Is Fuel Polishing really necessary?

[geem]

I don't get polishing. Most engines recirculate fuel anyway. If you're looking to spend money on a solution that solves the problem of fuel induced engine failure are you not better of having a parallel filter system with a switchover when one circuit gets blocked?

I guess it depends on your Individual set up. We have water in fuel alarm as standard on our Perkins. The fuel filters are super fast to swap. 1/4 turn type. No o rings to faf about with. If we got a blocked filter I can have a new one in a couple of mins.

I think of our portable fuel filtering set up as a mechanism for understanding the tank condition as much as anything. If all is clean and bug free I am happy. Last time I got some diesel bug going on. I vacuumed it all out and dosed with more M16. It's under control but a regular check with the pump tells me that

 

[noelex]

A fuel polishing system is not essential, but it is one of the helpful systems designed to reduce the chances of fuel related problems. Long distance cruising boats that often are forced to buy poorer quality fuel benefit the most.

Following the last fuel polishing thread, I checked how much fuel my electric pump was circulating. 500% of normal fuel use. A built in polisher!

That is still a tiny volume of fuel that is being filtered, compared to most fuel polishing set ups. Our polishing system is typical and process on average about 500 L a day. When sailing offshore (where polishing does the most good) it is over 2000L a day. This is all fuel picked up at the very bottom of the tank, where the water and junk lies, rather than the raised pick up that feeds the engine.

 

[geem]

A fuel polishing system is not essential, but it is one of the helpful systems designed to reduce the chances of fuel related problems. Long distance cruising boats that often are forced to buy poorer quality fuel benefit the most.



That is still a tiny volume of fuel that is being filtered, compared to most fuel polishing set ups. Our polishing system is typical and process on average about 500 L a day. When sailing offshore (where polishing does the most good) it is over 2000L a day. This is all fuel picked up at the very bottom of the tank, where the water and junk lies, rather than the raised pick up that feeds the engine.

We would you want to circulate that much fuel? Most commercial systems circulate 5% daily.
My tank is built in to the boat so we don't have a large bottom section to it. The keel shape provides a natural sump for any debris. We don't need to run anything like that flowrate to achieve good fuel filtration

 

[thinwater]

Perhaps it would be helpful to discuss what we are trying to accomplish:

• Remove water. This is of two sorts; free water, which settles fast and came in through a leaky filler cap, and emulsified/dissolved water, which may have been absorbed from the air (see note).
• Remove fine solids. How fine? Can this simply be handled by the engine filter?
• Remove coarse solids. These settle fast and can be stirred up in strong weather. Biosolids that are sloughing off. Are these best removed by slow, fine filtration, or fast filtration (how fast--turn the tank over in minutes or hours?)
• Bugs. They are sub-micron and will go through any filter. Are you using a preventative biocide (Biobor JF)? It will kill them, but the bodies still need to be remove, and once they die they will slough and float loose. If the fuel is kept dry, you use Biobor JF, and you turn over your fuel a few times each year like you should, the likelyhood of getting bug is minuscule to zero. Prevention is a LOT smarter than trying to cure it with filters, which really does not work well.

Note on absorption of water. Some theorize that because an MT tank does not fill with water, this is a myth. The problems is that this is poor analogy. A drop of dew falls into the oil, falls to the bottom, and is sealed in, and will not evaporate during the day. Any tank inspector will tell you that condensation in tanks is very real and does considerable damamge. Roof damamge from underside corrosion is one of the most common repairs in oil terminal tanks. The best control methods for absorption are silica gel vent filters and always using the diesel within 6 months or so.

There is also cleaning. It scares the bejesus out of many, but it's really not that hard if you know a few tricks (disclosure--first I worked in refineries, and now I work for the world's largest tank truck, IBC, and rail car cleaner, so petroleum tank cleaning is familiar ground for me).

The goals could be different for every boater. Maybe you barely use any fuel and keep it for 5 years. Maybe the tank was a mess when you bought the boat. Maybe you burn through your fuel every month. Maybe you buy questionable fuel in the 3rd world. So I'm not trying to judge. It also follows that the system design is different for each case.

The BEST polishing method is to use the fuel. It was never intended to last for years and the longer it stays the greater the risk of trouble.

 

[[70521]]

This guy as an interesting angle...

It is an interesting angle, sounds like he has spent a year re-inventing the wheel! It's another version of a Racor or Separ filter, but not as good as you can't see the build up of water in the bowl.

