Running fuel polishing system

[Arthurc]

My fuel polishing system is on my Day tank (800g) and I haven’t really used it yet, although when I bought the boat I had the tanks cleaned, inspected and all the fuel fully polished, plus added a bunch new.
So my question is how often and when do you run your polishing system?

Thanks
AC

 

[Simi 60]

I would think most engines would have 50 to 90% of the fuel running through the system goes back to the tank so essentially, using the engine polishes the fuel.

How long it takes to do your tank I have no idea.

 

[O C Diver]

Is it part of your transfer system to move fuel into the day tank? I will use mine to transfer fuel and will run it on trips when I'm in seas that are sloshing the fuel and stirring up anything that might be on the bottom of the tank. Check your engine specifications to see how much fuel your lift pump moves per hour as this can also be a decent polishing system depending on flow rate.

Ted

 

[FF]

"I would think most engines would have 50 to 90% of the fuel running through the system goes back to the tank so essentially, using the engine polishes the fuel."

This depends on the injection system for the engines.

Some only return a part of a gallon per hour .

I would operate a "polishing" setup by monitoring the systems filter.

If the filter collects lots of water and gunk, keep "polishing".,and changing filters.

 

[Bay Pelican]

Once you have paid to install the system fuel polishing is essentially free. OK you must replace the filter - mine was a roll of Bounty Paper Towels. However, my system drained from the bottom of the tank and I could tell when I drained the filter container that I was doing something useful. Side effect was that my primary and secondary Racor filters never looked like they needed changing.

Especially when I had shore power I ran the fuel polishing system. Also when I had a strong wind for the wind generator or topped batteries with solar power.

In 15 years with the fuel polishing system (simple pump, F1 Filter housing) I never had an engine slow down because of fuel.

 

[Arthurc]

My fuel transfer system is totally independent.

 

[Roger Long]

The fuel polishing system should run continuously whenever the engines are running and have a provision for running when they are off in case contaminated fuel is taken aboard.


Filtering is a highly statistical process. At the micro level, filters are like a bundle of sticks and not a screen. 10 micron filters will pass some larger particles, you need multiple passes to insure that larger particles are not going to the engine.


I'll post more later as I learned a lot from a consultant in filtering.

 

[Rossland]

My fuelling strategy:
-I buy fuel only from marinas that pump a lot of fuel. These are usually the ones with the lowest prices.
-I run the fuel polisher for at least half an hour immediately after refuelling to see if it is catching anything. If not, there is no need to run the fuel polisher any longer.
- Every day I monitor the fuel filters on the engine to see if there are any contaminants.
- I change fuel filters only when indicated by the vacuum gages. Whenever I change the primary engine filters, I also change the secondary engine filter.
- About twice a year I drain the fuel tank sumps into a clear jar to see if there is anything there but clean fuel.

In the last year and a half, and over 2000gal of fuel burned, I have not had to change the fuel polishing filters, have changed the engine filters once, and have never found any contaminants in the tank sumps. But I have not had to refuel an any remote third world countries either.

I look on the fuel polishing system almost like a fire extinguisher. It is good to have one, but hopefully you will never need it.

 

[DavidM]

How not to polish your fuel:

This story is an example of bad advice from a surveyor, owner ignorance, and incompetence of a fuel polishing service.

I sold my Mainship Pilot 34 a few weeks ago. After the sea trial the surveyor noted water about half way up the Racor filter housing. Not surprising, this happens after every winter as condensate collects in the tanks. A few runs to bring up the bow, push the water back to the pickup and draining the Racor is all it takes to deal with the problem until next winter. The gauge on the Racor showed very low pressure drop so the filter element was fine.

The surveyor insisted that the fuel be polished to remove the water. I compromised by running the engine for an hour at the dock to see if more water got picked up. Unsurprisingly no more water got picked up because the water level was below the pickup tube due to the earlier sea trial run.

But the buyer was nervous and had a fuel polishing company come out and do their stuff. They disconnected the fuel hose from tank to the Racor and used that as their suction point. They ran their circulating pump for a few hours. Don't know what if anything they picked up, but I doubt much.

Using the fuel hose from the tank as the pick up point meant that nothing was removed from below the interior tank pick up level and I knew that there was no water above it due to the earlier sea trial and draining of the Racor. Also the very low circulating volume limited by the 3/8" diameter connection to the tank meant that nothing was stirred up inside the tank, so no water or sludge was likely removed from the bottom.

The total cost of this effort was more than $1,000 and from what I could tell, was entirely worthless. A couple of runs up to planing speed (raising the bow) and draining the Racor would have done much, much more. That is what Racors are for, right?

