Diesel bug - can it be filtered out?

[ianj99]

Does the diesel bug change the fuel chemically or just contaminate it in a way which can be filtered out?

I have twin tanks with about 10galls in each and I suspect its a few years old and possibly contaminated.

I was thinking of pumping out the tanks through a filter (a standard fuel filter)into an oil drum and then returning it to the tanks.

(although the engine filters would remove the contamination, if this is severe, they'd clog up quite quickly, hence my external prefiltering idea)

 

[Tim Lamb]

I think what you are planning is called 'fuel polishing'.
If you do a search on some of the obvious words you should find loads of previous info on fuel, diesel bug, filters etc., it comes up fairly regularly and there have been some long threads full of interesting ideas (aplogies if you know this already).
Regards
TJL

 

[ianj99]

I think what you are planning is called 'fuel polishing'.
If you do a search on some of the obvious words you should find loads of previous info on fuel, diesel bug, filters etc., it comes up fairly regularly and there have been some long threads full of interesting ideas (aplogies if you know this already).
Regards
TJL

Thanks, didn't find anything under diesel bug but did here:
http://www.ybw.com/forums/showthread.php?t=234151&highlight=fuel+polishing

So to sum up, the fuel can be filtered and returned to the tank, and then biocide added to keep it free.
I can't swill out the tanks, so may have to repeat the process in a month or so once and sludge has been stirred up. (I can't easily drain them but have to extract via the dipstick hole using an 8mm tube and Shurflow pump.)

 

[Bilgediver]

I can't swill out the tanks, so may have to repeat the process in a month or so once and sludge has been stirred up. (I can't easily drain them but have to extract via the dipstick hole using an 8mm tube and Shurflow pump.)

Can you trim your boat so that the place where the dip tube goes in is the lowest part of the tank. maybe a few friends on the bow and one or two on the port rail This can remove the last dregs of water which is as important as the biocide. The water/oil barrier is the incubator.

Age does not come into the equation. These critters can breed faster than rabbits if the conditions are right and where as a ten year old boat can be bug free you can find a 3 month old boat severely affected.

 

[Bandit]

Firstly it depends on how bad your contamination is. If it not extreme:

you could treat the diesel with a biocide such as Grotamar 71 , you will need to mix it with the diesel either mix it into a gallon of diesel and add it to the two tank or stir up the tanks. Then leave for three days.


You could then filter it and return it to the tank. Depending on the cost of filters pump tanks etc and how you cost your time alternatively you could dump it in a dirty oil tank and refill with fresh diesel and fresh Grotamar 71.

You must make all efforts to remove any water from the tank, is there a sump and drain or a stripping line?

You will then need to carry spare fuel prefilter elements and keep an eye on your prefilters.

 

[ianj99]

Firstly it depends on how bad your contamination is. If it not extreme:

you could treat the diesel with a biocide such as Grotamar 71 , you will need to mix it with the diesel either mix it into a gallon of diesel and add it to the two tank or stir up the tanks. Then leave for three days.


You could then filter it and return it to the tank. Depending on the cost of filters pump tanks etc and how you cost your time alternatively you could dump it in a dirty oil tank and refill with fresh diesel and fresh Grotamar 71.

You must make all efforts to remove any water from the tank, is there a sump and drain or a stripping line?

You will then need to carry spare fuel prefilter elements and keep an eye on your prefilters.

I will check for drains (only bought the boat in December and don't recall seeing one and there's no inspection covers so can't eyeball the interior)

It will come down to how bad the contents looks when pumped out. I might use it to swill out the tanks, then discard it.

 

[davidbfox]

From experience 4 years ago:

In a small tank syphoning works well into a 5l clear bottle. I fixed a clear tube to a cane and 'hoovered' the bottom of the tank with a running syphon. This cleared the water and black lumps of crud floating above water and below diesel. Fascinating when in viewed in bottle off the boat - like a lava lamp when shaken, then all separating out.

After changing filters, treating with soltron and regularly checking no water has got into tank, I have had no problem since.

