Diesel: To treat or not to treat

[TT23844]

Water on the surface of fuel ??????

Water, from condensation, humid air or "dirty" fuel or whatever, is heavier than diesel fuel and will sink to the bottom of the tank. The water particles will sink to the bottom and accumulate untill eventually there will be a large enough amt. that can be a problem. Water droplets can be held in suspension in fuel if it is agitated sufficiently for a long enough time, but as soon as things quiet down the water will drop to the bottom again.Sorry Tom, I don't buy the 'equalization' theory. Furnace oil tanks here are in common usage & frequently will have rust perforation from the inside, due to water condensate accumulating on the bottom of the tank, under the fuel.

 

[RichH]

Those large 'farm' tanks dont have problems ......

typically they will have little water, extremely small amounts of bio-fouling, etc. The 'secret' is these tanks are continuously 'sparged' by large entrainment nozzles in the tank bottom thereby continually 'moving' and turning over the liquid; plus, it takes a long time for the fuel oil to cool down after its refining stage. Fungal-forms and bacteria thrive on 'stagnant' fluid if they can use it as a nutrient source.

 

[RichH]

Sorry TT .....

Unless the water in fuel has 'coalesced' (smaller macromolecular sized particles agglomerating into larger and larger 'packets') it will stay in suspension for a very long time (even existing on the 'surfaces' of the fuel. Not until the small particles of water reach a fairly large size do begin they settle to the bottom by 'gravimetric settling'. In many applications such 'non-free' water is removed first by liquid-liquid 'coalescing filters' to remove the 'small' particles ~1uM (making bigger and bigger (water) particles and then by subsequently by passing the fuel through large banks of water absorbing filters filled with a starch (usually hydroxymethylcellulose) ... otherwise it stays in 'suspension' for a very long time. The higher the viscosity the oil, the longer for the gravimetric settling.

 

[TT23844]

Common sense ??

RichH - I don't have your apparent technical expertise on the subject and based my comments on a couple of observations. Large oil storage tanks in refineries are a little beyond the scope of this forum, and I admit to knowing nada about them.First, in this area it was common practice untill recently to use steel tanks for furnace oil & these tanks regularly rust out from the inside, due to accumulated water at the bottom of the tank. The most probable source is condensation, as the tanks are often left with little oil in them during the summer, however it is possible that the oil delivery guys are supplying 'dirty' fuel. The point I was trying to illustrate was simply that water, from whatever source, will and does settle in the bottom of the tank in sufficient quantity & concentration to cause the tanks to rust.Secondly, I've seen globules of water that have formed and lie at the bottom of tanks & plastic fuel containers. The source is irrelevant to my point that the water does come together to form a globule or whatever the correct tech. term for a blob of water is. Finally, I rely on the information in sources like Nigel Callder's "Boatowners Mechanical & Electrical Manual" : it says "When leaving the boat unused for long periods.......fill the fuel tank to the top. This eliminates air space and cuts down on the condensation in the tank"

 

[Benny]

I'm just trying to make head and tails

of this whole water in the tank issue. I did a search on the net and found some information which I listed in the previous posting. It seems we are all getting to the same point coming from different directions. Here is my last attempt at piecing this together;We have mostly agreed upon the most common sources of water getting into the tanks; 1) Condensation 2) Emulsified in the fuel 3) Suspended in the fuel 4) Leaks from deck cap, backing up vent or tank hardware  5) Pumped in from dock tanks.We have analyzed condensation according to humidity in the air, changes in temperature and volume space in the tanks. I believe that over a long time period condensation can add up and contribute to the problem as the tank is connected to the outside air through the vent and humidity will seek equilibrium.We have also observed our own and others experiences.I will modify my plan to keep just 1/4 of a tankful as Tom recommends. I will verify that there are no leaks into the tank. I will drain the water separator every 90 days. Will use a biocide and a fuel stabilizer and will cross my fingers when purchasing fuel. Accepting the premise that in over a short period of time condensation will not be a major factor and with the reasonable assumption (to be verified) that there are no water leaks into the tank I'm only left with the conclusion that water is being brought in emulsified with the fuel. As soon as fuel finds itself at rest the water will drain to the bottom. The conclusion follows that the less fuel brought in, the less water. Fuel degradation is a more difficult to handle problem. It is usually compounded with contamination. In simple words I will elect to avoid old fuel by keeping just a small amount and using it as quickly as possible. Please don't poke holes at my theory but if you find my revised plan to be flawed by all means let me have it.

