Diesel tank vents

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Graham_Wright

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Considering where to place these and nervous about on the deck, I wondered if there was any reason why they should not be led forward to the anchor locker. High up there is no chance of water ingress and the locker is both ventilated and drained.

Any views please?
 
I would be very nervous about putting it in the anchor locker - ask Becky!

Much better placed somewhere where you can get a good swans neck on it such as in the cockpit or over the stern.
 
As it is likely that your tanks are situated further aft, I would'nt have thought putting the vent so far forward very sensible or convenient.

FWIW, our vents (diesel and water) are placed in the aft end of the cockpit. The design of the vents is such that water cannot enter unless the cockpit is filled. It also means, of course, that the runs are as short as possible, minimising the risk of damage with the associated horrendous mess that would ensue!

I would also have thought that there was a risk of the vent acting more as a drain when the boat was well heeled, as it is possible that your tanks may be higher than the vent in those circumstances.

Finally, an anchor locker is inherently very damp. We aim to minimise the risk of condensation occuring in the diesel tank, and I'm not sure that an anchor locker helps this at all!!
 
My vent is a GFN vent out of cabin side right above tank ... it has a coiled loop in it before exiting. If you are worried about ingress ... which my boat in its 35 yrs literally hasn't suffered - then an inverted "half-cup" fitted over it ....
You can in fact vent to the filler line - as rarely are filler points air-tight .... but later fitting often have an o-ring making this not so good.
 
If you put the vent forward into the anchor locker then you could have fuel sloshing out of the vent when running down large waves. Also if you dry out nose down then the fuel could run out.
My tank is vented into the top of the stern locker and this works fine. I have heard of one or two problems with venting into the cockpit. One where a chap sat still for a long time with his oilies blocking the vent the other case was where large heeling caused fuel to leak into the cockpit and soaked the oilies of a crew memeber in diesel - has was sat in a pudlle of diesel for a while -YUK!
Given the amount of spray and rain around the cockpit I would vent to a covered locker every time.
Martin
 
Diesel gas .... ???

Sloshing diesel is not the same animal as sloshing gasoline .....

OK - it is not the best pong in the world .... but it is not explosive as gasoline vapours unless sufficiently compressed, in sufficient quantity and also temperature ....... isn't that one of the main reasons that diesel has overtaken petrol engines ??
 
Currently got a problem on our new boat diesel vent. It is taken to the rear but dips down to go under some of the boat construction. After heeling the low point fills with a slug of fuel that is forced out of the breather when filling up. Everyone shouts at you to stop as diesel is pouring out the vent! Side deck vents and bow vents will get water in them. I think solution is for me is to fit an expansion tank high up at the vent position.

Hence my advice make sure you can keep the pipe self draining back to the tank and a stern vent seems preferable. A swan neck is a good idea if you have the room.
 
Why not a side vent .... I have mine up high in cabin side ... when you see it - initial reaction is OH OH .... but in all the years I've had the boat - not one drop water has got in that way ....
 
I should have explained that the tanks are in the top of the bilge keels and the suggested position of the vent in the anchor locker a good 7 feet higher when on an even keel.

Do you not experience a pong when venting into the cockpit?

Venting into the fill line seems a bit odd unless the fill pipe exit is below the surface of the contents? Are they not doing the same thing?

As an addendum, how do forumites know when the tank is full? Do you wait until the deck fill overflows? Does the delivery hose shut off as in the filling station pumps (I believe there is a vacuum detect feedback)? Does the vent overflow first? Or do you all have sophisticated level sensors?

Thanks for all the feedback.
 
<<Venting into the fill line seems a bit odd unless the fill pipe exit is below the surface of the contents? Are they not doing the same thing?>>

A lot of tanks have fill pipes coming into the bottom ... but also you have to think about some baffled tanks have pocket problems even when fill pipe comes into top of tank - the vent pipe often serves other side of baffle.

As to not overflowing .... my boat is a two man op to refuel .... one at tank checking through the large observation cap opening and other on deck with the fuel gun ....
 
Your easiest solution....

Your easiest solution is to run a vent pipe up as high as possible in a swan-neck, then down to a proper vent fitting on the side of the hull, a few inches below deck level. THe vent pipe needs to be a reasonable internal diameter. The top of the swan-neck should be at least 20cm or so above the deck - more if you can manage. It's often possible to put the swan-neck in a locker or cockpit coaming in order to gain the height above deck. If the pipe shows signs of kinking, you can make a swan-neck out of metal pipe and insert it in the vent pipe. The skin fitting should have a mesh guard on it (see pic), and of course the mesh hole should face downwards! When you fill with fuel, the nozzle will shut off before fuel spills out of the vent. In certain circumstances, you might get a small dribble of fuel blown out of the vent by the escaping air whilst filling - this is a good reason never to vent the tank to a cockpit or locker.


305102.jpg
 
[ QUOTE ]
<<but also you have to think about some baffled tanks have pocket problems even when fill pipe comes into top of tank - the vent pipe often serves other side of baffle.


[/ QUOTE ]

Good point that. Sounds like baffles ought to connect at the top as well as the bottom.

Thanks.
 
Mine has a fairly thin metal tube coming up from about central in the tank with a 180 degree U bend at the top so the end points down .
It ends up inside the cockpit coaming , the top of the bend is roughly level with where the end of the pump nozzle reaches to in the filler pipe.
The tank is retrofitted and mounted quite high, above the level of the quarter berth.


Very little if any diesel comes out the vent , usually it fires back up the filler tube first ...
 
Re: Now I\'m baffled.... No-one said 100%

Having had to sort out odd tank on boats ... I've found where baffles had holes lightened into them ... but still pockets develop ...

No-one said baffles are solid .... now that would be silly ....

Often a tank has been atken from another work and pressed into boat service ... such as mine - a small truck tank ... now I know that this has baffles that could lead to pockets if not mounted in accordance with its original role.
 
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