I installed a water separator with glass bottom onto the fuel filter to that I can see if a water problem is developing.

I don't think all the diesel is contaminated, at least once treated with Soltron etc.. I think the crud that blocks the filters is only present at the interface between diesel and water, so in absence of water, lumps don't form even if 'bug' is present. May be wrong on that but it worked for me.

 

[oldsaltoz]

Only had the bug once, this is what I did to fix it.

Contacted the local filter-wash outlet and hired their fuel polishing rig, this sucks the fuel from the tank/s and passes it through 1 of 6 filters and returns it to the tank or a storage container.

The idea is to keep filtering, each filter has a gauge that indicates when the filter is near full of rubbish and you just select the next one without stopping.

How bad the contamination is will determine how many filters you will go through, every other filter is finer than one you just filled, so all rubbish is removed.

By returning fuel to the tank you can be sure the crud on the bottom is stirred up.

To prevent water getting into the tank due to condensation, lag or insulate the tank.

To prevent water getting in from the filling station, just make a double cone funnel, the inner liner made of mesh, then place a genuine chamois cloth inside, wet it with diesel and any water will bead on it but not pass through.

PS. I use Diesel Doctor.

Avagoodweekend.

 

[KellysEye]

Your idea is good, the normal routine. Use a 2 micron filter(s) though. As others have said then use a bug killer, we use Soltran.

 

[GerryM]

Diesel-Bug

Sympathies for having caught the plague. It is not so easy to get rid of and from all the posts above, a lot of hassle is involved in going through those procedures. Biggest problem is that there is a fairly good chance of it coming back again once you have had it once. Bugs are just like humans - they develop resistance to biocide just like we do to antibiotics, plus you have the problems with acid corrosion arising from dead bugs, water and biocides mixing. I recently came across a naval vessel that had to have deckplates replaced due to corrosion from bugs growing in bilge water.

You could try one of these : http://novatechengineering.ie

They are fitted to the fuel line and kill the bugs as they come out of the tank and burn them off harmlessly, leaving no residue in the tank. One of the problems with fuel polishing is that the fuel tank baffles cause dead zones in the tank where there is no turbulent flow to flush the critters out. You could leave a polishing unit running for days and still not get everything out of the tank. I have spoken to guys that have had to cut the top off the fuel tank to get behind the baffles to do do a proper clean out.

Another issue with fuel polishing rigs is that they are primarily designed to remove non biological particles - rust scale and the like. They work by filtering and since it is not possible to filter to "zero microns" something has to get through. Diesel Bug starts as airborne particles which are obviously quite small so fuel polishing just gets rid of the "big bits", leaving you with the "small bits" to start off a new family with. And don't forget that a polishing rig can pass the bug from one tank to another.

My experience is that the fuel polishing cost per liter is also quite close to the cost of the fuel whereas the De-Bug will most likely cost less or far less than a tank of fuel and fix the problem for good.

 

[ccscott49]

Does the diesel bug change the fuel chemically or just contaminate it in a way which can be filtered out?

I have twin tanks with about 10galls in each and I suspect its a few years old and possibly contaminated.

I was thinking of pumping out the tanks through a filter (a standard fuel filter)into an oil drum and then returning it to the tanks.

(although the engine filters would remove the contamination, if this is severe, they'd clog up quite quickly, hence my external prefiltering idea)

Simple answer yes it can. When you return the fuel to the tank, add some biocide.

 

[ianj99]

I pumped out some fuel from each tank last week. The port one's contents seemed visibly clean and clear, whereas the starboard one was visibly contaminated and hence a bit cloudy.

I am about to pump the contents of this tank through a large filter into an oil drum and if it looks okay, then tip it into the other.

I've already added soltron to both, so hopefully, when I add some fresh diesel + biocide to the tanks, the resulting contents will be useable without clogging the engine filters too rapidly.
I'll change these after a few hours running to be on the safe side.

There's no way to inspect the tanks' interior without an endoscope so I'll keep sampling the contents now and again.

