REFLECTOR: Grounding Point

John Dibble aminetech at bluefrog.com
Mon Oct 25 12:54:49 CDT 2004


I guess the question is where is the spark likely to occur?  If it is external to the
screen, then I can see how the screen is effective, but if it occurs in the tank, then
the screen is of no help.

John

Alex Balic wrote:

> Jim is right- with an OSHA type screen in the filler neck, the fuel will not
> ignite- the screen absorbs the heat from any flame that tries to start, and
> will not allow it to pass into the tank. I saw a video about this somewhere
> using an OSHA safety fuel can and  a propane torch- no flames in the can,
> just some flare off of the vapor leaving the opening.
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
> Behalf Of Jim Agnew
> Sent: Sunday, October 24, 2004 12:43 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: RE: REFLECTOR: Grounding Point
>
> The concept of a fire screen has been proven for many years in miners lamps.
> A
> fine mesh screen tube surrounding the filler inlet that goes to the bottom
> of
> the tank will prevent the passage of the flame front into the fuel tank even
> if
> the fuel vapors inside the fire screen tube ignite.  This screen does not
> depend on grounding.
>
> Jim
>
> --- Chuck Jensen <cjensen at dts9000.com> wrote:
>
> > Mmmmmm. Alex's idea of first checking for continuity between the fueler
> ring
> > and the exhaust pipe is a good one.  If there is continuity, then
> executing
> > Al's idea of a drooping chain from the cap down into the fuel seems to
> > assure there is a fuel-chain-exhaust-refueling stating ground (all this
> > assuming there is fuel ring to exhaust continuity).  Richard's method,
> from
> > a Very Large Aerospace Company, appears to do the same thing, just better
> > and with a higher degree of certainty.  Of course, if there's not
> > continuity, then its back to the drawing board.  It's somewhat comforting
> to
> > know that the incidence of Velos going off like Roman Candles is rare, but
> > I'd hate to be the first data point.
> >
> > Chuck
> >
> > -----Original Message-----
> > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
> > Behalf Of Richard Riley
> > Sent: Sunday, October 24, 2004 11:44 AM
> > To: Velocity Aircraft Owners and Builders list
> > Subject: RE: REFLECTOR: Grounding Point
> >
> >
> > We went around and round on this topic on one of the canard mailing lists
> a
> > few months ago.  Following all the suggestions, I talked with a fuel
> system
> > designer at the Very Large Aerospace Company where I work and came up with
> > the following for my plane...
> >
> > The fuel cap ring is attached to a coarse brass screen, shaped in a tube,
> > that goes from the fuel cap ring to bottom of the tank.  It is attached by
> > a brass ball chain to the fuel drain, and to a brass bolt in the outboard
> > fuel bulkhead.  That bolt is then attached by a wire to the engine, and
> > therefor to the exhaust pipes.
> >
> > Most of the static charge in refueling is created by the fuel falling from
> > the nozzle to the surface of fuel in the tank.  The brass screens strips
> > that away.  No matter what the level of the fuel, it's pierced by the
> chain
> > going to the fuel drain.  And then the whole thing is electrically bonded
> > to the engine block.  If the fuel truck attaches the ground strap to the
> > exhaust pipe, all the potential is equalized.
> >
> >
> > At 09:21 AM 10/24/04, Al Gietzen wrote:
> > >I guess there are different views on this, but I see little relation (as
> > >in maybe "none") between grounding the exhaust pipe, and refueling
> > >safety.  The static charge buildup is between the nozzle and the fuel
> > >(surface); or the nozzle and the potential existing static charge on the
> > >surface of the strake due air friction.  So have a metal chain or cable
> > >from the cap ring hanging into the fuel, and keep the nozzle against the
> > >ring; and, if you have just landed, wipe the surface of the strake with a
> > >damp cloth before contacting the nozzle to the ring.
> > >
> > >Anyway, that's my take; but I've been wrong once before in my lifeJ.
> > >
> > >Al
> > >Subject: REFLECTOR: Grounding Point
> > >
> > >I didn't find a direct reference in the archives, so I was still
> wondering
> > >if the exhaust pipes is an adequate grounding point when refueling?  I
> > >always assumed it was but I'd hate this to be a FireBall Falacy.
> > >
> > >Chuck
> > >_______________________________________________
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>
> =====
> James F. Agnew
> Jim_Agnew_2 at Yahoo.Com
> Tampa, FL
> Velocity 173 Elite Aircraft Completed & Flying
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