 

[tom]

Water in A lot of Stuff

There is even water in polyester fiberglass. Molecular water is what I am talking about. Diesel can hold 0.1% molecular water depending upon the temperature. Think of it like the water in air. You can't see it until it condenses to form fog. But water will reach a saturation point in diesel. The water can move back and forth from the diesel to the air. I guess the best fuel tank would be a flexible tank with no air space. But if you look at the physics condensation can't be a major source of water in a sailboats fuel tank.

 

[RichH]

Not knocking you down TT. Well, Nigel Caulder apparently doesnt know his ass from first base when it comes to 'condensation' as its simple chemical equilibrium thats the driving force. As I stated previously if the fuel is already saturated with water vapor it will condense on the walls, in the vent line, etc.; if the fuel is unsaturated it simply wont condense. The condensation is a symptom, not a means. Water vapor is going to equilibrate through the vent and no matter if the tank is full or nearly empty .... the equilibrium drive will continue until the oil is saturated with water vapor ... simply wont happen to an empty tank.  Buying water saturated fuel is all too common, thats why I visually 'test' it - if it isnt crystal clear, its crap. Buy your fuel from a high turnover source and you will have little to no problems. I simply dont want such crap to fly through the combustion chamber (it doesnt burn well) and then form 'coke' downstream in the exhaust header, etc. No problem with black iron tanks ... as I have one in my boat as well as home burner storage .... I keep the water OUT and have no problems. I actually prefer black iron as its stronger/cheaper ; and, I can epoxy line it ... and if I make it strong enough (vacuum rated) I can put a valve on the vent to prevent moisture uptake when Im not using the tank ... now thats KISS. ;-) Just because something is 'published' doesnt make it 'right' .... just look at all the WRONG theories of how a wing/sail works and these incorrect 'hypotheses' are still offered in 'sailing' books and highschool 'science' courses ... and just about everyone accepts them as fact when in fact they're dead wrong. ;-)

 

[RichH]

Benny ----

The simple solution is: as little fuel as you can stand in the tank and then an onboard recirculation/polishing system that has an independent/secondary filtration stage that contains a water 'knock-out-pot' and an additional 'starch loaded' filter for water absorbtion once it gets in there.In the electric power industry, water is BIG problem with the dielectric oils used in transformers, etc. .... simple solution is to occasionally drain off the visible water from the bottom and then run the oil through a water absorbing filter to remove the balance of the water thats not 'free water'. Thats probably the simplest conceptual solution for a boat. With respect to having a full tank .... fuel oil only has a relatively short shelf life in small lot storage such as a boat, why load up only to have it all go bad if you dont expect to use it soon?

 

[Ross]

RichH, I have no doubt about your credentials

I once worked with a mechanic who taught me how bad an engine could be and still run well. At what point do we really need to become concerned about the fuel we are feeding the engine? I have a racor filter with a glass bowl and particulate filter, I use clean fuel, and run it through two bronze screens when filling the tank. I realize that in an ideal world we would stand at the refinery with jerry can in hand and buy the fuel as it comes out of the tower but we live in a real world and must deal with that.

 

[Fred]

I must just be lucky. I buy pld boats that have

sat for years, change the fuel filters, bleed the system through the new filters, fire them up and I've never had a problem or noticed a difference in how the engine ran on new fuel when I finally ran the old fuel down a bit and refilled.I have done this with maybe 20 old boats over the years, my own and donations when I ran the boat school,and helping friends bring their new babies home, and if the filters were clean and there wasn't so much water in the tank that it got in the fuel pick up tube, the engines ran fine.I like a fuel tank with a drain on the bottom so you can drain the water off now and then, but I've also added various kinds of "fuel dryer" to absorb the water and never noticed the engine runnig badly. I think you have to keep the dryer down to 5% or so on older motors so the alcohol doesn't make old rubber gaskets degrade.I believe, mostly on the basis of dock side talk, that most water in fuel tanks comes from condensation because there is a constant flow of air in and out the vent. Slow, but 24/7. Condensation is less if you keep the tank fuller. Just my 2 cents.

