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Date: Tue, 10 Feb 2009 09:22:12 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: hauling gas
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Al Gietzen wrote:
>
> My simple approach is to use a metal chain, which serves as cap retainer,
> which hangs from the metal cap flange into the fuel, back to the cap.
> Contacting the end of the hose to cap/cap flange prior to removal takes car
> of any residual.  Maintaining contact between the hose and the flange
> (keeping the cap chain, or cable, hanging into the fuel) keeps fuel and hose
> at the same potential.
>
>  
Al, you're giving me the heebee-jeebees here.

The problem is that the can and fuel in the tank may already have a 
differential charge built up.  Then you may be getting an invisibly 
small spark connecting the can to the chain in the tank.  The spark 
would have to be at just the right place to get a fuel-air mixture to 
ignite, so chances of bad things happening are extremely low.  But such 
an easily remediated exposure.

Get an ESD wrist strap from RadioShack or other electronic supplier.  
For those who don't know, these are bungee straps woven with a 
conductive (carbon?) fiber.  They have a clip which connects to a coiled 
wire lead, terminated by an alligator clip.  The wire has a large value 
resistor in it.  You attach the alligator clip to what you want to be 
grounded to, and then the static potential energy drains through the 
wire.  The difference from just letting a chain contact is that the 
charge drains at a controlled rate.  It is slow enough to eliminate the 
spark.

Get a metal can and cinch one of these straps around the neck onto 
exposed metal.  Now you have your grounding wire that will extend and 
collapse like a telephone cord, and eliminates one more avenue of disaster.

-- 

http://www.ernest.isa-geek.org