Re: Stus-List Filling diesel tank Urban myths?

[Michael Brown via CnC-List]

The volume in the fuel tank is fairly small, most of our boats it would be less 
than 0.1 cubic meter.
At around 90 degrees Fahrenheit that would be about 1/10 of an ounce of water 
in the air in an
empty tank.



http://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm


If the temperature starts around 60F and drops to 20F about 0.03 ounces of 
water would condense
in a 0.1 cubic meter tank. Air changes volume about 3% for a 40F temperature 
swing, so per month
another 0.03 ounces of water might get in.



Note that the numbers assume the maximum amount of water in the air, or 100% 
relative humidity.
If the winter relative humidity is 50% then cut the numbers above in half.



Michael Brown
Windburn
C 30-1





Date: Fri, 26 Oct 2018 10:37:21 + 
From: "Della Barba, Joe"  
Subject: Re: Stus-List [EXTERNAL]   Re:  Filling diesel tank  Urban 
     myths? 

In Maryland we have high humidity and large temperature changes during the 
winter. I had to rebuild the wood supports for my fuel tank because so much 
water would condense on it the wood rotted! 
The aluminum tank is frequently covered with drops of water on the outside 
during the winter. 
Joe 
Coquina 
 
Sent: Thursday, October 25, 2018 5:34 PM 
Subject: [EXTERNAL] Re: Stus-List Filling diesel tank Urban myths? 
 
I?m not in total disagreement, but the urban myth may be more of a Great White 
North myth. In that, when it gets cold out it stays cold until spring.  But 
otherwise, when it get cold at night and warms up in the day, it best to keep 
the tank either full or empty. 
 
The reason is that a metal tank with some liquid will dehumidify the air inside 
(and outside) the tank during the daytime when ambient air starts to warm 
relative to the night time lows.  Think about a tank half full after a cold 
night.  The cold fuel is a big heat sink and will keep the tank fuel and metal 
container much colder than the warming daytime air.  Warming air + cold metal 
surface = condensation, i.e. cold sweat.  A full tank has less condensing 
surface and less air inside.  An empty Aluminum tank will warm and cool with 
ambient air so there will be little if any condensation.  I guess one could 
close up the tank (i.e. close of breather line) to try to eliminate the 
reoccurring condensation, but that?s likely not as easy as it sounds (and end 
up being a bigger PITA than filling the tank). 
 
With any luck, Global Warming will rid the Canadians of some urban myths?. 
 
- 
Paul E. 
1981 C Landfall 38 
S/V Johanna Rose 
Fort Walton Beach, FL 
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Re: Stus-List Filling diesel tank Urban myths?

[schiller via CnC-List]

Paul,

I spent a lot of time in your neck of the woods in the early 80's while 
working on the Paveway III Laser Guided Bomb.  The Air Force was adamant 
that we make our shipping containers have pressure relief valves (burp 
valves).  We took empty shipping containers (Hellfire shipping 
containers) and put them in the parking lot of Eglin AFB Building 999 
for a month in the summer.  At the end of the month, we open the 
containers up and poured the water out. Every afternoon the containers 
would heat up enough to open the burp valve to equalize the pressure.  
In the evening, as the container cooled, the valve would reopen and suck 
in the nice cool, humid air that would condense in the container.  There 
was about a half an inch of water in the container after a month.


The Army lost a bunch of Hellfire missiles during Desert Storm after 
shipping them on an open deck.  When they got to Kuwait, they were full 
of water.


I fill my tank just before haul out.  There is a little fuel used to 
change oil, get to the haul out well and for winterizing.  I have never 
had the tank overflow during storage.


Neil Schiller
1983 C 35-3, #028, "Grace"
Whitehall, Michigan
WLYC

On 10/25/2018 5:33 PM, Dreuge via CnC-List wrote:
I’m not in total disagreement, but the urban myth may be more of a 
Great White North myth. In that, when it gets cold out it stays cold 
until spring.  But otherwise, when it get cold at night and warms up 
in the day, it best to keep the tank either full or empty.