 

[Waffle]

onboard recirculation/polishing system

You don’t want to find out you have water and algae in the tank when you’re out in the heavy seas and your tank gets stirred up. The engine might quit or every worst become damaged!onboard recirculation/polishing systems are great for larger boats. You can make an off board system on a piece of plywood that can do the same think. The problem is tying it into the fuel system. This can be a tricky thing to do.I recommend a different trick if you think your fuel is suspect; drain all the old fuel out of the tank and replace it with new clean fuel. This is much easier than polishing your fuel. Here are the steps below:1.Close the fuel value at the tank.2.Remove the fuel line are the closest filter to the tank.3.Connect it to a cheap drill pump.4.Connect the other side to five gallon jug.5.Pump ALL the old fuel out of the tank.6.Replace with new fuel FROM A GAS STATION!You will need enough 5 gallon jugs to hold all the fuel. You can use the old fuel to heat your home if you use oil heat.

 

[Tom]

Why such expense and trouble???

Since the Exxon web site says that diesel is good for 3-6 months keep about what you use in 3 months in the tank if you sail year round as I do. If you haul out every year in the spring add about the amount of fuel you'll use over the summer. At the end of summer pump out the remaining fuel and leave the tank clean and dry over the winter. That way you never have old fuel and the chance of bugs growing is small. You can even save the old fuel at home and filter it before putting it back in the spring. It is just plain stupid to carry around enough fuel for 4-5 years. If you are still concerned about condensation a cheaper solution is a collapsable fuel tank. Fresher fuel no chance of condensation. But in my personal experience condensation is not a problem with my sailboat. My tank has only been full a couple of times in the 3 1/2 years that I've owned the boat. I only filled it then because I was motoring about 500 miles up the Tenn-Tom waterway and Tennessee river.

 

[RichH]

Tom- whats the URL of the Exxon website?

BP (Australia) used to have a very comprehensive website for the storage, shelf-life, recommended additives, etc. of diesel fuel but have withdrawn it (probably due to 'controversy'. Would you post the Exxon site, please. Thanx.

 

[Mike]

Just the basics

We're on the northern Chesapeake Bay. I use the KISS method, "Keep It Simple Stupid". I shut her down in early November and start her back up in early April. She remains in the water year round. I've left varying degrees of fuel in the tank over the winters. I always add the appropriate amount of biocide with every fill up. I have a Racor fuel filter with a glass bowl. I check the bowl periodically for water and or contaminates. I replace the filters according to Westerbeke's recommendations or annually, which ever comes first. I've purchased fuel from more marina's than I can remember without a problem. It's a basic approach that's worked successfully on two boats for the last 8 years. You'll find that basic precautions and maintenance are all that you need for most everything mechanical. Compare what you've done in the past, measure your success or failures and don't fix something that's not broken.Good luck

 

[Dave Groshong]

Startron/Soltron

I'm here in Puget Sound too. If you fuel up at Shilshole, and a few other places, they have biocide (not sure what brand) in the fuel. I swear by Startron, also goes by trade name/brand name Soltron; it works enzymatically and really diminished my diesel engine smoke.If your caps tight, you get good fuel and you have a good tank, you may get away without anything, but I feel better adding the $10 or so once a year, or fill up.

