Sloshing Fuel Vent

[kungfoo]

Hey guys,

This is probably a question that has already been answered somewhere, so please feel free to tell me to RTFM.

When I fill my diesel tank, any wave-motion at all results in diesel pouring out of the vent line, and I'm exploring options to fix that problem. I have two potential solutions:

1) Install a series of 90-degree elbows as a makeshift baffle.

2) Install parallel manual and check-valves. During filling, the manual valve could be opened to allow air to quickly leave the tank. The rest of the time, the check-valve would only allow air to come into the tank as diesel is consumed.

I don't really like either solution, though. The makeshift baffle may or may not actually work. If I have a check-valve, then a warm day will pressurize the tank.

Has anyone run into this issue before?

Thanks,
Harrison

[Uncle Bob]

Originally Posted by kungfoo

Hey guys,

This is probably a question that has already been answered somewhere, so please feel free to tell me to RTFM.

When I fill my diesel tank, any wave-motion at all results in diesel pouring out of the vent line, and I'm exploring options to fix that problem. I have two potential solutions:

1) Install a series of 90-degree elbows as a makeshift baffle.

2) Install parallel manual and check-valves. During filling, the manual valve could be opened to allow air to quickly leave the tank. The rest of the time, the check-valve would only allow air to come into the tank as diesel is consumed.

I don't really like either solution, though. The makeshift baffle may or may not actually work. If I have a check-valve, then a warm day will pressurize the tank.

Has anyone run into this issue before?

Thanks,
Harrison

Hi, is the vent line plumbed into the fill line by any chance? If so then re plumb the vent line to the tank proper and the fuel can only reach the vent when the tank is full.

[kungfoo]

It is properly plumbed to the vent port on the tank, and happens when the tank is full. We had to operate the engine for several hours last time before it quite sloshing in gentle water.

[Uncle Bob]

Originally Posted by kungfoo

It is properly plumbed to the vent port on the tank, and happens when the tank is full. We had to operate the engine for several hours last time before it quite sloshing in gentle water.

Possibly if you were to reroute the vent line higher then back down to the vent itself it may reduce the problem.

[kungfoo]

I thought about that, but if it *does* make it over the loop, then it guarantees that anything making it over the top will all leak out, instead of just a momentary squirt.

If I were to use the baffle solution described above, I would probably use it on the way up to a higher loop.

[Uncle Bob]

Originally Posted by kungfoo

I thought about that, but if it *does* make it over the loop, then it guarantees that anything making it over the top will all leak out, instead of just a momentary squirt.

If I were to use the baffle solution described above, I would probably use it on the way up to a higher loop.

Not knowing the type of boat that you have I will throw out the idea of moving the actual vent to a higher position on the boat, with a small vent line going higher the propensity to push diesel up the line would no doubt be greatly reduced.

[Pete7]

Something like this:

https://www.trademe.co.nz/motors/boa...2158452677.htm

Vetus also do one in their catalogue.

Oh and don't over fill the tank.

[kungfoo]

Cambria '48

Yeah, there are a couple of spots that I might be able to relocate the vents. I like having them go into the cockpit so that if it does happen, I don't automatically pollute.

I'll definitely try some sort of impedance solution before relocating though.

[kungfoo]

Yep...that's pretty much exactly what I was looking for. Thanks Pete7!

[Pete7]

No problem

Actually I would be interested in hearing if it works. We also have a surge but only just after filling. Move from one side of the yacht to the other or step off to go and pay and the rocking causes the diesel foam to rise up the vent and dribble on the cockpit seat. Wait 10 minutes for the foam to settle back to fuel and the problem stops, but on a busy fuel dock that's not really a solution.

Pete

[kungfoo]

That's how things were with my catalina, but the last time we filled this thing, we had to operate the engine for several hours before it stopped.

I'll dig into that part a little more tomorrow, and if I end up using it I'll post a review.