I'm not there yet, but how about dry ice, add crushed dry ice to the tank, and
when you see CO2 vapor coming out the top, it seems to me that all the other
vapor
should have been replaced. Then a spark should have no effect.
Harold Kovac #A 097
"David G. Watts" wrote:
> James Thursby wrote:
> > I thought you might like to be aware of the fact that the fuel tanks in our
> > airplanes while extremely safe and crashworthy, also have a small quirk
> > present. Even if the tank is drained and flushed with water repeatedly, the
> > plastic seems to permeate vapors afterwards. How do I know this you ask?
> > Last Wednesday I was installing a capacitance fuel gauge in a previously
> > flying Europa, that we had flushed with water and drained, and in the
> > process of cutting the 2 inch hole with a heated drill bit and pliers, set
> > off fumes in the tank when a little piece of the plastic caught fire. (if
> > you have ever seen a empty alcohol bottle lit with a match, you get the
> > idea) The tank had been flushed and then had sat overnight. Both of us had
> > smelled the filler and could not detect any fumes. We where cutting it with
> > a heated wire, so there wasn't any flame or sparking from an electric tool
> > present. I only waited a week to tell because it was difficult to type
> > earlier. The plane is fine and will be ready for it's third lease on life
> > shortly, and my left hand should be fine in a few weeks. (yes I am a lefty)
> > It just goes to show you that even when you take what you think are all the
> > necessary precautions, Murphy is still about.
>
> This might not necessarily be the case.
>
> With a background in motor racing I know of more than one case where
> people have set up fuel tanks with a hose water flush for several hours,
> only to have the thing explode as soon as they start welding. Petrol is
> a devil of a substance to purge when you are going to have sparks or
> flames around.
> Having said that, who knows what is happening in these plastic tanks??
>
> Dave Watts, G-BXDY
>
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