Diesel Bug

[nimbusgb]

Thats interesting. The arrows on my racor 500 are right but i thought it was bowl to filter not the other way round. The bug tends to start in the bowl of my separator over the winter while the tank seems to be staying clear of it.

Solution this year has been to drain the whole separator assembly and leave it empty. I'll fill and bleed before launching.

This cutaway of a racor suggests it is bowl then filter though. http://www.marinepartsexpress.com/racor.htm

 

[Pete7]

In your blog, you suggest that the CAV-type filter head has the in/out arrows incorrectly marked. This isn't the case. The unit is designed so that fuel goes in to the filter first, then down into the glass bowl, then up through the centre of the filter and out. The reason for this is that minute droplets of water in the fuel are agglomerated as they pass through the filter into larger droplets which can fall to the bottom of the glass bowl. If you plumb it the wrong way round, any water droplets will pass through to the engine.

Thanks, I did wonder.

Not my blog btw which is a shame, working in the SA sun building boats sounds idilic as I listen to the rain in Gosport tonight.

Pete

 

[pvb]

Thats interesting. The arrows on my racor 500 are right but i thought it was bowl to filter not the other way round. The bug tends to start in the bowl of my separator over the winter while the tank seems to be staying clear of it.

Solution this year has been to drain the whole separator assembly and leave it empty. I'll fill and bleed before launching.

This cutaway of a racor suggests it is bowl then filter though. http://www.marinepartsexpress.com/racor.htm

This old CAV publication explains their theory. Your Racor may have a different theory.

 

[PetiteFleur]

I changed my fuel filters a couple of days ago. The CAV primary filter had a trace of black sludge on the top of the filter(no way as bad as the earlier picture). The fuel filter on the engine was clear. I have a Vetus plastic tank fitted 8 years ago and do dose with Marine 16 yearly.

 

[Nicholas123]

I first came across diesel bug in the late 1980's! while working at a major construction equipment factory. It was in the in-factory (above ground) fuel storage tanks. No one knew about fuel bugs back then, it was mainly seen as a water ingress problem. It took months before the fuel supply company came up with some kind of additive and suggestions, but it was very experimental at the time. I am sure the bug has been around for a long time, it was probably just put down as "bad or dirty fuel" caused by poor storage facilities.

As far as I can see the fuel is put into our tanks in a pretty disgraceful unrefined state containing muck & water.Hence some of the photo's published here.One has to ask if there are quality standards for the refining & storage of Diesel before it is dispensed at the pumps?Presumably there are so then it becomes one of trading standards are they carrying out checks etc? Instead of treating the symptoms in the form of additives should'nt the trading standards just be enforced more vigorously?

 

[sailinglegend420]

This old CAV publication explains their theory. Your Racor may have a different theory.

I think your agglomerator is more of a water separator than a primary fuel filter. Doesn't make any sense to go through the filter first before going to the bowl. Most primary filter I think work like the Racor. Please correct me if I am wrong. So my post #15 was correct when I said:

"If the bugs don't get to the glass bowl of your primary fuel filter then you are OK."

But maybe I was half wrong because I didn't know about your crazy CAV filter - so you were also half wrong questioning my half right post!!!

So, new forumites, don't believe anything you read on these forums because half the postings are half right (or half wrong) half of the time!

 

[pvb]

I think your agglomerator is more of a water separator than a primary fuel filter. Doesn't make any sense to go through the filter first before going to the bowl. Most primary filter I think work like the Racor. Please correct me if I am wrong. So my post #15 was correct when I said:

"If the bugs don't get to the glass bowl of your primary fuel filter then you are OK."

But maybe I was half wrong because I didn't know about your crazy CAV filter - so you were also half wrong questioning my half right post!!!

So, new forumites, don't believe anything you read on these forums because half the postings are half right (or half wrong) half of the time!

It's not my "crazy CAV filter", it's probably the most common fuel filter in boat use in the UK. And it is a fuel filter, not simply a water separator. The CAV filter uses agglomeration to remove water, and plumbing it wrongly will destroy this benefit. So I'm afraid you were wrong in general terms. Many Racor filters pass the fuel through a centrifuge-type system first to remove water, and then filter it, but Racor filters are still fairly uncommon in the UK.

 

[alanwilson]

Don't block the breather (suggested early on in the thread): as the diesel & air expand & contract in the temperature difference between night & day, the pressure difference will at the least strain connections and possibly blow out the bung.

I'm not convinced that temperature difference won't cause enough air change for condensation to be a problem: remember that in the UK we live in a remarkably humid atmosphere and that fresh moist air is drawn into the tank every single night. Keeping the tanks topped up to reduce the volume of air is a good idea; also see the PBO comparison of additives (May 2011): there are biocides (used as a shock treatment, only when there is bug present: diesel drained out of the filter is black) and dispersants (used ongoing, every time you fill the tank, to remove any water).