 

[boatmike]

Very simply good clean fuel does not suffer too easily if used. What promotes bug growth seems to be leaving fuel stagnant in tanks, usually overwinter with the attendant water content it collects. I am not a fuel expert but I do consider that I know a bit about filtration having served my time with CAV/Lucas. To polish or clean up your fuel you need a setup like I have. I have 2 tanks with a gear pump that is capable of being switched to pump either way through a very large 10 micron Racor filter. Contrary to other advice I would NOT recommend an element with less than 10 micron rating as it will very quickly block. A 10 micron plastic or metallic element is best with a water seperating centrifuge and automatic dump. Water will damage the normal fuel element of a CAV filter and they just won't pass fuel when wet which is why many posts on here describe engines stopping because of water in the filter so you need something a bit better than this to polish sludge and dirt out. Water will NOT pass a 10 micron filter, nether will bio sludge. Ideally when polishing you need some way of agitating the fuel in the tank bottom to get it all out and make several passes back and forth between tanks. I always clean up my fuel that way once or twice a season but this is only a primary stage filtration process. I have a 5 micron filter in line as a secondary filter and the final stage engine filter is indeed 2 micron. I also dose with "fuel set" but that's just because I have always used it and never had a problem. Other stuff probably does just the same thing.

 

[pmyatt]

Very simply good clean fuel does not suffer too easily if used. What promotes bug growth seems to be leaving fuel stagnant in tanks, usually overwinter with the attendant water content it collects. I am not a fuel expert but I do consider that I know a bit about filtration having served my time with CAV/Lucas. To polish or clean up your fuel you need a setup like I have. I have 2 tanks with a gear pump that is capable of being switched to pump either way through a very large 10 micron Racor filter. Contrary to other advice I would NOT recommend an element with less than 10 micron rating as it will very quickly block. A 10 micron plastic or metallic element is best with a water seperating centrifuge and automatic dump. Water will damage the normal fuel element of a CAV filter and they just won't pass fuel when wet which is why many posts on here describe engines stopping because of water in the filter so you need something a bit better than this to polish sludge and dirt out. Water will NOT pass a 10 micron filter, nether will bio sludge. Ideally when polishing you need some way of agitating the fuel in the tank bottom to get it all out and make several passes back and forth between tanks. I always clean up my fuel that way once or twice a season but this is only a primary stage filtration process. I have a 5 micron filter in line as a secondary filter and the final stage engine filter is indeed 2 micron. I also dose with "fuel set" but that's just because I have always used it and never had a problem. Other stuff probably does just the same thing.

You say "Water will not pass a 10 micron filter" - is this any filter or just a fuel filter? I have a 5 micron filter on my watermaker and seawater goes through that OK.

 

[oldsaltoz]

Does the diesel bug change the fuel chemically or just contaminate it in a way which can be filtered out?

Proper filtering will result in usable fuel. Try 'Filter Wash" they have fuel polishing units for hire, depending on how much fuel you have on board it could most of the day to complete.

You pay for hire based on a day and it comes with a full set of filters, 6 in total I think, ranging from coarse to very fine.

Fuel can directed back to the boats tank or any other point.

I have twin tanks with about 10galls in each and I suspect its a few years old and possibly contaminated.

I was thinking of pumping out the tanks through a filter (a standard fuel filter)into an oil drum and then returning it to the tanks.

(although the engine filters would remove the contamination, if this is severe, they'd clog up quite quickly, hence my external prefiltering idea)

Hope this helps

 

[William_H]

Fuel

The aviation industry have battled with this problem and particularly water in the tanks for a long time.
The water gets in because with change of temp air is drawn int the tank containing water vapour this condenses to leave water in the bottom of the tank under the fuel. The bug grows in the water.
IMHO it is vital to have a sump in the tank. ie a low point which can be drained but which is below the fuel take off point. Half of one percent of total capacity is the standard capacity for the sump. or typically half to one litre.
It is important that fuel is drained from this point often. On aircraft before every flight and on fuel installations every day. For underground tanks they fit the cylindrical tank with a slope and run a suction tube from the low point up to a pump. (called the thief pump) The pick up is usually floating so always sucks from the top.
With a boat or plane the fuel is always agitated in use so floating pick up doesn't help so much.

