Fuel polishing

[lw395]

I don't think our opinions are poles apart.
But if I were doing anything to a tank installation again, I'd add a second standpipe drawing as low down in the tank as possible, preferably in a corner that can be made the low point by heeling the boat, for the purpose of polishing and removing water.
If you wait until you start seeing gunge in the filter, you are at risk of the filter blocking in rough weather.

I'm not sure your concept of 'simple' polishing is very effecive at removing any suspended water which may or may not be there, as I've seen too many filter bowls with next to zero water in them after hundreds of hours. While tthere is nearly always water in the bottom of the tank.

In general I don't like drain plugs as they tend to be hard to access and difficult to draw off fuel in a controlled way. A risk of spillage which is unnecessary. Hence the second standpipe from the top of the tank.

On bigger boats, I'd go for a day tank setup with a transfer pump which could also polish the main tank(s).

I'm not aware of anyone else using the simple/specific nomenclature.

 

[pvb]

But if I were doing anything to a tank installation again, I'd add a second standpipe drawing as low down in the tank as possible, preferably in a corner that can be made the low point by heeling the boat, for the purpose of polishing and removing water.

My old Hallberg-Rassy had a pipe going down to the bottom of the keel tank, with one of those nice Jabsco brass hand pumps mounted in the engine compartment. Every so often, you could draw fuel from the bottom of the tank to check its clarity. Simple idea, but great.

Oh, but it still got diesel bug....

 

[NormanS]

I am in the fortunate position of having tanks with small dirt/water sumps with drain valves which are accessible. Any dirt or water automatically gravitates into the sumps, so that there is almost zero opportunity for a fuel/water interface. Almost all proper fuel tanks used to be made like this, but obviously the modern design of shallow hulled yachts makes this more difficult. If, heaven forbid, I had a boat like that, I would install a day tank, supplied from the main tank(s) via suitable water traps and filters.

 

[duncan99210]

Just finished crossing the Med from Lefkas to Gib and on to Lanzarote in a mates catamaran. 300 litre tank, never had any previous bug problems. Approaching Messina after 36 hours in a washing machine sea the port engine died. Sight glass full of crud, cleaned and new filter fitted. Engine refused to prime, crud in the pipework between tank and filters, so I used scuba gear to produce medium pressure air to blow through the pipe work. Success.
In Milazzo, Luigi and co turn up, pump out the diesel, take it away for 'cleaning' and return it later the same day. Success. Depart Milazzo, renter washing machine seas and journey to Palma, Mallorca, mainly under sail. Engines work all the way when required. But crud still appearing insight glass, so in Palma I fitted new Racor filters into fuel system between the sight glass and engine filter. Pleased with modification but still concerned about crud in tank...
Four day trip to Gib, much under motor, so we were running low on fuel by the time we made our approach. When both engines died in quick succession. Cue frantic efforts to blow through fuel lines as both lines blocked in before filters. Success but only for about an hour or so before they died once more. By this stage we had enough wind to combat the tide, so I unblocked the lines once more, checked the engines and then we made our way through to Marina Bay under sail, only starting the engines as we were guided to our berth.
We then got a company to come and clean out the tank as best they could, disposing of the contaminated fuel. The chap who did the hard work had a contraption that could get into most corners of the tank from the filler pipe hole, coupled to a medium sized sludge gulper truck of the sort more usually associated with septic tank emptying. That did the trick, as there was no trace of crud in the sight glass during the trip down to Lanzarote a week later. The remaining fuel in the tank was disposed of as waste.
Why the story? I think it shows two things. First, make sure you're dealing with a reputable company who will do the complete job on the quayside, not some half baked crew who weren't clear on what they were up to. Second, as Charles said above, the real problem often isn't actually clogged filters or sight glasses, it's the pickup pipe that gets blocked. If I were building a set up from new, I'd probably build in some method of purging the system with compressed air via a three way valve, which would save partially dismantling the fuel system in a seaway, not something I'd recommend to my worst enemy.

 

[NormanS]

Yes, but better to stop the accumulation of crud in the first place.

 

[lw395]

Yes, but better to stop the accumulation of crud in the first place.

Yes.
And or have a reserve supply of trusted clean fuel.
And some sails...

