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Overfill Prevention System

Current methods of fueling and resulting problems:
As you look through boating periodicals you will read much advice on how to prevent spills when fueling a boat. They range from a catch container at the vent, stopping to check your fuel gauge regularly, stuffing oil absorbent pads around the fill fitting, and my favorite, which I was told by a boat manufacturer, listen to the vent and when you hear it gurgle, stop filling.
A trip to a busy fuel dock will quickly dispel any thought that these methods might work to consistently eliminate fuel spills. The effects on the environment are beyond the scope of this paper, however the fact that both gasoline and diesel are regularly spilled into our waters and evaporate into our atmosphere are not. There are several standards published by the ABYC concerning fuel systems and specifically fuel fill systems. These standards are followed in manufacturing a large number of the new boats sold in this country. The fact that you cannot take a new boat to a fuel dock and rely on the auto shutoff device on the nozzle to stop the fuel without spilling should be a sign that there needs to be a change in the standards. How many automobiles would the EPA allowed to be sold if they spilled fuel when you left the nozzle shut off automatically?

The following is a paragraph from this article: http://www.ehponline.org/members/2003/111-4/focus.html

In the 14 August 2002 Federal Register, the U.S. EPA published a proposal to require emission controls on boat fuel systems. The EPA proposal would require modifications to the current boat fuel hose, vent controls such as a pressure relief valve to reduce diurnal emissions, and permeation measures on plastic tanks. If these standards are established, the next step would be developing systems that prevent spills during fueling, says John McKnight, director of environmental and safety compliance for the NMMA.

The Enviro-Fill Overfill Prevention System is just such a system. The boats manufactured today (2007) use fuel fill systems that spill as much as they did thirty years ago. In a recent conversation with a boat manufacturer, I was told that it is the responsibility of the consumer to prevent fuel spills when fueling not the manufacturer. He had no interest in trying to manufacture a boat that can be fueled without spilling. It is our hope that the manufacturers will embrace this technology to help preserve our environment and enhance the image of both the boating community and their product for being proactive in solving a very well known problem.

There are three types of spills related to fueling. The following paragraphs describe the spills and some factors that cause them:

Spilling out the tank vent

One cause is the vent is mounted lower than the fuel fill fitting. For the auto shutoff in the nozzle to activate it needs to sense fuel at an aspirator hole near the end of the nozzle spout. For this to happen on current fuel fill systems the tank has to fill to the top and the fuel has to rise in the fill hose until it reaches the nozzle. With the vent lower than the nozzle spills are inevitable. The vent hose is connected to the top of the tank and as the fuel rises up the fill hose it also rises up the vent hose. The fuel is entering the tank through a 1 ½” hose and being forced at up to 25 gpm. The vent is open to atmospheric pressure and allows air to flow out freely as fuel enters the tank. The problem is, once fuel flows into the vent hose it also flows freely out the vent until the nozzle shuts off. Raising the vent above the fill fitting helps to a degree but, the velocity of the fuel entering the tank often forces it out the vent before the nozzle shuts off. Fuel air separators have been suggested to stop this from happening however, when fuel enters the separator the flow of air is stopped causing our second spill on the list.

Backsplash out the fill fitting

Backsplash is caused by air not being able to escape as fast as the fuel is entering the tank. This can be caused by a valve closing on the vent line or the fact that once the tank is full, fuel will not flow through the small vent line as fast as it is being pumped into the tank causing pressure that forces the fuel back up the fill hose after the nozzle is shut off. Another cause can be air pockets trapped in the tank. They build in pressure while fueling and when fueling stops that pressure forces the fuel contained in the fill hose back out the fill fitting.

Spills after refueling

The third spill source is very much overlooked because it usually happens when the boat is at its berth and no one is aboard. In current fill systems anytime you use the auto shutoff nozzle to stop fueling the fuel must fill the tank to the top. As was described earlier the fuel must rise up the fill hose. This allows no room for expansion. Fuel expands as the temperature rises from cool underground tanks to the high temperatures possible in a closed boat. ABYC suggests one method of meeting their standard regarding expansion is reserve 5% of the tanks volume for expansion. A boat that has a 200 gallon tank would need room for 10 gallons of fuel to be contained after the nozzle shut off, or that fuel will be forced out the vent as it expands.
The situations and the resulting problems described above can be eliminated by simply filling the tank 95% full and stopping. This was previously possible only by guessing. It can now be done automatically and consistently using our Overfill Prevention System. The OPS uses pressure transfer technology to sense the fuel level in the tank and activate the nozzle shutoff automatically when the fuel level reaches a predetermined level. An independent laboratory tested our system by filling a tank 25,000 times at 15gpm allowing the OPS to shut off the nozzle each time. Not one drop was spilled during the test, even better the nozzle was shut off when the tank was 95% full every single time.

Any issue related to overfilling a fuel tank can be eliminated without making any changes to the boat hull or deck. By simply installing our deck fill fitting and tank adapter and connecting them with a pressure transfer tube your tank can be filled reliably to a predetermined level without any guessing.

According to EPA document 4.6. Fuel Station Design. The USCG recognizes that gasoline spills pose an extreme explosion and fire threat and recommends that small gasoline spills be allowed to evaporate as quickly as possible without a boom placed around them. Preventing these spills will eliminate this threat from gasoline. There are considerable fines in place for those violating Section 311 of the Clean Water Act. It prohibits the discharge of any petroleum product in the waters of the United States. The costs of possible fines for spilling fuel in the water far exceed the cost of preventing the spill in the first place.

	$100.00	estimated cost of O.P.S.
less	$16.50	estimated cost of fill fitting		replaced by O.P.S. fill fitting
less	$50.00	estimated cost of fuel/air separator		not necessary to with O.P.S.
	$33.50	incremental cost to boat builder		passed on to consumer
	$41.70	saving in cleanup supplies		$1.39 x 30   (refueling 10 times per year for 3 years)
	($8.20)	actual cost to consumer

There is an environmental benefit to preventing gasoline spills but I would defer to the EPA to place a value on that.
You cannot put a dollar value on public perception, however in this time of environmental awareness it will certainly benefit the marine industries’ image.

“At Enviro-Fill, we choose to use technology rather than guess work to prevent overfilling.”