The best biocides were Wasp Biokem, Eradicate, Marine 16, Grotamar 82 & Star Brite Bio Diesel; the best dispersants were Starbrite Star Tron, Fuel Doctor, Soltron & Fuel Set.

 

[gordmac]

If you don't have the bug put a maintenance dose of Marine 16 in as per instructions. If you do have the bug put more in as per the instructions.

 

[Nicholas123]

This old CAV publication explains their theory. Your Racor may have a different theory.

My filter dos'nt look like that.The inlet & the outlet are reversed.I would like to post a photo but I can't make any sense of this sites uploading software.
I shall have to take another look in the spring & change any filters I find but for now I'm not going to spend thirty odd quid on stuff that I may not need.

 

[pvb]

My filter dos'nt look like that.The inlet & the outlet are reversed.

Note that the common CAV-type filter head has two ports one each side, one an inlet, one an outlet. This is to allow flexibility in plumbing it.

 

[vyv_cox]

My filter dos'nt look like that.The inlet & the outlet are reversed.I would like to post a photo but I can't make any sense of this sites uploading software.
I shall have to take another look in the spring & change any filters I find but for now I'm not going to spend thirty odd quid on stuff that I may not need.

There is a useful and more detailed description at http://www.donaldson.com/en/engine/support/datalibrary/070616.pdf Page 25 (third one down) Basically says exactly the same as the diagram posted above, i.e. water droplets coalesce in the bowl after passing through the filtration media.

 

[Nicholas123]

Mine has two ports on each side as pvb has mentioned & the diesel in the bottom looks pretty clean but there is half inch of water.I shall drain that out next time I go down there (I tried before but I think the bleed hole is blocked).In the spring I shall buy the two filters I think is in the system & clean up the whole system.
Any tips on where you can buy cheap filters for a BUKH DV 10 would be gratefully appreciated

Just a thought.When you slacken off the butterfly nut on the bottom should the water just drop out under gravity alone?

 

[Pete7]

Yes, the thread has a groove cut into it which allows water and diesel to trickle out. there is also second bolt on the top to break the seal and allow air into the filer which helps. However, you might as well take the thing apart and clean it all out. New seals are tricky to fit.

Pete

 

[Pete7]

I read an article recently in which some research into this widely held belief showed that in fact it doesn't happen.
Many fuel bunkers are contaminated with water, so maybe that is the major source?

Vyv, you may be right the water is already in the fuel. However, I found this when I opened the fuel filler this morning. Now bearing in mind this tank was emptied and cleaned thoroughly on the 2 Nov 13 and then had 20L of clean fuel from Premier Marina in Gosport added to a 90L tank so 1/4 full. I also replaced the fuel cap and fitted a new sealing washer at the same time.

Today (1 Dec 13) I find this on the inside of the fuel cap and this is just the cap, not sure what the inside of the tank above the fuel is like.

I think the acid test will be to check again in a months time because I filled the tank after seeing this.

Pete

 

[William_H]

As far as I can see the fuel is put into our tanks in a pretty disgraceful unrefined state containing muck & water.Hence some of the photo's published here.One has to ask if there are quality standards for the refining & storage of Diesel before it is dispensed at the pumps?Presumably there are so then it becomes one of trading standards are they carrying out checks etc? Instead of treating the symptoms in the form of additives should'nt the trading standards just be enforced more vigorously?

I don't think you can sit back and blame suppliers. The problem is encountered with any storage of fuel in a non sealed tank.
Aviation have had this problem since the beginning. With petrol the problem was more that the water would collect and simply cut the engine out by excluding petrol.
With the advent of jets using kerosene which is virtually the same as diesel the problems of bugs (cladisporum resinae) became apparent. This will corrode aluminium tanks as well as block filters. Further on high altitude aircraft the fuel gets so cold that the water can seperate out and present as ice crystals blocking filters. Large jet engines can accomodate a fair bit of water in the fuel and they actually heat the fuel with an oil cooler to avoid ice. Some smaller jets add antibug and anti ice additives as a regular thing.
Of course an aircraft tank has a lot more air transfer with changing altitudes and temps but it would seem that water can get into the tank via the breather letting in atmospheric air. Perhaps less of a problem in a boat but you still get less problems with a full tank with less air space.
In aviation they go to a lot of trouble to check for water in fuel supply storage tanks at least on a daily basis. Plus they fit water separators and filters at the pumps and check the tank drains on the aircaft after filling. (and before each flight) Certainly they go to a lot more trouble in supplying fuel to aviation. Indeed every batch of fuel sold comes with a batch number enabling quality back tracking back to the refinery if there is a problem. Where you have a marina selling diesel in small quantities with not much skill from the owner or care about such things you might get a grreater risk of water and contamination.
So the only defence against contamination is to use a high turn over supplier, keep your tanks full, check the bottom of your tank for water often, use an antimicrobial treatment often and check filters and water separators often.Cos if you don't you will get that silent engine at the most inconvenient time. good luck olewill