 

[GrahamM376]

Yes.
And or have a reserve supply of trusted clean fuel.

We do just that. 25L can in the cockpit locker adjacent to the engine and a spare length of flexible fuel hose which can be poked into it and then connected direct to the pump. Electric pump makes bleeding easy and polishes fuel whenever ignition is on.

 

[thinwater]

First, where is the crud coming from? Do you really think the fuel station has no filters? Would truck drivers put up with this muck? They would not. Next time you get fuel, place some in a sealed glass jar and see if is stable for a year. I bet you it will be.

Then how come the fuel generates crud in my tank? Do you have any copper alloys in the system? Do you realize that EVERY engine manufacture forbids copper and zinc alloys in fuel systems (Goolge it)? Take a second jar of that same fuel and place a few bits of copper and zinc in there. Whatever you have in your system. See if it generates sludge (you may need to add a trace or water to catalyze the required corrosion to free up some ions. Use some separator water. The cure, assuming you can't get rid of the valves and copper tube, is an effective metal deactivator.

And where did that water come from? I don't believe it came with the fuel. In your heart, you know it didn't, for if they were selling wet fuel the commercial guys would kill them dead. Do you have a fuel cap leak? Is some coming in through the breather? An o-ring fixes the first, a vent filter fixes the second.

Solve those problems, suck any pre-existing water out with an oil change pump, and the separators should be polished enough. If not, you have not solved the problems, you are just treating symptoms.

 

[Piers]

I don't think our opinions are poles apart. But if I were doing anything to a tank installation again, I'd add a second standpipe drawing as low down in the tank as possible, preferably in a corner that can be made the low point by heeling the boat, for the purpose of polishing and removing water.

Agreed.

If you wait until you start seeing gunge in the filter, you are at risk of the filter blocking in rough weather.

Agreed. If the tanks is free of 'crud', you'll always find the filters have 'dust' in them, regardless. This isn't the 'crud' to which I refer which would be bug, sand, and other nasties that are picked up from suppliers which have had a recent delivery and which has stirred up years of rubbish in the bottom of their tanks.

I'm not sure your concept of 'simple' polishing is very effective at removing any suspended water which may or may not be there.

'Simple polishing removes anything suspended in the fuel such as dust. When changing filters they will always tend to be blackened. This is fine. But it's when it has any brown sludge which is indicative of diesel bug.

In general I don't like drain plugs as they tend to be hard to access and difficult to draw off fuel in a controlled way. A risk of spillage which is unnecessary. Hence the second standpipe from the top of the tank.

Well, having neither on my Fleming 55, it's a pain. But, the fuel fillers are immediately above the tanks so we can dip them to the base and suck out a sample. But, the issue here is that many tanks (like ours) have baffles to reduce fuel slopping around in an emotional sea. hence, I cannot actually reach the absolute bottom of the tank.

On bigger boats, I'd go for a day tank setup with a transfer pump which could also polish the main tank(s).

Now that's a great idea.

I'm not aware of anyone else using the simple/specific nomenclature.

It's my oewn definition to separate dust from crud!

All the best. I agree we are on the same playing field.

 

[Trundlebug]

Well having had fuel bug problems myself I did three things which have worked well for me ever since.

1. Polished my fuel using the system described in the thread I referred to above. My fillers are not directly over the tanks, but go down from the deck via a curved hose to a 90deg elbow over the tank. For that reason I drilled an access hole at the top in the front and back halves of the tanks, i.e. either side of the baffle, so I could poke down the pick up pipe to the bottom of the tank and reach right into the corners.

As I have clear hose on the inlet side to the polishing filter system I can see what is being picked up, if anything. I can also stir up the contents using the pick up pipe if I wish.

It's quite rematkable how the colour of the diesel has changed from dark red with black gungy bits in, to light, clear red as the fuel has been cleaned up.

2. I fitted a second engine pre-filter, with changeover valves, to each tank. So in the event that I do get filter problems I can change over to the second filter whilst on the move, without stopping, getting dirty or delayed. OK if the fuel is really bad as Duncan described above it would only help me out for the first changeover, but it's given me much better flexibility and confidence.

3. Having polished the fuel I routinely treat it with Marine 16 every time I refill.

The above have worked for me very effectively over the last 4 years. I plan to give the fuel a polish again over this winter just to keep on top of things, as I have some longer trips planned next summer.