 

[Benny]

I don't think us sailors are going to solve the

fuel riddle. I don't think the fuel distributors are playing with a full deck. The fuel after being refined may be dry and clean but I do not think it is a priority for the distribution function to keep it tha way. Leaking storage tanks, rusty barges in rough seas, trucks and old fuel station tanks. I don't think fuel quality enters into the economics of moving fuel, as a matter of fact I wonder how many gallons of water are passed along and priced as fuel. We can take all precautions we want but it seems we are at the mercy of what we may find at the pumps. Contaminated and degraded fuel served under questionable filtration may have a very short shelf life. So I repeat my plan is to purchase as little fuel as possible and burn it as fast as I can. Luckily to do this won't be a burden, now if I had to get special filters and equipment to polish the fuel that would be going out of my way. A couple of gallons in a can can serve as an emergency supply or easily disposed off if not used. I have a lawnmower that I think will run on almost anything; by mixing some fresh gasoline and equal parts of used to be fuel it runs like a charm. I'm almost done with five gallons I had left of some old gas and two stroke oil mixture I had left.

 

[tom]

Benny the West Marine Filter Works

The bad news is that I have trapped some water and dirt using the WM filter. The good news is that most of the fuel that I've filtered has left no water or dirt in the filter. The filter is a funnel with a teflon coated stainless steel screen. It is fine enough to catch larger particles and the teflon is hydrophobic and stops free water from passing. It won't remove molecular water. I have a couple 5 gallon plastic cans that I fill using the funnel filter and then siphon this fuel into my tank. The filter is too slow to use to directly fill the tank. Also many marinas have large nozzles designed to fill big tanks. Service staion nozzles are smaller and the flow rate is less.Some marinas take pride in having great fuel. The Panama City Marina has always had good fuel with stabilizers and biocides already added. But I bought some really bad fuel from a marina on Dog River in Mobile Bay. I think that fuel distributors really have to work hard to keep fuel handling equipment clean and dry..some just don't try. The locals figure out which marinas take pride in their fuel. Transient sailers are the ones that get stuck with the bad fuel. I've bought fuel from a different Dog River Marina several times without any problems.

 

[Greg]

Fuel

Ok as an x marine mechanic let me put my 2 cents in. You can get bad fuel, and your fuel can go bad. A little biocyde and fuel stabelizer is pretty cheap. Use a fuel filter and a water separator. Tanks that are kept empty do tend to rust more than tanks that are kept full. I've replaced enough to KNOW this for a fact. But even then it takes years to rust a monnel tank out. New synthetic tanks aren't going to rust out, so drain them. Don't use one of those pumps that are powered by a drill. You can be blown up!!! Fuel pumps are made so that no static charges build up in the pump. Get a pump made for moving fuel. Adding fuel stabelizers, and even a little 2 cycle oil to the fuel for winter storrage will reduce rust in the tank. But will not give you good fresh fuel in the spring. Maybe the best way would be to fill the tank at storage time and drain when getting ready to relaunch. Ok, I don't do this and don't know anyone who does. Everything is a compromise. Do you have a clean out port? On most tanks this would be your fuel gauge sending unit. Pull it in the spring and look down into the tank with a flash light (not a match). Is there any water on the bottom? If so pump it out. Is there any black growth on the bottom or sides? This would be black, or blue green algee. Add more biocyde and clean out what you can. Get an extra fuel filter too. Rusty spots? May be time for a new tank. Think about one of the synthetic tanks for a replacement. I've seen boats that get little to no care go for years with no problems, and boats that no expense was spared on maintainance have nothing but problems. Maybe some are just lucky!

 

[Alex]

Lots of theory but KISS

I try to keep it simple but approach the problem from multiple angles(1) Got an air dryer from the machine shop supplier for spray paint guns and installed it in the vent line to reduce the moisture in the air space(2) Installed a electronic fuel pump and a water separation filter to cycle the fuel even when the motor is not running. By statistical filtering, water and dirt will be minimized. The pump setup has a valve to provide fuel pressure if the main lift pump quits.(3) Buy only enough fuel for a month or so from busy truck stop. Never top up or run dry. I usually buy a can and store in the laz until needed then replace the spare. I always have fresh fuel and spare.(4) Have a WM fine filter for filling up.(5) Inspect or replace the o-ring on the deck fill every year.(6) Take the old oil to recycling plant in the spring, usually just a few gallons.(7) Use biocide.Just my approach