SailNet Community - View Single Post - Myth of Condensation in Fuel Tanks
View Single Post
post #8 of Old 06-22-2008
Once known as Hartley18
Classic30's Avatar
Join Date: Aug 2007
Location: Melbourne, Australia
Posts: 5,179
Thanks: 52
Thanked 85 Times in 85 Posts
Rep Power: 11
Fuel (all hydrocarbon fuels - even LPG) contain water in differing amounts. I dunno what it is for Diesel, but for Aviation Kerosene the limit is 30ppm. The refiners don't worry about it too much because, in small quantities water can actually aid combustion - it's when there is too much it can be a problem. Two things...

1. Entrained water doesn't mix with oil and so settles out over time (several hours), causing the "condensation" you see in the bottom of the tank. ie. The water has "condensed" out of the fuel.

2. Most hydrocarbon fuels significantly change in volume with changes in temperature, so if you buy fuel at, say 70degF and fill your tank on a 60degF day, the fuel volume will decrease gradually drawing a small amount of air in through the vent. Any moisture in the air will then settle on the tank walls and add to the "condensation" at the bottom of the tank.

The way to avoid issues with water in your fuel?? You have two options: Either pump it out before you go or recirculate it though your fuel system on a regular basis..

Originally Posted by halekai36 View Post
Yes or .81oz EVERY DAY THE CONDITIONS ARE RIGHT FOR CONDENSATION!!!!!!!! Someone remind him there are 365 days per year and tanks in boats should be expected to last well into the 30 year mark..?? Even if your tank could only hold .01 oz of water vapor over time it ADDS UP!!!!!
Halekai, there's a small problem with your premise - an empty tank doesn't have any fuel in it.. If what you're saying is correct, over time an empty tank would magically fill itself with water - in practise it doesn't.

A bad day on a boat beats a good day in the office

Last edited by Classic30; 06-22-2008 at 10:28 PM.
Classic30 is offline  
Quote Share with Facebook
For the best viewing experience please update your browser to Google Chrome