 

[lw395]

First, where is the crud coming from? Do you really think the fuel station has no filters? Would truck drivers put up with this muck? They would not. Next time you get fuel, place some in a sealed glass jar and see if is stable for a year. I bet you it will be.

Then how come the fuel generates crud in my tank? Do you have any copper alloys in the system? Do you realize that EVERY engine manufacture forbids copper and zinc alloys in fuel systems (Goolge it)? Take a second jar of that same fuel and place a few bits of copper and zinc in there. Whatever you have in your system. See if it generates sludge (you may need to add a trace or water to catalyze the required corrosion to free up some ions. Use some separator water. The cure, assuming you can't get rid of the valves and copper tube, is an effective metal deactivator.

And where did that water come from? I don't believe it came with the fuel. In your heart, you know it didn't, for if they were selling wet fuel the commercial guys would kill them dead. Do you have a fuel cap leak? Is some coming in through the breather? An o-ring fixes the first, a vent filter fixes the second.

Solve those problems, suck any pre-existing water out with an oil change pump, and the separators should be polished enough. If not, you have not solved the problems, you are just treating symptoms.

Good point about active metals.
www.bp.com/content/dam/bp-country/en_au/media/.../long-term-storage-diesel.pdf
Some of the water comes from condensation. Some starts off dissolved in the fuel. Once you have 'the bug' some parts of it may be creating water as a byproduct of living on the diesel. Obviously a leaking deck filler is an open goal!

 

[Piers]

Some of the water comes from condensation. Some starts off dissolved in the fuel. Once you have 'the bug' some parts of it may be creating water as a byproduct of living on the diesel. Obviously a leaking deck filler is an open goal!

As you say, the most common source of water in diesel is from a leaky deck filler cap (how often do you change the O ring) and from condensation over winter especially if the tank isn't full.

Diesel bug thrives on the interface between the water and diesel and is believed to double its quantity every 24 hours. Hence the need to treat the fuel every fill up, and as I've said above, I re-treat the tanks as part of the winterisation checks.

If you've had a bad experience from bug, the only way to rid the tanks of their brown sludge residue is either by steam cleaning if you are able to get inside the tank, of by the 'specific' method I mention above which stirs everything up into the fuel for a major round of filtration.

 

[lw395]

We did once get a lot of stuff out using a rope end on a stick, spun in a power drill, as a sort of flail to stir up the tank.

It's a choice whether to have a full tank and reduce condensation over winter, or a near-empty tank to reduce the amount of ageing fuel.....
Our lack of planning seems to make the choice for us.

 

[thinwater]

As you say, the most common source of water in diesel is from a leaky deck filler cap (how often do you change the O ring) and from condensation over winter especially if the tank isn't full.

Diesel bug thrives on the interface between the water and diesel and is believed to double its quantity every 24 hours. Hence the need to treat the fuel every fill up, and as I've said above, I re-treat the tanks as part of the winterisation checks.

If you've had a bad experience from bug, the only way to rid the tanks of their brown sludge residue is either by steam cleaning if you are able to get inside the tank, of by the 'specific' method I mention above which stirs everything up into the fuel for a major round of filtration.

Regarding bugs, an interface is not strictly required (I've done research in the field). Even dissolved water can be enough. It is also not required that the fuel be infected as delivered; bugs from our environment can adapt.

Condensate can be eliminated with a vent filter. I've used one for 4 years and my fuel stays clearer than ever. They really work. Also no need to struggle with whether to keep the tank full. It doesn't matter.

You are right that consistent biocide treatment is required. Or more to the point, biocide treatment after you are infected is too late. The sludge has already formed. In my experience, you are better off rolling up your sleeves and getting it done. I've found that even if you can't get good access, a power washer and vacuum can do a very good job. It does generate some wastewater. But treating every fill is easier.

