually result in better performance.
Click to expand...

That can be a two way street. Most engines return quite a bit of fuel to the tank. The fuel is heated by the engine and unless the engine has a fuel cooler it returns warm or hot fuel to the tank. If it is insulated it can retain the heat in the fuel in the tank. Not saying this will happen but it can. It depends on how much fuel is returned to the tank, temp of that fuel and size of the fuel tanks among other things.
 
Comodave said:
That can be a two way street. Most engines return quite a bit of fuel to the tank. The fuel is heated by the engine and unless the engine has a fuel cooler it returns warm or hot fuel to the tank. If it is insulated it can retain the heat in the fuel in the tank. Not saying this will happen but it can. It depends on how much fuel is returned to the tank, temp of that fuel and size of the fuel tanks among other things.
Click to expand...

took 'em right outa my mouth.... I often wonder about that return fuel temp. I need to remember to grab hold of the return hose next time I an out running hard to "get a feel" for the temp.
 
Our last boat had Lehmans in ti and returned very little fuel. A previous boat I had was equipped with Detroits and they returned a bunch of fuel. The tank in that boat would get much warmer after a long run.
 
Water in warm air condenses on cooler surfaces. Look at your iced-drink glass! Sweats on the outside, drips on your shirt!


Some water in fuel tanks come from warm air being pulled in as the level drops, a small amount, since there must be a temperature or pressure differential to draw it in, and then the interior environment must be cooler than the outside air, unlikely after shutdown.


The MOST water in your fuel comes from the fuel supplier, from all the condensation taking place as large volumes of fuel are pumped out from cold underground tanks into tank trucks for distribution, and then into fuel dock tanks. Large volumes of moisture-laden air are transferred. Who knows how high (or tries to remove) the water layer at the bottom of the storage tank. When it gets mixed with the fuel, or gets high enough....it gets carried away, a lil' bit in each boat!



So the only defense is a good fuel filter, changed often.


Oh, and insulting the tanks...how does that keep the sound energy out of the salon?


Phil Little
 
Stainless steel fuel tanks weren't ABYC approved until 2005... With the exception of cylindrical versions up to 20 gallons capacity.
They are approved now if constructed of Stainless steel, if used for fuel tank construction, must be of the 316L or 317L alloy variety and a minimum of 0.0747 inch thick. Crevice corrosion was the concern .
 
Arc said:
Stainless is not high corrosion resistant when welded. In addition it is brittle and does not like vibration. It would be about the last material I would use for fuel tanks.
Click to expand...



What would you expect the highest natural frequency of a fuel tank damped by fuel and excited by in most instances a low revving Diesel engine ? I would expect the expected fatigue life of a sensibly sized 316L tank to be exceptional. It would be interesting to here from someone that had had some first hand experience of a fatigue failure. I’m surprised it’s a problem.
 
I am told, many military planes have bladders inside the metal fuel tanks. I wonder if this would have an application for leaky fuel tanks on boats?
 
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