Fuel tank venting - what materials are ok?

[naturewaterboy]

I want to install loops in my fuel tank vents so that any water that splashes into the screened vents will hopefully not be able to make it uphill and into my fuel tanks. I have limited space to make the loop, and my 5/8" vent line will not make these bends. I need to come off my thru hull vent fitting, turn 90 degrees up, go up about 6 inches, then turn 180 degrees and go down to my tank. I could do this with bronze 90s and hose barbs. These would be heavy and I'd need to strap these down or they'd bang around on the hull. Is there a better way to do this? Are nylon or fittiings allowed in gasoline systems?

[PAR]

Just use rubber fuel line.

[marshmat]

Hi naturewaterboy,
Nylon is chemically compatible with gasoline; however, I don't think there are any nylon fittings out there approved for fuel system use. The stuff tends to burn rather well, and fittings made from it can have a tendency to crack. There are glass-reinforced nylon through-hulls and fittings available, but they're not meant for fuel or fuel vents. 5/8" fuel hose should be able to handle a six-inch-radius bend; your easiest bet is probably to do it this way. If there's not enough space to bend hose, there's likely not enough space to work with threaded fittings either.

[naturewaterboy]

I have new 5/8" line that will not make the bends I need. I can fit bronze fittings there. Is there any other way to vent a tank and keep water from entering the vent line besides putting a loop above the thru hull fitting?

[steele m.a.]

With fuel lines - even fuel vent lines - you have to consider flammability of
the material you are building with , and you have to consider solubility
in the fuel . Many vent hoses will break down chemically when exposed to
gasoline , even gasoline vapour .
With stock vents that go immediately overboard , not only do they supply
a constant supply of fresh air into the vent , they allow fuel vapour to
dispurse overboard .
When you change this formula to stop backflow into your tank , you create
a place for fumes to collect , and may inadvertently create a flammability
hazard where there was none before .
One solution may be to attach a 'low point drain' into the existing vent line.

[naturewaterboy]

I ended up putting my vents down in the hull, and making a loop above to keep water out. I hear that new boats will have to have carbon canisters in the near future (like cars have had for years) to prevent gas vapors from polluting the air. When do boats have to be equipped with these?

[Submarine Tom]

You vented your gasoline fuel tanks into your hull.

You are a much braver man than I.

Even if you ventilate well (and God help you if you don't) can you imagine

how much vapour is going to be delivered into that hull when fueling?

I can't believe this is what you ended up doing.

You're having us on, no?

Please, say it isn't so...

Tom

[pamarine]

I think he meant he placed the fuel vents low (to the waterline) on the hull, not venting in to the hull.

I hope that's what he meant anyway. if not, lookout!

[jelmerwijma]

Please follow the ISO 10088 standard: Permanently installed fuel systems and fixed fuel tanks.

I recommend to use a ISO 7840 marked hose with a flame arrester at the hull located not next to a ventilation opening to the inner side of the hull.

6.2.2 Vent hoses located in the engine compartment shall be fire-resistant, of type A1 or A2 in accordance with ISO 7840. Other vent hoses shall be of either type A1 or A2 in accordance with ISO 7840, or type B1 or B2 in accordance with ISO 8469.

6.2.4 Vent lines shall not have valves other than those that permit free flow of air and prevent flow of liquid (fluid) both in and out of the tank.

6.2.5 Vent lines shall be self-draining when the craft is in its static floating position.

6.2.6 The vent-line termination shall be not less than 400 mm from any ventilation opening through which fuel vapour may enter the craft.

6.2.7 The vent-line shall be arranged to minimize intake of water without restricting the release of vapour or intake of air and shall not allow fuel or vapour overflow to enter the craft.

6.2.8 The vent-line termination or a gooseneck in the vent-line routing shall be arranged at sufficient height to prevent spillage of fuel through the vent line during filling and entry of water under normal operating conditions of the craft.

6.2.9 The vent lines on all fuel installations shall incorporate a flame arrester device.

I hope this information will help.

Jelmer

[naturewaterboy]

I didn't vent the tanks inside the hull, I installed the vents in the hull (screened vent outside the boat) - they are about 3 ft. above the waterline. I wanted to put them up above the rubrail, in the side of the cabin, so that it would be difficult for a wave to force water thru the vent. I could not make it work to get the vents up in the side of the cabin, so I just went ahead and put them back in the side of the hull where they originally were.

I don't use candles when I'm cleaning up with acetone either!

[Submarine Tom]

Ahhh, good to hear. Thanks for clearing that up.

Did you angle them aft at all? I think you'll find the new/old location good.

Tom

P.S. This is the first I've heard of carbon canisters being required soon, interesting.

[naturewaterboy]

The vents I bought are a stainless steel disk about 1" dia. by about 1/2" thick with two screened vent holes in the edge of the disk - the vent holes are about 45 degrees apart - so I have one aimed down and one aimed back.

I've read some stuff again on the USCG or ABYC website about the carbon canisters - they are coming real soon, but I forgot the date they will be required.

I hate smelling gas or diesel fumes or exhaust on a boat, so I'd add them to my boat if I found some that would just mount in my 5/8" vent lines. I'm sure they wouldn't make a big difference, but every little bit helps.

[Submarine Tom]

Mounting sounds favourable.

"...there you are!"