 

[ghostlymoron]

I've often wondered about the ideal fuel tank. My MD1 had a rectangular, flat bottomed tank with a sump. So far so good, however, the take off to the engine was from the bottom of the sump!!!???
Seemed to me that it would have been better with a seperate drawoff from the side of the main tank (above the sump) and a drain cock from the bottom of the sump.
The main drawback with an engine takeoff from 2" above the base is that gunge can accumulate in the tank and is never drawn up (or down) to be trapped in the filters (I had two). You therefore eventually accumulate 2" of gunge which will catch you out.
I suppose if you were starting from scratch you could incorporate features like dip tube drawoff and big inspection cover in the top for easier maintenance provided the location of the tank would allow it. Mine was located immediately under the cockpit seat and the engine needed to be fed by gravity but some improvements could probably have been made. Possibly a tee off the engine feed pipe for draining water/gunge.
I did at times have problems with blocked filters.

 

[lw395]

The attraction of drawing from the bottom of the sump is the reduced risk (inevitability) of drawing air into the fuel when the tank is low. Otherwise, you cannot use all the fuel, and may suck air when there's a fair amount left, if the boat heels or in heavy weather. So it can be right for a small tank, like the 5 Gallon one in my Impala, which I modifed this way. As I almost always filled from cans, there was little chance of enough water getting in to overwhelm the filters. It had given me a scare getting into a harbour with a low tank, but to be fair, the engine kept going after a bit of coughing.
So I think the ideal tank is different for race boat with minimalist engine use vs serious cruiser vs motor-sailer.
AFAIK most cars draw from the bottom of the tank and have a lot less issues than boats, despite never adding biocide?

 

[lw395]

...
Condensate can be eliminated with a vent filter. I've used one for 4 years and my fuel stays clearer than ever. ....r.

What kind of filter do you use? Something with dessicant in it?
I wondered about using a motorcycle-style non return valve on the vent, to reduce the in and out of air and so forth. You'd need a vent to open to let air out when filling. And the tank would have to witstand a little pressure.

 

[pvb]

I wondered about using a motorcycle-style non return valve on the vent, to reduce the in and out of air and so forth.

A non-return valve wouldn't work - air needs to go out when the tank is filling, and needs to go in as the fuel is used.

 

[Yngmar]

A non-return valve wouldn't work - air needs to go out when the tank is filling, and needs to go in as the fuel is used.

My tank has an accidental feature - the vent hose hangs down a bit before going up again and only then dropping down entering the tank. In that sagging area, due to a previous overfilling (first time - oops), rests a little bit of diesel, less than 200ml, creating an airlock - the accidental feature. This is a bit annoying when filling up, because while the air does come out, it bubbles through that diesel sitting there and takes a little bit of diesel spray out with it, which I catch with a oil-absorbing rag, so no big deal once you know it's going to happen. The changing burbling sound even tells me when the tank is almost full.

I imagine this airlock keeps moisture out of the tank pretty well, as the diesel in the sagging vent hose prevents air freely flowing when the tank is sitting, air only goes in/out when the level and thus the tank pressure changes (which is why we need vents). At least when I stuck the piece of copper tube I'd made for the purpose down an unused take-off (no inspection hatch) and pumped up the bottom dregs, only very minor dirt and absolutely no water came up, much to my delight. :encouragement:

If this works, it would be easy to recreate, and possibly even remove the spray by having the loop a little steeper or further away from the vent fitting.

 

[pvb]

My tank has an accidental feature - the vent hose hangs down a bit before going up again and only then dropping down entering the tank. In that sagging area, due to a previous overfilling (first time - oops), rests a little bit of diesel, less than 200ml, creating an airlock - the accidental feature. This is a bit annoying when filling up, because while the air does come out, it bubbles through that diesel sitting there and takes a little bit of diesel spray out with it, which I catch with a oil-absorbing rag, so no big deal once you know it's going to happen. The changing burbling sound even tells me when the tank is almost full.

I imagine this airlock keeps moisture out of the tank pretty well, as the diesel in the sagging vent hose prevents air freely flowing when the tank is sitting, air only goes in/out when the level and thus the tank pressure changes (which is why we need vents). At least when I stuck the piece of copper tube I'd made for the purpose down an unused take-off (no inspection hatch) and pumped up the bottom dregs, only very minor dirt and absolutely no water came up, much to my delight. :encouragement:

If this works, it would be easy to recreate, and possibly even remove the spray by having the loop a little steeper or further away from the vent fitting.

Yes, a downward loop in the vent pipe would be effective.