 

[fisherman]

Part of the problem seems to be that the crud doesn't move easily enough to drain it, but does when heading for the engine. In 1988 we made a separator, like a house, about 18" long,9" wide and 9" high, with a pitched roof and two chimneys. The fuel came in one end on the ground floor, went up through two small holes at the corners into the first floor and back to exit above the inlet, the chimneys were bleeders, and there was a drainoff at the bottom, we never got anything sinister out of this. Three years ago it was removed, and found to be completely full of crud. Likewise on this boat I have a drainoff in the sump of my tank, always comes out clean diesel, but filters need changing at about 400-600 hours, I also drain the agglomerator regularly, I have to shake the muck out, it's mounted on flexible pipes.

 

[vyv_cox]

Vyv, you may be right the water is already in the fuel. However, I found this when I opened the fuel filler this morning. Now bearing in mind this tank was emptied and cleaned thoroughly on the 2 Nov 13 and then had 20L of clean fuel from Premier Marina in Gosport added to a 90L tank so 1/4 full. I also replaced the fuel cap and fitted a new sealing washer at the same time.

Today (1 Dec 13) I find this on the inside of the fuel cap and this is just the cap, not sure what the inside of the tank above the fuel is like.

I think the acid test will be to check again in a months time because I filled the tank after seeing this.

Pete

I am guessing that the moisture that has condensed on the (colder?) filler cap was contained in the 70 litres of air that remained in the tank. If the theory that I posted earlier is correct then no more condensation would occur.

 

[Nicholas123]

I don't think you can sit back and blame suppliers. The problem is encountered with any storage of fuel in a non sealed tank.
Aviation have had this problem since the beginning. With petrol the problem was more that the water would collect and simply cut the engine out by excluding petrol.
With the advent of jets using kerosene which is virtually the same as diesel the problems of bugs (cladisporum resinae) became apparent. This will corrode aluminium tanks as well as block filters. Further on high altitude aircraft the fuel gets so cold that the water can seperate out and present as ice crystals blocking filters. Large jet engines can accomodate a fair bit of water in the fuel and they actually heat the fuel with an oil cooler to avoid ice. Some smaller jets add antibug and anti ice additives as a regular thing.
Of course an aircraft tank has a lot more air transfer with changing altitudes and temps but it would seem that water can get into the tank via the breather letting in atmospheric air. Perhaps less of a problem in a boat but you still get less problems with a full tank with less air space.
In aviation they go to a lot of trouble to check for water in fuel supply storage tanks at least on a daily basis. Plus they fit water separators and filters at the pumps and check the tank drains on the aircaft after filling. (and before each flight) Certainly they go to a lot more trouble in supplying fuel to aviation. Indeed every batch of fuel sold comes with a batch number enabling quality back tracking back to the refinery if there is a problem. Where you have a marina selling diesel in small quantities with not much skill from the owner or care about such things you might get a grreater risk of water and contamination.
So the only defence against contamination is to use a high turn over supplier, keep your tanks full, check the bottom of your tank for water often, use an antimicrobial treatment often and check filters and water separators often.Cos if you don't you will get that silent engine at the most inconvenient time. good luck olewill

Not really convinced by this William.The aircraft world is an entirely different world with entirely different standards because of the potential for loss of life.I know because my background is in Aircraft Engineering & everything is inspected to a much higher standard than for example automobile.
I would be interested to hear from big haulage Companies to hear how they find this situation.It seems to me that if there is such a known problem additives should be added at the refinery,it's all so amateurish!:ambivalence:
I can't help drawing parallels with the food Industry.They certainly don't hesitate to add additives & so on to make their ready meals palatable & ensure successful sales do they

 

[vyv_cox]

Not really convinced by this William.The aircraft world is an entirely different world with entirely different standards because of the potential for loss of life.I know because my background is in Aircraft Engineering & everything is inspected to a much higher standard than for example automobile.
I would be interested to hear from big haulage Companies to hear how they find this situation.It seems to me that if there is such a known problem additives should be added at the refinery,it's all so amateurish!:ambivalence:
I can't help drawing parallels with the food Industry.They certainly don't hesitate to add additives & so on to make their ready meals palatable & ensure successful sales do they

The bacteria that cause diesel bug (and any other form of hydrocarbon bug) come out of the well with the crude. They have been hanging around there for millions of years, have undergone a distillation and cracking process at the refinery at temperatures up to 200 C, pressures up to 40 bar in some cases along with various chemical processes. They have survived that without apparently being the slightest bit affected. Mankind's history of coping with infectious bacteria is not exactly exemplary on a far smaller scale. So how would you suggest they be destroyed in an industrial process?