So if you have a fuel polisher come out or if you install a dedicated system, make sure that the pickup is at the bottom of the tank and is large enough to allow significant flow. Otherwise it is no better than running your engine and letting the injector return flow polish the fuel. I do understand that some engines return very little fuel to the tank, so check that out first. This was a Yanmar 6LY which returns significant fuel volume, about 10 gph at a slow cruise speed.

David

 

[Xsbank]

Do the math on the amount of water that air can hold and you will see that condensation is not a problem, at least in northern latitudes. You boat had a rainwater leak if your Racor was half full of water after a winter.

 

[Fletcher500]

As noted, I would think a good size Racor with a common rail fuel supply/return is doing quite a bit of polishing. With a dual Racor I will often run with both filters on during longer runs for this reason.

 

[DavidM]

Do the math on the amount of water that air can hold and you will see that condensation is not a problem, at least in northern latitudes. You boat had a rainwater leak if your Racor was half full of water after a winter.

Well, ok let's do the math. Look at one cycle starting with saturated air at 65 degrees F (common during October haulout) and dropping to 20 degrees F which you will get in late November.

Saturated air at 65 degrees holds about .001 lb of water per cu foot. My half full tanks hold about 100 gallons of air or 13 cu feet. So the total water quantity is 0.013 lb. Saturated air at 20 degrees F holds 0.0002 lbs per cu foot. So about .0026 total. The difference which will drop out in the fuel is about 0.01 lb. So to get a couple of cups of water to drop out- about a lb., it would take a hundred such cycles.

So maybe that is unrealistic and I might have gotten water in through the o-ring on the filler caps. Snow builds up on the side decks and may then slowly melt wicking its way in past the o-rings.

David

 

[Xsbank]

Hi David, that's more likely. Air will not circulate in and out of the tank providing "fresh" air with a new load of moist air so the amount of water from condensation is miniscule.

 

[HiDHo]

Bay Pelican, I just changed my Gulf Coast filter element which is a big roll of Bounty paper towels, Bounty 2X, which is 175 sheets of 2 ply paper. ( see photo).
I also only change Racor elements because of age. My F-1 has been in use for ten years. The photo shows the contaminates, no telling how much condensate the roll has collected.

 

[Lepke]

Look up your engines total fuel flow. My twins pump about 60 gallons an hour more than they burn, so no need for fuel polishing. You should have a vacuum gauge after the primary filters or as part of their installation. That will tell you well in advance, when to change the filters. Keep your tanks full, especially over winter and you shouldn't have a water problem. Get in the habit of adding a good fuel conditioner every fueling and you won't have problems. I don't.

I have 1942 steel tanks and try to pump down each one once a year. Because they are mild steel, I go inside and carefully inspect, especially the bottom. Since I first opened them about 5 years ago, there has been zero sludge and so little water I could probably capture it with a paper towel.

 

[Simi 60]

As noted, I would think a good size Racor with a common rail fuel supply/return is doing quite a bit of polishing. With a dual Racor I will often run with both filters on during longer runs for this reason.

What does this do?
Surely it won't equal more fuel flow/more polishing as the flow is governed by the fuel pump right?

Doing some sort of polishing pump, ball valve addition is something I have been thinking on as I have the 1000fg x 2 setup yet only bring one into play and in 2 years have seen zero crud, water or vacuum so the second one "could" be brought into play as a polisher.
Logic says all is good and polishing is unwarranted but as the near future plan is to run away to Indonesia, Malaysia, Thailand some form of scrubber would be beneficial as stories of less than clean fuel are common.

 

[AusCan]

More important than a fuel polishing system is to have an outlet on the lowest point in your fuel tank, preferably with a slope running down to the outlet. As David mentioned, fuel polishing is a waste of time if it doesn't circulate the bottom 10% of the tank.

My electric fuel pump returns deliver about 20 litres/hour with the engine using 3 litres/hour, so it has the capability of filtering all my fuel in 24 hours. My fuel manifold allows me to choose drawing from the bottom of either tank or from a pick up tube.

The bottom valves are also tied into a shared sight glass which is mounted lower than the tanks. The sight glass will visually show me if there is any more than a trace of water.

If I see any water I can drain it off, and then run the engines of the bottom supply valve for a day or two. I consider this as good as any fuel polishing system.

 

[Delfin]

My fuel polishing system is on my Day tank (800g) and I haven’t really used it yet, although when I bought the boat I had the tanks cleaned, inspected and all the fuel fully polished, plus added a bunch new.
So my question is how often and when do you run your polishing system?