 

[davidej]

We have a translucent plastic diesel tank so you can see it’s contents. It then goes through the much maligned CAV separator/ filter and then the engine filter.

In about 15 years of ownership, I have yet to see the slightest trace of water or sludge in any part of the system.

Admittedly we have only bought fuel in reasonably civilized parts of the world - ie almost every country in Northern Europe.

 

[thinwater]

It is an interesting angle, sounds like he has spent a year re-inventing the wheel! It's another version of a Racor or Separ filter, but not as good as you can't see the build up of water in the bowl.

Also RCI. The water capacity is greater and they are less likely to plug (a Racor problem), but yeah, it's one more thing and you really don't have that much water.
RCI separators

 

[WoodyP]

A question for those more knowledgeable than me.
The return diesel is quite warm. Will this contribute to the bug. I have been laid up for nearly three years with full tanks treated with biocide. This is white diesel, which I have run on for quite a few years. I have pumped out a quantity of fuel for us in a tractor as I don't mind if the tractor dies, but don't want the boat engine to stop inconveniently as it once did coming out of Wells harbour. The fuel from one of the tanks in particular was quite cloudy, and this was the tank used last. The tractor hasn't stopped, yet!

 

[The Q]

My polishing system is not part of the boat, it's a separate system with a long copper tube which reaches to the bottom of the tank when I plug it in.
If you get diesel bug it will clog all your filters rapidly. Leaving you with no propulsion.
It most likely to happen in rough seas when all the bottom sludge and water gets mixed up, with the fuel.

 

[noelex]

One advantage of a fuel polishing system that has not been mentioned is as an early warning of fuel problems.

The very high volume of fuel that is sent through the polishing filter, even when the engine is not run for long periods, together with the fine filtration (we use a 2 micron filter in the polish system) combined with fact that this fuel is drawn from the very bottom of the tank means that bad fuel will clog the fuel polishing filter rapidly. A vacuum gauge on the polishing filter means that fuel problems will be apparent at an early stage.

 

[superheat6k]

Routine polishing may not achieve much, but ideally .../

1 Heavily grease your filler cap threads - this is where most water enters.

2 Draw from the lowest point on the tanks as this is where any water will lay.

3 Polish at least after every fuelling.

Keep it dry of water the defacto keep it devoid of bug.

 

[IanCC]

We have a translucent plastic diesel tank so you can see it’s contents. It then goes through the much maligned CAV separator/ filter and then the engine filter.

In about 15 years of ownership, I have yet to see the slightest trace of water or sludge in any part of the system.

Admittedly we have only bought fuel in reasonably civilized parts of the world - ie almost every country in Northern Europe.

Lucky you. ?

Bought boat last year from South coast up to Scotland. Adding m16 when filling up. Winterise. Sample bottom if tank nothing much,removed little bit of water. Filled tank to brim. Spring brings fuel bug. I pulled out 3 gallons of manky fuel.

 

[noelex]

1 Heavily grease your filler cap threads - this is where most water enters.

Deck mounted flush fuel fills seem a silly idea to me, but they are often seen modern yachts. Why the fuel fill is not more commonly a raised pipe, or situated in dry area is a mystery.

 

[geem]

One advantage of a fuel polishing system that has not been mentioned is as an early warning of fuel problems.

The very high volume of fuel that is sent through the polishing filter, even when the engine is not run for long periods, together with the fine filtration (we use a 2 micron filter in the polish system) combined with fact that this fuel is drawn from the very bottom of the tank means that bad fuel will clog the fuel polishing filter rapidly. A vacuum gauge on the polishing filter means that fuel problems will be apparent at an early stage.

Same with my very simple cheapo fuel pump, clear filter and flexible pipe and length of copper twigging. It's my barometer of fuel tank cleanliness. All for about £40.

 

[noelex]

Same with my very simple cheapo fuel pump, clear filter and flexible pipe and length of copper twigging. It's my barometer of fuel tank cleanliness. All for about £40.

I think that would be a good system, and as you point out it provides important warning of a developing problem, but it would not be easy to do with our tanks and it does not provide a continual indication of an issue.

Our fuel tanks have large inspection hatches, which allow for a visualisation of the tank bottom. This is perhaps the best means of thoroughly checking for issues, but removing an inspection hatch on each tank requires some effort. The hatches are mainly for cleaning the tanks, and our experience with our previous yacht suggests good fuel practices, including a polishing system means this is normally not needed. Hopefully our tanks can remain closed with the polishing system providing the warning system.