So to clear fuel bug you must clear out all the water. Then wipe the tank clean. Any tank without an inspection port and fuel drainage sump is just a problem waiting top happen. So for a proper fix modify the tank. Yes the fuel can be reused after being allowed to settle for 24 hrs undisturbed then only use the top 95%. olewill

 

[boatmike]

You say "Water will not pass a 10 micron filter" - is this any filter or just a fuel filter? I have a 5 micron filter on my watermaker and seawater goes through that OK.

You are of course correct that both water filters and fuel filters can be designed to any micron rating but they will not be the same media, structure or behaviour in terms of designed pressure or flow rate. What I should have said is that a Racor type filter with centrifuge and a 10 micron fuel element will generally stop water and bio-sludge. It will also have the incredibly high contaminate holding capacity needed for fuel polishing. The problem with using a 2 micron absolute filter designed as a last chance filter before the fuel pump for fuel polishing is that it will quickly become blocked. Water filtration elements are designed quite differently to accommodate the viscosity and surface tension of water rather than fuel and will in fact quite possibly fail completely if put to use as a fuel filter.

 

[ccscott49]

I dont need to "polish" my fuel, the engines do it for me, I have ford mermaids, which pump the fuel around the system and returns it to the tanks, a self bleeding arrangement, all the fuel in the tanks, goes through my seperate double separ filters, which I do change fairly regular, as they will block eventually if there is bug around, the fuel then goes through two cav filters, which seem to last forever, I do change them however, so this keeps my fuel clean, I use fuel set, as this always seems to work for me and keeps my fuel clean.

 

[boatmike]

I dont need to "polish" my fuel, the engines do it for me, I have ford mermaids, which pump the fuel around the system and returns it to the tanks, a self bleeding arrangement, all the fuel in the tanks, goes through my seperate double separ filters, which I do change fairly regular, as they will block eventually if there is bug around, the fuel then goes through two cav filters, which seem to last forever, I do change them however, so this keeps my fuel clean, I use fuel set, as this always seems to work for me and keeps my fuel clean.

That is indeed a good arrangement and Separ filters are a good alternative to Racor. The only thing you will find is that the flow rate is not very high and there is still a possibility of developing sediment in the tank bottom. With a higher flow rate (in my case 5 gallons per minute) the returning fuel is deliberately "hosing" the bottom of the tank and dislodges any sediment. As I said, I use Fuel Set too and would think that provided your engines are run regularly you should avoid problems permanently though with your set up. The advantage of my "on board polishing" is that I can run the fuel back and forth between two tanks several times without running the engine. Probably overkill for the average boat though and I only did it when I installed a second "long range" tank. Even then I can of course only do it when one tank is empty.

 

[ccscott49]

That is indeed a good arrangement and Separ filters are a good alternative to Racor. The only thing you will find is that the flow rate is not very high and there is still a possibility of developing sediment in the tank bottom. With a higher flow rate (in my case 5 gallons per minute) the returning fuel is deliberately "hosing" the bottom of the tank and dislodges any sediment. As I said, I use Fuel Set too and would think that provided your engines are run regularly you should avoid problems permanently though with your set up. The advantage of my "on board polishing" is that I can run the fuel back and forth between two tanks several times without running the engine. Probably overkill for the average boat though and I only did it when I installed a second "long range" tank. Even then I can of course only do it when one tank is empty.

My tanks are independant, there is a crossover valve, which is only really for emergencies, the fuel return is also crossed over, so I can run either engine from either tank. or both from either tank. Bit belt and braces I know, but the proper way to do things I'm told. (and agree with honestly)
I've found the flow arte is reasonable and will "polish" a tank of 330 gallons in about eight hours.
I understand about the stirring the bottom of the tank, but there is no way I could arrange this, easily anyway.