REFLECTOR: Grounding Point

[Fred Marconi]

We have certainly have grounded this point into the ground.  Not the first time it's been discussed at this length, that I remember. 

Lets see:  Planes have rubber wheels so there is no ground connection made here, hose has a rubber extension so no grounding here either.  It seems that the culprit is the operator.  If he were to stand on a rubber mat the ground connection could be broken.  Just a thought!

Fred
  ----- Original Message ----- 
  From: Alex Balic 
  To: Velocity Aircraft Owners and Builders list 
  Sent: Saturday, December 04, 2004 12:37 AM
  Subject: RE: REFLECTOR: Grounding Point


  John, I would bet that the brass screen is available through McMaster Carr- that is where I will go to get mine- they might even have brass screens already formed to the correct size for our use- the ones that come with the OSHA cans are too small in diameter.
    -----Original Message-----
    From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On Behalf Of John Dibble
    Sent: Friday, December 03, 2004 11:27 AM
    To: alex157 at direcway.com; Velocity Aircraft Owners and Builders list
    Subject: Re: REFLECTOR: Grounding Point


    After the previous round of discussion, I've been trying to understand this ground issue.  I've noticed as the weather gets colder and drier that I infrequently get a shock.  It seems that for the shock to happen I need to first rub something and then touch something that is GROUNDED, like a water faucet.  So it seems to me that an electrically insulated fiberglass tank is actually a good deal and why do we want to provide a ground where a static charge can discharge?? 
    Also I think it is unlikely that flowing fuel can develop a charge.  >From what I remember about boundary layer theory, the fuel molecules adjacent the hose/nozzle "stick" to the hose/nozzle surface and do not move.  There is a gradual transition of fluid velocity between the hose/nozzle surface and the bulk of the fluid flow.  So there is little opportunity for the fuel to "rub" against the hose/nozzle surface and develop a charge. 
    I think the safety screen is the best idea.  Where can I get or make one? 
    John 

    Alex Balic wrote: 

      Hey Al,I don't think that there is too much charge differential building up during actual fueling operations, I would think that when the fuel is flowing the charge could pass freely from the tank to the nozzle via the surface of the fuel and thereby keep the potential at or near zero- I will check up on this though..............I believe that the problem is that a spark occurs between the fuel nozzle and the aluminum cap, or between the nozzle and the skin in the vicinity of the cap when the two are brought into close contact just prior to fueling- assuming that the aircraft is not "grounded" to the fueling point.  There can be a lot of charge differential between the aircraft and the fuel truck due to many different reasons, and I am just trying to figure out the best way to make the differential zero before the fuel cap is opened, and/or placing the brass safety screen in the filler neck to prevent fire from entering the tank.  Like I said in a prior post I got severely jolted once re-fueling from a ground based pump station because I had the ground clip in one hand and touched the spam can I had just finished flying with the other- a mistake I will not repeat- and if I had fuel on my hand at the time I am pretty sure it would have ignited...About the chain- I was referring to the design that has the ball chain attached to the fuel drain line and it rolls around in the bottom of the tank- a chain that makes it into the fuel and attaches to the cap would certainly make more sense- and I think that touching the fuel ring with the nozzle before opening the cap would help as well.Alex


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