The reason is that a metal tank with some liquid will dehumidify the 
air inside (and outside) the tank during the daytime when ambient air 
starts to warm relative to the night time lows.  Think about a tank 
half full after a cold night.  The cold fuel is a big heat sink and 
will keep the tank fuel and metal container much colder than the 
warming daytime air.  Warming air + cold metal surface = condensation, 
i.e. cold sweat.  A full tank has less condensing surface and less air 
inside.  An empty Aluminum tank will warm and cool with ambient air so 
there will be little if any condensation.  I guess one could close up 
the tank (i.e. close of breather line) to try to eliminate the 
reoccurring condensation, but that’s likely not as easy as it sounds 
(and end up being a bigger PITA than filling the tank).


With any luck, Global Warming will rid the Canadians of some urban myths….

-
Paul E.
1981 C Landfall 38
S/V Johanna Rose
Fort Walton Beach, FL

http://svjohannarose.blogspot.com/

On Oct 25, 2018, at 4:12 PM, cnc-list-requ...@cnc-list.com 
 wrote:



Message: 1
Date: Thu, 25 Oct 2018 19:41:45 +
From: Marek Dziedzic >
To: "cnc-list@cnc-list.com " 
mailto:cnc-list@cnc-list.com>>

Subject: Re: Stus-List Filling diesel tank
Message-ID:
>


Content-Type: text/plain; charset="utf-8"

Consider not adding the fuel.

This is an urban myth that the condensation would add a lot of water 
to the fuel. The water in the fuel tank comes usually from the 
leaking fill hose cover. If you don?t believe it, do some 
calculations (;-).


Depending how much you motor, if you keep topping up the tank, you 
may end up with a lot of old fuel in the tank.


Many marinas don?t allow the topping up, because if you do it now, 
the fuel will expand in the spring and it would leak through the vent.


of course, your boat, your choice.

Marek
Ottawa, ON




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every one is greatly appreciated.  If you want to support the list - use PayPal 
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___

Thanks everyone for supporting this list with your contributions.  Each and 
every one is greatly appreciated.  If you want to support the list - use PayPal 
to send contribution --   https://www.paypal.me/stumurray

Re: Stus-List Filling diesel tank Urban myths?

[Dreuge via CnC-List]

I’m not in total disagreement, but the urban myth may be more of a Great White 
North myth. In that, when it gets cold out it stays cold until spring.  But 
otherwise, when it get cold at night and warms up in the day, it best to keep 
the tank either full or empty.   

The reason is that a metal tank with some liquid will dehumidify the air inside 
(and outside) the tank during the daytime when ambient air starts to warm 
relative to the night time lows.  Think about a tank half full after a cold 
night.  The cold fuel is a big heat sink and will keep the tank fuel and metal 
container much colder than the warming daytime air.  Warming air + cold metal 
surface = condensation, i.e. cold sweat.  A full tank has less condensing 
surface and less air inside.  An empty Aluminum tank will warm and cool with 
ambient air so there will be little if any condensation.  I guess one could 
close up the tank (i.e. close of breather line) to try to eliminate the 
reoccurring condensation, but that’s likely not as easy as it sounds (and end 
up being a bigger PITA than filling the tank).

With any luck, Global Warming will rid the Canadians of some urban myths….

-
Paul E.
1981 C Landfall 38 
S/V Johanna Rose
Fort Walton Beach, FL

http://svjohannarose.blogspot.com/

> On Oct 25, 2018, at 4:12 PM, cnc-list-requ...@cnc-list.com wrote:
> 
> 
> Message: 1
> Date: Thu, 25 Oct 2018 19:41:45 +
> From: Marek Dziedzic mailto:dziedzi...@hotmail.com>>
> To: "cnc-list@cnc-list.com " 
> mailto:cnc-list@cnc-list.com>>
> Subject: Re: Stus-List Filling diesel tank
> Message-ID:
>   
>   
> >
>   
> Content-Type: text/plain; charset="utf-8"
> 
> Consider not adding the fuel.
> 
> This is an urban myth that the condensation would add a lot of water to the 
> fuel. The water in the fuel tank comes usually from the leaking fill hose 
> cover. If you don?t believe it, do some calculations (;-).
> 
> Depending how much you motor, if you keep topping up the tank, you may end up 
> with a lot of old fuel in the tank.
> 
> Many marinas don?t allow the topping up, because if you do it now, the fuel 
> will expand in the spring and it would leak through the vent.
> 
> of course, your boat, your choice.
> 
> Marek
> Ottawa, ON

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every one is greatly appreciated.  If you want to support the list - use PayPal 
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