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Question regarding venting a gasoline fuel tank.

Are there any requirements around if the vent needs to be on the hull side such that any burping / spillage does not go into the boat or can the vent position be above the filler neck?

I was contemplating placing the vent on the vertical surface of the Bahia Mar cabin (where the original stripe would have been) but do not want to get into a problem if that is directionally incorrect.

Thanks in advance,

Ian.

Ian,
I can't get my ABYC CD standards to open on my computer. If I remember correctly the vent should be placed on the outside of the hull so that no gasoline enters the interior of the vessel. The vent should be higher than the tank top, the hose run should be as smooth as possible, the correct size (3/8" or 1/2" line, alcohol resistant approved hose, no sharp bends or kinks, this will allow the air to escape evenly. They make different styles of fuel vents, I have used the flush mounted vents that do not protrude out of the hull. The flame screen is under the flush mounted cover piece, I think it was made by Acorn Marine, it's all stainless.
There are new regulations for canister style recovery units for newly manufactured vessels, I think it's for California only, It's a canister style that is inline on the vent line, this unit prevents any fuel from going overboard, it recirculates fuel back into the tank. I don't remember if it has been entered into the newest ABYC standards yet. I haven't seen them in use on any vessels that I have surveyed lately, they are usually hidden behind a side panel so you can't see them if you wanted to. I remember when Capt. Pat did Buddy Boy he used a 1 gallon plastic bottle instead of a thru hull fitting for the fuel venting but that was for diesel fuel. I wouldn't put it on the house side because there is still a small section of deck below where you want it to go, this could allow fuel to go into the cockpit, if it ran down the deck surface and not overboard. Maybe someone else will chime in if they have access to the ABYC standards.
Pete Fallon

Pete/Ian:


When I was thinking about redoing the 25, I found some interesting information on the Perko site. They discuss the CARB requirements and the EPA requirements on below:

System Design
With government regulations now affecting system designers’ thinking, fuel systems will become more complex. The Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) have both imposed requirements that directly impact design. They begin to affect boats built for the 2012 model year. It has become even more important now for boat builders to consider fuel system design early in their overall boat design process.

When it comes to diurnal emissions, the EPA has taken the lead on regulations. At this time, CARB rule making is not finalized and CARB is viewing the EPA regulations as being acceptable for California. The American Boat and Yacht Council (ABYC) and the National Marine Manufacturers’ Association (NMMA) have worked together with industry volunteers to develop industry standards covering the installation and performance of these new fuel systems. The EPA is on record as stating that a boat that meets ABYC H-24 meets the EPA’s objectives in diurnal emissions and in controlling fuel spill during refueling.

In the automotive world the primary difference between CARB and the EPA versions involves whether or not to capture vapors generated during refueling through the pump nozzle or on-board. CARB has implemented Stage II vapor recover (at the pump nozzle) for automotive and if implemented for marine would impact the fuel fill and cap designs. As a precautionary measure, ABYC is recommending that fuel cap tethers not interfere with a CARB style fuel pump nozzle. A CARB system involves two independent vent lines. A high volume vent line is directed to a vented fill where refueling vapors are delivered to the pump nozzle. After refueling, a cap on the fill seals both the vent line and the fill pipe from the atmosphere. A second low volume line then channels vapor and make up air through a canister. Pressure relief systems can work the same way but without the canister. For automobiles the EPA requires 100% of the cars to provide on-board vapor recovery and active purge. These systems vent through the canister during refueling.

Working together, the NMMA and the ABYC have proposed an industry specification for installing carbon canisters and pressure relief systems, which the EPA and CARB have accepted. The actual, detailed ABYC specification is in development. Builders will be asked to demonstrate that their products are built in accordance with these specifications in order to obtain NMMA certification. This will demonstrate to the EPA & CARB that a boat is in compliance. Representatives from boat & engine builders, tank, fill, valve and canister manufacturers, test labs and the U.S. Coast Guard are among the authors of the new specifications.

The specification calls for compliance with the EPA rules and automatic shut off at the pumps. There is also a regulation to demonstrate that the boat can be refueled at rates of 4 gallons per minute to either 10 gallons per minute or 18 gallons per minute, depending on the size of the boat. Most marine fuel systems will require rework to do this as well as to comply with the other components of the new rules. There are numerous additional issues designers may want to address with solutions possibly differing with each system.

In systems using canisters, regulations require that steps be taken to assure that water and liquid fuel do not enter the canister. Options include a means of preventing tanks from overfilling (i.e. maintaining 5% to 10% empty space), which reduces (but may not eliminate) the chances of raw fuel entering canisters and/or forcing its way back up fill tubes. Designers can consider several new components and/or design features into these new systems to aid in addressing these issues:

•Carbon Canisters
•Tank Vent Valves (TVV) (also called grade valves or rollover valves)
•Fill Limit Valves (FLV)
•Inverted Loops
•Inlet (i.e. Fill Pipe) Check Valves (ICV)
•Ullage Tanks
•OPR (over pressure relief valve)


Tom

Thanks. I am vaguely aware of the new EPA regualtions, but that doesn't impact something from '68.

This is the vent that I have. Gemlux:

Sounds like hullside if the preferred location. I do have plenty of space for a high loop to avoid water working its' way back into the tank.

I will put up some pictures when I do this portion of the install.

Ian.

Ian:

You make an excellent point -- the standards only apply to new boats, not rebuilt better than new. I bet that carbon filter is expensive to add into the system too.

Best regards,

Tom

A word of caution...

Granted, factory installed back when Christ was in knickers, and left un-changed, will often be grandfathered. When someone refits an old boat with new parts, those parts and systems have to meet current CG regs...