Thanks
AC

Art, if it is just on the day tank, I'm not sure you would call it a polishing "system". It is the fuel in the bulk tanks that needs to be polished before transfer to the day tank, so a polishing "system" can run all the fuel on the boat through filters multiple times.

To your question, we cycle fuel through 30 micron filters, one tank at a time, when underway perhaps weekly. We transfer that fuel to a staging tank (250 gal) through a 10 micron filter, then Polish that tank through 30 cycles or so before it is used to refill the day tank. From there, 2 micron Racors before the OEM filter.

 

[JDCAVE]

I have a fuel polishing system and would run it all the time when running, however its an AC pump and isn't (yet) hooked up to the inverter side of the panel, so I do not (yet) use it while running.

There has been lots of discussion of the pro's and con's of centrifugal systems, vs ISI systems, but in my view the most important issue is timing when you to run the polishing system when there is AGITATION IN THE TANKS, i.e. when you are traveling when the seas are rough. Better still when the tank is near empty and the fuel is returned back to the tank. There is no point in using the system when you are at the dock (which is what I do).

Jim

 

[Bay Pelican]

Bay Pelican, I just changed my Gulf Coast filter element which is a big roll of Bounty paper towels, Bounty 2X, which is 175 sheets of 2 ply paper. ( see photo).
I also only change Racor elements because of age. My F-1 has been in use for ten years. The photo shows the contaminates, no telling how much condensate the roll has collected.

I am a big fan of the Gulf Coast Filter (Bounty Paper Towels as the element) and have collected both water and contaminates using the system.

Having designed the fuel tanks I was able to put in outlets at the very bottom of the tanks for fuel polishing. The original Krogen tanks drew from the bottom so over 33 years the fuel tanks had bottom outlets without issue.

When we opened the original tanks (removed for leaks) there was almost no gunk on the bottom.

 

[FF]

"More important than a fuel polishing system is to have an outlet on the lowest point in your fuel tank, preferably with a slope running down to the outlet. As David mentioned, fuel polishing is a waste of time if it doesn't circulate the bottom 10% of the tank."

Some fuel tanks have a plate with hundreds of holes installed low inside the box.
Fuel pickup is above the plate.

The concept is gunk will fall down past the holes and modest motion wont mix enough to foul the filters.

With a drain plug under the plate this is a cheap to build partial solution .

A far far better solution is a genuine sump like a 2 quart deep jar built into the tank bottom where the water can collect , along with the gunk.
The military version uses a cup built onto a strainer that can be lifted from the deck.

Imagine 25% water in a fuel delivery and ALL can be removed with no electric , no filters , and just time and gravity.

This is more expensive construction , and requires room , so is seldom seen.

 

[Mako]

The original Krogen tanks drew from the bottom so over 33 years the fuel tanks had bottom outlets without issue.



When we opened the original tanks (removed for leaks) there was almost no gunk on the bottom.

Personally I believe this is the simplest and best approach to fuel tank design. Why have a sump or a collection cup or baffle plate at all? Your Racor with water separator, even at 30 micron, is your “polisher.”

My previous boat’s 40 year old steel tank (1600 gallons) was sealed. No access plates either. But the pickup tube ran to the bottom and then the 6-71’s did their thing. No Racor was mounted either, just the stock primary and secondary.

Of course an improvement would be an electric transfer pump in front of a Racor, with a valve to return the flow back to the tank. Good practice after filling the tank from a questionable source would be to go anchor afterwards for 24 hours and let the crud settle out, before polishing.

 

[DDW]

MaineSail has tested the empty vs full tank condensation theory by leaving one tank near empty and one completely full throughout a Maine winter. No difference in water.

When I had the sailboat tanks made, each has a slope towards a low point, and at the low point there is a small sump, only about 6 x 6" and 2" deep. The dip tube extends even to the bottom of the tank but not into the sump. This guarantees that all of the fuel in the tank can be used except for the 2 cups or so in the sump. The sump collects all the water and dirt over time as it sinks to the low point. There is an access plug directly above it that can be removed and the dirty wet fuel in the sump sucked out and disposed of. It's really not that expensive at all to build, I think most builders just figure it's not a problem that will appear during the warrantee period so good bye and good luck.

Something that should be done but does cost a little extra is the tanks should be welded on the inside rather than (or in addition to) the outside. The inside weld on aluminum tanks will ofter be either incompletely penetrated (leaving a crack) or very rough and ugly due to inadequate shielding gas. Both of these trap dirt and water and that is often where corrosion starts. Of course you cannot weld all the inside seams, but you can at least do the bottom ones.