fuel tank vents ?

8 years 10 months ago #2121 by David Irwin
I have a problem with filling the starboard side fuel tank. With anything more than a trickle the fuel blows back up the pipe onto the deck to be soaked up by "diesel diapers". I was wondering if I was missing some conventional wisdom about not putting vents lines to these port and starboard tanks. WaS it a common oversite on Whitbys that none of my previous owners ever got around to?
thanks in advance for any and all information

David Irwin
S/V Comfort #121
The following user(s) said Thank You: Robert Snelling

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8 years 10 months ago #2122 by C. William Eilers, Jr
I had the same problem and determined that the tanks were vented but the vent line was getting filled when the boat heeled. On my brewer 12.8 the vent hoses pass through the aft end of the starboard locker in the aft cabin. I inserted a 3 way valve in the vent hose with a 2 foot piece if hose on the third leg. Before I fuel up, I open the tank filler and through the valve so that I can blow through the vent line to the tank and clear it of trapped fuel. This also stops fuel from spitting out the vent line when filling the tank. As soon as the line is blown clear of course you have to through the valve back to vent the tank to overboard.

Would have been a better solution to try to reroute the vent line so that the fuel would drain back by gravity but much more difficult.

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8 years 10 months ago #2123 by Frank Fitzpatrick
Replied by Frank Fitzpatrick on topic fuel tank vents ?
Just Desserts (ex Menehune) has only the stbd and center tanks, but has vents on both and both work OK (for details about "ok", read on -).

John Cece (the P.O.) made several changes in the tank vents. They originally exited through the transom (much too low, to my thinking), and John rerouted them to exit through the after ends of the cockpit coaming boxes (much better). John also installed Racor "Lifeguard" fuel/air separators in each vent line. As a result of John's efforts, we have never had fuel exit the vent lines. So the combination of better routing and the Lifeguard gizmos are apparently doing their job.

The vent lines are nicely run (continuously upward, with no low spots to trap fuel). But I suspect the Lifeguard gizmos create a bit of resistance in the vent line because filling can sometimes be a bit slow and there has been the rare "diesel belch" back through the fill pipe if I fill too rapidly. (I've learned to listen for some advance warning in the form of a change in the "gurgling" sound if I'm filling too rapidly.) (Also, there is a small valve on top of each tank that can be opened to insert a dipstick, and if I open this valve while filling, air would much rather vent through the valve than through the vent line.)

I'm not entirely certain the fuel/air separators are necessary, and John would be the best person to address the following and his reasons for installing the fuel/air separators -
- Both vents now exit through the after end of the cockpit coaming boxes. This is probably about 8" - 12" higher than the fill plates, so I wouldn't expect fuel would come out the vent line if the tank were filled beyond "full". And they are certainly enough above the top of the tanks that fuel would probably never come out of the vent line due to heeling. Perhaps the fuel/air separator's job is to trap any fuel "spray" being carried up the vent lines with the venting air? I don't know.

John gave a presentation on the new vent system during the 2014 Whitby Rendezvous at West River. Unfortunately I wasn't able to attend, so I don't have his information to offer here. I'm sure John is reading this and perhaps he can let us know his experience with the issue.

Hope this helps,
Just Desserts (#195)

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8 years 10 months ago #2125 by Robert Strickland
Replied by Robert Strickland on topic fuel tank vents ?
We also added a larger vent hose(5/8") to all tanks and routed them up behind the cockpit combing. Tha t really helped a lot.
The starboard tank fill makes a sharp right angle turm as it enters the tank, which can also contribute to the back up, but putting the larger vent lines in made it much improved. I have found that if I start the flow slowly and then gradually increase it, I can run the fill at full blast.
Allegria 199

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8 years 10 months ago #2126 by Edward Schwiebert
Replied by Edward Schwiebert on topic fuel tank vents ?
If the tanks have been filled in the past without incident (and that has to have been the case given the vessel's vintage), I would suspect a recent change in circumstances. On our B44, we had bugs build very intricate nests of leaves that prevented the vents from performing. We cleaned that out, installed new screening, and all has been fine since.

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8 years 10 months ago #2127 by John Cece
Replied by John Cece on topic fuel tank vents ?
My friend, Frank, knows me better than I thought !

The fuel tank vents were changed after I had overfilled the starboard tank, and subsequently spilled fuel out of the vent (located at the transom).

The now shorter, vertical vents have worked very well. If overfilling the tank, fuel will escape at the fuel-fill, first.... should never escape from the vent, which is approx. 6" above the fuel-fill.

The Racor fuel-air separator(s) located in the vent lines were not needed, but installed as extra precaution so as to NOT ever spill fuel again !

John Cece
ex-owner MENEHUNE (#195); now: JUST DESSERTS

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