Prevent water in diesel with silica gel?

[alanwilson]

Water in diesel tanks is a nightmare: it normally arrives through the vent as outside air is drawn in by thermal contraction at night and the water vapour condenses with the lower temperature. So how about connecting the vent tube to each end of a bottle of self-indicating silica gel? Wouldn't be hard to rig up: stainless gauze would ensure no gel gets into the tank. Of course the silica gel would need to be changed every so often (and is easily regenerated by heating in the oven), but it should completely prevent water vapour ingress. Any comments?

 

[lw395]

I'm not so sure that the majority of the water arrives by that route.
I suspect a lot goes in the filler, as a result of condensation on the metal nozzle.

You would probably need a secondary tank vent, to prevent the air in the tank pressuring during filling, open a bigger vent to let the air out while filling.
Yachts with restrictive tank vents have been known to belch diesel back through the filler.

I take the view that some water in the tank is inevitable, the fuel should be drawn from a sump so that any water is quickly in the filters. It's leaving the water swilling around a large area of the tank bottom that encourages the growth of gunge IHMHO.

 

[Avocet]

I think you'd need a lot of it - and would have to replace it regularly. Don't know how much, but if the "salt 'n shake" sized sachet in my recent hard drive box was necessary, you'd probably need half a tea-chest full for a boat fuel tank!

 

[alanwilson]

Don't think much water arrives via the filler nozzle, unless it's raining hard! The filler is only open for a short time and is then hermetically sealed (or sea water would get in). You wouldn't need a separate large vent during filling, unless the filler nozzle seals the inlet hole. It would be interesting to see how long a coffee jar (say) of silica gel would last: I reckon quite a time, since the volume of (wet) air passing through each day is not large. When I have time....

I agree about taking fuel from the bottom of the sump: the outlet pipe is usually a few cm above the bottom, which is silly and just allows water to build up until the next time you motor in heavy seas (which is when you really need the engine).

 

[lw395]

..... You wouldn't need a separate large vent during filling, unless the filler nozzle seals the inlet hole. ......

I will tell that to a mate of mine, not only does he have the teeshirt, it still smells of diesel.

I think it depends on the tank design, and how fast the filling pump runs. You had to be careful on my boat with some marina pumps, but some boats are much worse.
I think the diesel swirls down the filler pipe and seals it more effectively than you would guess.

Silica gel does not absorb that much water volume for volume, but any water not getting in the diesel would be good.

 

[RMC]

Silica gel breathers are commonly fitted to the vent pipes of oil filled HV/LV Mains Distribution Transformers at Electrical Substations this is to allow for moisture ingress when the oil heats and cools during changes in loading, so not too dissimilar to a diesel fuel tank - http://www.silicagel.in/silicagel-breather.html

 

[alanwilson]

Excellent: exactly what I'm looking for. Many thanks. Unfortunately their web site gives no details (hose connection type & size; price), but I've got an enquiry in with them.

 

[Jim@sea]

Every time I unscrew my diesel filler cap I notice drops of water in the plastic threads and round the seal. So now after I put diesel in I put a criss cross of Duck Tape over the cap and now when I unscrew the top its perfectly clear.
When I bought the boat it had a lot of water and krap in the tank. Presumably from a poor Diesel Filler Cap

 

[William_H]

[
I agree about taking fuel from the bottom of the sump: the outlet pipe is usually a few cm above the bottom, which is silly and just allows water to build up until the next time you motor in heavy seas (which is when you really need the engine).[/QUOTE]

The pick up pipe being above the bottom of the tank is to avert the suction of water into the engine. However this is quite pointless unless you have a drain (or an suck) the water etc from below the pick up pipe on a regular basis. If you are not going to or can't drain the bottom of the tank yes you would be better off sucking it out with the engine and rely on fuel filter/water trap. olewill

 

[rib]

aviation have filters that take out all water,put one off them between filler and tank no problem,not cheap i belive

 

[penfold]

Most of the water in your tank gets in there along with the fuel, the breather is a minor contributor. If you have a sump on your fuel tank, get into the habit of draining off a quantity every month or so and examining it. If you do not have a sump, think about having one fitted or use a sump pump to remove accumulated water and sludge.

 

[alanwilson]

A standard diesel filter with decent size water trap does the job: just inspect it regularly and if necessary drain off any water.

 

[alant]

aviation have filters that take out all water,put one off them between filler and tank no problem,not cheap i belive

So what about the tank vent?

 

[rib]

put a bit of the membrane over that too.mind you dont know how quick it will block up with salt,so must be some where its easy to get to for cleaning

 

[alanwilson]

Is that really so? Whenever I fill my tanks, I always put some in a jamjar and keep it in case I have fuel problems: I have never seen any water (or, indeed, any dirt) separating out between one fill and the next. Where do you get the information from, that most of the water comes with the diesel and not through the vent? Has that been verified or proven?

 

[alant]

Is that really so? Whenever I fill my tanks, I always put some in a jamjar and keep it in case I have fuel problems: I have never seen any water (or, indeed, any dirt) separating out between one fill and the next. Where do you get the information from, that most of the water comes with the diesel and not through the vent? Has that been verified or proven?

"always put some in a jamjar and keep it in case I have fuel problems:"

Must have a small engine, cos thats not much of a reserve!

 

[lw395]

Is that really so? Whenever I fill my tanks, I always put some in a jamjar and keep it in case I have fuel problems: I have never seen any water (or, indeed, any dirt) separating out between one fill and the next. Where do you get the information from, that most of the water comes with the diesel and not through the vent? Has that been verified or proven?

I would think that is one person's experience.
There are two ways into the tank, some water will inevitably get in via both.
If you only fill up twice a year, maybe most gets in the breather. If you fill every week, I expect most goes in the filler.


I've cleaned a few fuel tanks, there is always some water, sometimes quite a lot.

 

[rib]

smells a bit like hes been around planes too

 

[NormanS]

I'm not so sure that the majority of the water arrives by that route.
I suspect a lot goes in the filler, as a result of condensation on the metal nozzle.

You would probably need a secondary tank vent, to prevent the air in the tank pressuring during filling, open a bigger vent to let the air out while filling.
Yachts with restrictive tank vents have been known to belch diesel back through the filler.

I take the view that some water in the tank is inevitable, the fuel should be drawn from a sump so that any water is quickly in the filters. It's leaving the water swilling around a large area of the tank bottom that encourages the growth of gunge IHMHO.

If your tank has a sump, surely it is better to use the sump to catch any water, and dirt, long before it gets to the filters.

 

[srah1953]

I have never used it but there is a ready made product that will meet your needs, details at h2out.com