In terms of cost, fuel polishing systems are inexpensive. All that is needed is an simple fuel pump and standard boat fuel filter. The major drawback is the time taken for installation but this will vary considerably. Once installed it can be used anytime with the flick of a switch.

 

[thinwater]

Routine polishing may not achieve much, but ideally .../

1 Heavily grease your filler cap threads - this is where most water enters.

2 Draw from the lowest point on the tanks as this is where any water will lay.

3 Polish at least after every fueling.

Keep it dry of water the defacto keep it devoid of bug.

Does anyone ACTUALLY get water from a marina fuel dock? If so, why does ANYONE ever buy from that dock again? I seriously doubt the local powerboat folk would stand for that and the dock would be closed for lack of business and lawsuits. Same with dirt. In the US it is required by law and vigorously enforced, that every pump has a 30 micron filter. I imagine this is the same in the UK.

Corollary. The water is NOT coming from the fuel dock. It is leaks and condensation. The dirt is coming from bug or from long storage with copper piping.

Just sayin', if it was coming from the source, trucks wouldn't run. So I'm thinkin' that's not the problem.

 

[Star-Lord]

I'm obsessed with having clean fuel in our diesel tank. Last week we had the primary Racor and secondary fuel filter elements replaced as part of a general Engine Service. Both were very clean in-spite of being in-situ for several years. The Racor had some water in it, but very little (I check this regularly).

We also had an intermittent fault with the fuel gauge, which meant removing the sender. With access to the tank and my obsession about clean fuel, we used a Pela-type pump attached to a straight probe to remove any water at the bottom of the tank (there was about 3L but this has never previously been done - around 10 years).

So why do we need fuel "polishing systems"? With a standard diesel engine setup and the return-pipe for un-used diesel fuel, the fuel s getting "polished" every time you use the engine. The only fuel that isn't polished is that used by the engine. As long as you can get any water out through accessing the bottom of the fuel tank I don't see any reason to "polish" the fuel.

Is it just another "fad" or have I got the wrong end of the stick?

Is Fuel Polishing really necessary? Patrick Laine describes why and how to make a fuel polishing system in this video. If I had room this would be for me as well. Instead I use a 10 micron Racor (30 micron is recommended I believe for a Yanmar 3JH3E - my engine filter is also 10 Micron) as recommended by a mechanic I trust. I have read a 10 Micron Racor will/may cause a fuel shortage into engine? Mine seems to like the 10. But 10 Micron is great at start of season and then you can switch to a 30 Micron after you have changed the 10 Micron a couple of times). Also... I use M16 Bug treatment... once you have got rid of bug do not over use this.

 

[noelex]

Does anyone ACTUALLY get water from a marina fuel dock? If so, why does ANYONE ever buy from that dock again? I seriously doubt the local powerboat folk would stand for that and the dock would be closed for lack of business and lawsuits. Same with dirt. In the US it is required by law and vigorously enforced, that every pump has a 30 micron filter. I imagine this is the same in the UK.

Corollary. The water is NOT coming from the fuel dock. It is leaks and condensation. The dirt is coming from bug or from long storage with copper piping.

Just sayin', if it was coming from the source, trucks wouldn't run. So I'm thinkin' that's not the problem.

We always test the fuel by examining a sample in a glass jar before purchasing. We have never found any water, but dirty fuel, including one case of horrible rust particles, has caused us to reject a number of fuel providers.

 

[pmagowan]

All the fuel in our boat goes through a Racor funnel and so we see if there is any dirt or water. The fuel supply is generally good but you do get the odd bit of crud. We also store fuel in cans but you can see how clean it is. I intend to install a polishing system but twin Racors are the priority to allow a filter change while running

 

[noelex]

All the fuel in our boat goes through a Racor funnel and so we see if there is any dirt or water. The fuel supply is generally good but you do get the odd bit of crud. We also store fuel in cans but you can see how clean it is. I intend to install a polishing system but twin Racors are the priority to allow a filter change while running

These are very sensible steps.

Do not expect one system such as fuel polishing to guarantee you will not have fuel related problems. A combination of systems and practices is needed. Using a filter before the fuel enters the tank is also something we do.

A dual filter system that can be instantly switched over is also helpful. My only caution is that if you develop a diesel bug problem the filters can clog quickly. A switchover may not give you much running time.

I met a single handed sailor a few years ago that had been struggling with engine stoppages due to fuel problems after a rough passage stirred up his tank. He was continually switching filters to keep the engine running. He reported each new filter only gave 10-15 mins run time before it clogged.