On Thu, 30 Oct 2003 09:55:53 -0500, "Gary Warner"
wrote:
So yesterday we went up to see a boat restorer in upstate NY.
VERY nice guy. Anyway, while talking he reminded me that
I need to run a ground wire from my steel gas tank to the
engine or other ground point. ~ I'm sure this is a good idea
that can't hurt, but I'm just wondering:
#1 - What exactly could happen without that. I assume it's that
a static electric charge could build up on the tank or on me...and
when I touch the gas cap a spark happens in the tank?
Yes, sort of. Any positive static charge on you or the nozzle will
transfer to the filler hose or fitting. Most of the time, this is not
a problem. Sometimes it creates a spark, in the presence of fuel
vapor, which is a big problem.
#2 - Is the real purpose of the ground to the engine is because
the engine is grounded to the battery or is it because the engine
is connected to the drive shaft which is in the water (true ground).
Two different animals. The engine ground serves the electrical
operation of the engine and accesories. The fuel filler ground
attempts to dissipate any charge (electrical potential) difference
between you, the pump, and the boat. Static electrical charges occur
naturally. The problem arises when there is a *difference* in the
charges (potential=voltage). Contact will normally equalise the
potential.
#3 - What happens when the boat is on the trailer? Then none of
the boat is grounded....It's setting on wooden bunks and on rubber
tires? Couldn't I still get a spark then? ~ It's like a car...that has a
gas tank, but it's not grounded since it all sets on rubber tires?
Static charges can, and do, dissipate over the surface of
non-conductor materials. Contact is a primary ingredient in the
transfer. When you shuffle "sock feet" across the carpet and touch
the door knob, is the door knob grounded? No, not normally. Can you
get a spark? Absolutely, because you have built up a static
*difference* in potential (voltage). This spark is what can hurt you
while fueling.
#4 - Lastly, do the hoses at gas stations connect to ground? The
hoses appear to be rubber but I suppose maybe they are special
hoses with some ground wire embedded in the rubber to take
away any static charge ??
Yes, gas station fuel hoses are grounded. This is good, but also
presents a possible problem. If you create a static potential while
filling (i.e. let go of the nozzle and get back in the vehicle), there
is a possibility of a transfer (spark) when you re-touch the nozzle,
or remove it from the filler on your boat. It is rare, but it does
happen. To eliminate this potential hazard, always touch the pump
nozzle to the filler cap before you open it (discharges any static
potential difference), then do not let go of the nozzle while filling
(keeps the static potential equal).
Yes, I know, some gas nozzles have a "hold open" tab for convenience.
If you are concerned about safety and potential explosion; don't use
them.
THANKS
Gary
To email me, remove the "OT-" from wrecked.ot-boats.noah.
....as you were.
)