gas tank grounding

just purchased a used 29' formula...former owner installed new aluminum gas tanks but I noticed that they were not grounded ...what is the best way to ground these tanks please...fuel fill were factory grounded to negative wires on t6hat were part of deck lighting system
thanks
bob

 

Normally there is a connecter on the fuel guage fitting. If not loosen one of the screws and attach a ring or other connector and then run a wire from the connector to ground. Make sure you retighten the screw, and double check by having the tank pressure tested.

 

Do not forget a little big (often forgiven) issue: apart from grounding tanks on the hull, there is another very risky point:
at refueling time !!!
at the moment you connect the Service Pump hose to your tank, or a can you brought from Service Station, your body, clothes & even the can are fully loaded with static electricity at a determined microvoltage potential, high enough to produce a spark, since the ship is fully grounded (sea acts as a ground but surely you're wearing rubber shoes).
One caution you MUST not forget, is what on Petroleum Industry is called "BONDING" (interconnect with a cooper or aluminium wire the vessel's tanks to the fuel cans (closed, do not open them until bonding is completed, about 30sec) before pouring the fuel to the ship tanks. in case of a hose from Service Station, it is already grounded & periodically checked by the Company, but nobody can assure the metal nozzle bonds or ground connect to equalize static electricity on your ship, so you must check for sure your tanks are grounded to some bolt outside hull with at least 6mm2 wire.
A simple checking method is using a simple voltimeter (tester) in ohms range to check one lead to the metal part of the tank & the other to some piece of wire on the outside water, it must read less than 5 ohms. more than that, you have a real problem...

 

Electricity is hard to figure out for me. Aren't things like this, and the tank also, supposed to be 'grounded' to immovable objects like grounding plates or shaft struts and not to just nuetral wires running to the battery? If the battery is unhooked, won't that leave the above fuel fill ungrounded? Are there even nuetral wires in 12v dc? Sam

 

SamSam, You are right. All grounds should be run to one point or to a grounding bus that is connected to one point. Generally this is the engine block on an inboard boat. I wouldn't use the shaft struts. This could cause problems if you have a steel shaft, bronze prop etc. Anyway. THe negative side of the battery is not the place to run the ground wire. A seperate wire from the ground bus or engine block should go to the battery negative.

Solrac's comment is got with one exception. In the last two years accident investigations and research has shown that if your boat has a plastic fuel fill and you fuel your boat on the trailer at the local service station, then the fuel fill should not be grounded. See the CG link, http://www.uscgboating.org/alerts/alertsview.aspx?id=27

However if the fill fitting is metal then it should be grounded. Or if you always fuel your boat when it is in the water the fill should be grounded.

When filling at a gas station, portable fuel tanks should always be placed on the ground before filling. I have a really frightening video taken by a gas station's security camera of a portable tank exploding because the owner tried to fill it in the back of his pickup truck.

 

yeah Ike, seen the same video on a Security Course here at my job. really frightening
I apologize for a mistake on my previous post: An exception is ststed on the sec manual, "When receiving or sending any petroleum derivate from/to a ship, the hose MUST NOT be ground-connected. This proceed is for avoiding a direct current. However, the ship MUST BE GROUNDED, and the coast terminal (dispenser) MUST BE GROUNDED ALSO"
This is for the fact that from the ship's side the static electricity is "drained" much faster than it's equivalent on the ground side, so direct currents may be generated.

extracted from:
NFPA 77
API2003
ISG/OTT